References and Notes
<A NAME="RU08110ST-1">1</A>
Metal-Catalyzed Cross Coupling
Reactions
2nd ed., Vol. 1 and 2:
de Meijere A.
Diederich F.
Wiley-VCH;
Weinheim:
2004.
For recent examples of carbon-metal
and carbon-hydrogen bond coupling, see:
<A NAME="RU08110ST-2A">2a</A>
Giri R.
Maugel N.
Li J.-J.
Wang D.-H.
Breazzano SP.
Saunders LB.
Yu J.-Q.
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Am. Chem. Soc.
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3510
For reviews, see:
<A NAME="RU08110ST-2B">2b</A>
Li B.-J.
Yang S.-D.
Shi Z.-J.
Synlett
2008,
949
<A NAME="RU08110ST-2C">2c</A>
Chen X.
Engle KM.
Wang D.-H.
Yu J.-Q.
Angew. Chem. Int. Ed.
2009,
48:
5094
For recent examples of carbon-hydrogen
and carbon-halogen bond coupling, see:
<A NAME="RU08110ST-3A">3a</A>
Wang X.
Lane BS.
Sames D.
J.
Am. Chem. Soc.
2005,
127:
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<A NAME="RU08110ST-3B">3b</A>
Oi S.
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Inoue Y.
Org.
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<A NAME="RU08110ST-3C">3c</A>
Kobayashi K.
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<A NAME="RU08110ST-3D">3d</A>
Ackermann L.
Althammer A.
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<A NAME="RU08110ST-3E">3e</A>
Yanagisawa S.
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<A NAME="RU08110ST-3F">3f</A>
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<A NAME="RU08110ST-3G">3g</A>
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For reviews, see:
<A NAME="RU08110ST-3H">3h</A>
Bellina F.
Rossi R.
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<A NAME="RU08110ST-3I">3i</A>
Daugulis O.
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<A NAME="RU08110ST-3K">3k</A>
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For recent examples of carbon-hydrogen
and carbon-hydrogen bond coupling, see:
<A NAME="RU08110ST-4A">4a</A>
Stuart DR.
Fagnou K.
Science
2007,
316:
1172
<A NAME="RU08110ST-4B">4b</A>
Hull KL.
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<A NAME="RU08110ST-4C">4c</A>
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For representative examples, see:
<A NAME="RU08110ST-5A">5a</A>
Sezen B.
Sames D.
J. Am. Chem. Soc.
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<A NAME="RU08110ST-5B">5b</A>
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<A NAME="RU08110ST-5D">5d</A>
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In addition, we have also reported on rhenium-catalyzed
insertion of aldehydes into a C-H bond of aromatic and
olefinic compounds. See also:
<A NAME="RU08110ST-7B">7b</A>
Kuninobu Y.
Nishina Y.
Nakagawa C.
Takai K.
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<A NAME="RU08110ST-7C">7c</A>
Kuninobu Y.
Nishina Y.
Takai K.
Tetrahedron
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<A NAME="RU08110ST-7D">7d</A>
Kuninobu Y.
Fujii Y.
Matsuki T.
Nishina Y.
Takai K.
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2009,
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2711
<A NAME="RU08110ST-8">8</A>
Fujita K.-i.
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<A NAME="RU08110ST-9">9</A>
When (E)-3-methyl-3-penten-2-one
(2) was used as a hydrogen acceptor, 3-methylpentan-2-one
was formed. This result shows that the olefinic moiety of 2 was reduced.
<A NAME="RU08110ST-10">10</A>
Investigation of hydrogen acceptors
in dehydrogenation of alcohol 1a {hydrogen
acceptor: 1.5 equiv; [Cp*IrCl2]2:
0.50 mol%; K2CO3: 5.0 mol%;
toluene, 150 ˚C; 18 h}: (E)-3-methyl-3-penten-2-one >99%;
(1E,4E)-1,5-diphenyl-1,4-pentadien-3-one >99%;
3-methyl-2-cyclohexenone 92%; (E)-4-phenyl-3-buten-2-one
92%; 1-penten-3-one 82%;
p-benzoquinone
78%; 2-cyclohexenone 57%; 2-cyclo-pentenone 52%;
3-ethoxy-2-cyclohexenone 8%.
<A NAME="RU08110ST-11">11</A>
First, we conducted the reactions
between benzyl alcohol (1a), (E)-3-methyl-3-penten-2-one (2), 1-methyl-2-phenyl-1H-imidazole
(3a), and HSiEt3 in the presence
of catalytic amounts of an iridium complex, [Cp*IrCl2]2,
K2CO3, and a manganese complex, MnBr(CO)5,
in toluene. However, the desired reaction did not proceed at all.
Therefore, we carried out the coupling reactions in two steps.
<A NAME="RU08110ST-12">12</A>
3-Methyl-2-pentanone, which is formed
by hydrogenation of (E)-3-methyl-3-penten-2-one
(2), was observed by ¹H NMR
and GCMS.
<A NAME="RU08110ST-13">13</A>
General Procedure
of Formal Cross-Coupling Reaction
A mixture of alcohol
(1, 0.500 mmol), (E)-3-methyl-3-penten-2-one
(2, 73.6 mg 0.750 mmol), [Cp*IrCl2]2 (2.0
mg, 0.0025 mmol), K2CO3 (3.5 mg, 0.025 mmol),
and toluene (1.0 mL) was heated at 150 ˚C for
18 h. Then, imidazole
(3, 0.250
mmol), HSiEt3 (58.1 mg, 0.500 mmol), and MnBr(CO)5 (3.4
mg, 0.013 mmol) were added, and the mixture was stirred at 115 ˚C
for 24 h. The product was isolated by column chromatography on silica
gel [hexane-EtOAc = 5:1.
Before column chromatography, the silica
gel was treated
with Et3N {5% solution in hexane-EtOAc
(5/1)}.] to
give 4.
<A NAME="RU08110ST-14">14</A>
1-Methyl-2-[2-(
p
-tolyltriethylsilanyloxymethyl)phenyl]-1
H
-imidazole
(4c)
¹H NMR
(400 MHz, CDCl3): δ = 0.54 (q, J = 8.0 Hz,
6 H), 0.86 (t, J = 8.0
Hz, 9 H), 2.23 (s, 3 H), 2.69 (s, 3 H), 6.15 (s, 1 H), 6.74 (d, J = 8.8 Hz,
2 H), 6.81 (s, 1 H), 6.93 (d, J = 6.8 Hz,
2 H), 7.11 (d, J = 7.2
Hz, 1 H), 7.18 (s, 1 H), 7.28 (t, J = 7.2
Hz, 1 H), 7.50 (t, J = 7.2
Hz, 1 H), 8.03 (d, J = 7.6 Hz,
1 H). ¹³C NMR (100 MHz, CDCl3): δ = 4.7,
6.7, 32.4, 72.5, 120.2, 125.7, 126.1, 126.8, 127.8, 128.1, 128.3,
129.3, 129.8, 136.2, 141.7, 146.4, 146.6; IR (nujol): ν = 1178
(m), 1117 (m), 1072 (m), 1011 (m), 851 (m) cm-¹.
HRMS (EI+): m/z calcd
for C23H34N2OSi [M+]:
392.2284; found: 392.2291.
