Synthesis of 2,3,6,7-Tetramethylnaphthalene from 2,3-Dimethylsuccinic Anhydride ando-Xylene

2,3,6,7-Tetramethylnaphthalene (7b) was prepared from 2,3-dimethylsuccinic anhydride (1) and o-xylene in five steps, and the configurations of their intermediates were studied. The higher-melting isomer (threo form) of 1 gave higher-melting products in each step, while the lower-melting isomer (erythro form) of 1 gave lowermelting ones. The configurations of the intermediates were confirmed by the MNR spectral data of tetramethyltetralines (6b). Similar reactions were carried out with 3-benzoyl-2,3-dimethylpropionic acid (2a) in order to learn the configurations of the intermediates. 3-Aroyl-2,3-dimethylpropionic acids (2) gave 2,3-dimethyl-4-aryl-3-buten-4-oildes (3) upon heating with hydrochloric acid.