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Catalysis with Selenium and Sulfur
Published in Andrew M. Harned, Nonnitrogenous Organocatalysis, 2017
Successive reports on amino-thiocarbamate-catalyzed enantioselective bromocyclization were published by Yeung and coworkers in recent years. In 2010, the group developed an enantioselective bromolactonization of 1,1-disubstituted olefinic acids 90 to form γ-lactones 91 as shown in Scheme 5.21.54 The amino-thiocarbamate catalyst 89 incorporated the cinchona alkaloid (+)-cinchonine as the chiral scaffold. Notably, the enantioselectivity deteriorated significantly when the catalyst’s S was replaced with O, or when its N–H was replaced with N–Me, thus indicating the crucial role played by the thiocarbamate moiety. In subsequent studies, the group found that the enantioselectivity could be enhanced by modifying the N-aryl or the 6-alkoxy group of the quinoline in the cinchona alkaloid scaffold. A modified amino-thiocarbamate catalyst 92 was thus later applied successfully to the bromoaminocyclization of olefinic sulfonamides 93, affording enantioenriched pyrrolidines 94 (Scheme 5.22).55 Further, fine-tuning of the catalyst structure and reaction conditions allowed the protocol to flexibly accommodate other substrates of varying structures and alkene geometries. These included bromolactonizations of 1,2-disubstituted56,57 and trisubstituted58 olefinic acids and styrene-type carboxylic acids59 and bromoaminocyclizations of 1,2-disubstituted olefinic sulfonamides.60,61
Catalytic Asymmetric Michael Addition of Heteroatom-centered Nucleophiles to Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The Wang group showed an application of 4-nitrophthalimide 30 as N-centered nucleophile for enantioselective aza-Michael addition to nitroalkenes 1 (Scheme 7.23).35 The process has been catalyzed by chiral thiourea catalyst C22 derived from cinchonine to give Michael adducts 31 with up to 87% ee.
A Singular Remedy: Cinchona Across the Atlantic World, 1751–1820
Published in Ambix, 2022
Much the same can be said about the end of the story, which Gänger places in 1820. Historians familiar with the bark will know that this was the year that quinine was “discovered” in the Parisian laboratory of Joseph Bienaimé Caventou and Pierre-Joseph Pelletier (as Gänger rightly points out, they were building on the isolation of cinchonine by the Portuguese naval physician Bernardino António Gomes). This story of the alkaloid, however, is neatly dispatched in the introduction as a potentially reductive, anachronistic, and presentist artifact (p. 21) – rightly so, but to end the book in 1820 nonetheless raises questions as to how the emergence of “quinine” as an actors’ category represents a rupture in the narrative. Caventou, Pelletier, and Gomes are relegated to a single footnote at the bottom of p. 27. For readers of this journal, the bracketing of chemical analysis and laboratory science from the narrative is worth noting. The social construction of quinine will have to await the attention of another historian.
Morphine Dreams: Auguste Laurent and the Active Principles of Organised Matter
Published in Ambix, 2021
Pasteur's career went from success to success. In his next project, in the 1850s, he studied the production of alcohol, succeeding where Lavoisier had failed, and showing that fermentation was not an inert chemical process, but a “vital act,” which required the presence of a living “ferment” or germ to begin the process.76 Less well-known was that he also took up the study of alkaloids at this time, particularly crystallizable derivatives of morphine, cinchonine, and papaverine, another alkaloid extracted from the opium poppy.77 He found the same asymmetries as in tartaric acid. Another paper used the properties of optical rotation to distinguish between various alkaloids extracted from the cinchona plant, including quinine and cinchonine.78 Pasteur even embarked upon a set of secret experiments, trying to “introduce asymmetry into the chemical actions of the laboratory.”79 He combined cinchonicine (an active substance) with paratartrique acid (an inactive one) and was able to separate out the left tartrate, leaving the right tartrate behind. He had thus “made” an active substance from an inactive one, but as it required the active cinchonicine, he was left more convinced than ever of the “barrier” between natural and artificial chemistry, and that “the forces in play in our laboratories differ from those to which govern vegetable nature.”80