Studies of sodium azide with tetraphenylcyclopentadienones and various analogs

The reaction of sodium azide with 2-p-chloro- and 2-p–methoxyphenyl–3,4,5-triphenyl–2,4-cyclopentadien– Iâ one was studied to determine if the substituent would have any appreciable effect on the product distribution of the corresponding l,5,7,8–tetraphenyl-2,3,4–triazabicyclo[3.3.0]octa-2,7-dien-6-ones and the 3,4,5,6–tetraphenyl–2(lH)â pyridinones that were formed by an acid catalyzed rearrangement. It was found that the chloro substituent had no effect on the reaction. The methoxy substituent had a moderate effect in that the product arising from the stabilized intermediate cation was favored by a ratio of approximately 3 to l.

The two simple linear analogs studied were l,2,3,3–tetraphenyl-2-propen-l-one and 3,4,4-triphenyl-3–buten–2â one. These compounds did not react with azide, presumably due to charge delocalization. Also studied as a cyclic analog was 2,7-diphenyltropone which did not react due to the aromatic character of the tropone ring system. A reaction did occur with diphenylcyclopropenone to give an unidentified product. However, the reaction did not take place in the same fashion as for the tetracyclones.