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149 results on '"Biscoe, Mark R."'

12. A highly active catalyst for Pd-catalyzed amination reactions: cross-coupling reactions using aryl mesylates and the highly selective monoarylation of primary amines using aryl chlorides

Author

Fors, Brett P., Watson, Donald A., Biscoe, Mark R., and Buchwald, Stephen L.

Subjects
Amines -- Chemical properties, Arylation -- Analysis, Catalysis -- Analysis, Palladium catalysts -- Chemical properties, Chemistry
Abstract

The development of a new biaryldialkylphosphine ligand that shows excellent reactivity and stability in C-N cross-coupling reactions compared to other catalyst system is reported. The ligand allows Pd-catalyzed amination reactions of aryl mesylates as well as the highly selective monoarylation of primary amines using low catalyst loadings of a monophosphine-based catalyst.

Published
2008

13. A new class of easily activated palladium precatalysts for facile C-N cross-coupling reactions and the low temperature oxidative addition of aryl chlorides

Author

Biscoe, Mark R., Fors, Brett P., and Buchwald, Stephen L.

Subjects
Arylation -- Analysis, Oxidation-reduction reaction -- Analysis, Palladium catalysts -- Chemical properties, Chemistry
Abstract

A new class of air- and moisture-stable, one-component, Pd precatalysts activated standard reaction to obtain active, [L.sub.1]Pd(0) (L = biarylphosphine) complex is developed. The reaction can find potential application, where a highly active Pd complex is required to promote a difficult cross-coupling reaction or where functional group instability requires the use of low temperatures.

Published
2008

14. Pd-catalyzed amidations of aryl chlorides using monodentate biaryl phosphine ligands: a kinetic, computational, and synthetic investigation

Author

Ikawa, Takashi, Barder, Timothy E., Biscoe, Mark R., and Buchwald, Stephen L.

Subjects
Palladium -- Structure, Palladium -- Chemical properties, Palladium -- Spectra, Nuclear magnetic resonance spectroscopy -- Analysis, Sulfones -- Structure, Sulfones -- Chemical properties, Sulfones -- Spectra, Chemistry
Abstract

A monodentate biaryl phosphine-Pd catalyst is used for studying the amidation of aryl halides and sulfonates. The utilization of ligands possessing a methyl group ortho to the phosphorous center has allowed a variety of aryl and heteroaryl chlorides with various amides to be coupled in high yield.

Published
2007

15. Oxaziridinium salts as hydrophobic epoxidation reagents: Remarkable hydrophobically selectivity in olefin epoxidation

Author

Biscoe, Mark R. and Breslow, Ronald

Subjects
Oxidation-reduction reaction -- Analysis, Hydrophobic effect -- Analysis, Olefins -- Chemical properties, Chemistry
Abstract

The ability of hydrophobic oxaziridinium salts to effect relative rate increases in the selective epoxidation of hydrophobic olefins that are an order of magnitude greater than the largest increases observed in hydride reductions are reported. The importance of accurate transition-state models in the development of hydrophobic unit on a substrate is demonstrated.

Published
2005

18. Nickel-Catalyzed Kumada Cross-Coupling Reactions of Tertiary Alkylmagnesium Halides and Aryl Bromides/Triflates

Author

Joshi-Pangu, Amruta, Wang, Chao-Yuan, and Biscoe, Mark R.

Abstract

We report a Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.

Published
2024
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19. Simple, efficient protocols for the Pd-catalyzed cross-coupling reaction of aryl chlorides and dimethylamine

Author

Massachusetts Institute of Technology. Department of Chemistry, Lee, Brian K., Biscoe, Mark R., Buchwald, Stephen Leffler, Massachusetts Institute of Technology. Department of Chemistry, Lee, Brian K., Biscoe, Mark R., and Buchwald, Stephen Leffler

Abstract

Simple and efficient procedures for the Pd-catalyzed cross-coupling reaction of aryl chlorides and dimethylamine are described. At room temperature with a strong base, t-BuXPhos is employed as the supporting ligand; at 110 °C with a weak base, XPhos is employed as the supporting ligand. In each of these cases, commercially available solutions constitute the source of the dimethylamine, and recently disclosed precatalysts constitute the source of the ligand and Pd. This work further expands the utility of these precatalysts in reactions that benefit from an easily activated source of L[subscript 1]Pd(0)., National Institutes of Health (U.S.) (GM-058160), National Institutes of Health (U.S.) (Postdoctoral Fellowship GM-F32-75685), Amgen Inc., Merck & Co., Inc., Boehringer Ingelheim Pharmaceuticals, Massachusetts Institute of Technology. Undergraduate Research Opportunities Program (Summer Fellowship)

Published
2015

24. A New Class of Easily Activated Palladium Precatalysts for Facile C−N Cross-Coupling Reactions and the Low Temperature Oxidative Addition of Aryl Chlorides

Author

Massachusetts Institute of Technology. Department of Chemistry, Biscoe, Mark R., Fors, Brett P., Buchwald, Stephen Leffler, Massachusetts Institute of Technology. Department of Chemistry, Biscoe, Mark R., Fors, Brett P., and Buchwald, Stephen Leffler

Abstract

A new class of one-component Pd precatalysts bearing biarylphosphine ligands is described. These precatalysts are air- and thermally stable, are easily activated under normal reaction conditions at or below room temperature, and ensure the formation of the highly active monoligated Pd(0) complex necessary for oxidative addition. The use of these precatalysts as a convenient source of LPd(0) in C−N cross-coupling reactions is explored. The reactivity that is demonstrated in this study is unprecedented in palladium chemistry., National Institutes of Health (U.S.) (GM-058160), National Institutes of Health (U.S.) (postdoctoral fellowship (GM-F32-75685)), Boehringer Ingelheim Pharmaceuticals, Merck Research Laboratories, Amgen Inc.

Published
2014

25. Hydrophobically directed selective reduction of ketones

Author

Biscoe, Mark R., Breslow, Ronald, Wass, Duncan F., Steed, Jonathan W., and Tsukruk, Vladimir V.

Subjects
Molecules -- Research, Hydrophobic effect -- Observations, Ketones -- Research, Ketones -- Chemical properties, Chemistry
Abstract

The development of hydrophobic reducing agents and the first examples of hydrophobically directed atom-transfer hydride reactions in water with substrate selectivity and regioselectivity is reported. It is observed that the product ratios in the competition reactions with ketones on separate molecules are consistent with the ratios observed when the ketones are within the same molecule.

Published
2003

26. Stereospecific Palladium-Catalyzed Acylation of Enantioenriched Alkylcarbastannatranes: A General Alternative to Asymmetric Enolate Reactions.

Author

Wang, Chao ‐ Yuan, Ralph, Glenn, Derosa, Joseph, and Biscoe, Mark R.

Subjects
STEREOSPECIFICITY, ACYLATION, PALLADIUM catalysts, ENOLATES, STEREOCHEMISTRY
Abstract

We report the development of a Pd-catalyzed process for the cross coupling of unactivated primary, secondary, and tertiary alkylcarbastannatrane nucleophiles with acyl electrophiles. Reactions involving optically active alkylcarbastannatranes occur with exceptional stereofidelity and with net retention of absolute configuration. Because the stereochemistry of the resulting products is entirely reagent-controlled, this process may be viewed as a general, alternative approach to the preparation of products typically accessed via asymmetric enolate methodologies. Additionally, we report a new method for the preparation of optically active alkylcarbastannatranes, which should facilitate their future use in stereospecific reactions. [ABSTRACT FROM AUTHOR]

Published
2017
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28. Selective Monoarylation of Acetate Esters and Aryl Methyl Ketones Using Aryl Chlorides

Author

Massachusetts Institute of Technology. Department of Chemistry, Buchwald, Stephen Leffler, Biscoe, Mark R., Massachusetts Institute of Technology. Department of Chemistry, Buchwald, Stephen Leffler, and Biscoe, Mark R.

Abstract

Simple, efficient procedures for the monoarylation of acetate esters and aryl methyl ketones using aryl chlorides are presented. Previously, no general method was available to ensure the highly selective monoarylation of these classes of substrates using aryl chlorides. Using palladium precatalysts recently reported by our group, these reactions are easily accomplished under mild conditions that tolerate a wide array of heterocyclic substrates., National Institutes of Health (U.S.) (GM-46059), National Institutes of Health (U.S.) (Postdoctoral Fellowship GM-F32-75685), Merck & Co., Inc., Boehringer Ingelheim Pharmaceuticals

Published
2013

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