Flash vacuum pyrolyses (FVP) were conducted in a IO-cm vertical quartz tube (12-mm i.d.)
at ca. 0.01 torr. At 300 OC, homoazulene passed through unchanged. Such thermal stability
was not anticipated. At 435 "C, five isomeric products were formed in high overall yield
(reaction l), although a small amount of 1 still survived even at this temperature. Phenylcyclopentadienes 2 and 3 have been reported previously and interconvert by 1,s- hydrogen shifts at temperatures well below 435 OC5 Their presence in the pyrolysate
was obvious from the 'H NMR spectrum; however, further confirmation was obtained by GC