C-N Ring Construction: The Zhang/Yang Synthesis of (-)-Aurantioclavine
Gustavo Moura-Letts of Rowan University devised (Chem. Commun. 2015, 51, 13511. DOI: 10.1039/C5CC04813C) a general method for converting an aldehyde 1 into the diaziridine 2. Maurice A. Marsini of Boehringer Ingelheim showed (Org. Lett. 2015, 17, 5614. DOI: 10.1021/acs.orglett.5b02838) that the imine 3 could be methylenated to aziridine 4 in high de.
Debasis Koley of the Indian Institute of Science and Education Kolkata and Chandan K. Jana of the Indian Institute of Technology Guwahati activated (Chem. Eur. J. 2015, 21, 15290. DOI: 10.1002/chem.201502297) the pyrrolidine 5 with the imine 6 to give an intermediate that coupled with phenol 7 to give 8. Hong Liu of the Shanghai Institute of Materia Medica reported (Chem. Commun. 2015, 51, 12571. DOI: 10.1039/C5CC03706A) related results via the N-oxide of an N-benzyl pyrrolidine. Benjamin List of the Max-Planck-Institut für Kohlenforschung developed (J. Am. Chem. Soc. 2015, 137, 13268. DOI: 10.1021/jacs.5b09484) an organocatalyst that cyclized 9 to 10 in high ee. Tetsuhiro Nemoto and Yasumasa Hamada of Chiba University found (J. Org. Chem. 2015, 80, 10317) DOI: 10.1021/acs.joc.5b01954) that the ylide derived from the diazo ketone 11 rearranged efficiently to 12. Gregory C. Fu of Caltech designed (J. Am. Chem. Soc. 2015, 137, 3803. DOI: 10.1021/jacs.5b01944) a phosphine that catalyzed the addition of an arenesulfonamide to the racemic allene 13 to give 3-pyrroline 14 in high ee.
Indresh Kumar of the Birla Institute of Technology and Science condensed (Org. Lett. 2015, 17, 5582. DOI: 10.1021/acs.orglett.5b02744) the imine 16 with the dialdehyde 15, leading to the dihydropyridine 17. Mauro Pineschi of the Università di Pisa coupled (Chem. Commun. 2015, 51, 13694. DOI: 10.1039/C5CC04416B) the allylic alcohol 19 with the aldehyde 19 to give 20 in high ee and 10:1 de. Delong Liu and Wanbin Zhang of the Shanghai Jiao Tong University used (Adv. Synth. Catal. 2015, 357, 3627. DOI: 10.1002/adsc.201500550) an organocatalyst to mediate the addition of the aldehyde 22 to the imine 21, leading to 23.
The intramolecular dipolar cycloaddition of an azide to a distal alkene is a powerful but underdeveloped method for C-N ring construction. Taking advantage of the thermal isomerization of allylic azides, Paul V. Murphy of the National University of Ireland Galway warmed (Org. Lett. 2015, 17, 6226. DOI: 10.1021/acs.orglett.5b03209) the azide 24 to give, after acetolysis of the intermediate adduct, the piperidine 25.
Xian-Ying Tang and Min Shi of the Shanghai Institute of Organic Chemistry established (Chem. Commun. 2015, 51, 13937. DOI: 10.1039/C5CC05808B) a new route to medium rings, using a gold catalyst to convert 26 to 27. James P. Tam of the Nanyang Technological University described (J. Am. Chem. Soc. 2015, 137, 15398. DOI: 10.1021/jacs.5b11014) an enzyme recently isolated from Clitoria ternatea that efficiently cyclized the oligopeptide 28 to 29.
Carreira developed a powerful Ir-catalyzed protocol for enantioselective polyene cyclization. Hongbin Zhang of Yunnan University and Yu-Rong Yang of the Kunming Institute of Botany applied (Tetrahedron Lett. 2015, 56, 5933. DOI: 10.1016/j.tetlet.2015.09.039) this protocol to the cyclization of 30, leading to 31, that was carried on to the Penicillium aurantiovirens alkaloid (-)-Aurantioclavine (32).