| 摘要 |
<p>Prepn. is by (a) reacting piperylene with maleic anhydride to form 3-methyl-cyclohex-4-ene, 1,2-dicarboxylic anhydride (II), (b) dehydrogenating (II) pref. in the presence of Pd or Pt on carbon catalyst to 3-methyl-phthalic anhydride (III) and (c) oxidising (III) in the presence of HNO3 to (I). The piperylene is pref. the trans isomer but can be a mixture of cis- and trans-isomers and the stage (a) is carried out in the presence of I2. Hemimellitic acid is obtd. in good yield by an inexpensive process using a readily available, cheap starting material.</p> |
