Heterocycles: The Banwell Synthesis of Uleine
Yuefa Gong of the Huazhong University of Science and Technology showed (J. Org. Chem. 2016, 81, 4829. DOI: 10.1021/acs.joc.6b00161) that the donor-acceptor cyclopropane 1 could be rearranged to the furan 2. Mang Wang and Jun Liu of Northeast Normal University cyclized (Org. Lett. 2016, 18, 2162. DOI: 10.1021/acs.orglett.6b00785) 3 to the furan 4.
Mohammad Anary-Abbasinejad of Vali-e-Asr University assembled (Tetrahedron Lett. 2016, 57, 103. DOI: 10.1016/j.tetlet.2015.11.075) the pyrrole 7 by the Ph3P-mediated combination of 5 with 6. Till Opatz of Johannes Gutenberg University photochemically promoted (J. Org. Chem. 2016, 81, 4170. DOI: 10.1021/acs.joc.6b00511) the Co-catalyzed combination of 8 with 9 to make 10.
Frédéric Lamaty of the Université de Montpellier and Martin Kotora of Charles University described (Adv. Synth. Catal. 2016, 358, 1916. DOI: 10.1002/adsc.201600127) the preparation of 13 by Ru-catalyzed cyclization of 11 with 12. Sampak Samanta of the Indian Institute of Technology, Simrol prepared (J. Org. Chem. 2016, 81, 4378. DOI: 10.1021/acs.joc.6b00472) 16 by adding 15 to 14. Junichiro Yamaguchi of Nagoya University combined (Chem. Eur. J. 2016, 22, 4384. DOI: 10.1002/chem.201600351) 17 with 18 to make 19. Cyril Bressy, Xavier Bugaut and Jean Rodriguez of Aix Marseille Université achieved (Angew. Chem. Int. Ed. 2016, 55, 1401. DOI: 10.1002/anie.201509967) significant enantioselectivity (88% ee) in the addition of 21 to 20, and showed that this central chirality was carried over to the axial chirality of 22, with one atropisomer being favored over the other.
Bartlomiej Furman of the Polish Academy of Sciences observed (Org. Lett. 2016, 18, 149. DOI: 10.1021/acs.orglett.5b03449) that Schwartz reagent reduction of the initial product from the addition of a Grignard reagent to the isatin 23 gave an intermediate that could be coupled with 24 to give the indole 25. Yong Wu of Sichuan University described (Tetrahedron Lett. 2016, 57, 39. DOI: 10.1021/acs.orglett.5b03447) a convenient preparation (not illustrated) of such isatins. Rai-Shung Liu of the National Tsing-Hua University prepared (Org. Lett. 2016, 18, 412. DOI: 10.1021/acs.orglett.5b03447) the indole 28 by coupling the allene 27 with the nitrosobenzene 26. Hiriyakkanavar Ila of the Jawaharlal Nehru Centre for Advanced Scientific Research developed (J. Org. Chem. 2016, 81, 2035. DOI: 10.1021/acs.joc.5b02902) a practical protocol for the Pd-catalyzed cyclization of 29 to 30. Shu-Li You of the Shanghai Institute of Organic Chemistry established (Angew. Chem. Int. Ed. 2015, 54, 8475. DOI: 10.1002/anie.201502259) that the intial product from the enantioselective Ir-catalyzed cyclization of the readily-assembled 31 could be rearranged to 32.
Uleine (35) and related alkaloids are of interest, inter alia, for their ability to promote the in vivo production of nitric oxide. En route to 35, Martin G. Banwell of the Australian National University developed (J. Org. Chem. 2016, 81, 2950. DOI: 10.1021/acs.joc.6b00240) the elegant reductive cyclization of 33 to 34.