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Monday, March 20, 2023
Douglass F. Taber
University of Delaware

Reduction: The Odagi/Nagasawa Synthesis of Cepharatine A

Ai-Lan Lee of Heriot-Watt University developed a protocol for the decarboxylation of the carboxylic acid 1 to the hydride 2 (Org. Lett. 2022, 24, 686. ). Joseph R. Clark of Marquette University reduced the alkene 3 to the monodeuterated 4 (Chem. Eur. J. 2022, 28, e202104340. ). Qing-An Chen of the Dalian Institute of Chemical Physics decarbonylated the α,β-unsaturated aldehyde 5 to the monodeuterated alkene 6 (J. Am. Chem. Soc. 2022, 144, 11081. ). Guangbin Dong of the University of Chicago showed that it was possible to cleave a methyl ketone 7 to leave the mono-, di-, or, as illustrated, trideuterated hydrocarbon 8 (J. Am. Chem. Soc. 2022, 144, 9570. ).

Andreas Gansäuer of the Universität Bonn reduced the epoxide 9 to the monodeuterated alcohol 10 (Angew. Chem. Int. Ed. 2022, 61, e202114198. ). Xiaotian Qi and Qingquan Lu of Wuhan University used electrolysis to reduce the pinene-derived epoxide 11 to the secondary alcohol 12 (J. Am. Chem. Soc. 2022, 144, 1389. ).

Wanfang Li of the University of Shanghai for Science and Technology reduced the nitroalkene 13 in the presence of the N-acyl benzotriazole 14, to give directly the enamide 15 (Org. Lett. 2022, 24, 58. ). Davit Hayrapetyan and Andrey Y. Khalimon of Nazarbayev University showed that the intermediate from the Co-catalyzed reduction of the nitro alkane 16 could be condensed with an aldehyde, leading to the imine 17 that could be reduced to the secondary amine (Adv. Synth. Catal. 2022, 364, 601. ). Pavel Kočovsky of Charles University devised mild conditions for the reductive amination of the aldehyde 18 with allylamine 19 to give the N-allyl amine 20 (J. Org. Chem. 2022, 87, 920. ). Shū Kobayashi of the University of Tokyo developed a flow protocol for the intial diastereoselective reductive amination of the ketone 21 with the enantiomerically-pure secondary amine 22, followed by reductive debenzylation, to give the enantio-enriched product amine 23 directly (Angew. Chem. Int. Ed. 2022, 61, e202115643. ).

Tomoo Mizugaki of Osaka University optimized a Pt/Mo/ZrO2 catalyst for the reduction of an ester 24 to the ether 25 (JACS Au 2022, 2, 665. ). Even in the presence of two alkenes, Rongbiao Tong of the Hong Kong University of Science and Technology was able to reduce the cyclopropyl ketone 26 with Na/naphthalene and trap the resulting enolate as the enol triflate 27 (Angew. Chem. Int. Ed. 2022, 61, e202115384. ).

Cepharatine A (30), isolated from the Chinese vine Stephania cepharantha, showed bacteriostatic activity. En route to 30, Minami Odagi and Kazuo Nagasawa of the Tokyo University of Agriculture and Technology were able to reductively remove the bromide of 28 to give 29, without interference by the two readily-reduced alkenes (J. Org. Chem. 2022, 87, 1065. ).

D. F. Taber, Org. Chem. Highlights 2023, March 20.