OsO4-catalyzed oxidative cyclization of geranyl and neryl acetate to cis-2,5-bis(hydroxymethyl)tetrahydrofurans

OsO4 catalyzes the oxidative cyclization of the 1,5-dienes geranyl acetate, (E)-Me2CH:CH(CH2)2CMe:CHCH2OAc (I), and neryl acetate, (Z)-Me2CH:CH(CH2)2CMe:CHCH2OAc (II), to the cis-2,5-bis(hydroxymethyl)tetrahydrofurans III and IV, resp., in the presence of NaIO4 as cooxidant in DMF. The reaction is stereospecific and proceeds with the sequential syn addn. to both double bonds of the starting materials. The observed stereoselectivity can be explained by invoking the intermediacy of a square-based pyramidal osmium (VI) diester V that has been isolated and characterized. Evidence is reported that this substance is indeed an intermediate in the transformation of I to III