Synthesis and asymmetric diels-alder reactions of (S)-2- p-tolylsulfinyl-1,4-benzoquinone

Abstract

Optically pure (S)-2- p-tolylsulfinyl-1,4-benzoquinone ( 5) is readily obtained by deketalization of the corresponding quinone bisketal 4, synthesized by Andersen's type synthesis on 2-bromo-1,4-dimethoxybenzene ( 1) followed by anodic oxidation of the resulting sulfoxide. The Diels-Alder reaction of cyclopentadiene with 5 took place on C 5-C 6 dienophilic double bond showing high facial selectivity, which can be inverted by using different Lewis acids, and total endo selectivity.