The 1,2-diamino moiety can be frequently found as a substructure in pharmaceutical molecules. Substituted 3-aminopyrrolidines also belong to one of the most popular classes in this family. Bioactive compounds that contain these heterocycles include: bacterial peptide deformylase inhibitor 1,[1] NK2 receptor antagonist 2, [2] 11-b-hydroxysteroid dehydrogenase 1 inhibitor 3, [3] and the clinically used fluoroquinolone antibiotic Vigamox 4 (Figure 1). Probably the most famous 1,2-diamine-containing compound is oseltamivir (Tamiflu, 5), which has received enormous attention from the synthetic community because a more practical and economic route for preparing this antiflu drug is highly desired. [4,5] Although a number of enantioselective methods have been reported for the construction of 1,2-diamines, the development of conceptually different synthetic alternatives is still of great interest.Recently, there has been great progress in the organocatalytic Michael addition reactions of aldehydes to nitroolefins.[6] However, most of the attention has been devoted to exploring new catalyst systems in order to improve the reaction efficiency and selectivity; [7] attempts to extend the reaction scope by employing functionalized nitroolefins are rare. [5g, 7m, 8] We have reported that b nitroacrylates are suitable substrates for the catalyzed Michael additions of O-TMSprotected diphenylprolinol to aldehydes, [7m] which led to the efficient formation of cyclic b-amino acids. Soon after that, Hayashi and co-workers developed an elegant synthesis of Tamiflu using (E)-tert-butyl 3-nitroacrylate as a Michael acceptor.[5g] In their procedure, the ester moiety of the b nitroacrylate was subsequently transformed into an acetylamino group. Considering that this conversion requires three steps, and uses the toxic and hazardous sodium azide as a reagent, we decided to investigate organocatalytic Michael reactions of protected 2-amino-1-nitroethenes with aldehydes. If these transformations take place, we will be able to develop a general, facile approach for the synthesis of 1,2-diamines, such as Tamiflu and 3-aminopyrrolidines.With this idea in mind, we prepared (Z)-2-nitroethenamine 6 from nitromethane according to the procedure reported by Krówczyń ski and Kozerski (63 % yield over two steps).[9] Treatment of 6 with acetic anhydride and DMAP afforded enamide 7 in 92 % yield as fine crystals (Scheme 1). Only the Z isomer was formed, owing to strong intramolecular hydrogen bonding in the product. Initially, we expected that 7 could isomerize into its E isomer (8) under suitable reaction conditions, [10] and then subsequently react with aldehydes to give the desired adducts. Accordingly, the reaction of 7 with 2-(pentan-3-yloxy)acetaldehyde 10 a was carried out in the presence of 10 mol % of 9 c and 30 mol % of benzoic acid. The reaction in chloroform was complete in 1 hour, affording the adduct in excellent enantioselectivity (92 % ee for the major isomer) and moderate diastereoselectivity (syn/anti = 5:1, Scheme 1). The enantiosel...