In this question, the compound below was named 1-(propan-2-yl)-1,2,3,5-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one.
I assume that we can split this into three parts.
- The propyl group attached to the nitrogen, namely: 1-(propan-2-yl)- (basic part of nomenclature)
- The pyrazole derivative like ring, namely 1,2,3,5-tetrahydro-6H-pyrazolo (For this refer to this answer)
- The pyridine ring, namely [3,4-b]pyridin-6-one.
The third part is where I am confused, what does the [3,4-b] stand for?
Another example for said nomenclature is in Acdlabs
This leads me to assume the b stands for the fusing of the two bicyclo rings. But then, why [3,2-b] and why does the numbering not count the bridgehead carbons?