Abstract
For the purpose of synthesizing the title alkaloids starting from 2-aryl-5,5-ethylenedioxycyclohexanone (5b or 21), alkylation of 2-arylcyclohexanone (5a) in the presence of a phase transfer catalyst was examined. Namely, 5a was treated with alkyl halides in 50% aq.NaOH and benzene in the presence of 18-crown-6 to give regioselectively 2-alkyl-2-arylcyclohexanones (6) in moderate yields. The similar reaction of 5b or 21 with allyl bromide afforded 2-allyl-2-aryl-5,5-ethylenedioxycyclohexanone (9) or (22) in 69.5 or 60% yield. By use of 9 or 22, synthesis of (±)-mesembrine (1) and (±)-dihydromaritidine (17) or (±)-joubertiamine (2) was accomplished.
