Abstract

The reaction of {[4-(3,4-dimethoxyphenyl)tetrahydro-2H-pyran-4-yl]methyl}amine with diethyl oxalate was used to synthesize ethyl 2-({[4-(3,4-dimethoxyphenyl)tetrahydro-2H-pyran-4-yl]methyl}amino)-2-oxoacetate, whose cyclization with phosphorus oxychloroxide under Bischler–Napieralski reaction conditions gave 1-carbethoxy-substituted dihydroisoquinoline. By treatment with methylamine the latter was converted to the corresponding N-methylcarboxamide derivative, which was reduced to obtain N-methyl-6,7-dimethoxy-2,2',3,3',5',6'-hexahydro-1H-spiro[isquinoline-4,4'-pyran]-1-carboxamide. A series of novel derivatives of 4-spirotetrahydropyran-substituted dihydro- and tetrahydroisoquinolines with various different substituents in the first and second positions of the heterocyclic ring were prepared.