Dehydration studies of α- and β-ionol. I. With hexamethylphosphoric triamide

Abstract

α-Ionol (2) when heated under reflux with hexamethylphosphoric triamide gave principally one product (1'E)-6-(buta-1',3'-dienyl)-1,5,5-trimethylcyclohex-1-ene (4a) together with trace quantities of the (1'Z)-isomer (4b). Under similar conditions β-ionol (3) gave as major products (6E,2'E)- and (6Z,2'E)-6-(but-2'-enylidene)-1,5,5-trimethylcyclohex-1-ene (1a) and (1b) together with smaller quantities of (1'E)-1-(buta-1',3'-dienyl)-6,6-dimethyl-2-methylenecyclohexane (8) and 1,1,6-trimethyl- 1,2,3,4,5,6-hexahydronaphthalene (9). Minor products from this reaction included the isomeric trienes (1c) and (1d). Reaction pathways are suggested for the formation of all identified products.