Diamines conformational analysis

A quantitative estimation of the fraction of the 1,1 -cycles can be performed through a conformational analysis of the diepoxide molecules, i.e. determination of the number of their conformations in which the end-to-end distance is equal to the spacing between the nitrogen atoms in the corresponding diamine molecules. Such an analysis has given results qualitatively constistent with those obtained in the analysis of the molecular models by the Stewart-Brigleb method U0, n1,, I4>. 

A conformational analysis of the homologous series of the linear a,co-diamines (H2N(CH2)nNH2) (n=2 - 10, n=12) and the tri- and tetramines spermidine and spermine was undertaken (40-48). These molecules display a high conformational freedom, as well as an interdependence of the particular effects due to the nitrogens electronegativity and electron lone-pairs. 

These observations indicated that an intermolecular double condensation to give a bis N-(methylene-4-oxocoumarinyl)-l,4 aromatic diamine had occurred. Data from the elemental analysis indicated that the calculated and observed values were within the acceptable limits ( 0.4%) and in conformity with the assigned structure. In the addition of molar equivalents of 1,4-aromatic binucleophilic compounds to compound 72 we did not observe any heterocyclic compounds resulting from the further intermolecular nucleophilic attack on the single condensation product. Since the condensation of 3-(dimethylaminomethylene)-chromane-2,4-dione with aromatic binucleophilic compounds is the only route to the new coumarinic compounds, this represents a useful synthetic method. 

So far. X-ray analyses of free tetradentate Schiff bases have been carried out only in a very few cases. For acacenHj derivatives only two structures have been reported besides the thio analogue of acachxnHj." Some structural parameters of interest are listed in Table 10. The X-ray analysis results show that crystals consist, just as in solution, of discrete molecules characterized by an enaminoketone structure with intramolecular hydrogen bonding. However, the bond lengths Table 10) and the planarity of the two chromophores show that there is a certain amount of conjugation within the enamino ketone groups. The structure found in the solid state, with an approximate gauche conformation of the diamines, is consistent with that proposed as predominant in solution. 

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