4-Methylphthalic acid

Pseudocumene 200 Trimellitic acid, 23 Methylphthalic acid, 39 Dimethylbenzoic acid, 14... 

Ne es from ligroin. M.p. 95°. Sol. usual solvents. Very vdatile in steam. Hot dil. HNO3 —> 3-methylphthalic acid. 

The easy liberation of trifluoroethanol from 2,2,2-tnfluoroethyl hydrogen 3,6-di methylphthalate can be accounted for by nng closure to form 3,6 dimethylphthalic anhydride [57] (equation 56) The carboxylate anion is the intermediate needed for nng closure because the rate increases as the pH, while still acidic, increases... 

Other reagents used for the preparation of lactones from acid anhydrides are lithium borohydride [1019], lithium triethylborohydride (Superhydride ) [1019] and lithium tris sec-butyl)borohydride (L-Selectride ) [1019]. Of the three complex borohydrides the last one is most stereoselective in the reduction of 3-methylphthalic anhydride, 3-methoxyphthalic anhydride, and 1-methoxynaphthalene-2,3-dicarboxylic anhydride. It reduces the less sterically hindered carbonyl group with 85-90% stereoselectivity and is 83-91% yield [1019]. 

Other monoamic acids were investigated by p-NMR and the data are summarized in Table 17.2. A variety of complex phenomena was observed. For some cases, similar isomer compositions were seen in both NMP- and in CHCI, -prepared monoamic acids (compounds Ic and Ig), and in other syntheses, a reversal of the favored isomer was observed (compounds Id and le). Amoiuits of one isomer increased when NMP was used (compound lb). Finally, the 4-methylphthalic anhydride amic acid (If) displayed a single signal in the F-... 

C9H6BrF02 5-bromo-2-fluorocinnamic acid 102865-71- 25.00 1.6228 2 15940 C9H603 3-methylphthalic anhydride 4792-30-7 25.00 1.2778 2... 

Lam et al. 226) have reported syntheses of valsarin and 2,4-di-chloroemodin and a new synthesis of 2-chloroemodin (Scheme 18). Thus Friedel-Crafts acylation of a substituted resorcinol (162) with 3-methoxy-5-methylphthalic anhydride gave a crude benzophenone which was treated with boric oxide-sulfuric acid to yield the anthraquinones, 2-chloroemodin (163) and 2,4-dichloroemodin (164). 2,4-Dichloroemodin on treatment with boric acid and sulfuric acid gave valsarin (165). Tetra-O-methyl-valsarin was also synthesized via chlorination of xanthorin. 

An AB2-type monomer (1-13, Scheme 8), was synthesized by Yamanaka et al. [133] starting from 3,5-dimethoxyphenol via a polyamic acid methyl ester precursor. The aromatic hb-PIs were prepared by chemical imidization in the presence of acetic anhydride and pyridine. The synthesized polyimides were soluble in polar aprotic solvents and showed thermal stability, with a Tajo% of 470°C in nitrogen and a Tg of 193°C. In another work by Yamanaka et al. [134], the same AB2 monomer containing free amine end groups of the precursor was end-capped with acetyl, n-heptanoyl chloride, and 4-methylphthalic anhydride. By chemical imidization of these precursors in the presence of acetic anhydride and pyridine, hb-PIs were prepared. The DB of the hb-PIs was 50% as expected. The hb-PIs showed a above 395°C, and Tg values of 189, 138, and 186°C for the end groups of acetoamide, -heptanoamide, and 4-methylphthalimide, respectively. 

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