References and Notes
For recent review on carbazole derivatives, see:
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We have found that a Suzuki-Miyaura reaction of 12 and 13 mediated by ligand 1 provides biaryl product 14 even with the chloride, which is known as a low reactive halide (Scheme
[2 ]
).
Scheme 2
<A NAME="RU09907ST-10">10 </A>
Experimental Procedure for the Synthesis of Carbazole 5 (Table 1, Entry 6)
To a solution of 2-bromophenylboronic acid (2 , 30 mg, 0.15 mmol) and 2-iodoaniline (3 , 30 mg, 0.14 mmol) in toluene (0.5 mL) was added Pd2 (dba)3 (13 mg, 0.01 mmol), ligand 1 (6.9 mg, 0.02 mmol), and Cs2 CO3 (134 mg, 0.41 mmol) at r.t. under an argon atmosphere, then the mixture was stirred
at 100 °C for 2 h. The mixture was cooled to r.t., and then NaOt- Bu (16 mg, 0.17 mmol) was added and stirred at 100 °C for 19 h. After stirring, H2 O was added, and extracted with EtOAc. The organic layer was washed with H2 O, brine, dried over MgSO4 and evaporated. The residue was purified by column chromatography on silica gel (benzene-EtOAc,
99:1) to afford the 9H -carbazole (5 , 16 mg, 71%) as a colorless solid; R
f
= 0.82 (benzene-EtOAc, 99:1). 1 H NMR (500 MHz, CDCl3 ): δ = 8.08 (d, J = 7.9 Hz, 2 H), 8.03 (br s, 1 H), 7.50-7.40 (m, 4 H), 7.30-7.20 (m, 2 H). 13 C NMR (68 MHz, CDCl3 ): δ = 139.5, 125.8, 123.4, 120.3, 119.4, 110.6. MS-FAB: m/z = 168 [M + H]+ . HRMS-FAB: m/z calcd for C12 H10 N [M + H]+ : 168.0814; found: 168.0809.
<A NAME="RU09907ST-11">11 </A>
An isolation and structure determination of complex 4′ was not tested.
<A NAME="RU09907ST-12">12 </A>
Addition of Cs2 CO3 (1.2 equiv) instead of NaOt -Bu gave no improvement of chemical yields to give 5 and 4 in 26% and 31%, respectively. This result also supports that the complex 4′ plays a role in preventing the ring closure to 5 .
For recent reviews on biaryl phosphine ligand, see:
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Shimizu H.
Nagasaki I.
Saito T.
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Analytical Data of 9b
R
f
= 0.52 (hexane-benzene, 2:3). 1 H NMR (500 MHz, CDCl3 ): δ = 8.34 (s, 1 H), 8.23 (br s, 1 H), 8.10 (d, J = 7.9 Hz, 1 H), 7.66 (d, J = 8.5 Hz, 1 H), 7.55-7.40 (m, 3 H), 7.35-7.25 (m, 1 H). 13 C NMR (68 MHz, CDCl3 ): δ = 140.9, 139.4, 127.3, 126.8, 123.2, 123.0, 122.9, 122.8, 122.72, 122.67, 122.6,
122.0, 121.6, 120.6, 120.3, 118.02, 117.96, 117.9, 117.8, 110.9, 110.6. MS-FAB: m/z = 236 [M + H]+ . HRMS-FAB: m/z calcd for C13 H9 NF3 [M + H]+ 236.0687; found: 236.0678.
Analytical Data of 9g
R
f
= 0.20 (hexane-CH2 Cl2 , 1:1). 1 H NMR (500 MHz, CDCl3 ): δ = 7.94 (d, J = 7.9 Hz, 1 H), 7.87 (br s, 1 H), 7.51 (s, 1 H), 7.40-7.25 (m, 2 H), 7.24-7.15 (m,
1 H), 6.87 (s, 1 H), 4.00 (s, 3 H), 3.93 (s, 3 H). 13 C NMR (68 MHz, CDCl3 ): δ = 149.4, 144.4, 139.4, 134.2, 124.2, 123.6, 119.20, 119.18, 115.3, 110.5, 102.7,
94.2, 56.6, 56.1. MS-FAB: m/z = 227 [M + H]+ . HRMS-FAB: m/z calcd for C14 H14 NO2 [M + H]+ 228.1025; found: 228.1022.
<A NAME="RU09907ST-15A">15a </A> 4-Methoxycarbazole (9f ) has been synthesized by Pd-catalyzed intramolecular arylation reaction as a minor
product of regioisomeric mixture. See:
Liu Z.
Larock RC.
Tetrahedron
2007,
63:
347
<A NAME="RU09907ST-15B">15b </A> 4-Vinyl-substituted carbazoles have been prepared from N -phenyl-3-iodoaniline and internal alkyne via a vinylic to aryl palladium migration.
See:
Zhao J.
Larock RC.
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2-Iodoaniline derivatives were readily obtained by ortho iodination of aniline as well as selective reduction of 2-iodonitrobenzene. For recent
examples, see:
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Reddy VS.
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Seo JH.
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Hänisch C.
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3809
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The carbazole synthesis from aniline and 1,2-dihalobenzene was reported in ref. 6b.
<A NAME="RU09907ST-18">18 </A>
Experimental Procedure (Table 4, entry 2)
To a solution of 2-aminophenylboronic acid (10 , 15 mg, 0.11 mmol) and 1,2-diiodobenzene (11 , 33 mg, 0.10 mmol) in 1,4-dioxane (0.33 mL) was added Pd(OAc)2 (2.2 mg, 0.01 mmol), ligand 1 (5.0 mg, 0.01 mmol), and Cs2 CO3 (98 mg, 0.30 mmol) at r.t. under an argon atmosphere, then the mixture was stirred
at 80 °C for 24 h. The mixture was cool to r.t., and then NaOt- Bu (12 mg, 0.12 mmol) was added and stirred at 80 °C for 24 h. After stirring, H2 O was added, and extracted with EtOAc. The organic layer was washed with H2 O, brine, dried over MgSO4 , and evaporated. The residue was purified by column chromatography on silica gel
(benzene-EtOAc, 99:1) to afford the 9H -carbazole (5 , 13 mg, 76%) as a colorless solid.
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Hutchinson I.
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