Heterocycles fused to a benzene ring

Many interesting and important heterocyclic compounds contain fused ring systems. Some of the common ones are the result of fusing a heterocycle to 

Systematic names can he derived hy relating hack to the parent heterocycle and using the prefix henzo to indicate its fusion to benzene. It is necessary to define which of the bonds in the heterocycle is 

A few other examples are shown below. Note that the bonds of the heterocycle are lettered starting 

The final fused ring system is then given a completely new numbering system, different from that of the heterocycle. Typically, this starts adjacent to the bridgehead atom, then proceeds around the fused ring. The major criterion is to generate the lowest number for the first heteroatom. 

Note that, in most cases, we have little regard for 

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It is therefore not unexpected to find a similar effect in a heterocycle fused to a benzene ring. Reaction of the substituted benzothiazole, 71, with sodium hypochlorite in a mixture of sodium hydroxide and ammonia affords the sulfenamide, 72, probably by the intermediacy of the sulfenyl chloride. 

FIVE-MEMBERED HETEROCYCLES FUSED TO A BENZENE RING... 

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