Asymmetric Vinylogous Michael Addition of Furanones to Nitroolefines

Significance

Terada and Ando report the direct asymmetric vinylogous Michael addition of 3-(tert-butylthio)furan-2(5H)-one (1) to nitroolefins 2, catalyzed by the chiral guanidine base 3 (5 mol%). The corresponding γ-butenolide products were obtained in good yields and good enantio- and ­diastereoselectivities for a variety of different nitro­olefins. The tert-butyl substituent at the sulfur atom of 1 was found to be crucial for the observed selectivities. Some possible derivatizations of the Michael adducts are also presented.