A NEW METHOD FOR THE PREPARATION OF DIARYLPHTHALIDES¹

Abstract

During a study of synthetic laxatives it became necessary to obtain a supply of phenolphthalein (4',4"-dihydroxydiphenylphthalide) entirely free from the by-products which result during the manufacture of this substance. Certain of these by-products-presumably some type of anthraquinoneare extremely potent cathartics and yellow phenolphthalein, that is, phenolphthalein which has not been subjected to a thorough purification process and which is contaminated with a small quantity of a yellow, alkali-soluble, resinous material, is used extensively as a laxative.2 Furthermore, we wished to obtain a sample of isophenolphthalein (2,,4'/-

Grignard Reactions on Ortho Dicarboxylic Arene Derivatives. Synthesis of 1,3-Dithienylisothianaphthene Compounds

“…31 According to qualitative TLC analysis of the reaction mixtures, the best results were obtained in the solvent mixture with a ratio of 1:2 (boiling temperature of 58°C). Phthalic Anhydride and Thiophthalic Anhydride.…”

“…Since the reactivity toward a second nucleophilic substitution is seriously reduced after the opening of the anhydride ring system we performed the Grignard reaction at somewhat higher temperatures than usual. Therefore, we used refluxing solvent mixtures of toluene/ether in a ratio of 1:2, 1:3, and 4:1 . According to qualitative TLC analysis of the reaction mixtures, the best results were obtained in the solvent mixture with a ratio of 1:2 (boiling temperature of 58 °C).…”

“…However, only a yield of about 10% was obtained, and the material contained a certain amount of colored matter which was very difficult to remove. Even the slow addition of the Grignard reagent to a solution of 5a in THF at -78 °C or the use of a 1:2 toluene mixture 31 resulted in a very poor yield of the ortho diketone 7a besides the formation of alcohols and many other side products. These results were later confirmed by Ba ¨uerle et al, 16 who did not succeed at all in obtaining 7a.…”

“…Therefore, we used refluxing solvent mixtures of toluene/ether in a ratio of 1:2, 1:3, and 4:1. 31 According to qualitative TLC analysis of the reaction mixtures, the best results were obtained in the solvent mixture with a ratio of 1:2 (boiling temperature of 58 °C). After purification by means of column chromatography a yield of 15% of the ortho diketone 7a was obtained.…”

“…In a Grignard reaction with 2-thienylmagnesium bromide as the Grignard reagent one can use different substrates. In literature the use of 5a , , phthalic anhydride , and thiophthalic anhydride , has been reported in the synthesis of ortho diketones. However, the results of different authors appeared not to be entirely consistent with one another.…”