- Kinetic Analysis as an Optimization Tool for Catalytic Esterification with a Moisture-Tolerant Zirconium Complex
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This work describes the use of kinetics as a tool for rational optimization of an esterification process with down to equimolar ratios of reagents using a recyclable commercially available zirconocene complex in catalytic amounts. In contrast to previously reported group IV metal-catalyzed esterification protocols, the work presented herein circumvents the use of water scavengers and perfluorooctane sulfonate (PFOS) ligands. Insights into the operating mechanism are presented.
- Dalla-Santa, Oscar,Lundberg, Helena,Szabó, Zoltán,Villo, Piret
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p. 6959 - 6969
(2020/06/27)
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- High selectivity from configurational match/mismatch in carbon-hydrogen insertion reactions of steroidal diazoacetates catalyzed by chiral dirhodium(II) carboxamidates
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Diazo decomposition of steroidal diazoacetates, where the point of attachment is the 3-position of the steroid A-ring, catalyzed by chiral dirhodium(II) carboxamidates results in products from carbon-hydrogen insertion in high yield and selectivities. Use of S-configured catalysts shows a distinctive preference for insertion into the 3-position to form β-lactone products. The R-configured catalysts direct insertion preferentially to the equatorial C-H bond at the 2-position. Substituents or functional groups at the 5/6-position prevent C-H insertion from taking place at the 4-position. Even in the best case with the 5/6-positions fully saturated, however, insertion into the 3-position remains competitive with insertion into the 4-position. Corresponding 3-substituted phenyldiazoacetates give only β-lactone products, and selectivity here is highest with chiral dirhodium(II) prolinate catalysts. A model is presented to explain these results. Overall, this methodology is versatile for functionalization of the steroid A-ring at positions 2 and 3.
- Doyle, Michael P.,Davies, Simon B.,May, Eric J.
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p. 8112 - 8119
(2007/10/03)
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- A USEFUL METHOD FOR SELECTIVE ACYLATION OF ALCOHOLS USING 2,2'-BIPYRIDYL-6-YL CARBOXYLATE AND CESIUM FLUORIDE
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Primary and secondary alcohols are acylated under mild conditions by the of use 2,2'-bipyridyl-6-yl carboxylates and cesium fluoride.Furthermore, the reaction is successfully applied to selective acylation of a primary carbinol group of diols containing primary and secondary carbinol groups or exclusive O-acylation of aromatic amino alcohols.
- Mukaiyama, Teruaki,Pai, Fong-Chang,Onaka, Makoto,Narasaka, Koichi
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p. 563 - 566
(2007/10/02)
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