New Synthesis of Fischer Indole Hydrazone Intermediates

V. Khedkar; A. Tillack; M. Michalik; M. Beller

doi:10.1055/s-2005-921587

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Synfacts 2005(3): 0287-0287
DOI: 10.1055/s-2005-921587

Synthesis of Heterocycles

New Synthesis of Fischer Indole Hydrazone Intermediates

Contributor(s): Victor Snieckus, Till Vogel
V. Khedkar, A. Tillack, M. Michalik, M. Beller*
Leibnitz-Institut für Organische Katalyse an der Universität Rostock e.V., Germany

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Publication History

Publication Date:
22 November 2005 (online)

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Significance

A one-pot domino reaction sequence for the synthesis of tryptophols (3-hydroxyethylindole) and its homologues is reported. The key step is a titanium-catalyzed hydroamination of alkynes by aryl hydrazines to give azatitanacycles with excellent Markovnikov regioselectivity. Following rearrangement and removal of titanium, hydrazones are produced which, when subjected to Lewis acid-mediated Fischer indole cyclization, give substituted tryptophols in up to 95% yield.