Bridged and Spiro Heterocyclic Compounds

Thiophene as the first ring named in a fused system is shortened to thieno. 2-Methyl-2//-thiazolo [4,5 -e] -1,2-oxazine 

The name thiazole, like oxazole, means 1,3-thiazole. The atoms of thiazole are numbered and the sides of 1,2-oxazine are lettered. The fusion is drawn with atoms 4 and 5 of thiazole as atoms 5 and 6 of the oxazine. The system is then renumbered using the hierarchy of rules. You should flip your initial drawing about both the x andy axes to consider all four orientations to find the correct numbering. 

2-(4-Cyanophenyl)-l-[2-(3,4-dimethoxyphenyl)-ethyl]-l//-benz[6n imidazole-5-carboxylic acid ethyl ester 

The fusion in this ring places the benzene on the d side of the imidazole ring. Renumbering the new ring gives the locants as shown. 

Bridged and spiro heterocyclic compounds are named using the replacement nomenclature that is, the hydrocarbon name is used with oxa, aza, and so on to substitute heteroatoms for carbons as was seen in large ring monocyclic compounds in Section 1.6. 

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