Reduction: The Kobayashi Synthesis of Bromlaurenidificin
Robert G. Bergman, Kenneth N. Raymond and F. Dean Toste of the University of California, Berkeley used a supramolecular Rh catalyst to reduce sorbyl alcohol 1 selectively to leaf alcohol 2 (J. Am. Chem. Soc. 2019, 141, 11806. ). Johannes F. Teichert of the Technische Universitšt Berlin showed that an alcohol could be used in the presence of a Cu catalyst to reduce the alkyne 3 to the Z-alkene 4 (Chem. Commun. 2019, 55, 13410. ). Yuanhong Liu of the Shanghai Institute of Organic Chemistry found that even water with stoichiometric Zn and a Ni catalyst could reduce 3 to the alkane 5 (Org. Chem. Front. 2019, 6, 2619. ). Tomohiro Iwai and Masaya Sawamura of Hokkaido University reported a parallel investigation (Org. Lett. 2019, 21, 5867. ). Lung Wa Chung of the Southern University of Science and Technology and Jianwei Sun of the Hong Kong University of Science and Techology described the reductive rearrangement of 6 to 7 (J. Am. Chem. Soc. 2019, 141, 17441. ).
Using water (in this case D2O) and stoichiometric Zn, Professor Liu selectively reduced the dibromide 8 to the monobromide 9 (J. Org. Chem. 2019, 84, 13841. ). Lifu Ma of Tianjin University and Jie An of China Agricultural University devised conditions for the reductive removal of the cyano group of 10, leading to 11 (J. Org. Chem. 2019, 84, 15827. ). Dmitry Tsvelikhovsky of the Hebrew University of Jerusalem used proline to reduce 12 to 13 (Chem. Sci. 2019, 10, 9345. ). In the course of the reduction of 14, Mariola Tortosa if the Universidad Autůnoma de Madrid also set the geometry of the resulting alkene 15 (ACS Catal. 2019, 9, 6583. ).
Yuta Nishina of Okayama University used nitrogen-doped reduced graphene oxide as a catalyst for the selective hydrogenation of 16 to 17 (Org. Lett. 2019, 21, 8164. ). Yong Yang of the Qingdao Institute of Bioenergy and Bioprocess Technology showed that in the presence of methanol, the nitroarene 18 could be reduced to the N-methyl amine 19 (Org. Chem. Front. 2019, 6, 2726. ). Paul C. J. Kamer of the University of St. Andrews found that in flow, a Ru catalyst would reduce the nitrile 20 to the amine 21 (Chem. Sci. 2019, 10, 8195. ). By carrying out the reduction in the presence of aniline 23, Benudhar Punji of CSIR-National Chemical Laboratory was able to convert the nitrile 22 to the N-phenyl amine 24 (Adv. Synth. Catal. 2019, 361, 3930. ).
The textbook reduction of an ester 25 to the aldehyde 26 works best in the presence of electron-withdrawing substituents. Shoji Kobayashi of the Osaka Institute of Technology took advantage of this, and carried 26 on to bromlaurenidificin 27 (J. Org. Chem. 2019, 84, 15549. ).