5588
S. Tominaga et al. / Tetrahedron Letters 45 (2004) 5585–5588
17.8 (one carbon could not be detected); IR (neat) 3166,
References and notes
1695, 1599, 1557, 1479, 1443, 1404, 1335, 1290, 1230, 1161,
1110, 1038, 948, 786, 735, 693, 609 cmÀ1. Elemental
analysis, calcd for C19H2N2OClCu: C, 60.79; H, 5.37; N,
7.46. Found: C, 60.95; H, 5.54; N, 7.47.
1. Lipshutz, B. H.; Senguota, S. Org. React. 1992, 41, 135.
2. For organocopper chemistry, see: Organocopper Reagents;
Taylor, R. J. K., Ed.; Oxford University Press: Oxford,
1994; Lipshutz, B. H. In Organometallics in Synthesis;
Schlosser, M., Ed.; Wiley: Chichester, 2002; p 665; Modern
Organocopper Chemistry; Krause, N., Ed.; Wiley-VHC:
Weinheim, 2001.
3. Chiral copper complex-catalyzed enantioselective allylic
substitution reactions: with Grignard reagents: van Klav-
eren, M.; Persson, E. S. M.; del Villar, A.; Grove, D. M.;
7. To a suspension of CuCl–NHC complex 4 (0.02 mmol) in
ether (1 mL) was added Grignard reagent (0.7–1.5 M in
ether, 3.0 mmol) at 0 °C and the mixture was stirred for
0.5 h at this temperature. To this was added a solution of
allylic substrate 1 (2.0 mmol) in ether (2 mL) and the
mixture was stirred at 0 °C. After confirming the comple-
tion of the reaction by TLC analysis, saturated aqueous
NH4Cl was added. Usual extractive work-up and passing
through a short silica gel column yielded a mixture of
a- and c-products.
8. TLC analysis of the reaction mixture indicated that for
complete consumption of 1a it needed 2 h for the reaction
with 4a and 30 min for the reaction with 4b.
9. Synthesis and structural study of (NHC)Cu(I) methyl
complex were reported: Mankad, N. P.; Gray, T. G.;
Laitar, D. S.; Sadighi, J. P. Organometallics 2004, 23,
1191.
10. Compounds 4c–f were prepared from the corresponding
imidazolium salts,4c t-BuONa and CuCl in THF. The
resulting mixture was filtered through a pad of Celite and
the filtrate was stored under Ar. The THF-solution
containing 4c–f, respectively, thus obtained was charged
into the reaction vessel and THF was removed under
reduced pressure prior to use.
11. tert-Butyldimethyl(2-hexylbut-3-enyloxy)silane: 1H NMR
(CDCl3, 270 MHz): d 5.62 (ddd, J ¼ 8:4, 9.7, 17.8 Hz, 1H),
4.97–5.07 (m, 2H), 3.52 (dd, J ¼ 6:3, 11.2 Hz, 1H), 3.49
(dd, J ¼ 6:3, 11.2 Hz, 1H), 2.07–2.23 (m, 1H), 1.10–1.60
(m, 10H), 0.89 (s, 9H), 0.88 (t, J ¼ 7:1 Hz, 3H), 0.07 and
0.04(2s, each 3H); 13C NMR (CDCl3, 67.5 MHz): d 140.6,
115.2, 66.7, 31.8, 30.8, 29.4, 27.0, 26.0, 22.7, 18.4, 14.1,
)5.3, )5.4; IR (neat) 3076, 2926, 2854, 1644, 1470, 1383,
1365, 1254, 1101, 1008, 942, 915, 837, 777 cmÀ1. Elemental
analysis, calcd for C16H34OSi: C, 71.04; H, 12.67. Found:
C, 70.64; H, 13.00.
€
Backvall, J.-E.; van Koten, G. Tetrahedron Lett. 1995, 36,
3059; Karlstrom, A. S. E.; Huerta, F. F.; Meuzelaar, G.
€
€
J.; Backvall, J.-E. Synlett 2001, 923; Meuzelaar, G. J.;
Karlstrom, A. S. E.; van Klaveren, M.; Persson, E. S. M.;
€
€
del Villar, S.; van Koten, G.; Backvall, J.-E. Tetrahedron
2000, 56, 2895; Alexakis, A.; Malan, C.; Lea, L.; Benhaim,
C.; Fournioux, X. Synlett 2001, 927; Alexakis, A.; Croset,
K. Org. Lett. 2002, 4, 4147; Croset, K.; Polet, D.;
Alexakis, A. Angew. Chem., Int. Ed. 2004, 43, 2426; With
€
dialkylzinc compounds, Dubner, F.; Knochel, P. Angew.
Chem., Int. Ed. 1999, 38, 379; Dubner, F.; Knochel, P.
€
Tetrahedron Lett. 2000, 41, 9233; Malda, H.; van Zijl, A.
W.; Arnold, L. A.; Feringa, B. L. Org. Lett. 2001, 3, 1169;
Luchaco-Cullis, C. A.; Mizutani, H.; Muphy, K. E.;
Hoveyda, A. H. Angew. Chem., Int. Ed. 2001, 40, 1456.
4. Asymmetric conjugate addition reactions catalyzed by
copper imidazolium carbene complexes: (a) Guillen, F.;
Winn, C. L.; Alexakis, A. Tetrahedron: Asymmetry 2001,
12, 2083; (b) Fraser, P. K.; Woodward, S. Tetrahedron
Lett. 2001, 42, 2747; (c) Alexakis, A.; Winn, C. L.; Guillen,
F.; Pytkowicz, J.; Roland, S.; Mangeney, P. Adv. Synth.
Catal. 2003, 345, 345.
5. Other catalyses with copper imidazolium carbene com-
plexes in organic synthesis: (a) Jurkauskas, V.; Sadighi, J.
P.; Buchwald, S. L. Org. Lett. 2003, 5, 2417; (b) Kaur, H.;
Zinn, F. K.; Stevens, E. D.; Nolan, S. P. Organometallics
2004, 23, 1157, and references for recent structural studies
of N-heterocyclic carbene copper complexes cited therein.
6. Compounds 4a5 and 4b were prepared by the reaction of
CuCl, t-BuONa and the corresponding imidazolium
chloride in THF according to the reported procedure.5
The isolated 4a and 4b were used. 4b: Mp 268 °C; 1H
NMR (CDCl3, 500 MHz): d 7.31 (t, J ¼ 7:5 Hz, 2H), 7.21
(d, J ¼ 8:0 Hz, 4H), 7.10 (s, 2H), 2.17 (s, 12H); 13C NMR
(CDCl3, 125 MHz): d 137.4, 134.9, 129.6, 128.8, 122.1,
12. Dale, J. A.; Mosher, H. S. J. Am. Chem. Soc. 1971, 95,
512.
13. Gurjar, M. K.; Bhaket, P. Heterocycles 2000, 53, 143.
14. We found that the reaction of allylic 2-pyridyl ethers with
alkyl Grignard reagents in the presence of a catalytic
amount of CuCN in ether proceeded highly predomi-
nantly in an SN20 fashion (unpublished results).