Synthetic studies of cis-3a-aryloctahydroindole derivatives by copper- catalyzed cyclization of N-allyltrichloroacetamides: Facile construction of benzylic quaternary carbons by carbon-carbon bond-forming reactions

Sho Ichi Iwamatsu, Kouki Matsubara, Hideo Nagashima

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66 Citations (Scopus)

Abstract

Cyclization of N-(2-aryl-2-cyclohexen-1-yl)trichloroacetamides by a copper catalyst was investigated. It is crucially important for successful cyclization under mild conditions that alkoxycarbonyl groups are introduced to the nitrogen atom of the N-allyltrichloroacetamides as well as that CuCl- (bipyridine) is used as the catalyst. Three compounds, N-(2-phenyl-2- cyclohexen-1-yl)-, N-[2-(3,4-dimethoxyphenyl)-2-cyclohexen-l-yl]-, and N-[2- (3,4-methylenedioxyphenyl)-2-cyclohexen-1-yl]trichloroacetamides, where the Cbz or MeO2C- group was attached to the nitrogen atom, were instantly converted to the corresponding trichlorinated cis-3a-aryloctahydroindol-2- ones in high yields at room temperature. The reactions offer a facile access to alkaloid skeletons such as mesembrines and crinines; as the simplest examples, total synthesis of (±)-mesembrane and (±)-crinane was accomplished. The effect of alkoxycarbonyl substituents in the amide group was compared with that of the methyl substituent. N-Methyl-N-(2-phenyl-2- cyclohexen-1-yl)trichloro-acetamide quickly reacted in the presence of CuCl(bipyridine) catalyst; however, the products were a mixture of complicated materials including a small amount of the desired lactam. The role of the alkoxycarbonyl group was discussed in terms of rate of rotation of the N-C bond in the N-allyltrichloroacetamides; variable-temperature NMR studies and X-ray structure determination of related compounds were carried out as supporting evidence.

Original languageEnglish
Pages (from-to)9625-9631
Number of pages7
JournalJournal of Organic Chemistry
Volume64
Issue number26
DOIs
Publication statusPublished - Dec 24 1999

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

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