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

• Published in: Tetrahedron letters Vol. 40; no. 25; pp. 4707 - 4710
• Main Authors: Yokozawa, Tsutomu, Nishikata, Akira, Kimura, Takamasa, Shimizu, Kazuki, Takehana, Tomoyuki
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 18-06-1999
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/S0040-4039(99)00850-3

3,3,4,4-Tetracyanobutanal acetal 1, which is easily obtained from tetracyanoethylene, ethyl vinyl ether, and ethanol, yielded 2-aminopyridine derivative 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 cyanide and ethanol from 1, followed by double intramolecular nucleophilic additions to the cyano groups.
The pyridine-catalyzed reaction of acetal 1 leads to bicyclic 2-aminopyridine 2 in one pot. The reaction mechanism is also discussed.