Organocatalytic Enantioselective Approach to Spirocyclic Δβ,γ-Butenolides
摘要:
A novel method for the preparation of the spirocyclic (,)-butenolides is presented. The developed strategy is based on a trienamine-mediated [4+2]-cycloaddition between (E)-3-alkylidene-5-arylfuran-2(3H)-ones and 2,4-dienals. Target products containing three contiguous centres including one quaternary are efficiently formed in a highly enantiomerically enriched form in the presence of the silyl-protected diphenylprolinol aminocatalyst.
An asymmetric [3+2] cycloaddition reaction ofN-2,2,2-trifluoroethylisatin ketimines and 3-alkenyl-5-arylfuran-2(3H)-ones was developed with 1 mol% thiourea–tertiary amine.