Amines Schiffs base formulation

Niobium and tantalum halides form adducts with various nitrogen donor ligands including aliphatic and aromatic amines nitriles, Schiffs bases and imidazoles (Table 5). The reactions of MXS with pyridine and related ligands such as bipy or phen depend critically on the reaction conditions. With py at low temperature MX5 (X = Cl, Br) yielded 1 1 adducts that are rapidly reduced to [MX4(py)2] on increasing the temperature, with formation of l-(4-pyridyl)pyridinium halide. Similarly, bipy and phen reduced the metal in MeCN to oxidation state +IV and formed monoadducts of type [MX bipy)] at room temperature, while at 0°C the same reactions yielded [NbCls(bipy)(MeCN)] and [TaX5(bipy)(MeCN)J (X = C1 or Br). NbBrs and Tals formed [MX5(bipy)2], which were formulated as the eight-coordinate [MX4(bipy)2]X.1 Reduction of the metal can however be prevented, even at room temperature,... 

The accessibility of the primary amine functions of chitosan has been quantified in organic solvent by formation of a salicylaldimine Schiff base upon treatment with salicylaldehyde. When contacting salicylaldehyde the aerogel beads of chitosan become yellow and their UV-visible diffuse reflectance spectra exhibit the absorption band at 318 nm, characteristic of the Schiff base. Quantitative GC analysis of the remaining salicylaldehyde in the solution allows calculation of the fraction of reacted amino groups, which corresponds to the fraction of accessible sites. In the aerogel formulation, up to 70% of the amine groups are accessible [92]. 

Of the number of chromophoric derivatives of chiral amines for potential use in the establishment of their absolute configuration by BCD measurement only a few have proven to be generally useful. Of these, intensive investigation of the Af-salicylidene (Schiff base) derivatives of chiral primary amines, including unsubstituted and ring-substituted a- and S-arylalkylamines, a-amino acids, unsaturated and satnrated aliphatic and alicyclic amines, and amino sugars, has resulted in the formulation of the salicylidenamino chirality rule ° °. The application of this rule has recently been reviewed and has been successfully used for the establishment of absolute configuration of chiral primary amines in connection with other stereochemical studies. In related studies, the conformations of a series of pyridoxyl-L-a-amino acid Schiff bases were deduced from their CD spectra ... 

Primary and secondary amines can react readily with aldehydes and more slowly with ketones to give Schiffs bases or enamines, respectively. This reaction is particularly important with reducing sugars such as glucose, lactose and fmctose that may be incorporated in formulations with amines. For instance, if LDOPA were formulated in a tablet with lactose as a filler, the reaction shown in Figure 3.23 could occur. Such reactions, leading to discolouration of lactose-containing tablets, have been... 

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