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Monday, October 9, 2017
Douglass F. Taber
University of Delaware

Substituted Benzenes: The Reddy Synthesis of Fregenedadiol

C. Rikard Unelius of Linnaeus University used (Eur. J. Org. Chem. 2017, 3234. DOI: 10.1002/ejoc.201700173) trifluoroacetic acid as the solvent for the direct iodination of 1 to 2. Bin Chen and Chen-Ho Tung of the Technical Institute of Physics and Chemistry developed (Org. Lett. 2017, 19, 2206. DOI: 10.1021/acs.orglett.7b00463) a method for the direct oxidative methoxylation of 3 to 4.

Tomohiko Ohwada of the University of Tokyo used (Chem. Commun. 2017, 53, 1482. DOI: 10.1039/C6CC09618B) triflic acid as the solvent for the phosphate-mediated Friedel-Crafts acylation of 5 with 6 to give 7. Yoshiaki Nakao of Kyoto University devised (Org. Lett. 2017, 19, 584. DOI: 10.1021/acs.orglett.6b03741) a catalyst combination that mediated the addition of 8 to the unactivated alkene 9 to give 10.

Magnus Rueping of RWTH Aachen prepared (Org. Lett. 2017, 19, 1788. DOI: 10.1021/acs.orglett.7b00556) the amine 13 by coupling the imine 12 with the sulfamate 11. Motoki Ito and Shigeo Sugiyama of Meiji Pharmaceutical University oxidized (Eur. J. Org. Chem. 2017, 1272. DOI: 10.1002/ejoc.201601627) the aniline derivative 14 to the versatile diazonium salt surrogate 15.

Ming Bao of the Dalian University of Technology assembled (J. Org. Chem. 2017, 82, 5974. DOI: 10.1021/acs.joc.7b00678) the trisubstituted benzene 18 by coupling 16 with the allyl silane 17. Many methods have been developed (J. Org. Chem. 2000, 65, 254. DOI: 10.1021/jo991055q) for the preparation of unsymmetrical benzophenones. Mamoru Tobisu and Naoto Chatani of Osaka University established (J. Am. Chem. Soc. 2017, 139, 1416. DOI: 10.1021/jacs.6b12293) conditions for the conversion of the benzophenone 19 to the biphenyl 20.

Several strategies have been put forward recently for replacing the carboxylate of a benzoic acid with a different functional group. Professor Rueping found (Angew. Chem. Int. Ed. 2017, 56, 4282. DOI: 10.1002/anie.201611819) that the phenyl ester 21 could be coupled with 12 to give the aniline 22. Takashi Niwa and Takamitsu Hosoya of RIKEN devised (Angew. Chem. Int. Ed. 2017, 56, 2482. DOI: 10.1002/anie.201611974) a related protocol (not illustrated) for converting an arene carboxylate to the aryl boronic acid. Michal Szostak of Rutgers University, Newark showed (Org. Lett. 2017, 19, 3095. DOI: 10.1021/acs.orglett.7b01199) that the nitrile 24 could be prepared from the acyl imide 23. Professor Rueping prepared (Org. Lett. 2017, 19, 3091. DOI: 10.1021/acs.orglett.7b01194) aryl alkynes (not illustrated) from such acyl imides.

Sangho Koo of Myongji University observed (Tetrahedron Lett. 2017, 58, 2264. DOI: 10.1016/j.tetlet.2017.04.090) that NBS could efficiently oxidize the enone 25 to the phenol 26. James W. Herndon of New Mexico State University coupled (Tetrahedron Lett. 2017, 58, 1403. DOI: 10.1016/j.tetlet.2017.02.010) the Fischer carbene 28 with the hydrazone 27 to give an intermediate that added to the diester 29, leading to 30.

Fregenedadiol (33) is a labdane isolated from the rockrose Halimium viscosum. Diels-Alder cycloaddition of 31 with the diester 29 to give 32 was the key reaction in the synthesis of 33 described (Tetrahedron Lett. 2017, 58, 1262. DOI: 10.1016/j.tetlet.2017.02.010) by D. Srinivasa Reddy of the National Chemical Laboratory.

D. F. Taber, Org. Chem. Highlights 2017, October 9.