Premium
Pyrolysis of 2‐(2‐azidobenzoyl)pyridine and 3‐(2‐Pyridyl)‐2,1‐ benzisixazoles. Prepration and chemistry of some pyrido[1,2‐b]cinnolin‐6‐ium hydroxide inner salts
Author(s) -
Ning Robert Y.,
Chen Wen Yean,
Sternbach Leo H.
Publication year - 1974
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570110204
Subject(s) - chemistry , pyridine , hydroxide , mesoionic , electrophile , pyrolysis , alkylation , ring (chemistry) , medicinal chemistry , cleavage (geology) , catalytic hydrogenation , organic chemistry , catalysis , geotechnical engineering , fracture (geology) , engineering
The pyrolysis of 3‐(2‐pyridyl)‐2,1‐benzisoxazoles 5A, 5B, and 5C (A : unsubstituted; B : 5‐bromo; C : 5,7‐dibromo) at about 215° afforded 5,11‐dihydro‐11‐oxopyrido [1,2‐ b ] cinnolin‐6‐ium hydroxide inner salt 6A , the 2‐bromo ( 6B ) and the 2,4‐dibromo ( 6C ) compounds respectively in high yields. X‐ray crystallographic analysis of 6B unambiguously confirmed the structure. The benzisoxazoles 5A‐5C were obtained from the pyrolysis of the corresponding 2‐(2‐azidobenzoyl) pyridines 2A‐2C at about 112°. While 2A and 2B afforded the corresponding benzisoxazoles 5a and 5B in 82% and 51% yields respectively, 2‐(2‐azido‐3,5‐dibromobenzoyl)pyridine ( 2C ) afforded a mixture of the benzisoxazole 5C and the tricyclic compound 6C , isolated 43% and 41% yields respectively. The properties of the novel mesoionic compounds of type 6 , their oxidative and reductive ring cleavage products together with alkylation and catalytic hydrogenation products are described. Electrophilic substitutions, substitutions in position 11 via the 11‐thiones 11 and other miscellaneous trans of 6 are also presented.