EXPERIMENTAL TEST OF THE [3-CYCLOADDITION AND [2+2]-CYCLOADDITION PATHWAYS FOR THE BIS-CINCHONA ALKALOID-OSO4 CATALYZED DIHYDROXYLATION OF OLEFINS BY MEANS OF C-12(2])C-13 KINETIC ISOTOPE EFFECTS/

The C-12/C-13 kinetic isotope effects for the bis-cinchona-OsO4 cataly zed dihydroxylation of 4-nitrostyrene, 4-methoxystyrene and allyl 4-me thoxybenzoate have been measured at the olefinic carbons by the method of Singleton. For each olefin, the C-12/C-13 kinetic isotope values a re substantial and similar at the two olefinic carbons. These results accord well with prediction based on a [3+2] cycloaddition pathway but not with expectations for a [2+2] cycloaddition process. Copyright (C ) 1996 Elsevier Science Ltd