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DOI: 10.1055/s-0028-1083514
Phosphine-Dependent Selective Cross-Dimerization between Terminal Alkylacetylene and Silylacetylene by Iridium(I) Guanidinate Complex-Phosphine System
Publication History
Publication Date:
01 October 2008 (online)
Abstract
The new iridium(I)-guanidinate complex served as an efficient catalyst for phosphine-dependent selective cross-dimerization between silylacetylene and terminal alkyl- or arylacetylene. Especially, in case of cross-dimerization between silylacetylene and alkylacetylene, E/Z selectivity of resulting enynes could be controlled by changing phosphine.
Key words
alkynes - enynes - coupling - dimerizations - iridium
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References and Notes
Synthesis of {Ir[(N
2
(
i
-Pr)
2
CN(
i
-Pr)
2
](cod)} (1)
A
solution of [IrCl(cod)]2 (281 mg, 0.42
mmol) in THF (5 mL) was cooled to -78 ˚C,
and then a THF solution of Li[(N2 (i-Pr)2CN(i-Pr)2],
which was prepared by the reaction of the DIC (0.13 mL, 0.84 mmol)
with LDA solution (1.8 M in heptane-THF-ethylbenzene
solution, 0.48 mL, 0.86 mmol) at -78 ˚C,
was added. The mixture was allowed to warm to r.t. After 4 h, the
volatiles were removed under reduced pressure. The residual solid
was extracted with toluene and the filtrate was evaporated off under
high vacuum to give orange complex 1 (278
mg, 0.53 mmol, 63%). ¹H NMR (400 MHz,
C6D6): δ = 0.96 (d, J = 6.4 Hz,
12
H, i-PrCH3), 1.23 (d, J = 6.9 Hz,
12 H, i-PrCH3), 1.39 (d, J = 7.8 Hz,
4 H, cod), 2.20 (br, 4 H, cod), 3.43 (sept, J = 6.9 Hz,
2 H, i-PrCH), 3.80 (sept, J = 6.4 Hz,
2 H, i-PrCH), 4.09 (br, 4 H, cod). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = 22.8, 25.0, 32.5,
47.1, 48.6, 58.9 (cod, i-Pr), 128.5 (cod),
179.7 (NCN). Anal. Calcd for C21H40IrN3:
C, 47.88; H, 7.65; N, 7.98. Found: C, 47.82; H, 7.60; N, 8.00.
Crystal Data for
1
C21H40IrN3, MW = 526.79,
monoclinic, P21/n, a = 20.5195 (4) Å, b = 15.5067
(4) Å, c = 27.6890
(4) Å, β = 102.4145 (16)˚, V = 8604.4
(3) Å3, Z = 16, D
calc = 1.626
g/cm³, µ (Mo Kα) = 62.328
cm-¹, 84841 measured reflections, 24677 independent
(R
int = 0.063),
13318 observed [I > 2σ(I)]. R1 = 0.0353, wR2 = 0.0903
(all data). Atomic coordinates, thermal parameters, bond distances,
and angles have been deposited at the Cambridge Crystallographic
Data Center. CCDC number: 668977.
General Procedure
for Homodimerization of Terminal Alkynes (Table 1 and Scheme 2)
The
mixture of 1 (16 mg, 0.03 mmol), toluene
(3 mL), phosphine (16 mg, 0.06 mmol), and terminal alkyne (1.0 mmol)
was charged in a sealed tube under argon atmosphere. After stirring
for 6 h at 80 ˚C, the solvent was removed, and the residue
was chromatographed on SiO2, using hexane or Et2O-hexane
(1:3) as eluent. The solvent was removed to give dimeric product 3 or 4.
Results of dimerization of 1-octyne(2a) catalyzed by 1-trialkylphosphine system; 1-Et3P: yield 60%, E/Z = 42:58; 1-n-Pr3P: yield 79%, E/Z = 40:60
13
General Procedure
for Cross-Dimerization of Silylacetylene with Terminal Alkynes (Table
2 and Scheme 3)
The mixture of 1 (25
mg, 0.05 mmol), toluene (3 mL), phosphine (26 mg, 0.10 mmol), silylacetylene
(1.0 mmol), and terminal alkyne (2.0 mmol) was charged in sealed
tube under argon atmosphere. After stirring for 6 h at 80 ˚C,
the solvent was removed, and the residue was chromatographed on
SiO2, using hexane as eluent. Homo-dimer was eluted first.
Then the eluate containing cross-dimer 5 was
obtained. The solvent was removed to give cross-dimer 5 as colorless or pale-yellow oil.
Spectral
Data for New Compounds
Product (E)-5d: ¹H NMR (400 MHz,
CDCl3): δ = 0.18 (s,
9 H,
SiMe3), 0.87 (d, J = 7.0
Hz, 6 H, CH3), 1.20-1.30 (m,
2 H,
CH2), 1.50-1.60 (m, 1 H, CH), 2.00-2.20
(m, 2 H, CH2), 5.50 (dt, J = 15.8,
1.8 Hz, 1 H, CH=CH), 6.21 (dt, J = 15.8, 7.0
Hz, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3):
δ = 0.0
(s, SiMe3), 22.4, 27.3, 30.9, 37.6 (s, C6H13),
92.4, 104.2 (s, C=C), 109.4, 146.5 (C=C). HRMS
(EI): m/z [M - Me]+ calcd
for C11H19Si: 179.1256; found: 179.1259.
Product
(Z)-5d: ¹H
NMR (400 MHz, CDCl3): δ = 0.19 (s,
9
H, SiMe3), 0.90 (d, J = 6.4
Hz, 6 H, CH3), 1.20-1.30 (m,
2 H,
CH2), 1.50-1.60 (m, 1 H, CH), 2.30-2.40
(m, 2 H, CH2), 5.46 (d, J = 10.5
Hz, 1 H, CH=CH), 5.95 (dt, J = 10.5,
7.6 Hz, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = 0.0 (s, SiMe3),
22.4, 27.3, 30.9, 37.6 (s, C6H13), 88.7, 92.4
(s, C=C), 109.4, 146.5 (C=C). HRMS (EI): m/z [M - Me]+ calcd for
C11H19Si: 179.1256; found: 179.1213.
Product
(E)-5e: ¹H
NMR (400 MHz, CDCl3): δ = 0.17 (s,
9
H, SiMe3), 3.43 (d, J = 6.9
Hz, 2 H, CH2), 5.53 (dt, J = 15.6,
1.8 Hz, 1 H, CH=CH), 6.35 (dt, J = 15.6,
6.9 Hz,
1 H, CH=CH), 7.10-7.40 (m, 5
H, Ph). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = -0.1
(s, SiMe3), 39.3 (s, CH2Ph), 93.5, 103.7 (s,
C=C), 111.0, 126.4, 128.5, 128.7, 138.6, 144.2 (S, C=C,
Ph). HRMS (EI): m/z [M]+calcd
for C14H18Si: 214.1178; found: 214.1169.
Product
(Z)-5e: ¹H
NMR (400 MHz, CDCl3): δ = 0.22 (s,
9
H, SiMe3), 3.67 (d, J = 7.3
Hz, 2 H, CH2), 5.60 (d, J = 11.0 Hz,
1 H, CH=CH), 6.10 (dt, J = 10.6,
7.3 Hz, 1 H, CH=CH), 7.10-7.40 (m, 5 H, Ph). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = -0.02
(s, SiMe3), 36.5 (s, CH2Ph), 99.0, 101.8 (s,
C=C), 109.9, 126.2, 128.5, 128.5, 139.7, 143.2 (S, C=C,
Ph). HRMS (EI): m/z [M]+ calcd
for C14H18Si: 214.1178; found: 214.1158.
Product
(E)-5g: ¹H
NMR (400 MHz, CDCl3): δ = 0.22 (s,
9
H, SiMe3), 2.34 (s, 3 H, CH3), 6.12 (d, J = 16.5 Hz,
1 H, CH=CH), 6.98 (d, J = 16.5
Hz, 1 H, CH=CH), 7.10-7.30 (m, 4 H, Ar). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = 0.0 (s, SiMe3),
21.5 (s, CH3), 96.4, 104.6 (s, C=C), 106.9,
126.2, 129.0, 129.4, 138.9, 142.4 (s, C=C, Ph). HRMS (EI): m/z [M]+ calcd
for C14H18Si: 214.1178; found: 214.1171.
Product
(E)-5h: ¹H
NMR (400 MHz, CDCl3): δ = 0.11 (s,
9
H, SiMe3), 3.81 (s, 3 H, CH3, 6.16 (d, J = 19.2 Hz,
1 H, CH=CH), 6.48 (d, J = 19.2
Hz, 1 H, CH=CH), 6.84 (d, J = 9.2
Hz, 2 H, Ar), 7.37 (d, J = 9.2
Hz, 2 H, Ar). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = -1.6
(s, SiMe3), 55.2 (s, OCH3), 88.4, 89.9 (s,
C=C), 113.9, 128.4, 132.1, 133.0, 144.7, 159.6 (s, C=C,
Ph). HRMS (EI): m/z [M]+ calcd
for C14H18OSi: 230.1127; found: 230.1133.
Product
(E)-5i: ¹H
NMR (400 MHz, CDCl3): δ = 0.80-2.20 (m,
16 H, C6H13, i-PrCH),
1.07 (br d, 18 H, i-PrCH3),
5.52 (dt, J = 16.0,
1.4 Hz, 1 H, CH=CH), 6.20 (dt, J = 16.0,
6.9 Hz, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = 11.3, 14.1, 22.6,
28.6, 28.9, 31.7, 33.1 (s, C6H13, i-PrCH), 18.6 (s, i-PrCH3),
88.5, 106.1 (s, C=C), 109.8, 145.8 (s, CH=CH).
HRMS (EI): m/z [M]+ calcd
for C19H36Si: 292.2586; found: 292.2583.
Product
(Z)-5i: ¹H
NMR (400 MHz, CDCl3): δ = 0.80-2.40 (m,
16 H, C6H13, i-PrCH),
1.09 (br d, 18 H, i-PrCH3),
5.50 (d, J = 10.5
Hz, 1 H, CH=CH), 6.0 (m, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ = 11.3, 14.1, 22.6,
28.8, 29.0, 30.4, 31.7 (s, C6H13, i-PrCH), 18.6 (s, i-PrCH3),
94.6, 103.9 (s, C=C), 109.6, 145.2 (s, CH=CH).
HRMS (EI): m/z [M]+ calcd
for C19H36Si: 292.2586; found: 292.2587.
Product
(E)-5j: ¹H
NMR (400 MHz, CDCl3): δ = 0.11 (s,
6
H, SiMe2), 0.80-2.20 (m, 13 H, C6H13),
0.94 (s, 9 H, t-Bu), 5.50 (d, J = 15.8 Hz,
1 H, CH=CH), 6.21 (dt, J = 15.8,
7.0 Hz, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ =
-4.6
(s, SiMe2), 14.1, 16.6, 22.6, 28.6, 28.8, 31.6, 33.1 [s, C6H13, C(CH3)3],
26.1 [s, C(CH3)3],
90.6, 104.8 (s, C=C), 109.6, 146.2 (s, CH=CH).
HRMS (EI): m/z [M]+ calcd
for C16H30Si: 250.2117; found: 250.2116.
Product
(Z)-5j: ¹H
NMR (400 MHz, CDCl3): δ = 0.13 (s,
6
H, SiMe2), 0.80-2.40 (m, 13 H, C6H13),
0.96 (s, 9 H, t-Bu), 5.48 (d, J = 10.8 Hz,
1 H, CH=CH), 5.96 (dt, J = 10.8,
7.4 Hz, 1 H, CH=CH). ¹³C{¹H} NMR
(100 MHz, CDCl3): δ =
-4.6
(s, SiMe2), 14.1, 16.6, 22.6, 28.7, 28.9, 30.3, 31.6 [s, C6H13, C(CH3)3],
26.1 [s, C(CH3)3],
96.6, 102.8 (s, C=C), 109.2, 145.6 (s, CH=CH).
HRMS (EI): m/z [M]+ calcd
for C16H30Si: 250.2117; found: 250.2108.
Formation ratio of (E)-5a/(E)-3a = 77:23 (determined by ¹H NMR).
15Result of cross-dimerization between 2c and 2a catalyzed by 1-Et2PhP system: yield 88%, E/Z = 9:91.