Awesome and Easy Science Experiments about 4254-15-3

In homogeneous catalysis, the catalyst is in the same phase as the reactant. The number of collisions between reactants and catalyst is at a maximum.In a patent, Recommanded Product: 4254-15-3, name is (S)-Propane-1,2-diol, introducing its new discovery. Recommanded Product: 4254-15-3

New Symmetrical Chiral Dibenzyl- and Diphenyl-Substituted Diamido-, Dithionoamido-, Diaza-, and Azapyridino-18-crown-6 Ligands

Eleven new chiral macrocycles (1-11, see Figure 1) of the pyridino-18-crown-6 type have been prepared.Nine diazapyridino-crown ligands contain two amide (1, R = benzyl; 4, R = phenyl), two N-methylamide (7, R = phenyl), two thionoamide (2, R = benzyl; 5, R = phenyl), two N-methylthionoamide (8, R = phenyl), two amine (3, R = benzyl; 6, R = phenyl), or two N-methylamine (9, R = phenyl) groups incorporated into the macroring.The appropriate chiral diamine was treated with dimethyl 2,6-pyridinedicarboxylate (or 2,6-pyridinedicarboxyl dichloride),O,O’-dimethyl 2,6-pyridinedicarbothioate, or 2,6-pyridinedimethyl ditosylate to prepare these materials.The macrocyclic diamides were also converted to the macrocyclic dithionoamides using Lawesson’s reagent and the latter macrocycles were reduced to the diamines.A new symmetrically substituted dimethylazapyridino-18-crown-6 ligand (10) and its N-acetyl derivative 11 were also prepared.The interactions of some of the new chiral ligands with (R)- and (S)-ammonium perchlorate were studied by 1H NMR spectral techniques.The degree of enantiomeric recognition was determined by the difference of the free energy of activation values (DeltaDeltaGexcit.) and the difference in log K values for these interactions.The X-ray analyses of the dithionoamido ligands (2, 5, and 8) showed severe deviations of the S and N atoms from the plane of the pyridine ring, especially in the case of 8.The optical rotations of 8 changed with time due to conformational changes.The relevant conformations of 8 are discussed in light of the X-ray crystallography, molecular mechanics, and 1H NMR spectra.

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Reference£º
Synthesis and Crystal Structure of a Chiral?C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur¨Cnitrogen¨Coxygen ligand derived from aminothiourea and sodium?D-camphor-¦Â-sulfonate