Asymmetric Michael additions of a chiral phosphite to nitroalkenes and knoevenagel acceptors

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