Development of a Carbonyl Cyclopentannulation Reagent Based on a 1,4-Dithiane-Fused Nazarov Reaction.

Cyclopentanes are common substructures in biologically relevant molecules, but methods for their de novo synthesis from simple building blocks are limited. In this work, we report the development of a novel reagent that allows the direct transformation of ketones and aldehydes into an interesting cyclopentenone moiety. The reagent design hinges on a β-keto phosphonate incorporating a 1,4-dithiane-fused vinylketone. This sulfur heterocycle facilitates a one-pot Horner-Wadsworth-Emmons olefination followed by a Nazarov reaction of the resulting divinylketone.