The chemistry of santonene. Part X. Products of the action of phosphorus pentachloride on santonin

Abstract

Reaction of santonin (1) with phosphorus(V) chloride affords 3-chloroeudesma-1,3,5,7(11)-tetraen-12,6-olactone (2) and 1α,2β,3-trichloroeudesma-3,5,7(11)-trien-12,6-olactone (4). In (4), the 2β-chlorine is easily replaced by other groups with retention of configuration. Under more forcing conditions, 14-substituted 3-chloroeudesma-1,3,5,7(11)-tetraen-12,6-olactone derivatives (12) are obtained. The trichloro-triene (4) loses hydrogen chloride when treated with strong base to give 1,3-dichloroeudesma-1,3,5,7(11)-tetraen-12,6-olactone (6), and loses chlorine when treated with iodide in dimethylformamide to give (2). Hydrogenation of either (2) or (4) affords 3-chloroeudesma-3,5,7,(11)-trien-12,6-olactone (5).