Abstract
1,4-Addition of organocopper reagents to CpMo(CO) 2 (η 3 -1-trans-COCH=CHR-allyl) (R = Ph (1), 2-furyl (2), methyl (3)) proceeded in reasonable diastereoselectivities that can be improved to excellent levels in the presence of BF 3 ·Et 2 O at one equimolar proportion. The stereochemistry of the major diastereomeric products was elucidated from X-ray structural analysis, which indicated that the minor species of 1-3 in solution, the s-trans-enone conformer, is the active species. The cis-enolates of these major products were selectively generated by LiN(SiMe 3 ) 2 which condensed with aldehydes in excellent diastereoselectivities, and X-ray structures of representative products were determined. Further utilization of these aldol products for stereoselective synthesis of 2,3,4,5-tetrahydrofurans is demonstrated. © 1994 American Chemical Society.