| 摘要 |
Dicarboxylic acid derivs. of formula (I) are prepd. by (A) mixing (II) and (III) in a solvent at 10-30 deg.C and (B) reacting at 60-80 deg.C. Where X,X'=halogen, R, R1=H, lower alkyl or Ar. Thus, reflux p-aminobenzoic acid, MeOH and H2SO4 for 1hr, neutralize with Na2CO3, extract with CHCl2 twice and back-extract with water to eliminate impurities, dry with MgSO4 to eliminate moisture in soln. and dry off CH2Cl2, recryst. from MeOH to give p-aminobenzoic acid methyl ester (yield 70%, m.p. 114-115 deg.C).
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