Regio- and stereoselective addition of Grignard and organolithium reagents to 4-hydroxy-2-cyclopentenones

a highly regio- and stereoselective method for the 1,2- or 1,4-addition reactions to 4-hydroxy- 2-cyclopentenones has been devised, which makes use of readily available organolithium and Grignard reagents. This procedure allows for stereochemistry complementary to that observed in the 1,4-addition of organocuprates and makes possible the attachment of aromatic groups to carbons C-2 and C-3 of cyclopentenones 5 or 6 and carbons C-4 and C-5 of cyclopentanones 7, which are of interest for further elaboration into biologically active targets