PYROLYSIS OF 1-SUBSTITUTED PYRAZOLES AND CHLOROFORM AT 550-DEGREES-C - FORMATION OF ALPHA-CARBOLINE FROM 1-BENZYLPYRAZOLES

Pyrolysis of (CH3)-C-13 labelled 1-methylpyrazole 8 with chloroform at 550 degrees C in a continuous flow reactor yields unlabelled 2-chloro pyrimidine 9 and 2-cyanopyrrole 10 labelled at the cyano group, Howeve r, pyrolysis of 1-benzylpyrazole 14 with chloroform under similar cond itions gives 9, 2-phenylpyrimidine 13 and, as the major product, alpha -carboline 15, Pyrolysis of several substituted 1-(arylmethyl)pyrazole s and the use of C-13 and N-15 labelled compounds provides direct evid ence by which the positions of 7 atoms of 1-benzylpyrazole can be loca ted in the alpha-carboline. These data support the mechanisms suggeste d for the formation of 9, 10, and 15.