As a team, consider the following historic preparation of a tris(1,1-dimethylethyl) derivative of Dewar benzene, B, by

Question:

As a team, consider the following historic preparation of a tris(1,1-dimethylethyl) derivative of Dewar benzene, B, by the photochemical isomerisation of 1,2,4-tris(1,1-dimethylethyl)benzene by van Tamelen and Pappas (1962). B does not revert to A via either a thermal or a photochemical electrocyclic mechanism. Formulate a mechanism for the conversion of A to B and explain the kinetic robustness of B with respect to the regeneration of A.

Dewar benzene A B