Stable Vicinal Bisketene Equivalents for Aryne Diels-Alder Reactions.

Abstract

2,5-Bis(tert-butyldimethylsilyloxy)thiophenes are introduced as bench-stable Diels-Alder dienes for reaction with arynes as dienophiles. Ring-opening of the cycloadducts can be achieved via TBAF-promoted desilylation, providing convergent redox-neutral access to a library of substituted naphthoquinones. Strategically, this two-step sequence represents the application of stable vicinal bisketene equivalents as Diels-Alder dienes. Extension to anthraquinone is also demonstrated, in this case via mild autoxidation of a readily accessible cyclohexenyl-fused derivative.