3-Isochromanone

Abstract

In connection with other studies we required an authentic sample of 3-isochromanone 2. Only one route to this compound has been reported in the literature and that method afforded a 26% yield of 2 in four steps from a, a'-dibromo-g- xylene.^1,2 we, therefore, directed our attention to the Baeyer-Villiger rearrangement of 2-indanone 1. This report summarizes a ccmparison of three different procedures for this oxidative rearrangement. Contrary to our expectations, none of the desired lactone was obtained upon teatment of 1 with peroxytrifluoroacetic acid.^3,4 The use of caro's acid, potassium persulfate in sulfuric acid,⁵ afforded 32% of 2. The method of choice, however, was the recetly reported procedure of Gringauz and Tosk.⁶ By this method (90% hydrogen peroxide in sulfuric acid-acetic anhyride) we obtained

3-isochromanone in 75% yield in one step. The advantages of these conditions have been noted by the originators.⁶ Thus, it is concluded that this new method merits preferential consideration for Beayer-Villiger rearrangements.