Rearrangements of Nonracemic Vinyl Phosphates to β-Keto Phosphonates

Article abstract of DOI:10.1021/jo00105a042

A series of chiral auxiliaries has been tested for viability in the vinyl phosphate/β-keto phosphonate rearrangement.While dienyl phosphates derived from ephedrine, pseudoephedrine, and isopinocampheol succumbed to competing elimination reactions, ones derived from menthol and (S)-2-methylbutanol were found to undergo rearrangement to the desired β-keto phosphonates.The bis((S)-2-methylbutyl) phosphorochloridate then was used to prepare the vinyl phosphates of the prochiral ketone 4-methylcyclohexanone, and modest diastereoselectivity was observed upon rearrangement of these phosphates to the corresponding β-keto phosphonates.The de of this rearrangement was established by degradation of the β-keto phosphonate to 3-methyladipic acid and determination of the optical rotation.This sequence allowed identification of the major rearrangement product as the 4R-diastereomer of β-keto phosphonate 13.Finally, two other prochiral cyclohexanones were found to be suitable substrates for the vinyl phosphate/β-keto phosphonate rearrangement.