THE PHOSPHATE-PHOSPHONATE AND PHOSPHONATE-PHOSPHATE REARRANGEMENTS AND THEIR APPLICATIONS - 7[1]: USE OF t-BUTYL AS PROTECTING GROUP AND SYNTHESIS OF CHIRAL, NONRACEMIC α-HYDROXYPHOSPHONATES
摘要:
The regioselectivity of metallation of hexyl diisopropyl phosphate (1) depends oil the solvent, the temperature, and the base used. The best results are obtained with s-BuLi/TMEDA in hexane and diethyl ether at -78 degreesC, the CH2O group being deprotonated preferentially over the CHO group (3:1 versus 2.5:1). The intermediate phosphonyloxy-substituted alkyllithiums (+/-)-4 and (+/-)-5 rearrange to phosphonates (+/-)-6 and (+/-)-7, respectively. The isopropyl groups can be replaced by t-butyl groups to direct metallation exclusively to CH2O. Homochiral diamines in place of TMEDA give chiral, nonracemic alpha -hydroxyphosphonates.