Functional Group Oxidation: The Xie Synthesis of Tochuinyl Acetate
Claude Spino of the Université de Sherbrooke showed (Heterocycles 2017, 95, 894. DOI: 10.3987/COM-16-S(S)58) that the sulfoxide derived from 1 could be eliminated to the alkene 2 at reflux temperature in toluene. Tao Yang and Congshan Zhou of the Hunan Institute of Science and Technology converted (Synlett 2017, 28, 1079. DOI: 10.1055/s-0036-1588948) the acid 3 to the nitro alkene 4. Ryo Yazaki and Takashi Ohshima of Kyushu University used (Org. Lett. 2017, 19, 3187. DOI: 10.1021/acs.orglett.7b01293) TEMPO to effect α-hydroxylation of 5, leading to 6. Gui-Fa Su and Dong-Liang Mo of Guangxi Normal University demonstrated (Org. Biomol. Chem. 2016, 14, 6795. DOI: 10.1039/C6OB01203E) that the oxidation of 7 to 8 proceeded via the intermediate alkene.
Akira Yoshimura and Viktor K. Zhdankin of the University of Minnesota Duluth employed (Chem. Eur. J. 2017, 23, 691. DOI: 10.1002/chem.201604475) 10 to oxidize the amide 9 to the carbamate 11. Masayuki Wasa of Boston College devised (J. Am. Chem. Soc. 2017, 139, 95. DOI: 10.1021/jacs.6b11908) a catalyst system that mediated the addition of 12 to 13 to give 14.
Mahiuddin Baidya of the Indian Institute of Technology Madras established (Org. Lett. 2017, 19, 516. DOI: 10.1021/acs.orglett.6b03686) oxidative conditions for the combination of the silyl enol ether 15 with the aniline 16 to give the protected hydroxylamine 17. Jian-Ping Qu of Nanjing Tech University and Yan-Biao Kang of the University of Science and Technology of China directly oxidized (ACS Catal. 2017, 7, 4000. DOI: 10.1021/acscatal.7b01008) the aldehyde 18 to the unsaturated aldehyde 19.
Guangbin Dong of the University of Chicago developed (J. Am. Chem. Soc. 2017, 139, 7757. DOI: 10.1021/jacs.7b04722) conditions for the oxidation of the lactam 20 to the unsaturated lactam 21. Fanhao Meng of China Medical University optimized (Synlett 2017, 28, 386. DOI: 10.1055/s-0036-1588905) the Curtius oxidation of the unsaturated acid 22 to the ketone 23. Alexander O. Terent'ev of the N. D. Zelnisky Institute of Organic Chemistry brominated (Tetrahedron Lett. 2017, 58, 352. DOI: 10.1016/j.tetlet.2016.12.036) the aldehyde 24 to give an intermediate that could be quenched with methanol to give the ester 25. Note that aldehydes are readily monobrominated with the dioxane.Br2 complex. Sayam Sen Gupta of the National Chemical Laboratory effected (Org. Lett. 2017, 19, 746. DOI: 10.1021/acs.orglett.6b03359) the direct oxidation of the cyclic ether 26 to the lactone 27.
The stereocontrolled construction of adjacent cyclic alkylated quaternary centers is a challenging task. En route to tochuinyl acetate (30), Weiqing Xie of Northwest A&F University showed (Angew. Chem. Int. Ed. 2017, 56, 350. DOI: 10.1002/anie.201609975) that on oxidation, enantiomerically-enriched and diastereomerically-pure 28 was converted cleanly to 29.