Long Range Electronic Effects on the Host-Guest Complexation within the Oxygen Depleted 5,5'-Bicalixarene Cavities.

We report the synthesis of a series of the oxygen-depleted conjugated 5,5'-Bicalix[4]arene compounds bearing various substituents at the terminal positions of the conjugated chain and their fluorescence response to the presence of a cationic N-methylpyridinium guest. The complexation of this cation within the bicalixarene cavity results in the fluorescence quenching, with the host molecules bearing electron-donating groups demonstrating a stronger fluorescence response. These results show the importance of the electronic effects on the host-guest complexation within the hydrophobic calixarene scaffolds.

Enantioselective Synthesis of Chiral 2-Nitroallylic Amines via Cooperative Cation-Binding Catalysis.

Chiral allylic amines are valuable building blocks for biologically important compounds and natural products. In this study, we present the use of cooperative cation-binding catalysis as an efficient method for synthesizing chiral allylic amines. By utilizing a chiral oligoEG and potassium fluoride as a cation-binding catalyst and base, respectively, a wide range of biologically relevant chiral 2-nitroallylic amines are obtained with excellent enantioselectivities (up to >99 % ee) through the organocatalytic asymmetric aza-Henry-like reaction of ß-monosubstituted and ß,ß-disubstituted nitroalkenes with α-amidosulfones as imine precursors. Extensive experimental studies are presented to illustrate plausible mechanisms. Preliminary use of a chiral 2-nitroallylic amine as a Michael acceptor demonstrated its potential application for diversity-oriented synthesis of bioactive compounds.

Access to Chiral GABA Analogues Bearing a Trifluoromethylated All-Carbon Quaternary Stereogenic Center through Water-Promoted Organocatalytic Michael Reactions.

Water enables the highly challenging enantioselective Michael addition of sterically congested ß-trifluoromethyl-ß-aryl- or -alkyl-substituted nitroolefins with dithiomalonates. Under on-water conditions, the reaction rates were remarkably accelerated as a result of enforced hydrophobic interactions between catalysts and reactants. Takemoto-type thiourea catalysts are very effective for this transformation, affording highly enantioenriched Michael adducts that provide simple access to chiral γ-aminobutyric acid (GABA) analogues with a ß-trifluoromethylated quaternary stereocenter.

Cu(OAc)2-Promoted Ortho C(sp2)-H Amidation of 8-Aminoquinoline Benzamide with Acyl Azide: Selective Formation of Aroyl or Acetyl Amide Based on Catalyst Loading.

An efficient method for the C(sp2) amidation of 8-aminoquinoline benzamide by acyl azide in the presence of copper acetate has been achieved via C-H activation. Interestingly, the loading of copper acetate has a strong influence on the outcome of the reaction. The use of 1 equiv of copper acetate produces the corresponding aroyl amide, whereas the use of 2 equiv led to acetyl amide. A series of substituted benzoyl and acetyl amides has been obtained.

Palladium-Catalyzed Ligand-Free Decarboxylative Coupling of α- Oxocarboxylic Acid with Aryl Diazonium Tetrafluoroborate: An Access to Unsymmetrical Diaryl Ketones.

Diaryl ketones are of much importance in organic synthesis as versatile intermediates and in industry for their useful properties. A mild and efficient palladium-catalyzed traditional ligand-free decarboxylative coupling of aryl α-keto carboxylic acid with aryl diazonium fluoroborate has been developed. A series of unsymmetrical diaryl ketones has been synthesized in moderate to good yields using this procedure. A radical pathway involving the acyl radical has been suggested.

Cobalt-Catalyzed Remote C-4 Functionalization of 8-Aminoquinoline Amides with Ethers via C-H Activation under Visible-Light Irradiation. Access to α-Heteroarylated Ether Derivatives.

A cobalt-catalyzed selective remote C-4 alkylation of 8-aminoquinoline amides via C-H activation under irradiation with a CFL lamp in the presence of eosin Y at room temperature has been achieved. A series of pharmaceutically important C-4 quinoline amide-substituted ether derivatives has been obtained by this procedure. The C-4 functionalization of quinoline amides with inert ether is of much significance and was not reported earlier.

Transition-Metal-Free Iodine Catalyzed Selenocayanation of Styrenyl Bromides and an Easy Access to Benzoselenophenes via Intermediacy of Styrenyl Selenocyanate.

A convenient procedure has been developed for the synthesis of styrenyl selenocyanates and benzoselenophenes from readily available styrenyl bromides by reaction with potassium selenocyanate in the presence of iodine under specified conditions. A series of both compounds have been obtained by this procedure. The synthesis of styrenyl selenocyanates has not been previously reported, and thus this method is of much significance.

Cobalt-catalyzed intermolecular C(sp(2))-O cross-coupling.

Cobalt(II)-catalyzed C(sp(2) )O cross-coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of Cu(I) has been achieved under ligand-free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the CO coupling. This unique Co/Cu-dual catalyst system provides an easy access to a library of aryl-vinyl, heteroaryl-styryl, aryl-aryl, and heteroaryl-heteroaryl ethers in the absence of any ligand or additive.

A direct synthesis of selenophenes by Cu-catalyzed one-pot addition of a selenium moiety to (E,E)-1,3-dienyl bromides and subsequent nucleophilic cyclization.

An efficient protocol for the synthesis of selenophenes and selanyl selenophenes has been achieved by a simple one-pot reaction of 1,3-dienyl bromides and 1,3-dienyl-gem-dibromides respectively with KSeCN catalyzed by CuO nanoparticles. Several aryl, alkenyl, heteroaryl, and alkyl substituted selenophenes were obtained with a broad array of functional group tolerance. This is found to be a general methodology for chalcogenophenes being effective for the synthesis of thiophenes too.

Copper-assisted nickel catalyzed ligand-free C(sp2)-O cross-coupling of vinyl halides and phenols.

A convenient and efficient protocol has been achieved for the cross-coupling of phenols and vinyl halides by a unique Ni/Cu catalytic system for the first time, where the reaction is catalyzed by Ni and Cu is involved in the transmetalation process. This procedure provides an easy access to a library of aryl-vinyl and aryl-styrenyl ethers.