Interrupted Houben-Hoesch Nucleophilic Cascade Strategy for the Synthesis of 6,7-Oxoannulated Indoles
Hamza Enesi Ozomarisi1, Victor K Outlaw1
1Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
Abstract:
An interrupted Houben-Hoesch cascade strategy is reported for the synthesis of 6,7-oxoannulated indoles, analogs of 6,7-carboannulated indole natural products, from pyrrolyl succinonitrile silyl ethers. The cascade proceeds through an initial nucleophilic attack by the pyrrole on a Lewis acid-activated nitrilium, followed by a second nucleophilic attack on the resulting iminium intermediate by an in situ-deprotected alcohol. The strategy enables the synthesis of a broad range of substituted dihydrofurano- and tetrahydropyranoindoles, scaffolds that are synthetically challenging by other means, in a single step.
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