De Novo Synthesis of Tricyclic 5,5-Benzannulated Spiroketals

Abstract

The synthesis of tricyclic 5,5-benzannulated spiroketal scaffolds was accomplished from 2′-hydroxyacetophenones and gem-dibromoalkenes involving a one-pot domino strategy. The hitherto unknown transformation afforded the tricyclic 5,5-benzannulated spiroketals as single diastereomers in high yields with a broad substrate scope.

Rearrangement-Driven Molecular Diversity: Synthesis of Functionalized Pyrones, Orthoesters, and Xanthones from Spiroketals

“…This approach enriches the synthesis of various natural products and building blocks in synthetic organic chemistry . Among the various rearrangement reactions, the semipinacol/α-ketol rearrangements are used to access various privileged molecular skeletons and to synthesize different natural products. , We recently reported a one-pot method for the synthesis of tricyclic 5,5-benzannulated spiroketals 1 from gem -dibromoalkenes and 2′-hydroxyacetophenones under base-mediated conditions . The tricyclic 5,5-benzannulated spiroketal 1 embedded with three contiguous quaternary centers, enol ether, spiroketal and tertiary alcohol functionalities is supposed to be reactive toward acidic conditions.…”

“…2d,4 We recently reported a one-pot method for the synthesis of tricyclic 5,5benzannulated spiroketals 1 from gem-dibromoalkenes and 2′-hydroxyacetophenones under base-mediated conditions. 5 The tricyclic 5,5-benzannulated spiroketal 1 embedded with three contiguous quaternary centers, enol ether, spiroketal and tertiary alcohol functionalities is supposed to be reactive toward acidic conditions. So, it was of interest to understand the reactivity of spiroketals 1 under acidic conditions.…”