3- Aza-l,5-enynes

Substituted pyridines are prepared via cyclization 3-aza-l,5-enynes in a facile, one-pot approach (Scheme 15) (13T10245).This reaction works with various substituents present on the arene electron-donating, electron-withdrawing, and halides. Steric hindrance slows the reaction rate. If the aryl ring at C-2 is replaced with alkyl groups, the reaction fails to provide any cyclized product. 

Polyfluoroalkyl-functionalized cyclobutenes with an exo cyclic double bond have been shown to form from 3-aza-l,5-enynes via a thermal aza-Claisen rearrangement to give an allene-imine intermediate and subsequent cyclization to give the cyclobutene core (Scheme 32)... 

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