I am little confused about when it comes to assigning configuration of planarly chiral cyclophanes - and I think it comes down to selection of pilot atom.

All sources I have came across say that the pilot atom is the first out of the plane atom and it should be selected in order assign configuration of chiral plane. However, these sources present slightly different strategies for selecting a pilot atom.

(a) One says that the pilot atom should be the one which is on the same side as the highest priority substituent which is causing desymmetrization the plane (i.e. the one that is closer).

(b) While the other source says simply that the pilot atom should be selected according to CIP priority rules.

In most cases it doesn't make any differences. Actually, it doesn't make a difference for any of the examples that I have came across. However, when thinking about it a structure came to my mind that brings conflict between these two strategies, it looks like this:

enter image description here

Seems to me that if we followed strategy (a), then the pilot atom would have to be a carbon from the top CH2 group and chiral plane would be assigned with Rp configuration. However, following strategy (b) means that oxygen atom gets the pilot status and chiral plane has to be assigned with Sp configuration. Only one approach can (if any of these) can be correct - could you tell me which one is it?

I have checked IUPAC recommendations (https://iupac.qmul.ac.uk/BlueBook/PDF/P9.pdf), but I didn't find an answer to my question.



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