A series of new hypervalent iodine reagents based on the 1,3-dihydro-3,3-dimethyl-1,2-benziodoxole and 1,2-benziodoxol-3-(1H)-one scaffolds, which contain a functionalized tetrafluoroethyl group, have been prepared, characterized, and used in synthetic applications. Their corresponding electrophilic fluoroalkylation reactions with various sulfur, oxygen, phosphorus, and carbon-centered nucleophiles afford products that feature a tetrafluoroethylene unit, which connects two functional moieties. A related λ(3) -iodane that contains a fluorophore was shown to react with a cysteine derivative under mild conditions to give a thiol-tagged product that is stable in the presence of excess thiol. Therefore, these new reagents show a significant potential for applications in chemical biology as tools for fast, irreversible, and selective thiol bioconjugation.
This review is oriented toward the asymmetric transfer hydrogenation (ATH) of imines regarding mostly fundamental, yet important topics from the practical point of view. Development of analytical methods for the monitoring of ATH (i.e., kinetics and stereoselectivity) belongs to those topics, as well as studies on the influence of reaction conditions and structural variations on the reaction performance. The second part is devoted to the reaction mechanism with the emphasis on imine ATH and catalyst behaviour under acidic conditions. The review also addresses the asymmetric hydrogenation (AH) of ketones and imines using molecular hydrogen and the application of ATH in pharmaceutical projects. The contributions of our group to each area are included.
Subnanometer
(d = 0.8 ± 0.2 nm) gold particles
homogeneously dispersed on amino-functionalized silica catalyze Glaser-type
alkyne coupling, providing corresponding 1,3-diynes under mild conditions.
Readily available λ3-iodane PhI(OAc)2 is
used as an oxidant and 1,10-phenanthroline is used as an additive.
Ten symmetrical 1,3-diynes and three products of heterocoupling containing
various functionalities are isolated in high yields. The catalyst
can be recycled at least five times, giving consistently high isolated
yields and maintaining the size and distribution of gold clusters.
This unique combination of stable subnanometer gold clusters and hypervalent
iodine thus paves a hitherto unexplored avenue in organic synthesis
employing heterogeneous gold catalysis.
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