Heteroaromatics: The Cho Synthesis of Tubifolidine

Antonio J. Moreno-Vargas of the Universidad de Sevilla drove the retro Diels-Alder disassembly of the 7-oxanorbornadiene 1 by reacting it selectively with benzyl azide, leading to the furan 2 (J. Org. Chem. 2020, 85, 8923. ). Christopher W. Jones and Stefan France of Georgia Tech prepared the furan 5 by combining ribose 3 with acetylacetone 4 (J. Org. Chem. 2020, 85, 15337. ).

Haiyan Fu of Sichuan University assembled the pyrrole 8 by reacting the pyridinium salt 6 with methyl methacrylate 7 (Org. Lett. 2020, 22, 6107. ). Shannon S. Stahl of the University of Wisconsin effected benzylic azidation of 9, then cyclized that product to the pyrrole 10 (J. Am. Chem. Soc. 2020, 142, 11388. ). Mi-Na Zhao of the Baoji University of Arts and Sciences prepared the pyrrole 12 by adding acetylacetone 4 to the 2H-azirine 11 (Tetrahedron Lett. 2020, 61, 152319. ). Haipeng Hu and Peng Cao of Sichuan Normal University reported a parallel investigation (Org. Chem. Front. 2020, 7, 3686. ). Qiuping Ding of Jiangxi Normal University combined the aniline 14 with the nitroalkene 13 to give the pyrrole 15 (Org. Biomol. Chem. 2020, 18, 8908. ).

Wen Luo, Jingjing Zhao and Pan Li of Henan University showed that visible light could promote the coupling of the alkenyl aziridine 16 with the difluoroacetate 17, leading to the pyridine 18 (Org. Lett. 2020, 22, 9658. ). Gui-Fa Su and Dong-Liang Mo of Guangxi Normal University cyclized the N-vinyl nitrone 19 to the pyridine 20 (Org. Lett. 2020, 22, 8446. ).

Debashis Adhikari of the Indian Institute of Science Education and Research used a borrowed hydrogen strategy to combine the aniline 21 with benzyl alcohol 22, leading to the indole 23 (Chem. Commun. 2020, 56, 15442. ). Jeh-Jeng Wang of Kaohsiung Medical University devised the oxidative coupling of benzhydrol 24 with the enamine 25, leading to the indole 26 (Adv. Synth. Catal. 2020, 362, 2911. ). Martin Hiersemann of TU Dortmund used UV irradiation to convert the alkyne 27 to the indole 28 (Chem. Eur. J. 2020, 26, 11974. ). Christopher M. Beaudry of Oregon State University designed the Diels-Alder cyclization of the alkyne 29 to give the indole 30 (Chem. Eur. J. 2020, 26, 16655. ).

The Strychnos alkaloids, represented by tubifolidine (34), exhibit a wide range of physiological activites. En route to 34, Cheon-Gyu Cho of Hanyang University achieved regioselectivity in the Fischer indole construction of 33 by first selectively forming the enol triflate 31 from the corresponding ketone, then coupling that with the protected phenylhydrazine 32, and cyclizing the product (Org. Lett. 2020, 22, 3464. ).