Sugasawa indole synthesis

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. 

Electrophilic cyclizations abound in organic synthesis, and several such methods afford the indole nucleus in the key step. In addition to the following chapters, 23 through 38, several other named indole ring syntheses that involve electrophilic cyclization at some stage in their reaction sequence are more appropriately relegated to separate chapters. 

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Nucleophilic cyclization is a common tactic in all branches of organic chemistry, and several indole ring syntheses, which are presented in Chapters 8 through 22, employ this reaction as the central theme in the synthesis. The Sugasawa indole synthesis (Chapter 22) uses both nucleophilic and electrophilic reactions. 

INDOLES FROM ANILINES via o-CHLOROACETYLATION-THE SUGASAWA SYNTHESIS... 

Sugasawa, T., Adachi, M., Sasakura, K., Kitagawa, A. Aminohaloborane in organic synthesis. 2. Simple synthesis of indoles and 1-acyl-3-indolinones using specific ortho a-chloroacetylation of anilines. J. Org. Chem. 1979,44, 578-586. 

It is possible to directly chloroacylate an aniline using chloroacetonitrile and boron trifluoride, ortho to the nitrogen. After (V-acylation, ring closure produces iV-acetyl-indoxyls. The Sugasawa synthesis of indoles utilises these same orf/to-chloroacetyl-anilines, via borohydride reduction and ring closure. ... 

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