Asymmetric Michael reaction: novel efficient access to chiral β-ketophosphonates

The asymmetric Michael reaction between chiral β-enaminophosphonates derived from (S)-1-phenylethylamine and various electrophilic alkenes furnished β,β-disubstituted ketophosphonates in good yields and with excellent enantioselectivity.

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Diethyl (S)-[2-(2-benzenesulfonylethyl)-3-oxo-but-2-yl]-phosphonateC16H25O6PSEe = 94%[α]D20=-26 (c 2.0, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

Diethyl (S)-[2-(2-benzyloxycarbonylethyl)-3-oxo-but-2-yl]-phosphonateC18H28O6PEe = 88%[α]D20=+11 (c 2.0, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

Diethyl (S)-[2-(2-methoxycarbonylethyl)-3-oxo-but-2-yl]-phosphonateC12H23O6PEe = 88%[α]D20=-10 (c 1.9, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

Diethyl (S)-[2-(2-cyanoethyl)-3-oxo-but-2-yl]-phosphonateC11H20NO4PEe = 85%[α]D20=-45 (c 1.5, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

Dibenzyl (S)-[2-(2-benzenesulfonylethyl)-3-oxo-but-2-yl]-phosphonateC26H29O6PSEe = 70%[α]D20=+8 (c 1.0, CH2Cl2)Source of chirality: asymmetric synthesisAbsolute configuration: (S)