Reductions

Abstract

Manfred T. Reetz at the Max-Planck-Institut Mülheim and Philipps-Universität Marburg developed (J. Am. Chem. Soc. 2013, 135, 1665) a mutated Thermoethanolicus brockii alcohol dehydrogenase for the enantioselective reduc­tion of 4-alkylidene cyclohexanone 1. Using a new C₂-symmetic chiral bisphos­phine ligand (Wingphos, 5), Wenjun Tang at the Shanghai Institute of Organic Chemistry reported (Angew. Chem. Int. Ed. 2013, 52, 4235) the rhodium-catalyzed asymmetric hydrogenation of β-aryl enamide 3. Qi-Lin Zhou of Nankai University utilized chiral spirophosphine oxazoline iridium complexes 8a and 8b for the asymmetric hydrogenation of unsaturated piperidine carboxylic acid 6 (Angew. Chem. Int. Ed. 2013, 52, 6072) and 1,1-diarylethylene 9 (Angew. Chem. Int. Ed. 2013, 52, 1556) with excellent selectivities. The iron- catalyzed chemoselective hydrogenation of α,β-unsaturated aldehyde 11 was demonstrated (Angew. Chem. Int. Ed. 2013, 52, 5120) by Matthias Beller at the University of Rostock. Jeffrey S. Johnson at the University of North Carolina at Chapel Hill showed (J. Am. Chem. Soc. 2013, 135, 594) that asymmetric trans­fer hydrogenation of racemic acyl phosphonate 14 yielded β-stereogenic α- hydroxy phosphonate 16, a reversal in diastereoselectivity observed in the case of α-keto ester analogues. Gojko Lalic of the University of Washington developed (Org. Lett. 2013, 15, 1112) a monophasic copper catalyst system for the selective semireduction of terminal alkyne 17. Alois Fürstner and coworkers at Max-Planck-Institut Mülheim reported (Angew. Chem. Int. Ed. 2013, 52, 355) the ruthenium-catalyzed trans- selective hydro­genation of alkyne 19. Macrocyclic alkynes could also be selectively hydrogenated to E- alkenes using this methodology. Bernhard Breit at the University of Freiburg found (Angew. Chem. Int. Ed. 2013, 52, 2231) that a bimetallic Pd/ Re/ graphite catalyst system was highly active for the hydrogenation of tertiary amide 21 to amine 22. Professor Beller also discovered (Chem. Eur. J. 2013, 19, 4437) that a commercially available ruthenium complex allowed for the effective transfer hydrogenation of aromatic nitrile 23 to benzyl amine 24. Notably, no reductive amination side products were observed. Maurice Brookhart at the University of North Carolina at Chapel Hill used (Org. Lett. 2013, 15, 496) tris(pentafluorophenyl)borane as a highly active catalyst for the selective reduction of carboxylic acid 25 to aldehyde 26 with triethylsilane as a hydride source.