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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. ) 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. ) a method for the direct oxidative methoxylation of 3 to 4.

Tomohiko Ohwada of the University of Tokyo used (Chem. Commun. 2017, 53, 1482. ) 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. ) 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. ) 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. ) 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. ) the trisubstituted benzene 18 by coupling 16 with the allyl silane 17. Many methods have been developed (J. Org. Chem. 2000, 65, 254. ) for the preparation of unsymmetrical benzophenones. Mamoru Tobisu and Naoto Chatani of Osaka University established (J. Am. Chem. Soc. 2017, 139, 1416. ) 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. ) 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. ) 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. ) that the nitrile 24 could be prepared from the acyl imide 23. Professor Rueping prepared (Org. Lett. 2017, 19, 3091. ) aryl alkynes (not illustrated) from such acyl imides.

Sangho Koo of Myongji University observed (Tetrahedron Lett. 2017, 58, 2264. ) 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. ) 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. ) by D. Srinivasa Reddy of the National Chemical Laboratory.

D. F. Taber, Org. Chem. Highlights 2017, October 9.
URL: http://www.organic-chemistry.org/Highlights/2017/09October.shtm