No slow down: A microporous recyclable heterogeneous catalyst made from a 1,1′‐binaphthalene‐2,2′‐diol (binol)‐derived phosphoric acid chloride is as active as the corresponding homogeneous catalyst when using the same mass of both in different reactions. Reaction rates, yields, and enantioselectivities are comparable.
Microporous polymer networks, composed of structure-directing monomers (tectons), can exhibit high permanent surface area and porosity. By choice of suitable tectons various functionalities can be introduced into such networks. Here we introduce chiral BINOL derivatives as novel tectons to generate microporosity in polymer networks. The use of such monomers enables the formation of networks composed solely out of enantiomerically pure compounds. This porous network can be used as a heterogeneous organocatalyst in asymmetric reactions and gives higher enantioselectivty than the homogeneous reaction.
The formation of chiral and sterically congested cyclohexanone derivatives has been achieved through a multistep sequence with one single purification step. (n-Butoxymethyl)-diethylamine was identified as a highly efficient reagent for the direct trapping of aluminum enolates. The Lewis acidic character of aluminum suffices to activate the α-aminoether to form in situ an electrophilic iminium species. In return the aluminum enolate is rendered more nucleophilic by coordination of the butoxy group and formation of an aluminate.
The first catalytic enantioselective total synthesis of riccardiphenol B, a sesquiterpene derivative isolated from a Japanese collection of the liverwort Riccardia crassa, has been achieved. A copper-catalyzed asymmetric conjugate addition of trimethylaluminum was used at an early stage to generate the quaternary stereogenic center with high enantiomeric excess. The corresponding sterically encumbered aluminum enolate was directly trapped with an α-amino ether, allowing after oxidation, the release of a key intermediate in the total synthesis of the target natural product
Keine Verlangsamung: Ein mikroporöser wiederverwendbarer heterogener Katalysator, hergestellt aus einem von 1,1′‐Binaphthalin‐2,2′‐diol (binol) abgeleiteten Phosphorsäurechlorid, ist in verschiedenen Reaktionen genauso aktiv wie der entsprechende homogene Katalysator. Die Reaktionsgeschwindigkeiten, Ausbeuten und Enantioselektivitäten sind vergleichbar.
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