Reduction: The Huang/Yang Synthesis of Waihoensene
Geoffrey W. Coates of Cornell University developed a Mn/Al catalyst to effect the deoxygenation of the epoxide 1 to the alkene 2 with inversion of stereochemistry (J. Am. Chem. Soc. 2020, 142, 8029. ). Qiang Liu of Tsinghua University devised conditions for the migration and reduction of the alkyne 3 to the internal alkene 4 (Angew. Chem. Int. Ed. 2020, 59, 6750. ). Jian-Ping Qu of Nanjing Technical University and Yan-Biao Kang of the University of Science and Technology effected the reduction of the fluoroarene 5 to 6 (Org. Lett. 2020, 22, 3084. ). Takuji Kawamoto of Yamaguchi University used 8 to reduce the nitrile 7 to 9 (J. Org. Chem. 2020, 85, 6137. ).
Krzysztof Kuciński and Grzegorz Hreczycho of the Adam Mickiewicz University in Poznań showed that KF catalyzed the reduction of the ketone 10 to the alcohol 11 (Eur. J. Org. Chem. 2020, 552. ). Mengtao Ma of Nanjing Forestry University reported related results with catalytic Grignard reagents (Tetrahedron 2020, 76, 131145. ). Robert A. Flowers II of Lehigh University and Andreas Gansäuer of the Universität Bonn found that the Ti-catalyzed reduction of 12 to 13 could, under irradiation by visible light, be mediated by excess amine (Angew. Chem. Int. Ed. 2020, 59, 9355. ). Masahisa Nakada of Waseda University prepared 15 by trapping the enolate generated by the reduction of 14 (J. Am. Chem. Soc. 2020, 142, 5556. ). Yang Chen of Chengdu University showed that a Cu catalyst could promote the reduction of the azide 16 to 17 (Tetrahedron Lett. 2020, 61, 151702. ).
Michael G. Kallitsakis and Ioannis N. Lykakis of the Aristotle University of Thessaloniki used ultraviolet light to promote the reduction of the nitroarene 18 with methylhydrazine 19, to give the hydroxylamine 20 (Org. Lett. 2020, 22, 4339. ). Davit Hayrapetyan and Andrey Y. Khalimon of Nazarbayev University assembled the imine 23 by reducing the nitrile 21, then adding the aldehyde 22 (Chem. Eur. J. 2020, 26, 4963. ). Sharanappa Nembenna of NISER (J. Org. Chem. 2020, 85, 4999. ) and Axel Jacobi von Wangelin of the University of Hamburg (Org. Chem. Front. 2020, 7, 960. ) also described the catalyzed HBPin reduction of nitriles.
Eunsung Lee, Young Ho Rhee and Jaiwook Park of POSTECH observed that irradiation in the presence of a Ru catalyst cleaved the azido alcohol 24 to an intermediate aldehyde imine. This was reduced with NaBH4 to the amino alcohol 25 (Org. Lett. 2020, 22, 4608. ).
In the course of a synthesis of waihoensene 28, Jun Huang and Zhen Yang of Peking University Shenzhen Graduate School achieved high diastereoselectivity in the reduction of 26 to 27 (J. Am. Chem. Soc. 2020, 142, 6511. ). Deuterium labelling showed that the reaction proceeded by intramolecular H atom transfer. Reduction of the ketal led to the opposite diastereomer.