Regiochemistry of Wacker-type oxidation of vinyl group in the presence of neighboring oxygen functions. Part 2

Abstract The regioselectivity of the palladium(II) oxidation of (±)-17α-vinyl-1,3,5(10)-gonatriene derivatives bearing a lactonic bridge on the α or β-face (β-face: obtention of the expected acetyl derivatives; α-face: presence of aldehydes, anti-Markovnikov addition) may be rationalized by an intramolecular coordination of the metal with the two lactonic oxygen atoms. Calculations carried out using ZINDO I method confirm the existence of such a chelation and the possibility of a cis-hydroxy or a cis-acetoxypalladation in the course of the Wacker process. An experimental confirmation was given by the regioselective mono-oxidation of the vinyl group syn to the methoxycarbonyl group of (3R ∗ ,6S ∗ ,9S ∗ )-3- methoxycarbonyl-3-(2-propyl)-6,9-divinyl-1-oxaspiro[4.4]nonan-2-one .