Unusually reactive and selective carbonyl ylides for three-component cycloaddition reactions

Abstract

Conditions are described for the Rh-catalyzed formation of highly functionalized dihydro- and tetrahydrofuran products via three-component reactions of aldehydes, α-alkyl-α-diazoesters, and dipolaro- philes. The alkyl-substituted carbonyl ylides that are generated in this fashion are highly reactive in cycloaddition reactions and display a scope of reactivity that is much broader than the three-component reactions of carbonyl ylides derived from ethyl diazoacetate or α-aryl-α-diazoesters. The reactions of alkyl- substituted carbonyl ylides proceed with high regioselectivity and diastereoselectivity that are rationalized in terms of an asynchronous, endo-selective transition state. © 2009 American Chemical Society.