Cs⁺/Alcohol Promoted[4C+2C]Annulation: ASynthetic Strategy for Polysubstituted Phenols

Abstract

A cesium ion/alcohol promoted [4C + 2C]annulation with the easily available diacetyl ketene dithioacetals as 4 C components to give poly-substituted phenols is reported. It is revealed for the first time that in the presence of cesium ion and alcohol under mild alkaline conditions, the acetyl methyl carbon of ketene dithioacetals can be utilized as a carbon nucleophile. This nucleophile can attack at a carbonyl carbon of a ketone to form a CÀ C bond to initiate a [4C + 2C] annulations, which lead to a poly-substituted phenol product via intramolecular cyclization followed by aromatization. This reaction provides a new and practical route to the construction of poly-substituted phenols between the same (two diacetyl ketene dithioacetals) or different ketones (a diacetyl ketene dithioacetal and a ketone) under very mild reaction conditions.