Thermal Ring Annulation of α-Vinylcinnamate Methyl Esters. A Method for the Generation of 3,4-Dihydro-2-naphthoate and 2-Naphthoate Methyl Esters

Article abstract of DOI:10.1021/jo00255a010

Ring annulation of methyl-2-benzylidene-3-buten-1-oates (methyl α-vinylcinnamates) to generate a series of methyl 3,4-dihydro-2-naphthoates has been accomplished by a thermal reaction.The thermolysis is performed either in the vapor phase at 425 deg C or by heating the compound in a high-boiling solvent for an extended period of time.Regiochemistry is entirely predictible with para- and ortho-substituted methyl α-vinylcinnamates generating exclusively 6-substituted and 8-substituted 3,4-dihydro-2-naphthoates,respectively.Meta-substituted α-vinylcinnamates generate a mixture of 5-and 7-substituted 3,4-dihydro-2-naphthoates. 2-Naphthoate methyl esters can also be obtained by including a palladium on carbon catalyst in the liquid-phase version of this thermolysis.