Diastereo- and enantioselective synthesis of 2,3- and 1,2-disubstituted 4-oxophosphonates via asymmetric Michael addition

✍ Scribed by Dieter Enders; Heiner Wahl; Kyriakos Papadopoulos

• Book ID: 104208027
• Publisher: Elsevier Science
• Year: 1997
• Tongue: French
• Weight: 974 KB
• Volume: 53
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(97)00814-4

✦ Synopsis

Asymmetric Michael addition of lithiated SAMP hydrazones (S)-2 to a variety of alkenylphosphonates (E)-3 followed by oxidative cleavage of the 1,4-adducts 4 afforded 2,3-disubstituted 4-oxophosphonates 5 with good to very good yields (58-80%), low to moderate diastereomeric (de 6-74%) and excellent enantiomeric excesses (ee = >93%). Pure anti-diastereomers (ee = >93%) of 5 were obtained by separation of the stereoisomers by HPLC. In addition, the tithiated SAMP hydrazone (,~-2a was added to alkenylphosphonates (E)-3, and the lithio phosphonate anions were trapped with atkyl halides or sulfates, yielding 1,2-disubstituted 4-oxophosphonates 8 with moderate to good yields (38-69%), low to good diastereomeric (de = 10-77%) and high enantiomeric excesses (ee >90%) after oxidative cleavage.