The mechanism of allylic oxidation by selenium dioxide

Abstract

In the course of the SeO₂-oxidation of 5-cyclopentyl-2-methyl[1-¹³C]pent-2-ene and its isotopomer (2), which stereoselectively yields the E-products (7)–(10), the ¹³C label is distributed between C-1 and the C-2 substituent, indicating that two separate steps in the sequence determine the stereochemical features of the products; the ene-reaction proceeds in favour of the trans-methyl-group of the olefin by a factor of 7 : 3 and the following [2,3] sigmatropic rearrangement generates the E-configuration of the resulting alcohols.