The reactivity of 3-Ethenyl-4-methylcyclohex-2-en-1-one and related compounds towards some carbanionic nucleophiles

Abstract

The reaction of 3-ethenyl-4-methylcyclohex-2-en-1-one (4) with 2-methylcyclopentane-1,3-dione in refluxing toluene containing pyridine gave 6% of 9bξ-hydroxy-3a,6-dimethyl-3a,4,5,6,7,9b-hexahydro-1H-benz[e]indene-3,9(2H,8H)-dione (10). When the same reactants were heated at 100-110º (sealed tube) in benzene containing t-butyl alcohol and diethylamine the main product (61%) was 5',6-dimethylspiro[bicyclo[3.2.1]octane-1,2'-cyclohexane]-3,6',8'-trione (11); the yield of (11) was 72% when the reaction was carried out in the presence of silica gel. Attempts to effect a similar reaction of the dienone (4) with methyl 1β-t-butoxy-7aβ-methyl-5-oxo-1,2,3,3aα,4β,6,7,7a-octahydro-indene-4-carboxylate (21a) gave no conjugate Michael addition product, but (21a) underwent aminolysis to the corresponding diethylamide (21b). Attempts to alkylate the t-butoxy β-keto ester (21a) under various conditions with 7-acetyloxy-7-ethenyl-8 ξ methyl-1,4-dioxaspiro[4,5]decane (41) failed. Similarly, attempts to effect alkylation of the anion of the t-butoxy keto ester (21a) with 7-ethenyl-8-methyl-1,4-dioxaspiro[4,5]dec-6-ene (43) under Lewis acid catalysis were also unsuccessful.