Oxidation: The Khan Synthesis of Iridomyrmecin
Phil S. Baran of Scripps/La Jolla showed that the ether 3 could be assembled by the electrolysis of the acid 2 in the presence of the alcohol 1 (Nature 2019, 573, 398. ). In support of the widening use of electrochemistry in organic synthesis, Matthew S. Sigman, Henry S. White and Shelley D. Minteer of the University of Utah published an overview of electroanalytical tools for studying reaction mechanisms (Chem. Sci. 2019, 10, 6404. ). Can Jin of the Zhejiang University of Technology prepared 5 by the selective allylic oxidation of 4 (Synlett 2019, 30, 1479. ). Rudolf K. Allemann and Thomas Wirth of Cardiff University developed a protocol for the generation of singlet oxygen in flow, and used it to convert 6 to 7 (Chem. Eur. J. 2019, 25, 12486. ). Chengrong Ding, also of the Zhejiang University of Technology, oxidized the nitrile 8 to the cyanamide 9 (Org. Biomol. Chem. 2019, 17, 7684. ).
Mekhman S. Yusubov of the Tomsk Polytechnic University and Viktor V. Zhdankin of the University of Minnesota, Duluth developed the powerful oxidant IBX-ditriflate, that cleanly converted 10 to 11 (Chem. Commun. 2019, 55, 7760. ). Sarah E. Wengryniuk of Temple University showed that the equatorial alcohol 12 could be oxidized to the ketone 14, leaving the axial alcohol 13 unreacted (Org. Lett. 2019, 21, 5889. ). Hong-Mei Sun of Soochow University assembled the protected cyanohydrin 16 by coupling the nitrile 15 with 4-methoxybenzoic acid (Tetrahedron Lett. 2019, 60, 150969. ). Alicia Boto of the Instituto de Productos Naturales y Agrobiología del CSIC opened a new strategy for peptide modification, oxidizing 17 to 18 (J. Org. Chem. 2019, 84, 8392. ).
Cheng Chen of the Wuhan University of Technology and Francis Verpoort of the Ghent University Global Campus used a Ru catalyst to oxidize the diol 19 selectively to the acid 20 (Chem. Commun. 2019, 55, 8591. ). Hai-Yan Fu and Rui-Xiang Li of Sichuan University described related results (J. Org. Chem. 2019, 84, 9151. ). Miguel A. Esteruelas of the Universidad de Zaragoza and Carlos Sáa of the Universidade de Santiago de Compostela assembled the amide 23 by coupling the amine 22 with the terminal alkyne 21 (Org. Lett. 2019, 21, 5346. ). Sabuj Kundu of the Indian Institute of Technology Kanpur showed that the oxime derived from 24 could be oxidized in the presence of methanol to the N-methyl amide 25 (Adv. Synth. Catal. 2019, 361, 5357. ). Anna Chrobok of the Silesian University of Technology devised a flow system for the enzymatic generation of AcOOH for Baeyer-Villiger oxidation of the ketone 26 to the lactone 27 (Org. Process Res. Dev. 2019, 23, 1386. ).
The iridoid lactones, exemplified by iridomyrmecin (30), are of commercial interest as insect repellants. In the course of a synthesis of 30, Tabrez Khan of the Indian Institute of Technology Bhubaneswar effected regioselective elimination of the tosylate of 28, and oxidation of the resulting enol ether to the lactone 29 (Org. Biomol. Chem. 2019, 17, 6831. ).