Abstract
Organic lithium reagents add to the carbonyl group of CpW(CO) 2 (n 3 -γ-lactonyl) 4a to give the π-allyl n 3 -hydroxycarbonyl tungsten complexes 5a-5d with good yields (79-94%). An X-ray study of compound 5a revealed the acetyl group has π-delocalization with a tungsten-π-allyl group. A subsequent reaction of 5a with DIBAL-H, RMgBr (R = Ph, Et), and n BuLi gave the diols CpW(CO) 2 [(3R*,4S*)-π-2-CMe(OH)R-CH 2 CCHCMe(OH)] (R = H 6a, Ph 6b, Et 6c, n Bu 6d) as a single diastereomer; the yields were 64%-86%. The acyl group of CpW(CO) 2 [(3R*,4S*)-π-2-COMe-CH 2 CCHCMe(OTBS)] (7) was deprotonated by LDA at -78°C to form an enolate that condensed with RCHO (R = i Pr, i Bu) to form a pair of aldol products 8a,8b and 9a,9b, which were separated by column chromatography. In the presence of n Bu 2 BOTf, the diastereoselectivities of 8b and 9b were improved significantly. The structures of these aldol products were elucidated by X-ray diffraction study of the representative product 8b. © 2000 American Chemical Society.