Tandem intramolecular cyclisation/1,3-aryl shift in N-(4,4-diethoxybutyl)-1-arylmethanimines (Kazan reaction): synthesis of 3-benzylidene-1-pyrrolines

A. V. Smolobochkin; A. S. Gazizov; A. S. Melyashova; J. K. Voronina; A. G. Strelnik; S. Z. Vatsadze; A. R. Burilov; M. A. Pudovik; O. A. Fedorova; O. G. Sinyashin

doi:10.1039/C7RA11216E

Tandem intramolecular cyclisation/1,3-aryl shift in N-(4,4-diethoxybutyl)-1-arylmethanimines (Kazan reaction): synthesis of 3-benzylidene-1-pyrrolines†

A. V. Smolobochkin,^a A. S. Gazizov,

*^a A. S. Melyashova,^a J. K. Voronina,^a A. G. Strelnik,^a S. Z. Vatsadze,

^b A. R. Burilov,^a M. A. Pudovik,^a O. A. Fedorova

^c and O. G. Sinyashin^a

Author affiliations

* Corresponding authors

^a A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, Arbuzova str., 8, Kazan, Russian Federation
E-mail: agazizov@iopc.ru

^b Lomonosov Moscow State University, Chemistry Department, 1, GSP-1, 1-3 Leninskiye Gory, Moscow, Russian Federation

^c A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, GSP-1, V-334, Vavilova str. 28, Moscow, Russian Federation

Abstract

In this article, a novel tandem reaction, which transforms N-(4,4-diethoxybutyl)imines into 3-arylidene-1-pyrrolines, is described. The substrate scope of the starting acetals includes arenes with electron-donating and withdrawing groups. The X-ray study of products confirmed the E-stereochemistry of the double bonds formed. The best yields (99%) are found in boiling xylene in the presence of TsOH (or 2-nitroresocinol) during 40 (50) hours. The study of substituents effect on the course of the reaction revealed that cascade process takes place, combining acid-catalyzed intramolecular cyclization of N-(4,4-diethoxybutyl)imines and unusual 1,3-sigmatropic shift of the aryl fragment. Cyclic imines that are formed in high/excellent yields are of interest both from the viewpoint of their biological activity and synthetic usefulness.

RSC Advances

Tandem intramolecular cyclisation/1,3-aryl shift in N-(4,4-diethoxybutyl)-1-arylmethanimines (Kazan reaction): synthesis of 3-benzylidene-1-pyrrolines†

Abstract

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Tandem intramolecular cyclisation/1,3-aryl shift in N-(4,4-diethoxybutyl)-1-arylmethanimines (Kazan reaction): synthesis of 3-benzylidene-1-pyrrolines

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