Catalyst-controlled Wacker-type oxidation of homoallylic alcohols in the absence of protecting groups

Abstract

Homoallylic alcohols are oxidized to β-hydroxy ketones using a TBHP-mediated Pd-catalyzed Wacker-type oxidation. The use of a bidentate ligand, quinoline-2-oxazoline (Quinox), and TBHP((aq)) as the terminal oxidant provides good yields of the desired products with reaction times significantly reduced as compared to the Tsuji-Wacker oxidation. Additionally, bis- and tris-homoallylic alcohols are oxidized to provide cyclic peroxyketals, presumably via nucleophilic attack of the methyl ketone product.

Figure 1

a) Proposed syn-oxypalladation. b) Acetate-protected homoallylic alcohol 6 is converted exclusively to methyl ketone 7 in high yield.

Scheme 1

Proposed formation of peroxyketals 11 and 13.