Benzene Derivatives: The Banwell Synthesis of Galanthamine
Ramesh C. Samanta and Hisashi Yamamoto of Chuba University showed (Chem. Eur. J. 2015, 21, 11976. DOI: 10.1002/chem.201502234) that the encumbered aniline 2 was an effective organocatalyst for electrophilic bromination, as exemplified by the selective conversion of 1 to 3. Chao-Jun Li of McGill University developed (Angew. Chem. Int. Ed. 2015, 54, 14487. DOI: 10.1002/anie.201506751) conditions for directly coupling a phenol 4 with an amine 5 to give the aniline 6.
An ether such as 9 would usually be prepared from a primary halide and the phenol. David W. C. MacMillan of Princeton University was able (Nature 2015, 524, 330. DOI: 10.1038/nature14875) to invert this procedure, preparing 9 by coupling 7 with 8. The preparation of the amide 12 by the coupling of 10 with 11 requires carbon monoxide. Kami L. Hull of the University of Illinois Urbana-Champaign devised (Org. Lett. 2015, 17, 3236. DOI: 10.1021/acs.orglett.5b01385) a protocol for generating the necessary CO in situ from chloroform. Tibor Grazca of the Slovak University of Technology reported (Org. Lett. 2015, 17, 5618. DOI: 10.1021/acs.orglett.5b02840) an alternative method for the in situ CO generation, reduction of oxalyl chloride with Zn.
Mark Stradiotto of Dalhousie University achieved (Chem. Eur. J. 2015, 21, 11006. DOI: 10.1002/chem.201500834) the room temperature coupling of the aryl bromide 10 with acetone to give 13. Chau Ming So and Fuk Yee Kwong of the Hong Kong Polytechnic University established (Org. Lett. 2015, 17, 4612. DOI: 10.1021/acs.orglett.5b02344) that at elevated temperature, aryl chlorides (not illustrated) could also participate. Xiuling Cui and Yangjie Wu of Zhengzhou University effected (J. Org. Chem. 2015, 80, 7333. DOI: 10.1021/acs.joc.5b01377) the selective amination of 14 to 15.
Masilamani Jeganmohan of the Indian Institute of Science Education and Research described (Chem. Eur. J. 2015, 21, 13934. DOI: 10.1002/chem.201502284) the regioselective coupling of 16 with 17 to give 18. Frank Glorius of the Westfälische Wilhelms-Universität Münster reported (Org. Lett. 2015, 17, 3714. DOI: 10.1021/acs.orglett.5b01701) related results with a Co catalyst. Peng-Fei Xu and Yong-Min Liang of Lanzhou University (ACS Catal. 2015, 5, 4927. DOI: 10.1021/acscatal.5b00516) and Zhenhua Gu of the University of Science and Technology of China (Angew. Chem. Int. Ed. 2015, 54, 12669. DOI: 10.1002/anie.201506446) independently reported an extension of the Catellani protocol that enabled the coupling of the iodide 19 with the anhydride 20 and ethyl acrylate 21 to give 22.
Gang Li of the Fujian Institute of Research on the Structure of Matter effected (Chem. Sci. 2015, 6, 5595. DOI: 10.1039/C5SC01737H) the selective meta coupling of 23 with ethyl acrylate 21 to give 24. Debabrata Maiti of the Indian Institute of Technology Mumbai designed (J. Am. Chem. Soc. 2015, 137, 11888. DOI: 10.1021/jacs.5b06793) the silyl ether 25 that underwent selective para coupling with 21 to give 26.
David Tejedor and Fernando García-Tellado of the Instituto de Productos Naturales y Agrobiologia heated (Chem. Eur. J. 2015, 21, 18280. DOI: 10.1002/chem.201503171) the propargyl ether 27 with a catalytic amine, leading to the salicylaldehyde 28. Michael S. Sherburn of the Australian National University devised (Org. Lett. 2015, 17, 5517. DOI: 10.1021/acs.orglett.5b02412) the cascade cyclization of 29 to 30.
Martin G. Banwell, also of the Australian National University, prepared (Eur. J. Org. Chem. 2015, 3771. DOI: 10.1002/ejoc.201500365) 31 from cyclohexane 1,4-dione. Diels-Alder addition with 32 followed by oxidation led to 33, that was carried on to Galanthamine (34).