It's a wrap! The inclusion of Rh(nbd)2BF4 (nbd=norbornadiene) in a deep‐cavity cavitand produces a catalytically active species that promotes the hydrogenation of norbornadiene to norbornene (see ...picture). The structure of the cavitand acts as a second‐sphere ligand and modifies the stability, selectivity, and reactivity observed for the free organometallic complex in solution.
A family of enantiopure diphenylphosphinooxazolines (PHOX) containing in their structures a sterically tunable alkoxymethyl group (‐CH2OR) has been optimized for the palladium‐catalyzed asymmetric ...allylic amination. The optimal catalyst (R=CH3), depicting very high catalytic activity and broad scope applicability, has been further modified to include an ω‐alkynyloxy substituent of variable length for polymer supporting via click chemistry, and has been anchored onto slightly cross‐linked azidomethyl poly(styrene). The length of a polymethylene chain connecting the PHOX unit with the 1,2,3‐triazole linker has been optimized, and the first polymer‐supported PHOX ligands for the highly enantioselective allylic amination have been prepared in this manner. Conditions for catalyst recovery and reuse in microwave‐promoted amination reactions have been established, and the system has been finally adapted to continuous flow operation.
We report the synthesis and characterisation of tetra{4-N,N-(4,4'-dimethoxydiphenylamino)phenyl}ethene () as an efficient and robust hole transport material for its application in methyl ammonium ...lead iodide (MAPI) perovskite solar cells. The solar cells show light-to-energy conversion efficiencies as high as 11.0% under standard measurement conditions without the need of additional dopants.
Highly efficient and enantioselective hydrogenation reactions for α‐(acylamino)acrylates, itaconic acid derivatives and analogues, α‐substituted enol ester derivatives, and α‐arylenamides (25 ...substrates) catalyzed by chiral cationic rhodium complexes of a set of POP ligands have been developed. The catalytic systems derived from these POP ligands provided a straightforward access to enantiomerically enriched α‐amino acid, carboxylic acid, amine, and alcohol derivatives that are valuable chiral building blocks. Excellent efficiencies (full conversion in all cases) and extremely high enantiomeric excesses (94–99% ee) were achieved for a wide range of α‐substituted enol ester derivatives, regardless of the substitution pattern. The R‐oxy group of the ligand (methoxy or triphenylmethoxy) strongly influences the enantioselectivity and catalytic activity. Greater steric bulk around the metal centre correlated to greater (or similar) enantioselectivity, but also to slower hydrogenation. Furthermore, the hydrogenation rates observed with the four model substrates follow the same trend, independently of the R‐oxy group of the ligand: methyl 2‐acetamidoacrylate>dimethyl itaconate>1‐phenylvinyl acetate>N‐(1‐phenylvinyl)acetamide. A substrate‐to‐catalyst ratio (S/C) of up to 10,000:1 was sufficient for total hydrogenation of a model substrate of intermediate reactivity (dimethyl itaconate), and did not imply any loss in conversion or enantioselectivity.
A library of enantiomerically pure POP ligands (phosphine–phosphite), straightforwardly available in two synthetic steps from enantiopure Sharpless epoxy ethers is reported. Both the alkyloxy and ...phosphite groups can be optimized for maximum enantioselectivity and catalytic activity. Their excellent performance in the Rh‐catalyzed asymmetric hydrogenation of a wide variety of functionalized alkenes (26 examples) and modular design makes them attractive for future applications. The lead catalyst incorporates an (S)‐BINOL‐derived (BINOL=1,1′‐bi‐2‐naphthol) phosphite group with computational studies revealing that this moiety has a dual effect on the behavior of our POP ligands. On one hand, the electronic properties of phosphite hinder the binding and reaction of the substrate in two out of the four possible manifolds. On the other hand, the steric effects of the BINOL allow for discrimination between the two remaining manifolds, thereby elucidating the high efficiency of these catalysts.
Hop on POP: Modular POP ligands (see figure), easily prepared in two synthetic steps, serve as highly efficient catalysts in the Rh‐mediated asymmetric hydrogenation of functionalized alkenes.
Herein is reported the effect of different polyether binders (alkali metal, alkaline earth metal, and lanthanide salts) as regulation agents to enhance the catalytic properties of palladium complexes ...derived from enantiopure bisphosphite ligands in allylic substitutions. The addition of RbOAc or M(OTf) x (M = Mg2+, La3+, or Ho3+) led to positive effects in enantioselectivity (by up to 16% ee) for the allylic substitution reactions. These ligands coordinated in the usual cis-fashion or in an unprecedented trans-fashion to the palladium center, depending on the phosphite group, and presented different reactivity in the allylic substitutions.
The catalytic insertion of copper carbenoids into O-H bonds affords synthetically useful α-alkyl/aryl-α-alkoxy/aryloxy derivatives. Herein, the design, preparation and application of supramolecularly ...regulated copper(
i
) complexes of bisoxazoline ligands is reported. We have demonstrated that the catalytic performance of these systems can be modulated by the use of an external molecule (
i.e.
the regulation agent), which interacts with a polyethyleneoxy chain on the ligand (
i.e.
the regulation site)
via
supramolecular interactions. This approach has been applied to an array of structurally diverse alcohols (cycloalkyl, alkyl and aryl derivatives). Moreover, we have used this methodology to synthesise advanced synthetic intermediates of biologically relevant compounds.
Maximisation of the yield by the choice of the regulation agent (RA).
POP art: Rhodium complexes of POP ligands serve as highly efficient and enantioselective catalysts in asymmetric hydrogenation leading to various valuable pharmaceutical building blocks and several ...direct precursors of chiral drugs such as LY2497282, lacosamide, rivastigmine, and aprepitant and 12 further examples (see scheme; nbd=norbornadiene; XC(O)G=NHAc, NHBoc, NHCbz, 2‐oxopyrrolidin‐1‐yl, OAc).
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