Trifluoroacetic acid → rac-cis-1,3,3a,4,5,9b-hexahydro-6-methoxy-2H-benzo[e]indol-2-one

Participants

Reaction Steps

A suspension of 150 g (0.7 mol) of 1,3,4,5-tetrahydro-6-methoxy-2H-benzo[e]indol-2-one in 1.5 l of methylene chloride was treated with 333 ml (2.1 mol) of triethylsilane and then slowly dropwise at 0° and while stirring with 240 ml of trifluoroacetic acid. After stirring for three hours 400 ml of 20% sodium hydroxide solution were added slowly while cooling until a pH of 14 had been reached. Subsequently, the mixture was poured into water and extracted with methylene chloride. The organic phase was washed with sodium chloride solution, dried with sodium sulphate, filtered and evaporated. The residue was treated with 500 ml of ether, whereupon the solid was filtered off and dried at 50°/20 Torr. There were obtained 123 g (81%) of rac-cis-1,3,3a, 4,5,9b-hexahydro-6-methoxy-2H-benzo[e]indol-2-one with m.p. 192°-194°. The material showed a Rf value of 0.14 in a thin-layer chromatogram (silica gel, ethyl acetate).

Provenance & Evidence