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Aza-Wittig reaction of
N-vinylic phosphazenes (1,2 addition), derived fro
m diphenyl
methylphosphine orderived fro
m tri
methylphosphine with
![](/i<font color=)
mages/gifchars/alpha.gif" BORDER=0>,
![](/i<font color=)
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
middle">-unsaturated aldehydes, leads to the for
mation of 3-azatrienesthrough a [2 + 2]-cycloaddition-cycloreversion sequence. The presence of an alkyl substituent in position3 of
N-vinylic phosphazenes increases the steric interactions, and [4 + 2] periselectivity (1,4 addition)is observed. Reaction of azatrienes with
![](/i<font color=)
mages/gifchars/alpha.gif" BORDER=0>,
![](/i<font color=)
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
middle">-unsaturated aldehydes yields pyridines.