title: Asymmetric synthesis of highly functionalized tetrahydropyrans via a one-pot organocatalytic Michael/Henry/ketalization sequence.
abstract: A diastereo- and enantioselective Michael/Henry/ketalization sequence to functionalized tetrahydropyrans is described. The multicomponent cascade reaction uses acetylacetone or β-keto esters, β-nitrostyrenes, and alkynyl aldehydes as substrates affording tetrahydropyrans with five contiguous stereocenters. Employing a bifunctional quinine-based squaramide organocatalyst, the title compounds are obtained in moderate to good yields (27-80%), excellent enantiomeric excesses (93-99% ee), and high diastereomeric ratios (dr > 20:1) after one crystallization.
authors: Institute of Organic Chemistry, RWTH Aachen University , Landoltweg 1, 52074 Aachen, Germany.
authors: Robert
authors: R
authors: Hahn
authors: Gerhard
authors: G
authors: Raabe
authors: Dieter
authors: D
authors: Enders