A novel series of (S)-N-arenesulfonyl-2-aminomethylpyrrolidines were prepared in high overall yield starting from N-Boc-l-proline. The mono-sulfonyldiamines were evaluated as organocatalysts in the asymmetric a-amination of propanal using diethyl azadicarboxylate (DEAD) as the amine source. The initially formed a-aminated aldehyde was reduced in situ to the corresponding Naminooxazolidinone, which was obtained in moderate to high yield in up to 87% ee.Keywords: asymmetric catalysis; diamines; organic catalysis; pyrrolidines; sulfonamides Asymmetric organocatalysis, using simple enantiomerically pure amino acid catalysts, has emerged as a powerful tool and alternative to organic processes typically catalyzed by either chiral metal complexes or enzymes and other biocatalysts. In particular, the use of proline (1) as the organocatalyst has been highly successful in asymmetric organic transformations involving enamine chemistry. [1,2] Currently there are an extensive number of reports on reactions catalyzed by proline, and the common theme in most of the cases is processes showing high reactivity and stereoselectivity. However, the rather poor solubility of proline in many solvents has resulted in the use of sub-stoichiometric amounts of the catalyst, often up to 30 mol %, which effectively reduce the turnover number. This drawback has emphasized the need for further development of novel organocatalysts with better solubility properties. [3] We envisioned the use of mono-N-sulfonyl derivatives of chiral diamines to be proper alternatives to proline. Such compounds, here exemplified by 2, can easily be reached by a few simple transformations starting from proline. Although compound 2 is a diamine, it fulfils all the criteria necessary to work as an organocatalyst in reactions where proline normally is used. The secondary amine allows for a reversible formation of the enamine intermediate present in proline-catalyzed reactions, and the sulfonyl group on the primary amine would effectively increase its acidity to facilitate required proton transfers. Furthermore, significantly better solubility properties can be expected by choosing a proper R group on the sulfonyl moiety. In fact, both acidity and solubility can be finetuned by varying the R group and hence a modular catalyst system can be obtained.In addition, to be potentially useful as an organocatalyst the mono-sulfonyl diamine 2 can be expected to serve as a ligand for transition metal catalysts. Ruthenium complexes based on similar mono-sulfonyldiamines, e.g., TsDPEN (3), have been shown to be powerful and selective catalysts in asymmetric reduction of ketones under transfer-hydrogenation conditions. [4,5] We have previously developed dipeptide-like ligands based on amino acids and amino alcohols for this particular process and, based on our results using these catalysts, [6] along with the successful catalysts developed by Noyori and co-workers, [5] we envisioned ligand 2 to be of potential use.Herein we present the preparation of a novel class of pyrr...

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Enantioselective syntheses O 0031 Novel Organic Catalysts for the Direct Enantioselective α-Oxidation of Carbonyl Compounds. -Proline-derived catalysts (I) are investigated in the reaction of cyclohexanone with nitrobenzene. The derivative (Ia) is used for further transformations. The formation of by-products of type (V) can be avoided by slow addition of the electrophile to the reaction mixture. -(SUNDEN, H.; DAHLIN, N.; IBRAHEM, I.; ADOLFSSON*, H.; CORDOVA, A.; Tetrahedron Lett. 46 (2005) 19, 3385-3389; Dep. Org. Chem., Arrhenius Lab., Univ. Stockholm, S-106 91 Stockholm, Swed.; Eng.) -Mais 36-032