Page 717 - Advanced Organic Chemistry Part B - Reactions & Synthesis

Scheme 8.4. (Continued) 693

SECTION 8.1
a. S. Nunomoto, Y. Kawakami, and Y. Yamashita, J. Org. Chem., 48, 1912 (1983).
b. C. C. Tseng, S. D. Paisley, and H. L. Goering, J. Org. Chem., 51, 2884 (1986). Organocopper
c. E. J. Corey and A. V. Gavai, Tetrahedron Lett., 29, 3201 (1988). Intermediates
d. U. F. Heiser and B. Dobner, J. Chem. Soc, Perkin Trans. 1, 809 (1997).
e. Y.-T. Ku, R. R. Patel, and D. P. Sawick, Tetrahedron Lett., 37, 1949 (1996).
f. E. Keinan, S. C. Sinha, A. Sinha-Bagchi, Z.-M. Wang, X.-L. Zhang, and K. B. Sharpless, Tetrahedron Lett., 33,
6411 (1992).
g. D. Tanner, M. Sellen, and J. Backvall, J. Org. Chem., 54, 3374 (1989).
h. G. Huynh, F. Derguini-Boumechal, and G. Linstrumelle, Tetrahedron Lett., 1503 (1979).
i. E. L. Eliel, R. O. Hutchins, and M. Knoeber, Org. Synth., 50, 38 (1971).
j. S.-H. Liu, J. Org. Chem., 42, 3209 (1977).
k. T. Kindt-Larsen, V. Bitsch, I. G. K. Andersen, A. Jart, and J. Munch-Petersen, Acta Chem. Scand., 17, 1426 (1963).
l. V. K. Andersen and J. Munch-Petersen, Acta Chem. Scand., 16, 947 (1962).
m. Y. Horiguchi, E. Nakamura, and I. Kuwajima, J. Am. Chem. Soc., 111, 6257 (1989).
n. T. Fujisawa and T. Sato, Org. Synth., 66, 116 (1988).
o. F. J. Weiberth and S. S. Hall, J. Org. Chem., 52, 3901 (1987).

catalyst
2 9
2
3
CH 3 (CH ) MgBr + CH CHCH CH 3 CH (CH ) CHCH CH 3
2 9
2
3
O SCH 3 CH 3
3
Catalyst Yield
Li CuCl 4 17%
2
CuBr/HMPA 30%
) , LiBr, LiSPH 62%
CuBr–S(CH 3 2
These reactions presumably involve fast metal-metal exchange (see Section 7.1.2.4)
generating a more nucleophilic organocopper intermediate. The reductive elimination
regenerates an active Cu(I) species.
–
RMgBr + Cu(I) [RCuBr] + Mg 2+
R′
–
[RCuBr] + R′X R Cu III X
R′ Br
–
R Cu III X R R′ + Cu(I) + X + Br –
Br

Other examples of catalytic substitutions can be found in Section A of Scheme 8.4.
Conjugate addition to -unsaturated esters can often be effected by copper-
catalyzed reaction with a Grignard reagent. Other reactions, such as epoxide ring
opening, can also be carried out under catalytic conditions. Some examples of catalyzed
additions and alkylations are given in Scheme 8.4. These reactions are similar to
those carried out with the stoichiometric reagents and presumably involve catalytic
cycles that regenerate the active organocopper species. A remarkable aspect of these
reactions is that the organocopper cycle must be fast compared to normal organomag-
nesium reactions, since in many cases there is a potential for competing reactions.
The alkylations include several substitutions on allylic systems (Entries 2, 3, and 7).
Entry 8 shows that the catalytic process is also applicable to epoxide ring opening.
The latter example is a case in which an allylic chloride is displaced in preference to
an acetate. The conditions have been observed in related systems to be highly regio-
S 2 and stereo- (anti) specific. 65 The conjugate additions in Entries 9 to 12 show

N
65
J.-E. Backvall, Bull. Soc. Chim. Fr., 665 (1987).