Use of the electrophilic c-arylation by aryllead triacetates in the construction of synthons for aizoaceae and amaryllidaceae alkaloid synthesis

The vinylogous β-keto esters, ethyl 2-methyl-4-oxocyclohex-2-ene-carboxylate (Hagemann's Ester) (4), ethyl 4-oxocyclohex-1-ene-carboxylate (7a) and its double bond isomer (7b), undergo regiospecific arylation with aryllead triacetates at C1; reaction of the mixture of isomers (7a) and (7b) with aryllead compounds (5a), (5c) and (5d) provides intermediates for the synthesis of (±)-o-methyl-joubertiamine (1), (±)-mesembrine (2) and (±)?lycoramine (3) respectively.