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On the bromination of thieno[ c ]‐fused 1,5‐naphthyridines and their isomeric N ‐oxides using dibromoisocyanuric acid in fuming sulfuric acid
Author(s) -
Malm Johan,
Hörnfeldt AnnaBritta,
Gronowitz Salo
Publication year - 1994
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.5570310244
Subject(s) - chemistry , sulfuric acid , halogenation , thiophene , ring (chemistry) , yield (engineering) , oxide , medicinal chemistry , organic chemistry , metallurgy , materials science
Thieno[2,3‐ c ]‐1,5‐naphthyridine ( 3 ), thieno[2,3‐ c ]1,5‐naphthyridine 5‐oxide ( 7 ), thieno[3,2‐ c ]‐1,5‐naphthyridine ( 5 ) and thieno[3,2‐ c ]‐1,5‐naphthyridine 5‐oxide ( 9 ) could conveniently be brominated at room temperature using dibromoisocyanuric acid in fuming sulfuric acid. Bromination occurred in good to moderate yields at the β position in the thiophene ring. Thieno[2,3‐ c ]‐1,5‐naphthyridine 9‐oxide ( 12 ) and thieno[3,2‐ c ]‐1,5‐naphthyridine 9‐oxide ( 13 ) also gave substitution in the thiophene ring at 95°. It was also found that 12 was deoxygenated under these reaction conditions. Direct oxidation of the brominated thieno[ c ]naphthyridines with m ‐chloroperbenzoic acid gave the 5‐oxides in high yield.