ON THE BROMINATION OF THIENO[C]-FUSED 1,5-NAPHTHYRIDINES AND THEIR ISOMERIC N-OXIDES USING DIBROMOISOCYANURIC ACID IN FUMING SULFURIC-ACID

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-n aphthyridine 5-oxide (9) could conveniently be brominated at room temp erature using dibromoisocyanuric acid in fuming sulfuric acid. Bromina tion occurred in good to moderate yields at the beta position in the t hiophene 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 t hiophene ring at 95-degrees. It was also found that 12 was deoxygenate d under these reaction conditions. Direct oxidation of the brominated thieno[c]naphthyridines with m-chloroperbenzoic acid gave the 5-oxides in high yield.