6533b82efe1ef96bd129301d

RESEARCH PRODUCT

Stereoselectivity in the Addition of Organotitanium Reagents to Carbonyl Compounds

subject

description

Although great strides have been made in the area of stereoselective C—C bond forming reactions [1], many problems persist. Early studies concerning chemo- selective reactions of organotitanium reagents (Chapter 3) suggested that they might also behave stereoselectively in relevant cases. In fact, the first such observation goes back to 1979 when it was noted that dichlorodi- methyltitanium (2) adds to the ketone 1 in CH2C12 to produce a mixture of tertiary alcohols 4/5 instead of the desired (±) cuparene (3) [2, 3]. The striking aspect of this transformation is the high disastereoselectivity in favor of 4. Methyllithium shows the opposite stereoselectivity (4:5 = 34:66), in line with the simple assumption that attack occurs at the sterically less hindered side (aryl groups are usually considered to be bulkier than methyl groups) [4].