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Paper | Regular issue | Vol 48, No. 5, 1998, pp.981-992
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8147
A New Regioselective Synthesis of Isopavine and Pavine Alkaloids via Double Cyclization of N-(1,2-Diarylethyl)-N-(2-phenylsulfinylethyl)formamide

Tatsumi Shinohara, Akira Takeda, Jun Toda, and Takehiro Sano*

*Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

Pummerer reaction of N-[1,2-(3,4-dimethoxyphenyl)ethyl]-N-(2-phenylsulfinylethyl)formamide (9) using trifluoroacetic anhydride and boron trifluoride etherate caused double cyclization to give N-formylisopavine (21). Acid catalyzed cyclization of the 1,2-dihydroisoquinoline (23) prepared from 4-phenylthio-1,2,3,4-tetrahydroisoquinoline (11) gave N-formylpavine (26). LiAlH4 reduction of the N-formates (21 and 26) gave (±)-O-methylthalisopavine (4) and (±)-argemonine (5), respectively.