Synthesis 2017; 49(17): 3937-3944
DOI: 10.1055/s-0036-1589011
special topic
© Georg Thieme Verlag Stuttgart · New York

C–H and N–H Bond Annulation of Benzamides with Isonitriles Catalyzed by Cobalt(III)

Deepti Kalsi
Fine Chemical Laboratory, Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India   Email: basker@iitk.ac.in
,
Nagaraju Barsu
Fine Chemical Laboratory, Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India   Email: basker@iitk.ac.in
,
Pardeep Dahiya
Fine Chemical Laboratory, Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India   Email: basker@iitk.ac.in
,
Fine Chemical Laboratory, Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India   Email: basker@iitk.ac.in
› Author Affiliations
Financial support provided by SERB (EMR2016/000136) to support this research work is gratefully acknowledged. D.K. thanks IITK, N.B. and Pardeep express gratitude to CSIR for their fellowships.
Further Information

Publication History

Received: 03 March 2017

Accepted after revision: 04 April 2017

Publication Date:
11 May 2017 (online)

 

Published as part of the Special Topic Cobalt in Organic Synthesis

In memory of Prof. Shunsuke Murahashi for pioneering work in cobalt-catalyzed C–H bond functionalization

Abstract

A simple efficient, atom-economical procedure was developed for the cobalt-catalyzed C–H bond annulation of benzamides with isonitriles under mild conditions. The reaction tolerates a variety of functional group including heterocycles. Diverse 3-(alkylimino)-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-ones were synthesized using isonitriles as the C1 source through C–H and N–H bond annulation via C–H bond activation in a ‘green’ solvent. Vinylamides were also used similarly with tert-butyl isonitrile to give 3-(tert-butylimino)-1-quinolin-8-yl-1H-pyrrol-2(5H)-ones.


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Zoom Image
Scheme 1 Overview of Co-catalysis for formal [4+1] C–H bond annulation

C–H bond functionalization has become an integral part of various transformations ranging from simple to complex molecules in a few steps.[1] Although these transformations operate well with the utilization of a directing group strategy, improved synthetic applications have led to significant developments in this field. Among the directing groups, amides have proven to improve the synthetic applications through C–H bond activation with good reactivity and selectivity.[1f] [2] Since the early 2000s, Noble metals have been exploited for this process. However, due to economical concerns, the use of inexpensive first-row transition metals for C–H bond functionalizations has become an emerging target.[3] In 1955, Murahashi reported the first cobalt-catalyzed carbonylation of azobenzene via C–H bond activation using a low valent cobalt–carbonyl complex (Scheme [1], Ia).[4] In a different approach, Daugulis reported the C–H carbonylative annulation of benzamide using high valent Co(III) under mild conditions (Scheme [1], Ib).[5] In 2017, our group[6a] and the Gaunt group[6b] independently reported the carbonylative cyclization of aliphatic amides using a similar directing group strategy (Scheme [1], II). In continuation of our previous work, we envisaged replacing carbon monoxide by isonitriles as the C1 source for the formal [4+1] C(sp2)–H bond annulation of benzamides (Scheme [1], III). Isonitriles are versatile building blocks and a unique C1 source, which facilitates transformations that could not be achieved with carbon monoxide with very high atom efficiency.[7] Only very few examples were reported for the annulation of benzamide with isonitriles under oxidative conditions.[8] Within our program for C–H bond functionalization using first row transition metal catalysts,[6a] , [9] [10] [11] we wish to report the cobalt-catalyzed formal [4+1] annulation of benzamides and isonitriles using CPME as a ‘green’ solvent under mild conditions.[12] [13]

Table 1 Reaction Optimizationa

Entry

[Co]

Base (equiv)

Oxidant (equiv)

Yield (%)

 1

Co(OAc)2

NaOPiv (2)

Ag2CO3 (2)

80b

 2

Co(OAc)2

NaOPiv (2)

Ag2CO3 (1)

53b

 3

Co(OAc)2

NaOPiv (2)

Ag2CO3 (1)

78c

 4

Co(OAc)2

NaOPiv (2)

Ag2CO3 (1)

85

 5

Co(OAc)2

NaOPiv (2)

Mn(OAc)3 (1)

29c

 6

Co(acac)2

NaOPiv (2)

Ag2CO3 (1)

95

 7

Co(acac)3

NaOPiv (2)

Ag2CO3 (1)

41

 8

Co(acac)3

Ag2CO3 (2)

70

 9

Cp*Co(CO)I2

NaOPiv (2)

Ag2CO3 (1)

58

10

Co(OAc)2

NaOPiv (2)

Ag2CO3 (1)

70d

11

Co(acac)2

NaOPiv (1)

Ag2CO3 (1)

78

12

Co(acac)2

NaOPiv (1)

Ag2CO3 (0.5)

68

13

Co(acac)2

NaOPiv (2)

Ag2CO3 (0.5)

80

14

Co(acac)2

NaOPiv (2)

17

15

Co(acac)2

Ag2CO3 (1)

21

16

NaOPiv (2)

Ag2CO3 (1)

n.d.

17

Co(acac)2

NaOPiv (2)

Ag2CO3 (1)

n.d.e

18

Co(acac)2

NaOPiv (2)

AgNO3 (1)

41

a Reaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), [Co] (0.02 mmol), base (0.2–0.4 mmol), oxidant (0.1–0.4 mmol), CPME (1 mL), air atmosphere, 100 °C (oil bath temperature), 24 h; n.d. = not determined.

b Reaction performed under argon atmosphere.

c Under O2 atmosphere.

d Dimethyl carbonate (DMC) (1 mL) was used as solvent.

e PhCONHOMe was used as amide instead of 1a.

We began our investigation by screening various reaction parameters using the eco-friendly solvent cyclopentyl methyl ether (CPME) as the reaction medium, with benz­amide 1a and tert-butyl isonitrile (2a) as model substrates; the results are summarized in Table [1]. Iminoisoindolinone 3a was isolated in 80% yield, when cobalt(II) acetate was used as a catalyst precursor, along with sodium pivalate as the base and silver carbonate as the oxidant at 100 °C for 24 h (entry 1). Reduction in the amount of silver carbonate significantly lower the yield of 3a, suggesting that excess oxidant is required to access high product formation (entry 2). The reaction was performed under oxygen and air atmospheres. Both gave similar yields as to that obtained under argon (entries 3 and 4). Replacement of silver carbonate with another commonly used oxidant in cobalt catalysis, such as Mn(OAc)3, gave a lower yield (entry 5). Several cobalt catalysts were screened for further improvement. Among them, Co(acac)2 is an effective catalyst that provides complete conversion with the isolated yield of 3a in 95% (entries 6–9). Changing CPME to another eco-friendly solvent, dimethyl carbonate, gave a lower yield (entry 10). Further lower the quantity of oxidant or base gave satisfactory results (entries 11–13). Our control experiments reveal that the catalyst, base, oxidant, and quinoline for bidentate chelation were crucial for the reaction to proceed (entries 14–18). Other solvents were not efficient under the standard reaction conditions. With the best reaction conditions in hand, we next examined the scope of amides and results are given in Scheme [2].

Zoom Image
Scheme 2 Reaction scope; a Ag2CO3 (2 equiv) was used.
Zoom Image
Scheme 3 Control experiments

A methyl substituent at o-, m-, and p-positions of the arene gave good to excellent yields of 3bd. Arylamides with electron-rich (t-Bu, SMe) and electron-deficient (F, CF3, Ar) functional groups at different positions work equally well giving 3en in moderate to excellent yields. We next examined m-substituted benzamides, which possess two electronically and sterically biased ortho-protons. Functionalization of ortho-C–H bonds provides two regioisomers, of which the major product 3c,l obtained is from the sterically less hindered C–H bond. On the other hand, a 1:1 ratio of 3k/3k′ was obtained, when the NO2 group was placed at the meta position perhaps due to stereoelectronic reasons. Annulation with tert-butyl isonitrile (2a) was further extended to amides derived from thiophene-2-carboxylic acid, which led to 46% of 3o. Next we extended the scope to access γ-lactams through β-C–H bond activation by employing α,β-unsaturated amides derived from the parent carboxylic acids. Gratifyingly, all substituted vinylamides provide the cycloaddition products 3ps however with moderate efficiency. Further, cyclohexyl isonitrile (2b) was used in place of tert-butyl isonitrile (2a) with benz­amide 1a under standard conditions provides corresponding iminoisoindolinone 3t in good yield as a mixture of E/Z-stereoisomers in 2.2:1 ratio.

Notably, benzamide 1u derived from naphthaleneacetic acid did not give the cycloaddition product 3u, this may be due to the incompetence to form a six-membered cobaltacycle. To understand the reaction pathways, some control experiments were carried out and the results are presented in Scheme [3]. A competitive experiment was performed with electron-rich and -poor amides. An equimolar amount of amide 1b and 1m was subjected under standard conditions, 63% of 3m and 35% of 3b was isolated, suggesting that electrophilic activation is unlikely (Scheme [3, a]). A radical trapping experiment was carried out with TEMPO (2 equiv) and this gave 65% of 3a, indicating that the 1e process may not be involved (Scheme [3, b]). To shed light on the cleavage of C–H bonds, further H/D exchange experiments were conducted using D2O as the deuterium source. Under the standard conditions, no deuterium incorporation was observed with or without 2a indicating that the C–H bond cleavage is irreversible (Scheme [3, c]).

Finally, we have also shown the selective C–H bond functionalization of amide containing strongly coordinating pyrimidine 1v provide the expected iminoisoindolinone 3v in 74% yield (Scheme [4]).

Zoom Image
Scheme 4 Overcoming the limitation of strongly chelating directing groups

Based on the above experiment, a plausible mechanism is proposed in Scheme [5].

Zoom Image
Scheme 5 Proposed mechanism

Initial oxidation of Co(II) to Co(III) is facilitated by silver(I) under air followed by N,N-coordination of benzamide 1a leading to intermediate A, which undergoes irreversible C–H bond activation that leads to cobaltacycle B. Further coordination of isonitrile 2a with B followed by insertion leads to intermediate D. Reductive elimination of D gives iminoisoindolinone 3a along with Co(I). Co(III) is regenerated by oxidation of Co(I) mediated by silver(I) for the next catalytic cycle. Silver(I) will possibly be recycled by oxidation of Ag(0) under air/oxygen.

In conclusion, we have reported a new method for the preparation of isoindolinone, a highly useful intermediates for bioactive compounds,[14] catalyzed by high-valent cobalt­(III) under mild conditions. The scope of the reaction reveals that the reaction is regioselective with very high functional group tolerance. Our preliminary control experiments suggest that C–H bond cleavage is irreversible and the reaction did not proceed through 1e pathway. Also, stoichiometric oxidant was necessary to re-oxidize the Co(I) to Co(III) in order to regenerate active catalyst. Further isolation of reactive organometallic intermediates is currently pursued in our laboratory.

Unless otherwise mentioned, all catalytic reactions were carried out under an O2/air atmosphere; starting materials were prepared under an argon atmosphere. HPLC grade CH2Cl2 and reagent grade CPME and DMC were used as such from commercial sources, as were all other chemicals. 1H and 13C NMR were recorded on a Jeol (400 and 500 MHz) using CDCl3 with the solvent signals used as references (CDCl3: δC = 77; residual CHCl3 in CDCl3: δH= 7.26). All the reactions were monitored by analytical TLC using commercial aluminum sheets precoated with silica gel. Chromatography was conducted on silica gel (Merck, 100–200 mesh). ESI-MS was recorded on a Waters-Micromass Quattro Micro triple-quadrupole mass spectrometer. GC-MS was used to analyze our samples on a Shimadzu GC 2010 plus and MS 2010SE system. LC-MS was recorded on a Agilent technologies 6120 Quadrupole LC/MS. IR samples were analyzed on a Perkin Elmer FTIR spectrophotometer.


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5-(Alkylimino)-1-quinolin-8-yl-1H-pyrrol-2(5H)-one Derivatives 3a–t,v; General Procedure

To an oven-dried Schlenk tube charged with magnetic stirrer was added benzamide/vinylamide (0.2 mmol), Co(acac)2 (0.02 mmol, 10 mol%), sodium pivalate (0.4 mmol, 2.0 equiv), and Ag2CO3 (0.2 mmol, 1.0 equiv) and finally CPME (1 mL) as the solvent. To this mixture, tert-butyl isonitrile (2a, 0.3 mmol, 1.5 equiv) was added under air. The closed Schlenk tube containing the mixture was placed in preheated oil bath at 100 °C for 24 h. The mixture was allowed to cool to r.t. The solvent was removed and the residue was purified by flash column chromatography (silica gel, EtOAc/hexane) to afford iminoisoindolinones and iminopyrrolones 3 in good yield.


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(E)-3-(tert-Butylimino)-5-(methylthio)-2-quinolin-8-yl-2,3-dihydro­-1H-isoindol-1-one (3f)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 30:70) gave 3f as a pale white solid; yield: 48 mg (64%); Rf = 0.4 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.82 (dd, J = 4.1, 1.6 Hz, 1 H), 8.18 (dd, J = 8.1, 1.6 Hz, 1 H), 7.92 (d, J = 8.0 Hz, 2 H), 7.87 (dd, J = 8.0, 1.5 Hz, 1 H), 7.69 (dd, J = 7.1, 1.4 Hz, 1 H), 7.64–7.60 (m, 1 H), 7.48 (dd, J = 7.8, 1.5 Hz, 1 H), 7.37 (dd, J = 8.2, 4.1 Hz, 1 H), 2.60 (s, 3 H), 1.31 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 167.34, 150.09, 146.80, 144.89, 144.81, 135.91, 133.13, 131.08, 130.39, 130.38, 128.90, 128.27, 127.82, 125.74, 123.93, 123.83, 121.11, 53.61, 30.56, 15.51.

HRMS: m/z [M + H] calcd for C22H22N3OS: 376.1484; found: 376.1481.


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(E)-3-(tert-Butylimino)-2-quinolin-8-yl-2,3-dihydro-1H-benzo[e]isoindol­-1-one (3g)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 30:70) gave 3g as a bright yellow solid; yield: 58 mg (76%); Rf = 0.45 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 9.29 (d, J = 8.2 Hz, 1 H), 8.83 (dd, J = 4.1, 1.6 Hz, 1 H), 8.19–8.12 (m, 3 H), 7.94 (d, J = 8.3 Hz, 1 H), 7.89 (dd, J = 8.0, 1.1 Hz, 1 H), 7.78 (dd, J = 7.2, 1.3 Hz, 1 H), 7.70–7.60 (m, 3 H), 7.37 (dd, J = 8.2, 4.1 Hz, 1 H), 1.34 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 169.33, 150.94, 150.28, 145.20, 135.98, 134.51, 133.57, 132.89, 131.21, 131.48, 128.98, 128.84, 128.66, 128.33, 127.99, 127.86, 127.56, 125.82, 125.64, 122.52, 121.19, 53.98, 31.04.

HRMS: m/z [M + H] calcd for C25H22N3O: 380.1763; found: 380.1768.


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(E)-3-(tert-Butylimino)-5-fluro-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3i)

Following the general procedure on a 0.2-mmol scale using Ag2CO3 (2 equiv) with purification by flash column chromatography (EtOAc/hexane, 20:80) gave 3i as a yellow solid; yield: 63 mg (90%); Rf = 0.4 (EtOAc/hexane). NMR data are in accordance with the literature.[3]

1H NMR (CDCl3, 400 MHz): δ = 8.82 (dd, J = 4.0, 1.6 Hz, 1 H), 8.17–8.14 (m, 1 H), 8.02 (dd, J = 8.1, 5.5 Hz, 1 H), 7.86–7.84 (m, 1 H), 7.77 (dd, J = 9.1, 2.0 Hz, 1 H), 7.69 (dd, J = 7.5, 1.6 Hz, 1 H), 7.63–7.59 (m, 1 H), 7.37–7.32 (m, 2 H), 1.30 (s, 9 H).

13C NMR (CDCl3, 100 MHz): δ = 166.6, 166.37, 163.85, 150.19, 144.77, 136.0, 132.97, 131.07, 129.88, 128.96, 128.46, 125.79, 125.70, 121.21, 118.35, 118.11, 114.62, 53.79, 30.57.

19F NMR (CDCl3, 471 MHz): δ = –104.99.

HRMS: m/z [M + H] calcd for C21H19FN3O: 348.1512; found: 348.1518.


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(E)-3-(tert-Butylimino)-5-nitro-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3j)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 25:75) gave 3j as a yellow solid; yield: 49 mg (65%); Rf = 0.5 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.95 (d, J = 1.8 Hz, 1 H), 8.80 (dd, J = 4.2, 1.8 Hz, 1 H), 8.53 (dd, J = 8.2, 1.8 Hz, 1 H), 8.19–8.16 (m, 2 H), 7.99 (dd, J = 8.1, 1.3 Hz, 1 H), 7.72 (dd, J = 7.3, 1.4 Hz, 1 H), 7.64 (m, 1 H), 7.38 (dd, J = 8.2, 4.1 Hz, 1 H), 1.32 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 165.62, 150.48, 150.34, 148.53, 144.55, 144.45, 138.31, 136.05, 132.50, 130.92, 128.95, 128.86, 126.23, 125.79, 124.69, 121.88, 121.41, 54.29, 30.76.

HRMS: m/z [M + H] calcd for C21H19N4O3: 375.1457; found: 375.1454.


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(E)-3-(tert-Butylimino)-6-nitro-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3k)

Following the general procedure on a 0.3-mmol scale with purification by flash column chromatography (EtOAc/hexane, 10:90) gave 3k as a yellow solid; yield: 42 mg (37%); Rf = 0.55 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.73 (dd, J = 4.1, 1.7 Hz, 1 H), 8.25–8.20 (m, 2 H), 7.89 (dd, J = 8.2, 0.52 Hz, 1 H), 7.72 (dd, J = 8.2, 1.2 Hz, 1 H), 7.61–7.57 (m, 1 H), 7.39 (dd, J = 8.3, 4.1 Hz, 1 H), 7.26 (dd, J = 7.2, 1.3 Hz, 1 H), 6.90–6.89 (m, 1 H), 1.96 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 166.68, 150.59, 150.17, 150.04, 145.20, 140.07, 137.47, 136.14, 130.38, 129.28, 126.81, 126.42, 123.82, 123.70, 121.70, 119.87, 117.50, 59.89, 29.54.

HRMS: m/z [M + H] calcd for C21H19N4O3: 375.1457; found: 375.1454.


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(E)-3-(tert-Butylimino)-4-nitro-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3k′)

Following the general procedure on a 0.3-mmol scale with purification by flash column chromatography (EtOAc/hexane, 20:90) gave 3k′ as a yellow solid; yield: 45 mg (40%); Rf = 0.55 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.84–8.82 (m, 2 H), 8.59–8.56 (m, 1 H), 8.27 (d, J = 8.6 Hz, 1 H), 8.21 (dd, J = 8.3, 1.7 Hz, 1 H), 7.92 (dd, J = 8.1, 1.4 Hz, 1 H), 7.72 (dd, J = 7.2, 1.5 Hz, 1 H), 7.67–7.64 (m, 1 H), 7.41 (dd, J = 8.2, 4.0 Hz, 1 H), 1.29 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 150.44, 150.40, 149.36, 144.46, 143.76, 141.77, 136.25, 132.50, 131.07, 129.03, 128.94, 127.60, 127.19, 127.17, 125.89, 121.50, 119.02, 54.42, 30.76.

HRMS: m/z [M + H] calcd for C21H19N4O3: 375.1457; found: 375.1454.


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(E)-3-(tert-Butylimino)-2-quinolin-8-yl-4-(trifluoromethyl)-2,3-dihydro-1H-isoindol-1-one (3l) and (E)-3-(tert-Butylimino)-2-quinolin-8-yl-6-(trifluoromethyl)-2,3-dihydro-1H-isoindol-1-one (3l′)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 20:80) gave 3l/3l′ as a yellow oil; yield: 60 mg (76%); ratio 3l/3l′ 9.1:1.0; Rf = 0.45 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.80 (dd, J = 4.0, 1.6 Hz, 1 H), 8.32 (m, 1 H), 8.23 (d, J = 8.1 Hz, 1 H), 8.17 (dd, J = 8.3, 1.7 Hz, 1 H), 7.99–7.97 (m, 1 H), 7.87 (dd, J = 8.2, 1.4 Hz, 1 H), 7.71 (dd, J = 7.4, 1.5 Hz, 1 H), 7.65–7.61 (m, 1 H), 7.36 (dd, J = 8.2, 4.3 Hz, 1 H), 1.32 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 166.34, 150.29, 144.59, 136.68, 136.03, 134.30, 133.98, 132.67, 131.03, 128.95, 128.69, 128.14, 125.78, 124.89, 124.28, 123.71, 122.17, 121.32, 54.0, 30.62.

19F NMR (CDCl3, 471 MHz): δ = –62.64.

HRMS: m/z [M + H] calcd for C22H19F3N3O: 398.1480; found: 398.1483.


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(E)-3-(tert-Butylimino)-2-quinolin-8-yl-5-(trifluoromethyl)-2,3-dihydro-1H-isoindol-1-one (3m)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 15:85) gave 3m as a pale yellow solid; yield: 67 mg (84%); Rf = 0.45 (EtOAc/hexane). NMR data are in accordance with the literature.[3]

1H NMR (CDCl3, 400 MHz): δ = 8.81 (dd, J = 4.2, 1.7 Hz, 1 H), 8.35 (s, 1 H), 8.17 (t, J = 7.8 Hz, 2 H), 7.96–7.87 (m, 2 H), 7.71 (dd, J = 7.3, 1.5 Hz, 1 H), 7.65–7.61 (m, 1 H), 7.39–7.36 (m, 1 H), 1.32 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 166.37, 150.29, 144.59, 136.68, 136.03, 134.62, 134.30, 133.98, 133.65, 132.67, 131.03, 128.95, 128.69, 128.14, 125.78, 124.89, 124.28, 123.78, 122.17, 121.32, 54.0, 30.62.

19F NMR (CDCl3, 471 MHz): δ = –62.39.

HRMS: m/z [M + H] calcd for C22H19F3N3O: 398.1480; found: 398.1483.


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(E)-3-(tert-Butylimino)-2-quinolin-8-yl-4,6-bis(trifluoromethyl)-2,3-dihydro-1H-isoindol-1-one (3n)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 10:90) gave 3n as a yellow oil; yield: 47 mg (50%); Rf = 0.50 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.81 (dd, J = 4.1, 1.5 Hz, 1 H), 8.38 (s, 1 H), 8.28 (s, 1 H), 8.21 (dd, J = 8.1, 1.5 Hz, 1 H), 7.97 (dd, J = 8.3, 1.3 Hz, 1 H), 7.84 (dd, J = 7.1, 1.3 Hz, 1 H), 7.71–7.67 (m, 1 H), 7.42 (dd, J = 8.4, 3.9 Hz, 1 H), 0.79 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 168.51, 151.14, 148.69, 145.23, 140.22, 136.17, 135.51, 134.67, 132.89, 132.85, 132.55, 131.67, 129.76, 129.13, 128.48, 127.03, 125.86, 123.57, 122.07, 55.66, 30.68.

19F NMR (CDCl3, 471 MHz): δ = –59.42, –62.57.

HRMS: m/z [M + H] calcd for C23H18F6N3O: 466.1354; found: 466.1354.


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(E)-5-(tert-Butylimino)-3-methyl-1-quinolin-8-yl-1H-pyrrol-2(5H)-one (3p)

Following the general procedure on a 0.3-mmol scale using Ag2CO3 (2 equiv) with purification by flash column chromatography flash column chromatography (EtOAc/hexane, 40:60) gave 3p as a brown oil; yield: 27 mg (30%); Rf = 0.50 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.85 (dd, J = 4.1, 1.7 Hz, 1 H), 8.13 (dd, J = 8.3, 1.7 Hz, 1 H), 7.81 (dd, J = 7.7, 1.8 Hz, 1 H), 7.62–7.55 (m, 2 H), 7.35 (dd, J = 8.2, 4.2 Hz, 1 H), 6.95–6.94 (m, 1 H), 2.16 (d, J = 1.7 Hz, 3 H), 1.26 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 170.38, 152.42, 150.12, 144.13, 141.44, 135.97, 132.42, 130.88, 129.04, 128.15, 125.82, 122.95, 121.15, 55.40, 32.18, 11.48.

HRMS: m/z [M + H] calcd for C18H20N3O: 294.1606; found: 294.1615.


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(E)-5-(tert-Butylimino)-4-phenyl-1-quinolin-8-yl-1H-pyrrol-2(5H)-one (3q)

Following the general procedure on a 0.2-mmol scale using Ag2CO3 (2 equiv) with purification by flash column chromatography (EtOAc/hexane, 20:80) gave 3q as a yellow solid; yield: 45 mg (63%); Rf = 0.45 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.86 (dd, J = 4.2, 1.6 Hz, 1 H), 8.18 (dd, J = 8.2, 1.6 Hz, 1 H), 7.93–7.89 (m, 3 H), 7.81 (dd, J = 7.2, 1.3 Hz, 1 H), 7.67–7.63 (m, 1 H), 7.44–7.42 (m, 3 H), 7.40 (dd, J = 8.3, 4.2 Hz, 1 H), 6.75 (m, 1 H), 0.79 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 173.86, 151.92, 150.89, 145.77, 144.42, 136.02, 135.83, 132.07, 130.07, 129.44, 129.09, 129.02, 128.82, 127.87, 125.83, 122.00, 121.76, 55.45, 30.87.

HRMS: m/z [M + H] calcd for C23H22N3O: 356.1763; found: 356.1765.


#

(E)-5-(tert-Butylimino)-4-(4-methoxyphenyl)-1-quinolin-8-yl-1H-pyrrol-2(5H)-one (3r)

Following the general procedure on a 0.2-mmol scale using Ag2CO3 (2 equiv) with purification by flash column chromatography (EtOAc/hexane, 40:60) gave 3r as a yellow solid; yield: 32.5 mg (42%); Rf = 0.40 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.86 (dd, J = 4.2, 1.7 Hz, 1 H), 8.18 (dd, J = 8.3, 1.7 Hz, 1 H), 7.96–7.92 (m, 2 H), 7.90 (dd, J = 8.3, 1.5 Hz, 1 H), 7.80 (dd, J = 7.3, 1.4 Hz, 1 H), 7.65 (dd, J = 8.1, 7.3 Hz, 1 H), 7.39 (dd, J = 8.3, 4.1 Hz, 1 H), 6.97–6.94 (m, 2 H), 6.67 (s, 1 H), 3.87 (s, 3 H), 0.79 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 174.15, 160.80, 151.46, 150.89, 145.85, 144.75, 136.03, 136.01, 132.14, 131.61, 129.11, 128.96, 125.85, 124.61, 121.75, 119.97, 113.43, 55.42, 55.30, 30.89.

HRMS: m/z [M + H] calcd for C24H24N3O2: 386.1869; found: 386.1866.


#

(E)-5-(tert-Butylimino)-1-quinolin-8-yl-4-[4-(trifluoromethyl)phenyl]-1H-pyrrol-2(5H)-one (3s)

Following the general procedure on a 0.2-mmol scale using Ag2CO3 (2 equiv) with purification by flash column chromatography (EtOAc/ hexane, 20:80) gave 3s as a brown solid; yield: 23 mg (27%); Rf = 0.40 (EtOAc/hexane).

1H NMR (CDCl3, 500 MHz): δ = 8.86–8.85 (m, 1 H), 8.19 (d, J = 8.0 Hz, 1 H), 8.02 (d, J = 7.7 Hz, 2 H), 7.92 (d, J = 8.0 Hz, 1 H), 7.81 (d, J = 7.3 Hz, 1 H), 7.69–7.64 (m, 3 H), 7.41 (dd, J = 7.9, 4.0 Hz, 1 H), 6.81 (s, 1 H), 0.785 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 173.40, 150.99, 150.51, 145.68, 144.05, 136.11, 135.56, 135.44, 135.43, 132.09, 130.26, 129.23, 129.14, 125.88, 124.76, 124.72, 123.27, 121.89, 55.63, 30.85.

19F NMR (CDCl3, 471 MHz): δ = –62.65.

HRMS: m/z [M + H] calcd for C24H21F3N3O: 424.1637; found: 424.1633.


#

(E)-3-(Cyclohexylimino)-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3t) and (Z)-3-(Cyclohexylimino)-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3t′)

Following the general procedure on a 0.2-mmol scale using cyclohexyl isonitrile with purification by flash column chromatography (EtOAc­/hexane, 25:75) gave 3t/3t′ as a colorless oil; yield: 50 mg (70%); ratio E/Z 2.28:1.0; Rf = 0.45 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 8.87–8.84 (m, 1 H), 8.22–8.16 (m, 1 H), 8.04 (d, J = 7.7 Hz, 1 H), 7.96 (d, J = 7.3 Hz, 1 H), 7.91–7.86 (m, 1 H), 7.73–7.61 (m, 4 H), 7.38–7.35 (m, 1 H), 4.28–4.23 (m, 1 H), 1.85–1.82 (m, 1 H), 1.74–1.65 (m, 2 H), 1.64–1.58 (m, 1 H), 1.45–1.18 (m, 6 H).

13C NMR (CDCl3, 101 MHz): δ = 167.51, 150.30, 149.80, 144.70, 136.05, 133.13, 133.04, 132.35, 131.31, 130.95, 130.12, 129.80, 129.09, 128.59, 125.65, 123.96, 121.27, 57.59, 34.03, 25.47, 24.50.

HRMS: m/z [M + H] calcd for C23H22N3O: 356.1763; found: 356.2.


#

(E)-3-(tert-Butylimino)-5-pyrimidin-2-yl-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-one (3v)

Following the general procedure on a 0.2-mmol scale with purification by flash column chromatography (EtOAc/hexane, 40:60) gave 3v as a white solid; yield: 60 mg (74%); Rf = 0.50 (EtOAc/hexane).

1H NMR (CDCl3, 400 MHz): δ = 9.31 (s, 1 H), 8.88–8.79 (m, 4 H), 8.19 (dd, J = 8.2, 1.7 Hz, 1 H), 8.14 (d, J = 8.0 Hz, 1 H), 7.88 (dd, J = 8.1, 1.3 Hz, 1 H), 7.73 (dd, J = 7.4, 1.5 Hz, 1 H), 7.66–7.63 (m, 1 H), 7.38 (dd, J = 8.2, 4.2 Hz, 1 H), 7.30–7.26 (m, 1 H), 1.42 (s, 9 H).

13C NMR (CDCl3, 101 MHz): δ = 167.2, 163.4, 157.4, 150.1, 147.3, 144.8, 141.5, 136.0, 135.7, 133.0, 131.1, 130.8, 130.0, 128.9, 128.3, 127.1, 125.8, 123.8, 121.1, 119.8, 53.9, 30.6.

HRMS: m/z [M + H] calcd for C25H22N5O: 408.1824; found: 408.1825.


#
#

Supporting Information

  • References

    • 1a C–H Bond Activation and Catalytic Functionalization I, Topics in Organometallic Chemistry. Dixneuf PH. Doucet H. Springer; Berlin: 2016
    • 1b Ye B. Cramer N. Acc. Chem. Res. 2015; 48: 1308
    • 1c Ackermann L. Acc. Chem. Res. 2014; 47: 281
    • 1d Girard SA. Knauber T. Li CJ. Angew. Chem. Int. Ed. 2014; 53: 74
    • 1e Collins KD. Glorius F. Nat. Chem. 2013; 5: 597
    • 1f Corbet M. Decampo F. Angew. Chem. Int. Ed. 2013; 52: 9896
    • 1g Li B. Dixneuf PH. Chem. Soc. Rev. 2013; 42: 5744
    • 1h Yamaguchi J. Yamaguchi AD. Itami K. Angew. Chem. Int. Ed. 2012; 51: 8960
    • 1i Neufeldt SR. Sanford MS. Acc. Chem. Res. 2012; 45: 936
    • 1j Arockiam PB. Bruneau C. Dixneuf PH. Chem. Rev. 2012; 112: 5879
    • 1k Satoh T. Miura M. Chem. Eur. J. 2010; 16: 11212
    • 1l Colby DA. Bergman RG. Ellman JA. Chem. Rev. 2010; 110: 624
    • 2a Zhu R.-Y. Farmer ME. Chen Y.-Q. Yu J.-Q. Angew. Chem. Int. Ed. 2016; 55: 10578
    • 2b Misal Castro LC. Chatani N. Chem. Lett. 2015; 44: 410
    • 2c Rouquet G. Chatani N. Angew. Chem. Int. Ed. 2013; 52: 11726

      Selected reviews on C–H bond functionalization using first-row transition-metal catalysts, see:
    • 3a Moselage M. Li J. Ackermann L. ACS Catal. 2016; 6: 498
    • 3b Yoshikai N. ChemCatChem 2015; 7: 732
    • 3c Liang Y. Liang Y.-F. Jiao N. Org. Chem. Front. 2015; 2: 403
    • 3d Hyster T. Catal. Lett. 2015; 145: 458
    • 3e Cai X.iH. Xie B. ARKIVOC 2015; (i): 184 ; http://www.arkat-usa.org
    • 3f Bauer I. Knölker H.-J. Chem. Rev. 2015; 115: 3170
    • 3g Tasker SZ. Standley EA. Jamison TF. Nature (London) 2014; 509: 299
    • 3h Gao K. Yoshikai N. Acc. Chem. Res. 2014; 47: 1208
    • 3i Ackermann L. J. Org. Chem. 2014; 79: 8948
    • 3j Yamaguchi J. Muto K. Itami K. Eur. J. Org. Chem. 2013; 19
    • 3k Gephart RT. Warren TH. Organometallics 2012; 31: 7728
    • 3l Yoshikai N. Synlett 2011; 1047
    • 3m Nakao Y. Chem. Rec. 2011; 11: 242
    • 3n Nakamura E. Yoshikai N. J. Org. Chem. 2010; 75: 6061
    • 3o Kulkarni AA. Daugulis O. Synthesis 2009; 4087
  • 4 Murahashi S. J. Am. Chem. Soc. 1955; 77: 6403
    • 5a Grigorjeva L. Daugulis O. Org. Lett. 2014; 16: 4688
    • 5b Liu X.-G. Zhang S.-S. Jiang C.-Y. Wu J.-Q. Li Q. Wang H. Org. Lett. 2015; 17: 5404
    • 5c Ni J. Li J. Fan Z. Zhang A. Org. Lett. 2016; 18: 5960
    • 6a Barsu N. Bolli SK. Sundararaju B. Chem. Sci. 2017; 8: 2431
    • 6b Williamson P. Galván A. Gaunt MJ. Chem. Sci. 2017; 8: 2588

      For selected recent reviews on isonitrile insertion including C–H bonds, see:
    • 7a Song B. Xu B. Chem. Soc. Rev. 2017; 46: 1103
    • 7b Nenajdenko V. Isonitrile Chemistry: Applications in Synthesis and Material Science. Wiley-VCH; Weinheim: 2012
    • 7c Vlaar T. Ruijter E. Maes BU. Orru RV. Angew. Chem. Int. Ed. 2013; 52: 7084
    • 7d Lang S. Chem. Soc. Rev. 2013; 42: 4867
    • 7e Gulevich AV. Zhadanko AG. Orru RV. A. Nenajdenko VG. Chem. Rev. 2010; 110: 5235
    • 7f Dçmling A. Ugi I. Angew. Chem. Int. Ed. 2000; 39: 3168
    • 7g Isonitrile Chemistry . Academic Press; New York: 1971
    • 8a Hao W. Tian J. Li W. Huang Z. Lei A. Chem. Asian J. 2016; 11: 1664
    • 8b Takamatsu K. Hirano K. Miura M. Org. Lett. 2015; 17: 4066
    • 8c Wang D. Cai S. Ben R. Zhou Y. Li X. Zhao J. Wei W. Qian Y. Synthesis 2014; 46: 2045
    • 8d Zhu C. Xie W. Falck JR. Chem. Eur. J. 2011; 17: 12591

      For C(sp2)–H bond functionalization, see:
    • 9a Kalsi D. Laskar RA. Barsu N. Premkumar JR. Sundararaju B. Org. Lett. 2016; 18: 4198
    • 9b Barsu N. Sen M. Sundararaju B. Chem. Commun. 2016; 52: 1338
    • 9c Barsu N. Kalsi D. Sundararaju B. Chem. Eur. J. 2015; 21: 9364
    • 9d Sen M. Kalsi D. Sundararaju B. Chem. Eur. J. 2015; 21: 15529
    • 9e Kalsi D. Sundararaju B. Org. Lett. 2015; 17: 6118

      For C(sp3)–H bond functionalization, see:
    • 10a Sen M. Emayavaramban B. Barsu N. Premkumar JR. Sundararaju B. ACS Catal. 2016; 6: 2792
    • 10b Barsu N. Rahman MA. Sen M. Sundararaju B. Chem. Eur. J. 2016; 22: 9135

      See selected recent reports on cobalt(III)-catalyzed C–H bond functionalization:
    • 11a Prakash S. Muralirajan K. Cheng C.-H. Angew. Chem. Int. Ed. 2016; 55: 1844
    • 11b Du C. Li P.-X. Zhu X. Suo J.-F. Niu J.-L. Song M.-P. Angew. Chem. Int. Ed. 2016; 55: 13571
    • 11c Maity S. Kancherla R. Dhawa U. Hoque E. Pimparkar S. Maiti D. ACS Catal. 2016; 6: 5493
    • 11d Lerchen A. Vásquez-Céspedes S. Glorius F. Angew. Chem. Int. Ed. 2016; 55: 3208
    • 11e Tan G. He S. Huang X. Liao X. Cheng Y. You J. Angew. Chem. Int. Ed. 2016; 55: 10414
    • 11f Manoharan R. Sivakumar G. Jeganmohan M. Chem. Commun. 2016; 52: 10533
    • 11g Yamaguchi T. Kommagalla Y. Aihara Y. Chatani N. Chem. Commun. 2016; 52: 10129
    • 11h Landge VG. Jaiswal G. Balaraman E. Org. Lett. 2016; 18: 812
    • 11i Hummel JR. Ellman JA. J. Am. Chem. Soc. 2015; 137: 490
    • 11j Patel P. Chang S. ACS Catal. 2015; 5: 853
    • 11k Wang H. Koeller J. Liu W. Ackermann L. Chem. Eur. J. 2015; 21: 15525
    • 11l Thrimurtulu N. Dey A. Maiti D. Volla CM. R. Angew. Chem. Int. Ed. 2016; 55: 12361
    • 11m Grigorjeva L. Daugulis O. Angew. Chem. Int. Ed. 2014; 53: 10209
    • 11n Yoshino T. Ikemoto H. Matsunaga S. Kanai M. Angew. Chem. Int. Ed. 2013; 52: 2207
    • 11o See also ref. 5a.
  • 12 During the preparation of our manuscript, Wang and Ji reported similar work under different reaction conditions, see: Gu Z.-Y. Liu C.-G. Wang S.-Y. Ji S.-J. J. Org. Chem. 2017; 82: 2223

    • Green solvents for sustainable processes, see:
    • 13a Byrne FP. Jin S. Paggiola G. Petchey TH. M. Clark JH. Farmer TJ. Hunt AJ. McElroy CR. Sherwood J. Sustainable Chem. Processes 2016; 4: 7
    • 13b Fischmeister C. Doucet H. Green Chem. 2011; 13: 741
  • 14 Murthy AR. K. Wong OT. Reynolds DJ. Hall IH. Pharm. Res. 1987; 4: 21

  • References

    • 1a C–H Bond Activation and Catalytic Functionalization I, Topics in Organometallic Chemistry. Dixneuf PH. Doucet H. Springer; Berlin: 2016
    • 1b Ye B. Cramer N. Acc. Chem. Res. 2015; 48: 1308
    • 1c Ackermann L. Acc. Chem. Res. 2014; 47: 281
    • 1d Girard SA. Knauber T. Li CJ. Angew. Chem. Int. Ed. 2014; 53: 74
    • 1e Collins KD. Glorius F. Nat. Chem. 2013; 5: 597
    • 1f Corbet M. Decampo F. Angew. Chem. Int. Ed. 2013; 52: 9896
    • 1g Li B. Dixneuf PH. Chem. Soc. Rev. 2013; 42: 5744
    • 1h Yamaguchi J. Yamaguchi AD. Itami K. Angew. Chem. Int. Ed. 2012; 51: 8960
    • 1i Neufeldt SR. Sanford MS. Acc. Chem. Res. 2012; 45: 936
    • 1j Arockiam PB. Bruneau C. Dixneuf PH. Chem. Rev. 2012; 112: 5879
    • 1k Satoh T. Miura M. Chem. Eur. J. 2010; 16: 11212
    • 1l Colby DA. Bergman RG. Ellman JA. Chem. Rev. 2010; 110: 624
    • 2a Zhu R.-Y. Farmer ME. Chen Y.-Q. Yu J.-Q. Angew. Chem. Int. Ed. 2016; 55: 10578
    • 2b Misal Castro LC. Chatani N. Chem. Lett. 2015; 44: 410
    • 2c Rouquet G. Chatani N. Angew. Chem. Int. Ed. 2013; 52: 11726

      Selected reviews on C–H bond functionalization using first-row transition-metal catalysts, see:
    • 3a Moselage M. Li J. Ackermann L. ACS Catal. 2016; 6: 498
    • 3b Yoshikai N. ChemCatChem 2015; 7: 732
    • 3c Liang Y. Liang Y.-F. Jiao N. Org. Chem. Front. 2015; 2: 403
    • 3d Hyster T. Catal. Lett. 2015; 145: 458
    • 3e Cai X.iH. Xie B. ARKIVOC 2015; (i): 184 ; http://www.arkat-usa.org
    • 3f Bauer I. Knölker H.-J. Chem. Rev. 2015; 115: 3170
    • 3g Tasker SZ. Standley EA. Jamison TF. Nature (London) 2014; 509: 299
    • 3h Gao K. Yoshikai N. Acc. Chem. Res. 2014; 47: 1208
    • 3i Ackermann L. J. Org. Chem. 2014; 79: 8948
    • 3j Yamaguchi J. Muto K. Itami K. Eur. J. Org. Chem. 2013; 19
    • 3k Gephart RT. Warren TH. Organometallics 2012; 31: 7728
    • 3l Yoshikai N. Synlett 2011; 1047
    • 3m Nakao Y. Chem. Rec. 2011; 11: 242
    • 3n Nakamura E. Yoshikai N. J. Org. Chem. 2010; 75: 6061
    • 3o Kulkarni AA. Daugulis O. Synthesis 2009; 4087
  • 4 Murahashi S. J. Am. Chem. Soc. 1955; 77: 6403
    • 5a Grigorjeva L. Daugulis O. Org. Lett. 2014; 16: 4688
    • 5b Liu X.-G. Zhang S.-S. Jiang C.-Y. Wu J.-Q. Li Q. Wang H. Org. Lett. 2015; 17: 5404
    • 5c Ni J. Li J. Fan Z. Zhang A. Org. Lett. 2016; 18: 5960
    • 6a Barsu N. Bolli SK. Sundararaju B. Chem. Sci. 2017; 8: 2431
    • 6b Williamson P. Galván A. Gaunt MJ. Chem. Sci. 2017; 8: 2588

      For selected recent reviews on isonitrile insertion including C–H bonds, see:
    • 7a Song B. Xu B. Chem. Soc. Rev. 2017; 46: 1103
    • 7b Nenajdenko V. Isonitrile Chemistry: Applications in Synthesis and Material Science. Wiley-VCH; Weinheim: 2012
    • 7c Vlaar T. Ruijter E. Maes BU. Orru RV. Angew. Chem. Int. Ed. 2013; 52: 7084
    • 7d Lang S. Chem. Soc. Rev. 2013; 42: 4867
    • 7e Gulevich AV. Zhadanko AG. Orru RV. A. Nenajdenko VG. Chem. Rev. 2010; 110: 5235
    • 7f Dçmling A. Ugi I. Angew. Chem. Int. Ed. 2000; 39: 3168
    • 7g Isonitrile Chemistry . Academic Press; New York: 1971
    • 8a Hao W. Tian J. Li W. Huang Z. Lei A. Chem. Asian J. 2016; 11: 1664
    • 8b Takamatsu K. Hirano K. Miura M. Org. Lett. 2015; 17: 4066
    • 8c Wang D. Cai S. Ben R. Zhou Y. Li X. Zhao J. Wei W. Qian Y. Synthesis 2014; 46: 2045
    • 8d Zhu C. Xie W. Falck JR. Chem. Eur. J. 2011; 17: 12591

      For C(sp2)–H bond functionalization, see:
    • 9a Kalsi D. Laskar RA. Barsu N. Premkumar JR. Sundararaju B. Org. Lett. 2016; 18: 4198
    • 9b Barsu N. Sen M. Sundararaju B. Chem. Commun. 2016; 52: 1338
    • 9c Barsu N. Kalsi D. Sundararaju B. Chem. Eur. J. 2015; 21: 9364
    • 9d Sen M. Kalsi D. Sundararaju B. Chem. Eur. J. 2015; 21: 15529
    • 9e Kalsi D. Sundararaju B. Org. Lett. 2015; 17: 6118

      For C(sp3)–H bond functionalization, see:
    • 10a Sen M. Emayavaramban B. Barsu N. Premkumar JR. Sundararaju B. ACS Catal. 2016; 6: 2792
    • 10b Barsu N. Rahman MA. Sen M. Sundararaju B. Chem. Eur. J. 2016; 22: 9135

      See selected recent reports on cobalt(III)-catalyzed C–H bond functionalization:
    • 11a Prakash S. Muralirajan K. Cheng C.-H. Angew. Chem. Int. Ed. 2016; 55: 1844
    • 11b Du C. Li P.-X. Zhu X. Suo J.-F. Niu J.-L. Song M.-P. Angew. Chem. Int. Ed. 2016; 55: 13571
    • 11c Maity S. Kancherla R. Dhawa U. Hoque E. Pimparkar S. Maiti D. ACS Catal. 2016; 6: 5493
    • 11d Lerchen A. Vásquez-Céspedes S. Glorius F. Angew. Chem. Int. Ed. 2016; 55: 3208
    • 11e Tan G. He S. Huang X. Liao X. Cheng Y. You J. Angew. Chem. Int. Ed. 2016; 55: 10414
    • 11f Manoharan R. Sivakumar G. Jeganmohan M. Chem. Commun. 2016; 52: 10533
    • 11g Yamaguchi T. Kommagalla Y. Aihara Y. Chatani N. Chem. Commun. 2016; 52: 10129
    • 11h Landge VG. Jaiswal G. Balaraman E. Org. Lett. 2016; 18: 812
    • 11i Hummel JR. Ellman JA. J. Am. Chem. Soc. 2015; 137: 490
    • 11j Patel P. Chang S. ACS Catal. 2015; 5: 853
    • 11k Wang H. Koeller J. Liu W. Ackermann L. Chem. Eur. J. 2015; 21: 15525
    • 11l Thrimurtulu N. Dey A. Maiti D. Volla CM. R. Angew. Chem. Int. Ed. 2016; 55: 12361
    • 11m Grigorjeva L. Daugulis O. Angew. Chem. Int. Ed. 2014; 53: 10209
    • 11n Yoshino T. Ikemoto H. Matsunaga S. Kanai M. Angew. Chem. Int. Ed. 2013; 52: 2207
    • 11o See also ref. 5a.
  • 12 During the preparation of our manuscript, Wang and Ji reported similar work under different reaction conditions, see: Gu Z.-Y. Liu C.-G. Wang S.-Y. Ji S.-J. J. Org. Chem. 2017; 82: 2223

    • Green solvents for sustainable processes, see:
    • 13a Byrne FP. Jin S. Paggiola G. Petchey TH. M. Clark JH. Farmer TJ. Hunt AJ. McElroy CR. Sherwood J. Sustainable Chem. Processes 2016; 4: 7
    • 13b Fischmeister C. Doucet H. Green Chem. 2011; 13: 741
  • 14 Murthy AR. K. Wong OT. Reynolds DJ. Hall IH. Pharm. Res. 1987; 4: 21

Zoom Image
Scheme 1 Overview of Co-catalysis for formal [4+1] C–H bond annulation
Zoom Image
Scheme 2 Reaction scope; a Ag2CO3 (2 equiv) was used.
Zoom Image
Scheme 3 Control experiments
Zoom Image
Scheme 4 Overcoming the limitation of strongly chelating directing groups
Zoom Image
Scheme 5 Proposed mechanism