A General Catalytic Enantioselective Transfer Hydrogenation Reaction of beta,beta-Disubstituted Nitroalkenes Promoted by a Simple Organocatalyst

作者：Bernardi Luca^*; Fochi Mariafrancesca

来源：Molecules, 2016, 21(8): 1000.

DOI：10.3390/molecules21081000

• asymmetric catalysis
• Hantzsch ester
• H-bond
• nitroalkanes
• nitroalkenes
• organocatalysis
• reduction
• thiourea
• transfer hydrogenation

Given its synthetic relevance, the catalytic enantioselective reduction of beta,beta-disubstituted nitroalkenes has received a great deal of attention. Several bio-, metal-, and organo-catalytic methods have been developed, which however are usually applicable to single classes of nitroalkene substrates. In this paper, we present an account of our previous work on this transformation, which implemented with new disclosures and mechanistic insights results in a very general protocol for nitroalkene reductions. The proposed methodology is characterized by (i) a remarkably broad scope encompassing various nitroalkene classes; (ii) Hantzsch esters as convenient (on a preparative scale) hydrogen surrogates; (iii) a simple and commercially available thiourea as catalyst; (iv) user-friendly procedures. Overall, the proposed protocol gives a practical dimension to the catalytic enantioselective reduction of beta, beta-disubstituted nitroalkenes, offering a useful and general platform for the preparation of nitroalkanes bearing a stereogenic center at the beta-position in a highly enantioenriched form. A transition state model derived from control kinetic experiments combined with literature data is proposed and discussed. This model accounts and justifies the observed experimental results.

• 出版日期2016-8