Oxidation in Organic Synthesis: The Banwell Synthesis of Neocosmosin A
K. A. Woerpel of New York University oxidized (Org. Lett. 2015, 17, 2704. DOI: 10.1021/acs.orglett.5b01120) the alkynyl alkene 1 in the presence of N-OH phthalimide 2 to give the α-alkoxy ketone 3. Xiang-Qiang Pan and Jian-Ping Zou of Soochow University prepared (J. Org. Chem. 2015, 80, 5348. DOI: 10.1021/acs.joc.5b00641) the α-phenylthio aldehyde 5 by adding thiophenol to the terminal alkyne 4 in the presence of t-BuO2H. Timothy R. Newhouse of Yale University developed (J. Am. Chem. Soc. 2015, 137, 5875. DOI: 10.1021/jacs.5b02243) a reagent combination that introduced a double bond adjacent to an ester or a nitrile, converting 6 into 8. Liming Zhang of the University of California, Santa Barbara rearranged (Tetrahedron Lett. 2015, 56, 3144. DOI: 10.1016/j.tetlet.2014.11.138) the propargylic sulfoxide 9 to the thioester 10.
Dirk E. De Vos of the University of Leuven effected (Chem. Commun. 2015, 51, 6528. DOI: 10.1039/C5CC00181A) the oxidative decarboxylation of the α-amino acid 11 to the nitrile 12. Bhisma K. Patel of the Indian Institute of Technology, Guwahati oxidized (J. Org. Chem. 2015, 80, 3440. DOI: 10.1021/jo502903d) the benzylic amine 13 to the bis acyl acetal 15. Yoshinari Sawama and Hironao Sajiki of Gifu Pharmaceutical University found (Adv. Synth. Catal. 2015, 357, 1205. DOI: 10.1002/adsc.201401123) that under reduced pressure to promote H2 release, an alcohol 16 could be oxidized to the acid 17. Wiktor Kasprzyk of the Cracow University of Technology used (Synlett 2014, 25, 2757. DOI: 10.1055/s-0034-1379211) a Zn catalyst to selectively oxidize the diol 18 to the ketone 19.
Jean-Philip Lumb and Bruce A. Arndtsen of McGill University devised (Angew. Chem. Int. Ed. 2015, 54, 4208. DOI: 10.1002/anie.201411483) oxidative conditions mild enough that 20 could be converted to 21 with maintenance of alkene geometry. Zhenlu Shen and Xinquan Hu of the Zhejiang University of Technology oxidized (Tetrahedron Lett. 2015, 56, 2768. DOI: 10.1016/j.tetlet.2015.04.033) the ether 22 to the aldehyde 23. Prasanta Ghorai of the Indian Institute of Science Education and Research, Bhopal, developed (Org. Lett. 2015, 17, 1393. DOI: 10.1021/acs.orglett.5b00190) what appears to be a general procedure for preparing a t-butyl ester 25 from the aldehyde 24. Lei Yu of Yangzhou University and Qing Xu of Wenzhou University used (Adv. Synth. Catal. 2015, 357, 955. DOI: 10.1002/adsc.201400957) the diselenide 27 to catalyze the Baeyer-Villiger oxidation of 26 to 28.
Neocosmosin A (31) is representative of the resorcylic acid lactones isolated from the fungus Neocosmospora sp., some of which display good in vitro binding affinity for human opiod and cannabinoid receptors. In the course of a synthesis of 31, Martin G. Banwell of the Australia National University prepared (J. Org. Chem. 2015, 80, 4828. DOI: 10.1021/acs.joc.5b00590) the ketone 30 by Pd-mediated rearrangement of the epoxide derived from 29.