The synthesis and stereochemistry of some substances derived from 1,1'-binaphthyl-8,8'-dicarboxylic acid

Abstract

Experimental data have been accumulated in order to compare the optical stabilities of several 8,8'-disubstituted-1,1'-binaphthyls, thus extending the work already done on the 8,8'-acid and its esters to blocking groups of distinctly different character. The compounds studied are 1,1'-binaphthyls substituted in 8 and 8' positions by hydroxymethyl, bromomethyl, methyl, methylene quinolinium bromide and methoxy carbonyl groups; in addition benzo-1',2'-7,8-benzanthrone-3'-carboxylic acid and its methyl ester have been prepared.All these compounds have been synthesised for the first time (except benzo-11,2'-7,8-benzanthrone-3'-carboxylic acid and its ester)and have been obtained in their optically active state for the first time. Their rate co-efficients for racemisation have been determined at several temperatures covering the range 30°-40° (except 8,8'-bisbromomethyl and 8,8'-bis(methylenequinolinium bromide)-1,1'-binaphthyls which were decomposed in N,N-dimethylformamide). The solvent used for all the compounds was N,N-dimethylformamide. From the experimental results the Arrhenius parameters E and log10A and the Transition State Theory functions have been calculated using the equations. In the discussion the optical stability of optically labile substituted 1'1-binaphthyls have been described. A comparison of the racemisation parameters has been made which appears to show that the CH3, and the CH2OH groups, which are rounded (or three dimensional) produce larger angular blocking area to passing than the -COOH and COOCH3 or C00C2H5 groups do, which are "flat". That is, 8,8'-bishydroxymethyl, 8,8'-dimethyl and 8'-hydroxymethyl-8'-methoxy carbonyl-1,1'-binaphthyls are more stable than 1,1'-binaphthyl-8,8'-dicarboxylic acid and its ester. All these compounds are also concluded to be strained in their ground state as they are much less stable than the 1,1'-binaphthyl-2,2'-dicarboxylic acid. The strain is obvious also from the models.In the experimental section the syntheses and the methods by which the optical activity was gained have been described. In the final part some infrared spectral data for 1,1'-binaphthyl-8,8'-dicarboxylic acid, its ester and 1',2'-7,8-(benzanthrone)"3,-carboxylic acid is given. No complete conclusion can be drawn from these spectra, but it may be seen in 1,1'-binaphthyl-8,8'-dicarboxylic acid the (+) and (-) forms have similar infrared spectra and hence have the same molecular configuration apart from the mirror image isomerism, while in (+) acid the infrared spectrum shows distinct differences therefore it probably has a different configuration. The difference could be because of the hydrogen bonding which may be different in the two cases owing to different spatial configuration of the carboxylic acid groups relative to each other.