Selective dihydroxylation of non-conjugated dienes in favor of the terminal olefin

Non-conjugated dienes were dihydroxylated using the commercially available osmium tetroxide AD-mix-alpha reagent resulting in highly regioselective dihydroxylation of the terminal olefin rather than the internal, more substituted olefin. These findings now allow for the use of allylmetal reagents on substrates where preexisting internal olefins are present. The resultant diol can be cleaved to the aldehyde allowing for subsequent transformations. This selectivity is controled by a steric effect imposed by the allylic silyl ether adjacent to the internal olefin. (C) 1997 Elsevier Science Ltd.