Heterocyclic compounds, conformational analysis

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. 

See G.F. Riddell, "The Conformational Analysis of Heterocyclic Compounds", pags. 139-140, Academic Press, London, 1980. 

B-80MI20401 F. G. Ridell The Conformational Analysis of Heterocyclic Compounds ,... 

Conformational Analysis of Five- and Six-Membered Rings and Related Non-Bridged Systems (Saturated Heterocyclic) , F. G. Riddell, in Aliphatic, Alicyclic and Saturated Heterocyclic Compounds , ed. W. Parker, Royal Society of Chemistry, London, 1974, vol. 1, pt. 3, pp. 69-91. 

Conformational Analysis in Saturated Heterocyclic Compounds E. L. Eliel, Acc. Chem. Res., 1970, 3, 1-8. 

At the end of this conformational analysis it is essential to realize that the preferential con-former of both (DHQ)2-PHAL and (DHQD)2-PHAL contains a twofold rotation axis coinciding with the longitudinal axis of the central heterocycle. The existence of this rotation axis implies, for example, that the two difrydroquinuclidme subunits of each compound can be mapped onto each other through 180° rotation. This means that in a given compound one dihy-droquinuclidine subunit has exactly the same properties as the other. 

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