Asymmetric Michael Additions of a Chiral Phosphite to Nitroalkenes and Knoevenagel Acceptors

The diastereoselective Michael addition of an enantiopure phosphite to nitroalkenes and α,β-unsaturated malonates is described. High asymmetric inductions were obtained using a readily available TADDOL auxiliary. Racemization-free cleavage of the auxiliary led to α-substituted β-nitro phosphonates and β-substituted β-phosphono malonates in good yields and high enantiomeric excesses, respectively. An extension of the method to the synthesis of α,β-disubstituted β-nitrophosphonates with two new neighboring stereogenic centers is also reported.