Aluminum-Catalyzed Enantio- and Diastereoselective Carbonyl Addition of Propargylsilanes. A New Approach to Enantioenriched Vinyl Epoxides
摘要:
A new pathway involving a Lewis acid-catalyzed carbonyl addition reaction of propargylsilanes and its subsequent development into a general enantio- and diastereoselective process are described. Aliphatic propargylsilanes with both saturated and unsaturated sidechains were effective nucleophiles affording highly functionalized chiral vinyl epoxides in good enantioselectivities (85-94% ee), excellent diastereoselectivities (> 99:1 E:Z; > 99:1 anti:syn) and in moderate to good yields (49-97%).
[reaction: see text] The catalytic, enantioselective [3 + 2] cycloaddition reaction of 1-alkyl-substituted allenylsilanes with alpha-imino ester has been achieved by means of [Cu(MeCN)(4)]BF(4)/(R)-DM-SEGPHOS catalyst to afford silyl-substituted dehydroproline derivatives in high yields and enantioselectivities.