Sequential rearrangement of 1,2,4Z,7-tetraenes involving [1,5]-hydrogen migration and electrocyclization: an efficient synthesis of eight-membered cyclic compounds.

An efficient protocol for the synthesis of eight-membered bicyclic compounds from the cycloisomerization of 1,2,4Z,7-tetraenes has been established. The possible intermediate for this transformation was trapped by its Diels-Alder reaction with N-ethyl maleimide. Thus the reaction may proceed via the sequential processes involving [1,5]-hydrogen migration and electrocyclization.