Other Tin-Mediated Indole Syntheses

Indole Ring Synthesis From Natural Products to Drug Discovery, First Edition. Gordon W. Gribble. 2016 John Wiley Sons, Ltd. Published 2016 by John Wiley Sons, Ltd. 

Kim demonstrated that the substituted benzotriazoles can afford either indoles or 3-acylindoles depending on the R group (equations 2 and 3) [6]. As might be expected, phen-anthridines accompany the 3-acylindole pathway (up to 30%). This reaction is initiated by formation of an 0-stan-nyl ketyl radical and loss of N. Further cyclization and loss of either t-butyl radical or R CHO affords the indole products. Minakata, Komatsu, and coworkers generated 1,5-dipoles from either 0-staimylmethylated thioanilides or isothiocyanates that cyclize to form indoles (equations 4 

The several tin-promoted cyclizations that afford indo-lines (2,3-dihydroindoles) are not covered herein. Rather, if subsequent indole formation is reported, then that work is in the later chapter covering the conversion of indolines to indoles. 

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