Synthesis and structural examination of 4-azaindoles

Abstract

The literature on the methods of synthesis of azaindoles with particular reference to the 4-isomer is reviewed. Numerous methods of synthesis employ pyridine derivatives as starting materials, and methods via pyrrole are very limited. 4-azaindoles are synthesised from 4-amino-2-carboethoxy-1-methyl-pyrrole. There are many difficulties in the use of amino-pyrroles as starting materials because of their tendency to oxidative decomposition, and this subject is discussed at some length, The reagents used to condense and couple with the aminopyrrole are examined and some reaction mechanisms are included. Physical methods of structure determination of azaindoles are examined together with . discussion of the tautomerism of &, ¥-andeS -hydroxypyridines and quinolines. The infrared, ultraviolet and nuclear magnetic resonance spectra of the prepared beavatndoles are recorded and the amide/enol tautomerism of 2-carboethoxy-1-methyl-7-oxo-4-azaindole is studied.