Studies on the Synthesis of Isocarbostyril Derivatives. (1). A Novel Synthesis of Isocarbostyril Derivatives and Synthesis of Protoberberine and Dibenzoquinolizine Derivatives

Abstract

Reduction of homophthalimide derivatives (IIa, IIb, and IIc) with NaBH₄ gave 3, 4-dihydroisocarbostyril derivatives (IIIa, IIIb, and IIIc) which were converted to isocarbostyril derivatives (VIa, VIb, and VIc) by hydrochloric acid in ethanol. VIc was converted into 8-oxoprotoberberine derivative (VII). Hydrogenation of VIc with 10% Pd-C gave the amide (VIII). Bischler-Napieralski reaction of VIII followed by reduction with NaBH₄ gave the dibenzoquinolizine derivative (IX).