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ABSTRACT: The coupling of O-pivaloyl benzhydroxamic acids with donor/acceptor diazo compounds provides isoindolones in high yield. The reaction tolerates a broad range of benzhydroxamic acids and diazo compounds, including substituted 2,2,2-trifluorodiazoethanes. Mechanistic experiments suggested that C-H activation is turnover-limiting and irreversible and that insertion of the diazo compound favors electron-deficient substrates.
Journal of the American Chemical Society 04/2013; · 9.91 Impact Factor
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ABSTRACT: Enzymes provide an exquisitely tailored chiral environment to foster high catalytic activities and selectivities, but their native structures are optimized for very specific biochemical transformations. Designing a protein to accommodate a non-native transition metal complex can broaden the scope of enzymatic transformations while raising the activity and selectivity of small-molecule catalysis. Here, we report the creation of a bifunctional artificial metalloenzyme in which a glutamic acid or aspartic acid residue engineered into streptavidin acts in concert with a docked biotinylated rhodium(III) complex to enable catalytic asymmetric carbon-hydrogen (C-H) activation. The coupling of benzamides and alkenes to access dihydroisoquinolones proceeds with up to nearly a 100-fold rate acceleration compared with the activity of the isolated rhodium complex and enantiomeric ratios as high as 93:7.
Science 10/2012; 338(6106):500-3. · 31.20 Impact Factor
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ABSTRACT: An efficient strategy for the oxidative carbonylation of aromatic amides via C-H/N-H activation to form phthalimides using an Rh(III) catalyst has been developed. The reaction shows a preference for C-H bonds of electron-rich aromatic amides and tolerates a variety of functional groups.
Chemical Communications 11/2011; 47(44):12074-6. · 6.17 Impact Factor
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ABSTRACT: The synthesis of pyridines from readily available α,β-unsaturated oximes and alkynes under mild conditions and low temperatures using Rh(III) catalysis has been developed. It was found that the use of sterically different ligands allows for complementary selectivities to be achieved.
Chemical Communications 11/2011; 47(43):11846-8. · 6.17 Impact Factor
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ABSTRACT: The oxidative cycloaddition of benzamides and alkynes has been developed. The reaction utilizes Rh(III) catalysts in the presence of Cu(II) oxidants, and is proposed to proceed by N-H metalation of the amide followed by ortho C-H activation. The resultant rhodacycle undergoes alkyne insertion to form isoquinolones in good yield. The reaction is tolerant of extensive substitution on the amide, alkyne, and arene, including halides, silyl ethers, and unprotected aldehydes as substituents. Unsymmetrical alkynes proceed with excellent regioselectivity, and heteroaryl carboxamides are tolerated leading to intriguing scaffolds for medicinal chemistry. A series of competition experiments shed further light on the mechanism of the transformation and reasons for selectivity.
Journal of the American Chemical Society 08/2010; 132(30):10565-9. · 9.91 Impact Factor
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Angewandte Chemie International Edition 02/2009; 48(33):6121-3. · 13.45 Impact Factor
