Unexpected Heterocyclic Products from Cycloaddition Reactions of Nonsymmetrical Allenyl Aldoketazines with Substituted Alkynes

✍ Scribed by Juraj Galeta; Stanislav Man; Jean-Philippe Bouillon; Milan Potáček

• Book ID: 102829012
• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 855 KB
• Volume: 2011
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201001044

✦ Synopsis

Abstract

Thermally initiated cycloaddition reactions of nonsymmetrical allenyl azines 1 with alkynes or other dipolarophiles usually lead to compounds with three fused, five‐membered heterocyclic rings. With alkynes with pronounced “push–pull” systems, however, the reaction ends with the formation of substituted pyrrolidino[1,2‐b]pyrazoles 4 and, in the case of azines with trifluoromethyl substitution, ring opening leads to the isolation of compounds 9. Reaction mechanisms for these transformations are proposed. The molecular structures of the new heterocycles 4 and 9 were confirmed by X‐ray crystal structure analysis.