Diastereoselective Synthesis of Vicinal Diamines by Aza-Michael Addition of Chiral Phenethylamine to Nitroalkenes

An efficient aza-Michael addition of (R or S)-alpha-phenethylamine, a chiral nitrogen nucleophile to (E)-nitroalkenes 2a-f permits the synthesis of vicinal diamines (or 1, 2-di-amine) after reduction of the 1, 4-adducts 3a-f (or 3'a-f). The key adducts 3 a-f (or 3'a-f) can be obtained in good yields (up to 78%) and excellent diastereoselectivities (up to = 98:2 dr (diastereomeric excess ratio)). In addition, this is one of the scarce examples where chiral phenethylamine and nitroalkenes have been used in catalyst-free aza-Michael additions. Our developed strategy opens an efficient entry to synthetic building blocks of vicinal diamines for natural products and drugs.