Reduction of Organic Functional Groups
Shuhua Li and Xu Cheng of Nanjing University showed (Chem. Eur. J. 2016, 22, 9546. DOI: 10.1002/chem.201601819) that the Hantzsch ester 2 served as a photocatalyst for the reduction of the dibromide 1 to the alkene 3. Johannes F. Teichert of the Technische Universitšt Berlin prepared (Org. Biomol. Chem. 2016, 14, 10660. DOI: 10.1039/C6OB02271E) an air-stable Cu complex that catalyzed the hydrogenation of 4 to 5. Robert F. Standaert of the Oak Ridge National Laboratory reduced (J. Org. Chem. 2016, 81, 9957. DOI: 10.1021/acs.joc.6b01699) the phosphate ester derived from 6 to the hydrocarbon 7. Phosphates of primary alcohols could be reduced selectively in the presence of phosphates of secondary alcohols. Zhenyan Lin and Rongbiao Tong of the Hong Kong University of Science and Technology selectively deoxygenated (Org. Lett. 2016, 18, 4734. DOI: 10.1021/acs.orglett.6b02405) the bis epoxide 8 with the carbene derived from 9 to give the monoepoxide 10.
Several methods for the selective reduction of halides have been put forward. Chriss E. McDonald of Lycoming College found (J. Org. Chem. 2016, 81, 5903. DOI: 10.1021/acs.joc.6b00733) that with the Li salt of triethylurea as an additive, the dihalide 11 could be reduced to 12. Craig J. Hawker and Javier Read de Alaniz of the University of California, Santa Barbara developed (J. Org. Chem. 2016, 81, 7155. DOI: 10.1021/acs.joc.6b01034) an organocatalyst that mediated the selective photochemically-driven reduction of 13 to 14. On extending the reaction time, the bromide of 14 was selectively removed. Corey R. J. Stephenson of the University of Michigan also used irradiation (ACS Catal. 2016, 6, 5962. DOI: 10.1021/acscatal.6b01914) to drive the reduction of 15 to 16. Philippe Renaud of the University of Bern observed (Angew. Chem. Int. Ed. 2016, 55, 11221. DOI: 10.1002/anie.201604950) that a catechol could serve as the H-atom donor in the reduction of 17 to 18.
Sharanappa Nembenna of the National Institute of Science Education and Research (NISER) prepared (Org. Lett. 2016, 18, 4710. DOI: 10.1021/acs.orglett.6b02310) an Al catalyst that mediated the selective reduction of 19 to alcohol 20. Duk Keun An of Kangwon National University observed (Tetrahedron Lett. 2016, 57, 3247. DOI: 10.1016/j.tetlet.2016.05.100) that the simple combination of Red-Al with HMDS reduced aldehydes and ketones, including the conversion of 21 to 22, but did not reduce other common organic functional groups. Jun Okuda of RWTH Aachen devised (Angew. Chem. Int. Ed. 2016, 55, 13326. DOI: 10.1002/anie.201605236) a reagent combination that effected the complementary reduction of the amide of 23 in the presence of the ketone. Bing-Tao Guan of Nankai University achieved (Chem. Commun. 2016, 52, 10894. DOI: 10.1039/C6CC04531F) the remarkable reduction of the quaternary ammonium salt 25 to 26.
Robert R. Knowles of Princeton University established (J. Am. Chem. Soc. 2016, 138, 10794. DOI: 10.1021/jacs.6b06517) a protocol for C-C bond cleavage, converting the tertiary alcohol 27 to 28. Professor Okuda reduced (Chem. Commun. 2016, 52, 13155. DOI: 10.1039/C6CC06805G) pyridine 29 to the dihydropyridine 30. If this reduction works as well for substituted pyridines, it will be a valuable transformation.