REGIOSELECTIVE AND STEREOSELECTIVE TRANSFORMATIONS OF ENANTIOPURE P-BENZOQUINONE EQUIVALENTS

The selectivities of typical transformations of the p-benzoquinone Die ls-Alder adduct 2 and its dihydro derivative 3 are shown to be highly dependent on the mechanistic path followed. To avoid ambiguities and t o make sure of clearly defined regioselectivity, the monoketal 13 was examined and proven not only to be an excellent dienophile but, of cou rse, also to lead to reliable regioselectivity in subsequent transform ations. This led to the correction of an earlier provisional assignmen t of the alkylation products 11 and 12.