The highly enantioselective protonation of nitronates formed upon the addition of α-substituted Meldrum's acids to terminally unsubstituted nitroalkenes is described. This work represents the first enantioselective catalytic addition of any type of nucleophile to this class of nitroalkenes. Moreover, for the successful implementation of this method, a new type of N-sulfinyl urea catalyst with chirality residing only at the sulfinyl group was developed, thereby enabling the incorporation of a diverse range of achiral diamine motifs.
View Article and Find Full Text PDFThe highly enantioselective addition of thioacetic acid to nitroalkenes using a new sulfinyl urea organocatalyst is described. The addition of thioacetic acid proceeds in high yields and enantioselectivities for a variety of aromatic and aliphatic nitroalkene substrates. This new method is useful for preparing chiral 1,2-aminothiol derivatives, as demonstrated by the first enantioselective synthesis of the clinically used antifungal drug sulconazole.
View Article and Find Full Text PDFMechanistic evidence suggests that the Lewis acid-promoted allylic rearrangement of alpha-silyloxy allylic silanes proceeds along an ionic reaction pathway involving a contact ion pair. The driving force for this transformation is alleviation of steric congestion at the allylic position of the alpha-silyloxy allylic silane and stabilization of pi cc by hyperconjugation.
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