Showing papers by "Donna G. Blackmond published in 2015"
TL;DR: Examples from a variety of catalytic reactions spanning two decades of the author's work help to delineate nuances on a central mechanistic theme.
Abstract: The use of modern kinetic tools to obtain virtually continuous reaction progress data over the course of a catalytic reaction opens up a vista that provides mechanistic insights into both simple and complex catalytic networks. Reaction profiles offer a rate/concentration scan that tells the story of a batch reaction time course in a qualitative “fingerprinting” manner as well as in quantitative detail. Reaction progress experiments may be mathematically designed to elucidate catalytic rate laws from only a fraction of the number of experiments required in classical kinetic measurements. The information gained from kinetic profiles provides clues to direct further mechanistic analysis by other approaches. Examples from a variety of catalytic reactions spanning two decades of the author’s work help to delineate nuances on a central mechanistic theme.
228 citations
TL;DR: In this article, the Pd-catalyzed arylation of very hindered α,α,α-trisubstituted primary amines was reported, which was effective in coupling a wide range of functionalized aryl and heteroaryl halides under mild conditions.
Abstract: We report the Pd-catalyzed arylation of very hindered α,α,α-trisubstituted primary amines. Kinetics-based mechanistic analysis and rational design have led to the development of two biarylphosphine ligands that allow the transformation to proceed with excellent efficiency. The process was effective in coupling a wide range of functionalized aryl and heteroaryl halides under mild conditions.
116 citations
TL;DR: Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C-H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst.
Abstract: Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C–H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.
85 citations
TL;DR: Anomalous concentration dependences observed here may be reconciled by considering the role of phase transfer processes that mediate concentrations in each phase.
Abstract: Kinetic, spectroscopic, and computational studies of radical C–H arylations highlight the interplay between chemical and physical rate processes in these multiphase reactions. Anomalous concentration dependences observed here may be reconciled by considering the role of phase transfer processes that mediate concentrations in each phase. In addition, understanding interactions through phase boundaries enables their use in optimization of reaction performance.
28 citations
TL;DR: The development of improved reaction conditions and an interrogation into the fate of the metal center during the Achmatowicz rearrangement are described, allowing for easy isolation of product 3 and synthetically important derivatives.
Abstract: The Achmatowicz rearrangement is a powerful method for the construction of pyranones from simple furan derivatives. Here, we describe the development of improved reaction conditions and an interrogation into the fate of the metal center during this interesting transformation. The reaction to form the synthetically important lactol, 6-hydroxy-2H-pyran-3(6H)-one (3), proceeds cleanly in the presence of tert-butyl hydroperoxide (TBHP, 2) using low loadings of VO(OiPr)3 as catalyst. The nonaqueous conditions developed herein allow for easy isolation of product 3 and synthetically important derivatives, a key advantage of this new protocol. Detailed experimental, spectroscopic, and kinetic studies along with kinetic modeling of the catalytic cycle support a positive-order dependence in both furfurol and TBHP concentrations, first-order dependence in catalyst (VO(OiPr)3), and a negative dependence on the 2-methyl-2-propanol (4) concentration. 51V-NMR spectroscopic studies revealed that 2-methyl-2-propanol (4) c...
27 citations
TL;DR: Unusual sigmoidal kinetic profiles in the Machetti-De Sarlo base-catalyzed 1,3-dipolar cycloaddition of acrylamide to N-methylnitroacetamide are rationalized and a dual role is uncovered in which a substrate acts as a precursor to catalyze its own reaction.
Abstract: Unusual sigmoidal kinetic profiles in the Machetti–De Sarlo base-catalyzed 1,3-dipolar cycloaddition of acrylamide to N-methylnitroacetamide are rationalized by detailed in situ kinetic analysis. A dual role is uncovered in which a substrate acts as a precursor to catalyze its own reaction. Such kinetic studies provide a general protocol for distinguishing among different mechanistic origins of induction periods in complex organic reactions.
27 citations
TL;DR: In this article, a method for the cross-coupling of sterically hindered primary amines with a range of aryl or hetaryl chlorides or bromides equipped with various functional groups is developed.
Abstract: A generally applicable method for the cross-coupling of sterically hindered primary amines with a range of aryl or hetaryl chlorides or bromides, respectively, equipped with various functional groups is developed.
4 citations
TL;DR: The use of modern kinetic tools to obtain virtually continuous reaction progress data over the course of a catalytic reaction opens up a vista that provides mechanistic insights into both simple and complex catalytic networks as discussed by the authors.
Abstract: The use of modern kinetic tools to obtain virtually continuous reaction progress data over the course of a catalytic reaction opens up a vista that provides mechanistic insights into both simple and complex catalytic networks. Reaction profiles offer a rate/concentration scan that tells the story of a batch reaction time course in a qualitative “fingerprinting” manner as well as in quantitative detail. Reaction progress experiments may be mathematically designed to elucidate catalytic rate laws from only a fraction of the number of experiments required in classical kinetic measurements. The information gained from kinetic profiles provides clues to direct further mechanistic analysis by other approaches. Examples from a variety of catalytic reactions spanning two decades of the author’s work help to delineate nuances on a central mechanistic theme.
4 citations