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Monday, January 23, 2023
Douglass F. Taber
University of Delaware

Reactions of Alkenes: The Chida Synthesis of Paclitaxel (Taxol®)

Alison E. Wendlandt of MIT devised a protocol for the contrathermodynamic isomerization of the alkene 1 to the alkene 2 (J. Am. Chem. Soc. 2022, 144, 145. ). Robert R. Knowles of Princeton University (J. Am. Chem. Soc. 2022, 144, 137. ) and John F. Hartwig of the University of California, Berkeley (Org. Lett. 2022, 24, 1005. ) described parallel investigations. Wei Shu of the Southern University of Science and Technology reported that the thianthrenium salt 3, readily prepared from the corresponding alkene, could be converted into the allylic benzoate 4 (Chem. Sci. 2022, 13, 1003. ). Qiang Liu and Can-Cheng Guo of Hunan University showed that the terminal alkene 5 could be methylated with dimethyl sulfoxide, leading to the alkene 6 (J. Org. Chem. 2022, 87, 7022. ). Søren Kramer of the Technical University of Denmark and Ruben Martin of ICIQ coupled the alkene 7 with the secondary bromide 8 to give 9 (ACS Catal. 2022, 12, 3815. ).

Feng-Lian Zhang, Yao Fu, and Yi-Feng Wang of the University of Science and Technology of China assembled the amide 12 by combining the alkene 10 with the amide 11 (Angew. Chem. Int. Ed. 2022, 61, e202201329. ). Nuno Maulide of the University of Vienna added the aminal 14 to the alkene 13, leading to the α-amino ester 15 (Angew. Chem. Int. Ed. 2022, 61, e202115435. ). Mathieu Pucheault of the University of Bordeaux showed than an amine-borane complex was a practical radical initiator for the addition of bromotrichloromethane to the alkene 16 to give the bromide 17 (Chem. Commun. 2022, 58, 2124. ). Luca Dell'Amico of the University of Padova and Giacomo Filippini of the University of Trieste used a photocatalyst to assemble the iodosulfone 20 by the addition of the iodosulfone 19 to the alkene 18 (ACS Catal. 2022, 12, 4290. ).

Zheng-Wang Qu of the Rheinische Friedrich-Wilhelms-Universität Bonn and Martin Oestreich of the Technische Universität Berlin used a silylium ion to mediate the addition of the components of the silyl alkyne 22 to the alkene 21, leading to 23 (Angew. Chem. Int. Ed. 2022, 61, e202203347. ). Steven T. Diver of the University of Buffalo effected cross metathesis of the alkene 18 with the alkyne 24, followed by borylation of the resulting diene, leading to the boronate 25 (ACS Catal. 2022, 12, 6434. ). Xianqiang Kong and Xiaohui Chen of the Changzhou Institute of Technology and Zhong-Yan Cao of Hunan University assembled the nitrile 28 by electrolyzing the alkene 18, the cyanobenziodooxolone 26, and the α-keto acid 27 (J. Org. Chem. 2022, 87, 7013. ). Pinhong Chen and Guosheng Liu of the Shanghai Institute of Organic Chemistry used the alkynyl benziodooxolone 29 to convert the alkene 10 to the ester 30 (Chem. Commun. 2022, 58, 2544. ).

Paclitaxel (Taxol®) 33 is widely used clinically as an anti-cancer agent. In the course of a synthesis of 33, Noritaka Chida of Keio University showed that DMDO was particularly selective in the epoxidation of the bis enol ether derived from 31, leading to the diol 32 (Org. Lett. 2022, 24, 202. ). For a practical preparation of DMDO, see Org. Synth. 2013, 90, 350. ()

D. F. Taber, Org. Chem. Highlights 2023, January 23.