Studies on the syntheses of heterocyclic compounds. Part DXCVII. Novel formation of benzo[5,6]cyclohept[1,2,3-ij]isoquinolines from berbinium salts

Abstract

Heating coreximine methiodide (5) with methanolic potassium hydroxide solution gave the secoberbine (13) and 1,2,3,7,12,12a-hexahydro-6,10-dihydroxy-5,9-dimethoxybenzo[5,6]cyclohept[1,2,3-ij]isoquinoline (14). The latter was converted into its OO-dimethyl ether (16), which was also synthesised from laudanosine (18) with formalin in the presence of hydrochloric acid. Treatment of the monophenolic secoberbine (12) with acid gave the corresponding benzocycloheptisoquinoline.