A Stereoselective Approach to Functionalized Cyclohexenones
A catalytic enantioselective approach to 4-hydroxy-6-methylcyclohex-2-enones is presented herein. The stereogenic information is generated through a copper-catalyzed 1,4-addition to p-benzoquinone monoketal using a chiral, BINOL-based (BINOL = 1,1′-bi-2-naphthol) phosphane ligand, according to the procedure of Feringa et al. A CBS (Corey–Bakshi–Shibata) reduction of the 1,4-adducts gave the four possible isomers in two steps and 82–97 % ee (enantiomeric excess), starting from commercially available 4,4-dimethoxycyclohexa-2,5-dien-1-one (7).