Azacrown ether derivatives

P. Bako, T. Kiss, L. Toke, Chiral Azacrown Ethers derived from D-Glucose as Catalysts for Enantioselective Michael Addition , Tetrahedron Lett. 1997, 38, 7259-7262. 

P. Bako, K. Vizvardi, S. Toppet, E. V. der Eycken, G. J. Hoonaert, L. Toke, Synthesis, Extraction Ability and Application in Asymmetric Synthesis of Azacrown Ethers derived from D-Glucose , Tetrahedron 1998, 54, 14975-14988. 

The aminolysis of pentalenes 50 with aliphatic diamines or azacrown ethers, which play the role of diamines, results in A,iV -bis(diazatrithiapentalenyl)diamines 51 and azacrown ether derivatives 52. Aryloxy groups in diamines 51 can be also substituted by NR2R3 fragments. A combination of azacrown ethers and different diamines results in compounds 32, 53, and 54 (Scheme 4) <1994CB2209, 1994PS81>. 

Magennis et al. prepared two azacrown ether derivatives 53 and 54, which formed 1 1 complexes with Eu " and Tb " cations [134]. Addition of pi-colinate anion to a solution of Eu -53 or Tb -53 gave 250- or 170-fold enhancement in the emission signals. Eu -54 exhibited similar augmentations upon the addition of picolinate anion (120-fold). Since these crown ethers were non-chromophoric, the coordinated aromatic carboxylate guests worked as antennae switching on the lanthanide luminescence. 

Ring-opening with heteroatomic nucleophiles is certainly among the most thoroughly studied behavior of epoxides, and this reaction continues to be a versatile workhorse of synthetic utility. This is exemplified in the recent literature by the examples of the p-cyclodextrin-catalyzed aminolysis of simple epoxides by aniline derivatives (i.e., 53 - 54) <00SL339> and the synthesis of oxa-azacrown ethers through the treatment of Ws-epoxides 55 with diamines 56. Yields in the latter synthesis are sensitive to the size of the macrocycle and substitution on the bis-epoxide <00TL1019>. 

The asymmetric Darzens condensation, which involves both carbon-carbon and carbon-oxygen bond constructions, was realized by use of the chiral azacrown ether 75als2,s ,ss and the quaternary ammonium salts derived from cinchona alka-loids159"621 under phase transfer catalyzed conditions. The a,p-epoxy ketone 80 (R=Ph) was obtained with reasonable enantioselectivity by the reaction of... 

The success of 24 and its cousins can be extended by attaching extra functionalities to improve selectivity towards chosen saccharide derivatives. For instance, glucosamine can be specified in its protonated form by modifying 24 with an azacrown ether. The latter unit is known to bind ammonium ions and 9-anthrylmethyl azacrown is a luminescent PET system of 15 years standing [76], 95, due to Cooper and James at the University of Birmingham, England,... 

Shinkai and coworkers (see Ref. 200) recently synthesized very fascinating azacrown ether linked dendrons by utilizing a branch cell reagent derived from 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane. These dendrons were constructed via the controlled convergent strategy and advanced to generation = 2. Tri-dendrons were constructed as described in Sect. 5.2.2.4. 

Azacrown Ethers Functionalized with 8-Hydroxyquinoline and Its Derivatives as Metal-Ion Sensors... 

Schall and Gokel have reported the construction of molecular boxes derived from nucleic acid bases and azacrown ethers [23]. Detailed NMR studies provided evidence for the association of A-crown-A with T-crown-T in chloroform. Formation of a ternary receptor complex with a, m-diammonium compounds (Figure 12) was also suggested. 

The second method can be used to synthesize Vogtle-type podands [9,10] in two high-yielding steps from polyethylene glycol ditosylates. The ditosylate derivatives, which are also precursors of cyclic crown ethers, azacrown ethers and lariat ethers, can be prepared with pyridine as the base [11], However, they are synthesized more effectively in higher yields using aqueous sodium hydroxide and tetrahydrofuran (Figure 1.4) [12], These conditions also remove the necessity to... 

Carbohydrate-derived azacrown ethers have been intensely studied as phase-transfer catalysts for the conjugate addition of 2-nitropropane to chalcones [172]. Various structural modifications have been introduced both in the azacrown core and in the carbohydrate (o-glucose, o-mannitol, and o-mannose) unit in order to obtain good enantioselectivities, the best results been obtained with o-glucose and D-mannose derivatives 113-117 (Scheme 2.60). 

Varma et al. (2004) discnssed the metal complexation of different chitosan crown ethers derivatives in detail (Varma et al., 2004). Newly prepared Schiff base-type chitosan-azacrown ethers were prepared by a reaction of chitosan (CTS) with V-(4 -formylphenyl) aza-crown ethers, and were then converted to secondary-amino derivatives by the redaction of CTS-azacrown ethers with sodiiun borohydride (Malkondu et al.,... 

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