Flow-vacuum pyrolysis of 5H-dibenzo[a,d]cyclohepten-5-one oxime and 10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5-one oxime

Pyrolysis of SH-dibenzo[a,d]cyclohepten-5-one oxime (8) and 10,11-dihydro-5 H-dibenzo[a,d]cyclohepten-5-one oxime (9) in a flow system (at 1.33 mbar an d 650 degrees C) were examined comparatively with pyrolysis of benzophenone oxime (1a) using GC/MS. The pyrolysis products of 8 were: 1-cyanophenanthr ene (19), 3H-[3,4-a,5]isoxazolodibenzo[b,f]cycloheptene (20), dibenzosubere none (12), dibenzosuberenone imine (23), anthracene (21) and phenanthrene ( 22). In the pyrolysis of 9, 1-cyano-9,10-dihydrophenanthrene (24), 4-cyano- 9,10-dihydrophenanthrene (25), 3H-[3,4-a,5]isoxazolo-9,10-dihydrodibenzo[b, f]cycloheptene (26), dibenzosuberone (13) and dibenzosuberone imine (28) ar e accompanied by 21 and 22 as well as by dehydrogenation products 19 and 20 . Pyrolysis of 1a at 800 degrees C indicated formation of benzophenone (11) and benzophenone imine (18) along with the reported products benzonitrile (15), biphenyl (16), benzene (17) and 2-phenyl-benzoxazole (4a). The compar ative reaction mechanisms for 1a, 8 and 9 are discussed. Pyrolytic formatio n of ketone imines and corresponding ketones seems to be a general reaction route (also proved for isodibenzosuberone oxime 10) in conditions favourin g surface catalysis. (C) 2000 Elsevier Science B.V. All rights reserved.