[rolnor]

I am working with Cope-elimination and this is called a Ei according to the Ingold terminology. I have also seen in Marchs Advanced org. Chemistry that IUPAC calls it a Cyclo-DeDnAn mechanism, how does the IUPAC naming work? I can not find any information on google or my textbooks.

[pgk]

This nomenclature is introduced by R. Guthrie:
System for symbolic representation  of reaction mechanisms, Pure & Appl. Chem., Vol. 61, No. 1, pp. 23-56, (1989)
https://www.iupac.org/publications/pac/pdf/1989/pdf/6101x0023.pdf
On the other hand, a nomenclature system, which is published in the “Pure & Applied Chemistry” journal, does not obligatory mean that it is automatically adopted by  IUPAC.

[rolnor]

Thanks a lot! Something for my fifty year old brain to take in, interesting. I gave you a "molesnack".

[pgk]

Thanks for the "molesnack".