Insight into 6π Electrocyclic Reactions of 1,8-Dioxatetraene.

A variety of benzofuranone-based spiroisochromenes were originally designed and synthesized to gain insight into the oxa-6π electrocyclic reaction of cis,cis-1,8-dioxatetraene for the first time. The stability of the 1,8-dioxatetraene intermediate is governed by its steric congestion and can be fine-tuned through modification of the backbone structure, leading to the reactivity differences in the 6π electrocyclic reaction and the emergence of photochromic properties.