Optical rotatory dispersion of nitrobenzene derivatives. VII. Application of modified curtis rearrangement for determining the free carboxylic position in some partial esters of 3-nitro-phthalic and 4-nitrohemimellitic acid.

Abstract

Conclusive evidence was obtained for the position of chiral alkyl groups in the esters of 3-nitrophthalic and 4-nitrohemimellitic acid, which are key substances demonstrating interesting chiroptical property due to twisting of the nitrobenzene chromophore controlled by the remote chiral groups through in phase twisting of the intervening substituents. Diphenylphosphorylazide (DPPA) was used as the reagent for modified Curtius rearrangement with good success. Since it acts specifically on carboxylic acid but not on ester function, only the former is converted to amine function. The amino compounds so derived were proved to be identical with the known substances. The method seems useful generally for determining the free carboxylic position in some partial esters of polycarboxylic acids.