4-Alkenyl-5H-1,2,3-oxathiazole 2,2-dioxides in catalytic and enantioselective [4 + 2] cycloaddition through iminium activation. Straightforward access to the trans-decaline framework and to densely functionalized cyclohexanes

Abstract

We have employed 4-alkenyl-5H-1,2,3-oxathiazole 2,2-dioxides as useful reagents able to generate in situ an electron-rich diene intermediate that has the potential to undergo [4 + 2] cycloaddition with α,β-unsaturated aldehydes through the iminium/enamine activation. Under the optimized reaction conditions that comprise the use of O-TMS diphenylprolinol as an organocatalyst and a Brønsted base as a cocatalyst, a series of [4 + 2] cycloadducts has been prepared as single diastereoisomers with very high enantiomeric excess. Moreover, the cyclic sulfamidate entity can play the role of a masked β-aminoalcohol moiety in which these adducts can be converted by simple diastereoselective reduction/hydrolysis.