3-Acylindoles as versatile starting materials for pyridine ring annulation: synthesis of 1-deazapurine isosteres

The reaction of electron-rich aminoheterocycles with 3-acyl- and 3-formylindoles results in indole ring opening and cyclocondensation to give heteroannulated pyridines, which can be regarded as purine isosteres. The transformations reported herein represent rare examples of domino reactions, which include the cleavage of an indole moiety.