Tandem dimerization and double annulation of 3,3,4,4-tetracyanobutanal acetal. Synthesis of a bicyclic 2-aminopyridine derivative

3,3,4,4-Tetracyanobutanal acetal 1, which is easily obtained from tetracyan oethylene, ethyl vinyl ether, and ethanol, yielded 2-aminopyridine derivati ve 2 fused with cyclopentane in one pot in the presence of pyridine. On the basis of several experiments, the proposed mechanism involves the Michael reaction of 1 with the diene generated by the elimination of hydrogen cyani de and ethanol from, followed by double intramolecular nucleophilic additio ns to the cyano groups. (C) 1999 Elsevier Science Ltd. All rights reserved.