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

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

Organic letters (2013-04-12)

Thokchom Prasanta Singh, Suman Bhattarcharya, Okram Mukherjee Singh

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.

MATERIALS

Product Number

Brand

Product Description

Sigma-Aldrich

Tryptamine hydrochloride, 99%

Sigma-Aldrich

Indium, powder, 99.99% trace metals basis

Sigma-Aldrich

Indium, foil, thickness 0.25 mm, 99.995% trace metals basis

Sigma-Aldrich

Indium, wire, diam. 1.0 mm, 99.99% trace metals basis

Sigma-Aldrich

Indium, wire, diam. 0.45-0.55 mm, 99.995% trace metals basis

Sigma-Aldrich

Indium, bars, 99.95%

Sigma-Aldrich

Indium, foil, thickness 0.127 mm, 99.99% trace metals basis

Sigma-Aldrich

Indium, foil, thickness 1.0 mm, 99.999% trace metals basis

Sigma-Aldrich

Indium, foil, thickness 0.5 mm, 99.99% trace metals basis

Sigma-Aldrich

Indium, foil, thickness 0.25 mm, 99.99% trace metals basis

Sigma-Aldrich

Indium, foil, thickness 0.1 mm, ≥99.995% trace metals basis

Sigma-Aldrich

Indium, wire, diam. 2.0 mm, 99.995% trace metals basis

Sigma-Aldrich

Trifluoroacetic acid, ReagentPlus^®, 99%

Sigma-Aldrich

Trifluoroacetic acid, suitable for HPLC, ≥99.0%

Sigma-Aldrich

Trifluoroacetic acid, puriss. p.a., suitable for HPLC, ≥99.0% (GC)

Sigma-Aldrich

Trifluoroacetic acid, ≥99%, for protein sequencing

Sigma-Aldrich

Indium, beads, diam. 2-5 mm, ≥99.9% trace metals basis

Sigma-Aldrich

Indium, powder, −100 mesh, 99.99% trace metals basis

Sigma-Aldrich

Indium, beads, diam. 2-5 mm, 99.999% trace metals basis

Sigma-Aldrich

Indium, rod, diam. 6 mm, ≥99.999% trace metals basis

Supelco

Trifluoroacetic acid, analytical standard

Sigma-Aldrich

Tryptamine, ≥97%

Sigma-Aldrich

Indium, wire, diam. 1.0 mm, 99.995% trace metals basis