Organic Letters 2013-04-19

Indium/TFA-catalyzed synthesis of tetracyclic [6,5,5,6] indole ring, via a tandem cycloannulation of β-oxodithioester with tryptamine.

Thokchom Prasanta Singh, Suman Bhattarcharya, Okram Mukherjee Singh

Index: Org. Lett. 15(8) , 1974-7, (2013)

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Abstract

The cycloannulation of β-oxodithioesters and tryptamine in dichloromethane in the presence of a catalytic amount of InCl3 and TFA gave the novel 5-aryl/heteroaryl 2a(1),9b-dihydro-1H-2a,5a-diaza-cyclopenta[jk]fluorene-3(2H)-thiones in moderate to good yields. The reaction was proposed to involve a tandem transformation of thioamide, protonation, and dehydrative cyclization. KMnO4-oxidation of these newly prepared compounds yielded oxidative desulfurization products in good yields.