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206 results on '"Newman, Stephen G."'

10. Nickel-Catalyzed Transesterification of Methyl Esters.

Author

Zheng, Yan-Long, Daneshfar, Omid, Li, Jia-Yi, Masson-Makdissi, Jeanne, Pinault-Masson, Émile, and Newman, Stephen G.

Subjects
METHYL formate, TRANSESTERIFICATION, COUPLING reactions (Chemistry), ACYL chlorides, ESTERS, CATALYST poisoning, AMIDES, ORGANIC synthesis, ELECTROPHILES
Abstract

This article explores the nickel-catalyzed transesterification of methyl esters, which is an important process in synthetic chemistry. The authors discuss the challenges of activating esters for cross-coupling reactions and the development of a reversible transformation using a nickel catalyst and SIPr. They also investigate the optimization of the reaction and the identification of effective ligands for different types of esters. The goal is to develop a transesterification method that is different from traditional acid- and base-mediated pathways. The article presents the development of a catalytic transesterification reaction using methyl esters and aliphatic alcohols, with optimized conditions and successful formation of diverse esters. The reaction is advantageous because it only produces methanol as waste and does not require the use of acids or bases. Mechanistic studies suggest that the cleavage of the C(acyl)-O bond is reversible, and ongoing research is being conducted on the use of methyl esters as cross-coupling electrophiles. [Extracted from the article]

Published
2024
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13. Flow-Assisted Synthesis of Heterocycles at High Temperatures

Author

Sullivan, Ryan J., Newman, Stephen G., Maes, Bert, Series Editor, Cossy, Janine, Series Editor, Polanc, Slovenko, Series Editor, Enders, Dieter, Editorial advisor, Ley, S. V., Editorial advisor, Mehta, G., Editorial advisor, Noyori, Ryoji, Editorial advisor, Overman, Larry E, Editorial advisor, Padwa, Albert, Editorial advisor, Sharma, Upendra K., editor, and Van der Eycken, Erik V., editor

Published
2018
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20. Reductive Cleavage of C(sp2)–CF3Bonds in Trifluoromethylpyridines

Author

St. Onge, Piers, Khan, Shajia I., Cook, Adam, and Newman, Stephen G.

Abstract

A reductive detrifluoromethylation protocol has been developed making use of an earth-abundant alkoxide base and silicon hydride species. A variety of pyridine and quinoline substrates bearing alkyl, aryl, and amino functional groups are reduced in moderate to high yields. The reaction is chemoselective for C(sp2)–CF3groups located at the 2-position on the pyridine ring, leaving trifluoromethyl groups located elsewhere on the molecule intact. Preliminary mechanistic studies demonstrate that the combination of silane and base generates a strongly reducing system that may transfer an electron to electron-deficient π systems.

Published
2023
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41. The role of reversible oxidative addition in selective palladium(0)-catalyzed intramolecular cross-couplings of polyhalogenated substrates: synthesis of brominated indoles

Author

Newman, Stephen G. and Lautens, Mark

Subjects
Halocarbons -- Structure, Halocarbons -- Chemical properties, Indole -- Structure, Indole -- Chemical properties, Oxidation-reduction reaction -- Analysis, Palladium catalysts -- Chemical properties, Chemistry
Abstract

The various mechanisms involved in the selective palladium(0)-catalyzed intramolecular cross-couplings of polyhalogenated substrates are discussed. The reversible oxidative addition process is shown to play an extremely significant role in the reaction, which then leads to the formation of various brominated indoles.

Published
2010

45. A High-Throughput Approach to Discovery: Heck-Type Reactivity with Aldehydes.

Author

Vandavasi, Jaya Kishore and Newman, Stephen G.

Subjects
*HECK reaction, *ALDEHYDES, *CARBON-carbon bonds
Abstract

The classical Heck reaction is among the most powerful methods available for the construction of C-C bonds. Modification of this transformation to utilize diverse organohalide coupling partners has resulted in new reactions such as the silyl-Heck, aza-Heck, and boryl- Heck reactions. In contrast, modification of the olefin coupling partner is rare. For instance, use of the p-bond of an aldehyde instead of an alkene would provide ketones via a carbonyl-Heck process. This seemingly minor manipulation of the Heck reaction has proven surprisingly difficult to realize in practice. Through the use of high-throughput experimentation techniques, an efficient catalyst system for this transformation was identified, enabling the intermolecular coupling of organotriflates and aldehydes to synthesize diverse ketones. [ABSTRACT FROM AUTHOR]

Published
2018
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46. Catalytic Deuteration of Aldehydes with D2O.

Author

Isbrandt, Eric S., Vandavasi, Jaya Kishore, Wanying Zhang, Jamshidi, Mohammad P., and Newman, Stephen G.

Subjects
CATALYTIC activity, DEUTERATION, ALDEHYDES
Abstract

A procedure is presented that enables the direct deuteration of the formyl C-H bond of aldehydes using D2O as the deuterium source and commercially available RuHCl(CO)(PPh3)3 as the catalyst. Up to 84% deuterium incorporation can be achieved in a single experiment. Multiple iterations can be carried out to further increase the deuteration. [ABSTRACT FROM AUTHOR]

Published
2017
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