Die Phosphonat-Phosphat- und Phosphat-Phosphonat-Umlagerung und ihre Anwendung, Teil 2: Stereochemie der Phosphonat-Phosphat-Umlagerung am Kohlenstoff am Beispiel der Isomerisierung von (R)-(+)- und (S)-(?)-(1-Hydroxy-1-phenylethyl)-phosphons�ure-diethylester
摘要:
The phosphonate-phosphate-rearrangement of (R)-(+)- and (S)-(-)-6 was investigated at room temperature in various organic solvents and mixtures of organic solvent and of up to 7% of water, using potassium t-butoxide, potassium hydroxide, and DBU as bases. The rearrangement is shown to occur with retention of configuration at carbon. The highest enantiomeric excess (10.7%) for phosphate 8 was observed using a mixture of DMSO and water (100:7) containing DBU as base. Under these conditions the cleavage of phosphonate 6 into acetophenone and phosphite predominates and the yield of phosphate 8 is only 7.7%.