Novel isochroman‐3‐ones for the curing of unsaturated polyesters via Diels‐Alder reaction

The synthesis of some new 4-hydroxy, 4-butyloxy, 4-propionyloxy, and 4-acryloyloxy substituted isochroman-3-ones is described. The influence of the substitution pattern in position 1 and 4 on the CO 2 elimination, which leads to high reactive ortho-quinodimethanes, is investigated. The saturated compounds are used for model reactions with diethyl maleate to study the Diels-Alder reaction and to explain the curing mechanism of unsaturated polyesters. The acrylic ester is copolymerized with styrene to give a reactive copolymer which can easily cure unsaturated polyesters at 170 °C in two mins without toxic byproducts.