Diastereodivergent Asymmetric Michael Addition of Cyclic Azomethine Ylides to Nitroalkenes: Direct Approach for the Synthesis of 1,7-Diazaspiro[4.4]nonane Diastereoisomers

摘要

The first highly diastereoselective and enantioselective catalytic asymmetric Michael addition of cyclic azomethine ylides with nitroalkenes have been developed to diastereodivergently generate either the syn or anti adducts by employing N, O-ligand/Cu(OAc)(2) and N, P-ligand/Cu(OAc)(2) catalytic systems. Both catalytic systems exhibit broad substrate applicability to afford the corresponding Michael ad-ducts in good to excellent yields, with excellent levels of diastereo-(up to 99: 1 diastereomeric ratio) and enantioselectivities (up to > 99% enantiomeric excess). Importantly, the chiral 1,7-diazaspiro[4.4] nonane diastereomer derivatives can be easily obtained in good yields through facile NaBH4 reduction of the Michael adducts.