1.
Decompose in two simple cycles (Attention to the extra double bond!):
Pyridine and Thiophene
2.
Determine the priority cycle:
- A heterocycle has priority over a carbocycle (= only C atoms as ringmembers). A nitrogen heterocycle has priority over a non-nitrogen cycle. - A large nitrogen heterocycle has priority over a small nitrogen heterocycle.
In our case the priority cycle is pyridine.
3. Determine the name without numbers of substituents:
Non-Priority Cyle[o]Priority Cycle
In our case: Thiophenopyridine
4. Number the priority cycle by letters, the other by numbers:
5. Finally determine the name with the correct numbers, in our case:
Thiopheno[3,2-b]pyridine
1.-5.
In the case where the cycles contain several heteroatoms, one proceeds as above, then:
6.
Heteroatome numbers in cycles are bracketed. (These are the numbers in the isolated cycles!)
In our case: [1,4]Thiazino[3,2-b][1,4]oxazine
1H-Imidazo[5,1-c][1,2,4]triazole
2H-Furo[3,2-b]pyrane
5H-Pyrido[2,3-d][1,2]oxazine