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EXAMPLE 13 The Tetrakismaleamic Acid 28a This has the structure 28a shown in Scheme II where R3 and R4 are, respectively, STR20 To a magnetically stirred solution of 21 (5.535 g, 0.0075 mole in DMAC (35.0 ml), granular maleic anhydride (1.5375 g, 0.01569 mole) was added. A dark yellow solution obtained just after addition changes to a light yellow color. To this solution, powdered benzophenonetetracarboxylic dianhydride (1.2083 g. 0.00375 mole) was added and stirring continued at ambient temperature for 8-10 hrs. The solution was then poured over crushed ice. The light-yellow solid obtained was filtered, washed with water, and dried to yield tetrakismaleamic acid 28a. By using the appropriate molar proportions of maleic anhydride the maleamic acid 28b was prepared using a similar method.
Under a nitrogen atmosphere, a round bottom flask was charged with the prepared single carboranediamine monomer 1,2-bis (4-aminophenyl) -1,2-o-carborane(5.0000 g, 15.314 mmol) and 30ml DMF,Stir until the diamine monomer is completely dissolved and slowly add BTDA (2.4672 g, 7.657 mmol) and add 17.5 ml DMF to dilute the solution.After 4 h at room temperature, 4-PEPA (3.8014 g, 15.314 mmol) was added and the reaction continued for 12 h to obtain a 20percent solids polyamic acid solution.Additional acetic anhydride (9.43 g, 92.4 mmol) and triethylamine (1.56 g, 15.4 mmol) were added and the reaction was continued for 12 h at room temperature for chemical imidization.After the reaction was completed, the solution was poured into a large amount of deionized water, the precipitate was filtered, and the filter cake was washed with water until the filtrate became neutral.The solid was dried in a vacuum oven at 120°C for 12 h to give a yellow prepolymer, named "oligomer PI-CBA" (structure shown in Figure 8).
Under a nitrogen atmosphere, biphenyldiamine (5.0000 g, 27.14 mmol) and 50 ml DMF were added to a round bottom flaskStir until the diamine monomer is completely dissolved, slowly add BTDA (4.3723 g, 13.57 mmol), and add 18.0 ml DMF to dilute the solution.After 4 h at room temperature, 4-PEPA (6.7367 g, 27.14 mmol) was added.The reaction was continued for 12 hours to obtain a polyamic acid solution having a solid content of 20percent.Additional acetic anhydride (16.88 g, 165.36 mmol) and triethylamine (2.79 g, 27.56 mmol) were addedThe reaction was continued at room temperature for 12 hours for chemical imidization.After the reaction was completed, the solution was poured into a large amount of deionized water, the precipitate was filtered, and the filter cake was washed with water until the filtrate became neutral.The solid was dried in a vacuum oven at 120[deg.] C. for 12 h to give a yellow prepolymer, which was named "oligomer PI-BPA" (structure shown in FIG. 8).
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