C-N Ring Construction: The Kürti Synthesis of N-Methyl Euphococcine
László Kürti of Rice University showed that the ketone 3 efficiently mediated net nitrene transfer to 1, leading to the aziridine 2 (Nature Catal. 2020, 3, 386. DOI: 10.1038/s41929-020-0430-4). Robert G. Bergman, Kenneth N. Raymond and F. Dean Toste of the University of California, Berkeley used a tetrahedral macromolecule to catalyze the assembly of the aziridine 7 by the combination of 5 and 6 with aniline (J. Am. Chem. Soc. 2020, 142, 733. DOI: 10.1021/jacs.9b13177).
M. Christina White of the University of Illinois developed the oxidative methylation of the pyrrolidine 8 to 9 (Nature 2020, 580, 621. DOI: 10.1038/s41586-020-2137-8). Rahul A. Watile and Joseph S. M. Samec of the Stockholm University observed that the cyclization of 10 to 11 catalyzed by aqueous H3PO2 proceeded with clean inversion of absolute configuration (ACS Catal. 2020, 10, 1344. DOI: 10.1021/acscatal.9b03458). Robert R. Knowles of Princeton University used a chiral phosphate anion in conjunction with an Ir photocatalyst to achieve the enantioselective cyclization of 12 to 13 (J. Am. Chem. Soc. 2020, 142, 5974. DOI: 10.1021/jacs.0c01332). Xin-Yuan Liu of the Southern University of Science and Technology also used a chiral phosphoric acid, in conjunction with a Cu catalyst, to cyclize 14 to 15 (Angew. Chem. Int. Ed. 2020, 59, 1129. DOI: 10.1002/anie.201911742).
Chang-Mei Si of Fudan University assembled 18 by coupling 16 with 17 (Tetrahedron Lett. 2020, 61, 152051. DOI: 10.1016/j.tetlet.2020.152051). Matthew L. Clarke of the University of St. Andrews observed high ee in the preparation of 20 by Rh-mediated conjugate addition to 19 (Eur. J. Org. Chem. 2020, 3071. DOI: 10.1002/ejoc.202000336). K. N. Houk of UCLA and James M. Mayer and Jonathan A. Ellman of Yale University used 22 to arylate 21, leading to 23 (J. Am. Chem. Soc. 2020, 142, 8194. DOI: 10.1021/jacs.9b13165). Paul V. Murphy of the National University of Ireland Galway took advantage of the ready isomerization of allylic azides, cyclizing 24 to the piperidine 25 (Eur. J. Org. Chem. 2020, 2389. DOI: 10.1002/ejoc.201901875).
Lingyan Liu and Jing Li of Nankai University prepared the ring expanded enamine 28 by combining 26 with 27 (Adv. Synth. Catal. 2020, 362, 1525. DOI: 10.1002/adsc.201901644). Uxue Uria and Jose L. Vicario of the University of the Basque Country and Pedro Merino of the Universidad de Zaragoza also used a phosphoric acid organocatalyst to cyclize 29 to 30 (Angew. Chem. Int. Ed. 2020, 59, 6780. DOI: 10.1002/anie.202000650).
N-Methyl euphococcine (33) was isolated from the Colorado blue spruce Picea pungens. Professor Kürti prepared 33 by the internal dipolar cycloaddtion of the aldehyde derived from 31, leading to 32 (Org. Lett. 2020, 22, 2486. DOI: 10.1021/acs.orglett.0c00727).