Substituted Benzenes: The Tang Synthesis of Corynoline

Xiaochuan Chen and Yuanhua Wang of Sichuan University used the reagent 2 to prepare the azide 3 from 1 (Org. Lett. 2018, 20, 5732. DOI: 10.1021/acs.orglett.8b02446). Jerome Waser of the Ecole Polytechnique Fédérale de Lausanne reported a safer reagent (J. Org. Chem. 2018, 83, 12334. DOI: 10.1021/acs.joc.8b02068). Shaolin Zhu of Central China Normal University coupled 5 with 4 to give 6 (Org. Lett. 2018, 20, 7753. DOI: 10.1021/acs.orglett.8b03089).

Tobias Ritter of the Max-Planck-Institut für Kohlenforschung devised a protocol based on 8 for methylating benzene rings, converting 7 to 9 (Angew. Chem. Int. Ed. 2018, 57, 10697. DOI: 10.1002/anie.201804628). Rafał Loska of the Polish Academy of Sciences combined vicarious nucleophilic substitution with the Julia-Kocienski reaction, using 11 as a linchpin to combine 10 with 12 to give 13 (Eur. J. Org. Chem. 2018, 6649. DOI: 10.1002/ejoc.201801018).

Xueqiang Wang and Wanxiang Zhao of Hunan University found that a cyano group was sufficiently activating to enable the displacement of the methyl ether of 14 with 15, leading to 16 (Org. Lett. 2018, 20, 4267. DOI: 10.1021/acs.orglett.8b01696). Emmanuel Gras of the Université de Toulouse and David M. Perrin of the University of British Columbia showed that an organotrifluoroborate 18 could serve as the fluoride source for the Balz-Schiemann conversion of 17 to 19 (Chem. Eur. J. 2018, 24, 14933. DOI: 10.1002/chem.201803575). Jinbo Hu of the Shanghai Institute of Organic Chemistry described a complementary protocol using hypervalent iodine catalysis (Angew. Chem. Int. Ed. 2018, 57, 9896. DOI: 10.1002/anie.201802466).

Xiaojin Wu of Nanjing Tech University and Teck-Peng Loh of Nanyang Technological University used the 8-aminoquinoline amide of 20 to direct the reductive Heck coupling with phenyl triflate 21, leading to 22 (J. Am. Chem. Soc. 2018, 140, 9332. DOI: 10.1021/jacs.8b03619). Markus R. Heinrich of the Friedrich-Alexander-Universität Erlangen-Nürnberg found that freezing the aqueous solution of the diazonium salt 24 allowed slow addition to the reaction with 23 to give 25 (Tetrahedron 2018, 74, 5289. DOI: 10.1016/j.tet.2018.05.089).

In an application of the Catellani strategy, Qiuping Ding of Jiangxi Normal University used the norbornene 28 to mediate the preparation of 29 by the coupling of 27 with 26 (J. Org. Chem. 2018, 83, 13211. DOI: 10.1021/acs.joc.8b01933). Itaru Nakamura of Tohoku University devised conditions for the rearrangement of 30 to 31 (J. Am. Chem. Soc. 2018, 140, 8629. DOI: 10.1021/jacs.8b03669).

Ramendra Pratap of University of Delhi assembled the substituted benzene 34 by the addition of allyl cyanide 33 to the 2H-pyran-2-one 32 (Org. Biomol. Chem. 2018, 16, 5465. DOI: 10.1039/C8OB01270A). Professor Loh and Jie-Sheng Tian, also of Nanjing Tech University, prepared 37 by combining 35 with 36 (Org. Lett. 2018, 20, 3975. DOI: 10.1021/acs.orglett.8b01540).

Corynoline (41) is an antiinflammatory acetylcholinesterase inhibitor isolated from the East Asian herb Corydalis incisa. En route to 41, Wenjun Tang, also of the Shanghai Institute of Organic Chemistry, achieved high ee in the arylation of 38 with 39 to give 40 (Angew. Chem. Int. Ed. 2018, 57, 12328. DOI: 10.1002/anie.201807302).