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Evidence for atropisomerism in polycyclic γ-butenolides. Synthesis, scope and spectroscopic studies.

Design and development of a dominocyclizative approach for the synthesis of unexampled polycyclic g-butenolides from b-aryl-Z-enoate propargylic alcohols, through the interception of an intermediate of the z-enoate assisted Meyer-Schuster rearrangement has been reported. A systematic NMR analysis of various derivatives of this class revealed and supported the potential atropisomerism associated with them. These molecules represent first examples of butenolide ring based atropisomeric compounds in organic chemistry. The synthetic process involves a synchronous construction of both the rings with the concurrent creation of the potential stereogenic rotational axis.