I am trying to understand how the locants work for the following molecule (locants added by me).
I added the locants following IUPAC Blue Book rules from 2013, P-14.4. Basically, first numbering heteroatoms in the ring, assigning the highest locant to the one with an indicated hydrogen, and then number clockwise around the ring (red locants).
I assumed the same would go for the second ring, so the name would be:
However, Chemdraw says the name is:
I get the differences between the prime and composite locants (P-14.3.1), however it shows a numbering more like:
Is Chemdraw wrong or am I missing something here? If Chemdraw is right then I'd assume that for some reason the ring assembly has preference for a lower locant, but I can't find the rule that states this in the Blue Book.