Polycyclic or heterocyclic compound naming [closed]

Question

What is the order and name of the following polycyclic compound?

I am studying heterocyclic chemistry to teach some notions to my high school students even if it is outside curriculum (to give them advantages over those who don't know them at their age) and I am planning to make my own notes about the subject. However, I am not sure of the method of naming these classes of compounds, and after consulting the internet, I saw there are SEVERAL ways to name them (some of them confusing for me, specially the notation with [x.y.z.t...] notation. I can not understand where the numbers come from and the preference order between rings...

Remark: What are the rules to name polycyclic compounds?

References to name polycyclic and 3d organic compounds would be useful too.

Answer 1

First of all, it sometimes helps if you draw the structure correctly according to the IUPAC recommendations for orientation of fused ring systems (see Subsection P-25.3.2.3 for details).

Then you should start with the corresponding hydrocarbon parent component that has the maximum number of noncumulative double bonds (called mancude ring system). We will handle the saturation later.

Check if the mancude ring system is on the list of retained traditional names (like naphthalene) in Subsection P-25.1.1. If the whole structure is not on the list, check if there is at least a part of it. In this case, you should find indene.

Next you can do the fusion with a cyclobutane ring.

Numbers and letters [1,2-f] are used to indicate the side where the fusion occurs and the relative orientation of the fused ring system. The direction of the numbers of the attached component (e.g. ‘1,2’ or ‘2,1’) corresponds to the direction of the lettering of the peripheral sides of the parent component (i.e. a, b, c, etc.).

The corresponding Subsection P-25.3.1.3 in the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), reads as follows:

(…)
Isomers are distinguished by lettering, continuously, each peripheral side of the parent component (including sides whose locants are distinguished by letters, for example, 2a,3a) using the italic letters a, b, c, etc., beginning with a for the side numbered ‘1,2’, b for ‘2,3’ etc. To the letter as early in the alphabet as possible that denotes the side where the fusion occurs are prefixed, if necessary, the numbers of the positions of attachment of the other component. These numbers are chosen to be as low as is consistent with the numbering of the compound and their order conforms to the direction of lettering of the parent component. (…)

In this case the first two positions of cyclobutane (‘1,2’) are fused with the sixth side of indene (‘f’). That gives us cyclobuta[1,2-f]indene. However, all sides of cyclobutane look the same, so no indication of the position and orientation is actually necessary. Therefore, we can ignore this part and just keep cyclobuta[f]indene. Nevertheless, we will need these positions later.

We are still working with a mancude ring system, so we now have 1H-cyclobuta[f]indene.

Next you can do the fusion with a cyclopentane ring.

Remember that numerical locants (‘1,2’) were used for the first-order attached component cyclobutane. For the next fusion, we need to indicate the opposite side (‘3,4’).

The locants of the second-order attached components cyclopentane (‘1',2'’) are primed to contrast with those of the first-order attached components cyclobutane (‘3,4’). The two sets of locants are separated by a colon. This gives us cyclopenta[1',2':3,4]cyclobuta[1,2-f]indene. Again, all sides of cyclopentane look the same, so no indication of a position and orientation is actually necessary. Therefore, we can ignore this part and just keep cyclopenta[3,4]cyclobuta[1,2-f]indene.

Finally, you have to restore the saturation. Since the compound is completely saturated, no locants are needed. This gives us the complete name tetradecahydrocyclopenta[3,4]cyclobuta[1,2-f]indene.