A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal-organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported.
leahciM! The N‐heterocyclic carbene catalyzed umpolung of Michael acceptors proceeds through the formation of a deoxy‐Breslow intermediate (see scheme; EWG=electron‐withdrawing group). This nucleophilic species can react with other Michael acceptors in an intermolecular fashion, thereby resulting in the formation of homo‐ or heterodimeric olefins. This “Michael umpolung” should become a valuable method for the formation of densely functionalized olefins.
The synthesis of
α-amino carbonyl/carboxyl compounds is a
contemporary challenge in organic synthesis. Herein, we present a
stereoselective α-amination of amides employing simple azides
that proceeds under mild conditions with release of nitrogen gas.
The amide is used as the limiting reagent, and through simple variation
of the azide pattern, various differently substituted aminated products
can be obtained. The reaction is fully chemoselective for amides even
in the presence of esters or ketones and lends itself to preparation
of optically enriched products.
Recently, we have described the synthesis of chiral metal-organic frameworks iPr-ChirUMCM-1 and Bn-ChirUMCM-1 and their use in enantioselective separation. Here, we demonstrate for the first time the use of a chiral solvating agent (1-phenyl-2,2,2-trifluoroethanol, TFPE) for chiral recognition in iPr-ChirUMCM-1 and Bn-ChirUMCM-1 by means of solid-state(13)C NMR spectroscopy.
N-Heterocyclic carbene-catalyzed umpolung of aldehydes followed by their interception with diarylbromomethanes has been reported. This conceptually novel transition-metal-free cross-coupling of aldehydes with alkyl halides works well at low catalyst loadings and under mild reaction conditions leading to the formation of diaryl acetophenone derivatives in good yields. In addition, α-halo ketones and esters can also be used as aldehyde reaction partners.
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