100 years of Baeyer-Villiger oxidations

In the present review, we report the discovery of the formation of esters a nd lactones by oxidation of ketones with a peroxide derivative, namely the Baeyer-Villiger reaction. This reaction was first reported by Adolf von Bae yer and Victor Villiger a century ago in 1899, just one year after the oxid ant they used (KHSO5) has been described. Furthermore, Baeyer and Villiger established the composition of this new inorganic peroxide and showed that its instability was the reason of a controversy between several European ch emists between 1878 and 1893, For the first 50 years the mechanism of the B aeyer-Villiger reaction was a matter of debate. A side product, 1,2,4,5-tet raoxocyclohexane, was ruled out as an intermediate in the ester formation b y Dilthey. Criegee postulated a nucleophilic attack of the oxidant on the c arbonyl group. This mechanism was confirmed by von E, Doering by a labeling experiment with [O-18]benzophenone. The rearrangement step occurs with ret ention of the stereochemistry at the migrating center. The competitive migr ation and the rate-determining step are also discussed in this review.