Highly Enantioselective Organocatalytic Formation of Functionalized Cyclopentane Derivatives via Tandem Conjugate Addition/alpha-Alkylation of Enals
2012
Abstrakt
An enantioselective tandem reaction between dialkyl 2-haloethylmalonates and aromatic enals catalyzed by secondary amine catalysts is described. The reaction proceeds through a Michael/alpha-alkylation reaction sequence to afford the final 1,1,2,3-tetrasubstituted cyclopentanes in good yields (up to 75%) with high diastereoselectivity and enantioselectivity (up to 20:1dr and 93%ee).
Moreover, the Michael/alpha-alkylation reaction also proceeds with a low catalyst loading (5 mol-%) with only a slight influence on selectivity and Oand N-alkylation products were not observed.