3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles
to 3-pyridylnitrenes, but 4-pyrimidinylcarbenes and 4-quinazolinylcarbenes do not necessarily rearrange to the corresponding 3-pyridylnitrenes or 3-quinolylnitrenes. The ringcontraction reactions are interpreted in terms of ring opening of either the nitrenes or the diazacycloheptatetraenes to nitrile ylides.