Preparation of 6-benzyloxo-spirobenzopyran-indoline compounds and the evaluation of their optical activities

Substituted derivatives of spiropyran compounds bearing a benzyloxo fraction at the 6-position were prepared by direct Friedel–Crafts acylation. The novel compounds exhibited maximum absorption at 580 nm. According to the activation energy and kinetic rate constants, the Cl and Br derivatives were more stable in the open form than their analogues which did not contain the benzyloxo fraction.