名称:
Improved RuO4-catalysed oxidative cyclisation of geraniol-type 1,5-dienes to cis-2,5-bis(hydroxymethyl)tetrahydrofuranyldiols
摘要:
The oxidation of some representative 1,5-dienes based on the geraniol and nerol carbon skeletons, namely geranyl acetate (1), geranic acid methyl ester (5), trans,trans-2,6-dimethyl-2,6-octadiene-1,8-diol diacetate (9), neryl acetate (13) and neroic acid methyl ester (16), has been performed using catalytic amounts of RuO4 (from RuO2. 2H(2)O, 4%) in the presence of NaIO4 (4 equiv.) as co-oxidant in the solvent mixture EtOAc/CH3CN/H2O (3:3:1) at 0 degreesC for 4 min. These conditions assure a degree of stereoselectivity for the geraniol-type dienes higher than that obtained under the Sharpless conditions [RuCl3. (H2O)(n) (2.2%). NaIO4 (3.1 equiv), CCl4/CH3CN/H2O (2:2:3), 0 degreesC], furnishing the cis- and trans-THF diol products in 62-70 and 6-9% yields, respectively. In addition, the: amount of the tis-THF, C-2 overoxidised, product is strongly reduced (2 7%). A comparison with the related MnO4--induced process, tested on the same substrates, was made. (C) 2001 Elsevier Science Ltd. All rights reserved.