Sigmatropic Rearrangements

Hydrogen migrations in the ground state

A. [1,5] = [4n + 2]

suprafacial migration

Use LUMO of polyene (diene in this case) and HOMO of sigma bond in the ground state.

 

B.  [1,7] = 4n systems

antarafacial migration

Again use LUMO of polyene (diene in this case) and HOMO of sigma bond in the ground state.

 

C.  [3,3] migrations

1.  Cope rearrangment

 

2.  Claisen rearrangment