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Baeyer-Villiger oxidation of cyclic ketones is a classic synthetic method for lactones (1). A few years ago this Journal published an article on intramolecular esterification as a route to lactones (2) but no experiment using the Baeyer-Villiger reaction is reported therein.
Indan-1-ones are oxidized either by CF sub 3 CO sub 3 H, which is prepared from TFAA and 30% commercial H sub 2 O sub 2 (3), or by MCPBA in refluxing dichloroethane (4). The oxidation of 3-methyl-indan-1-one is a part of a multistep synthesis that can include the preparation of chiral products (5). A shorter experiment describes the qualitative monitoring of the oxidation of commercially available indan-l-one to dihydrocoumarin by two standard analytical techniques, vapor phase chromatography, and IR spectroscopy.
The TFAA/H sub 2 O sub 2 method is a more efficient way for synthesizing the dihydrocoumarins. The MCPBA method has been used for monitoring of the oxidation of the indan-1-one.
Identification of the Product Obtained
The Baeyer-Villiger reaction proceeds via an oxygen insertion, which, in the case of a cyclic unsymmetrical ketone, can lead to two lactone isomers.
*H NMR spectroscopy permits easy identification of the product obtained, chiefly by examining the chemical shift of the methylene situated either alpha to the carbonyl group in 2 or alpha to the oxygen in 3. The figure shows the spectrum of the crude reaction product obtained from the oxidation of indanone 1 (R = Me) by CF sub 3 CO sub 3 H. (figure omitted) (This indanone is obtained by the following reactions: Michael addition of Ph sub 2 CuMgBr to ethyl crotonate, or to a chiral crotonate for asymmetric synthesis (5), saponification of the adduct followed by intramolecular acylation of the acid chloride thus obtained.) The methylene appears...