Highly enantioselective catalytic Michael reaction of α-substituted malonates using La-linked-BINOL complex in the presence of HFIP (1,1,1,3,3,3-hexafluoroisopropanol)

Abstract

A catalytic asymmetric Michael reaction of α-substituted malonates with broad generality was developed using the La-linked-BINOL complex. To enhance the reactivity of unreactive α-substituted malonates, we examined the effects of concentration and additives; 1.0 M was the best concentration and HFIP (1,1,1,3,3,3-hexafluoroisopropanol) accelerated the reaction efficiently. Under the optimized conditions, the catalytic asymmetric Michael reaction of a variety of α-substituted malonates proceeded successfully in high yield (up to 93%) and excellent enantiomeric excess (up to 99% ee). The addition of HFIP was also effective for the reaction of nonsubstituted malonates. In this case, 5 mol% of the La-linked-BINOL complex was sufficient for completion of the reaction in approximately 24 h. Moreover, several Michael adducts were readily converted to the bicyclic compounds.