Pyrrolidine-2,4-dione derivative, formation

Imino derivatives 100 of compounds of type 95 were also directly prepared from cumulated ylides 82 or 4 and parabanic acid derivatives 99 by a presumed mechanism as depicted in Scheme 22 [70]. Attack of the nucleophilic ylidic carbon atom at the most electrophilic amide-type carbonyl carbon atom, ring opening with loss of phenyl isocyanate, and recyclization by N-C bond formation are the key steps. This reaction is reminiscent of an older one, furnishing 5,5-diethoxy- l-thiobenzoyl-4-triphenylphosphoranylidene-pyrrolidine-2,3-dione 102 from 2-phenylthiazoHne-4,5-dione 101 and 4 [71] in modest yield. 

The mechanism of the formation of lff-pyrrole-2,3-diones 494 involves first the Michael-type attack of nitrogen atom of NH2 group of the urea derivative on C(5) in the furandione ring. Later, the molecule of water was eliminated and compound 494 was obtained. Nucleophilic addition of 1,2-DABs 155 to pyrrole-2,3-dione 494 lead to quinoxalin-2-ones 495. These compounds arise fi om the sequential attacks of 1,2-DABs at the C(3) and C(2) atoms of pyrrolidine, respectively, followed by the elimination of water and pyrrole ring opening, and the basic hydrolysis of this intermediate provides the final product 495. A possible reaction scenario is outlined in Scheme 2.111. 

Monsal and coworkers have achieved the construction of pyrrolidine nucleus in the synthesis of tetrahy-dropyrrolo[3, 4 3.4]pyrrolo[2.1-fl]isoquinoline-9,ll-diones 57 derivatives in an aqueous micellar medium [53]. The S5mthesis involves a one-pot three-component reaction of variously substituted isoquinolines 54, 2-bromoacetophenone 55, and N-arylmaleimide derivatives 56 in the presence of triethylamine as a base (Scheme 18). The preliminary investigation indicated that the presence of surfactant was essential for the success of reaction. Accordingly, the reactions were carried out in cationic, anionic, and nonionic surfactants well above their critical micelle concentrations (CMC). The maximum yields were obtained in cetyltrimethylammonium bromide (CTAB) (CTABiCMC value 0.29 mM at 80mM concentration). The mechanism of formation involves an in situ generation of isoquinolinium ylides followed by [2 -h3] cycloaddition of N-aryl maleimides. 

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