Improved Synthesis of N-Substituted 2,3-Pyridinedicarboximides with Microwave Irradiation

Microwave-promoted synthesis of cyclic imides

“…Aqueous solutions of ammonia have proved suitable for the synthesis of phthalimide 80 and quinolinimide. 81 For instance, Perillo et al have studied the reaction of quinolinic acid or its anhydride with aqueous ammonia or with a reagent capable of generating ammonia in situ, such as urea, acetamide or ammonium carbonate, under MW irradiation in a modified domestic oven. The highest yields were obtained with 28% aqueous ammonia (Scheme 2).…”

“…80,86,100,101 Although one advantage of DMF as solvent is its capability to retain water formed during the course of the reaction, hence avoiding the need for a water separator, 102 the employment of molecular sieves can improve the results as is the case of the synthesis of quinolinimides from quinolinic anhydride. 81 Other neutral, acid or basic solvents with different polarity, have proved useful. Chorell has synthesized Nsubstituted phthalimides from phthalic acids and amines in one step employing acetonitrile, acetic acid or pyridine.…”

“…However, literature data describing the use of MW for cyclization are scarce. Perillo et al 81 have developed methods for the synthesis of N-substituted 2,3-pyridinedicarboximides (quinolinimides) by aminolysis of the anhydride. The authors observed that when the amine could be used directly as free base, it was convenient to isolate the amic acid intermediates and then proceed to their cyclization (Scheme 26).…”

“…81 The method represents a typical example of the MORE chemistry developed by Bose 95 . 133 The MW irradiation presented noteworthy advantages over the conventional heating.…”