The chemistry of santonene. Part VII. The action of phosphorus trihalides on the santonins, santonene, and related compounds

Abstract

Treatment of santonin with acetyl chloride–acetic anhydride–hydrogen chloride gives 3-acetoxyeudesma-3,5,7(11)-trien-6,13-olide and also cis- and/or trans-desmotroposantonin acetates, the corresponding compounds with AcO replaced by Cl. The same chloro-compounds can be obtained in greater yield by using phosphorus trichloride in acetic acid. The action of both phosphorus trichloride and the tribromide in acetic acid on β-santonin, pyrosantonin, santonene, β-santonenic acid, 8-oxosantonin and other derivatives of santonin is reported: either the eudesma-3,5,7-trien-6,13-olide or the eudesma-3,5-dien-6,13-olide chromophoric group with 1α- or 1β-halogen substituents is formed. In no other case apart from that of the two santonins is halogen found in the 3-position.