Sequential Acetalization-Pyrolysis of α-Acetylcinnamates and α-Acetylbenzalacetones. A Method for the Generation of 2-Carbonyl-Subsituted Naphthalenes

Article abstract of DOI:10.1021/jo00288a054

Substituted 2-acetonaphthones and 2-naphthoate methyl esters can be generated from benzaldehydes in a sequence of three reaction steps.Knoevenagel condensation of a benzaldehyde with 2,4-pentandione of methyl acetoacetate yields α-carbonyl-substituted benzalacetones.The α-carbonyl-substituted benzalacetones are then cyclized to generate the α-carbonyl-substituted naphthalenes by a sequential acetalization with trimethyl orthoformate followed by subsequent pyrolysis of the dimethyl acetal either in the vapor phase at 475 deg C or by being heated in boiling 1-methylnaphthalene. 2-Acetonaphthones are obtained when 2,4-pentanedione is used and 2-naphthoate methyl esters are obtained from methyl acetoacetate.