REARRANGEMENTS OF NONRACEMIC VINYL PHOSPHATES TO BETA-KETO PHOSPHONATES

A series of chiral auxiliaries has been tested for viability in the vi nyl phosphate/beta-keto phosphonate rearrangement. While dienyl phosph ates derived from ephedrine, pseudoephedrine, and isopinocampheol succ umbed to competing elimination reactions, ones derived from menthol an d (S)-2-methylbutanol were found to undergo rearrangement to the desir ed beta-keto phosphonates. The bis((S)2-methylbultyl) phosphorochlorid ate then was used to prepare the vinyl phosphates of the prochiral ket one 4-methylcyclohexanone, and modest diastereoselectivity was observe d upon rearrangement of these phosphates to the corresponding beta-ket o phosphonates. The de of this rearrangement was established by degrad ation of the beta-keto phosphonate to 3-methyladipic acid and determin ation of the optical rotation. This sequence allowed identification of the major rearrangement product as the 4R-diastereomer of beta-keto p hosphonate 13. Finally, two other prochiral cyclohexanones were found to be suitable substrates for the vinyl phosphate/beta-keto phosphonat e rearrangement.