C-N Ring Construction: The Hoye Synthesis of (±)-Leuconolactam
Manas K. Ghorai of the Indian Institute of Technology, Kanpur depended (J. Org. Chem. 2013, 78, 2311. DOI: 10.1021/jo302018a) on memory of chirality during deprotonation to convert 1 to the aziridine 3. X. Peter Zhang of the University of South Florida demonstrated (Angew. Chem. Int. Ed. 2013, 52, 5309. DOI: 10.1002/anie.201209599) that Co-catalyzed enantioselective aziridination is compatible with fluoroaromatics such as 5.
David M. Hodgson of the University of Oxford prepared (J. Org. Chem.2013, 78, 1098. DOI: 10.1021/jo3025225) the azetidine 8 by double deprotonation of 7 followed by acylation. Laurel L. Schafer of the University of British Columbia assembled (Org. Lett. 2013, 15, 2182. DOI: 10.1021/ol400729v) 11 by Ta-catalyzed aminoalkylation of 10 with 9, followed by cyclization.
Nicholas A. Magnus of Eli Lilly reduced (J. Org. Chem. 2013, 78, 5768. DOI: 10.1021/jo400589j) the ketone 12 to the alcohol 13, with high de and ee. Pei-Qiang Huang of Xiamen University effected (J. Org. Chem. 2013, 78, 1790. DOI: 10.1021/jo301277n) the reductive addition of 14 to 15 to give 16. The titanocene protocol reported (Angew. Chem. Int. Ed. 2013, 52, 3494. DOI: 10.1002/anie.201210088) by Xiao Zheng, also of Xiamen University, effectively mediated similar transformations. En route to (-)-Quinocarcin, Nobutaka Fujii and Hiroaki Ohno of Kyoto University cyclized (Chem. Eur. J. 2013, 19, 8875. DOI: 10.1002/chem.201300687) 17 to 18 with high diastereoselectivity.
Dipolar cycloaddition, long a workhorse of pyrrolidine synthesis, has been improved by enantioselective organocatalysis. For instance, Liu-Zhu Gong of the University of Science and Technology of China combined (Org. Lett. 2013, 15, 2676. DOI: 10.1021/ol400983j) 19, 20, and 21 to give the triester 22.
Qi-Lin Zhou of Nankai University reduced (Angew. Chem. Int. Ed. 2013, 52, 6072. DOI: 10.1002/anie.201301341) the tetrahydropyridine 23 to 24 in high ee. Takaaki Sato and Noritaka Chida of Keio University cyclized (Chem. Eur. J. 2013, 19, 678. DOI: 10.1002/chem.201202639) the intermediate from reduction of 25 to the piperidine 26. Yasumasa Hamada of Chiba University devised (Tetrahedron Lett. 2013, 54, 1562. DOI: 10.1016/j.tetlet.2013.01.034) the rearrangement of 27 to the piperidine 28. In a synthesis of (-)-Hippodamine, Shigeo Katsumura of Kwansei Gakuin University used (Org. Lett. 2013, 15, 2758. DOI: 10.1021/ol4010917) the chiral auxiliary 29 to direct the combination of 30 with 31 to give 32.
Thomas R. Hoye of the University of Minnesota devised (Chem. Sci. 2013, 4, 2262. DOI: 10.1039/C3SC00056G) the cyclization of maleimides such as 33. The product 34 was the key intermediate for the synthesis of Leuconolam 35.