Iodine-mediated one-step synthesis of ipomone from gibberellic acid

Abstract

A fast and efficient method for synthesising ipomone (4), a bicyclo[3.2.1]octanone containing aromatised derivative, from gibberellic acid (1) has been developed using molecular iodine as a mild and effective mediator under heating conditions in a single step. Evidence was obtained that the reaction simultaneously proceeds through aromatisation and pinacol-pinacolone type 1,2-alkyl shift. Use of excess iodine afforded iodomethyl derivative (5) that could serve as starting material for the synthesis of additional analogs.