This review recaps the achievements in the field of metal-catalyzed asymmetric direct hydrogenation of nonactivated and activated imines. A summary of the reported catalytic systems with the corresponding reactivity, selectivity, and limitations are given including a discussion about the effects of some reaction conditions on the enantioselectivity of imine hydrogenation. An analysis of proposed imine hydrogenation mechanisms is discussed.
Biaryls have widespread applications
in organic synthesis. However,
sequentially polysubstituted biaryls are underdeveloped due to their
challenging preparation. Herein, we report the synthesis of dissymetric
2,3,2′,3′,4-substituted biaryls via pericyclic reactions
of cyclic diaryl λ3-bromanes. The functional groups
tolerance and atom economy allow access to molecular complexity in
a single reaction step. Continuous flow protocol has been designed
for the scale-up of the reaction, while postfunctionalizations have
been developed taking advantage of the residual Br-atom.
Simple ligand-free copper systems were found as efficient catalysts for the addition of 1,3-dicarbonyl compounds to N-allenyl derivatives. This highly regio- and stereoselective reaction has been accomplished in the presence of malonates, 1,3-ketoesters, and 1,3-diketones with good to excellent yields under mild conditions. This methodology represents the first allylation of 1,3-dicarbonyl compounds with allenes catalyzed by copper.
An additive‐free copper catalytic system was used to perform the addition of (hetero)aryl nucleophiles to N‐allenyl derivatives. This intermolecular C–C bond formation occurs with both complete regio‐ and stereoselectivity to afford the linear (E) allylic product with moderate to excellent yields. This atom economical method is the first example of hydroarylation of allenes catalyzed by copper.
The desymmetrized meso-chimonantine core of leptosin C was prepared in a short stereoselective convergent sequence in 5 steps as the longest linear path from methyl L-tryptophan hydrochloride as starting material. The key step of this approach was a diastereoselective [4+2] cycloaddition between the bromooxindole and tryptophan derivatives allowing to define the adjacent quaternary benzylic centers in a high chemical yield.
Ambidentate ligand pyridyldiketones were used in combination with copper to catalyze amination of aryl halides under very mild temperatures with aqueous ammonia. This novel catalytic system allow efficient coupling in one of the smoothest conditions ever reported in literature.
Ambidentate ligand pyridyldiketones were used in combination with copper to catalyze amination of aryl halides under very mild temperatures with aqueous ammonia. This novel catalytic system allow efficient coupling in one of the smoothest conditions ever reported in literature.
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