Synthesis of Photochromic Monomers Derived from 1′‐(2‐Methacryloxyethyl)‐3,3‐Dimethyl‐2‐[2H]‐Spirobenzopyran Indoline

Abstract

The syntheses of five photochromic monomers derived from N‐ (2‐methacryloxyethyl)‐3′, 3′‐dimethylspiro‐[2H‐1] benzopyrane‐2, 2′‐indoline are reported. The preparation of these compounds involves the heterogeneous reaction between the N‐(hydroxyethyl)‐2,3,3‐trimethylindolenonium bromide and methacryloyl chloride in a polar solvent. The esterificated salt is easily purified by crystallization in chloroform‐hexane. Further condensation with the proper 2‐hydroxybenzaldehyde produces the photochromic monomer in high yield. This method can also be applied in the preparation of other spiropyrane derivatives.

Keywords:

• Photochromic monomers
• spirobenzopyranes
• photochromic polymers