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Transformation of 5,8-dimethyl-1-tetralone: Synthesis of ar-occidol

Abstract:

Reduction of 5,8-dimethyl-1-tetralone 1 with sodium borohydride in methanol followed by methylation of the resulting alcohol with methyl iodide and sodium hydride yielded a methyl ether. This was oxidised with potassium permanganate and acetonitrile to give 4-methoxy-5,8-dimethyle-1-tetralone. Methoxycarbonylation of the ketone with dimethylcarbonate (DMC) in the presence of sodium hydride in dimethoxyethane (DME) afforded β-ketoester 5 which on heating with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dioxane underwent aromatisation and elimination to furnish a naphthalene. The mesyl derivative the phenol on hydrogenation produced methyl 5,8-dimethyl-2- naphthoate. The transformation of naphthoate into ar-occidol was accomplished by a Grignard reaction with methyllithium in ether.