Polyfunctional building blocks are essential for the implementation of diversity-oriented synthetic strategies, highly demanded in small molecule libraries’ design for modern drug discovery. Acyl(imidoyl)ketenes are highly reactive organic compounds, bearing both oxa- and aza-diene moieties, conjugated symmetrically to the ketene fragment, enabling synthesis of various skeletally diverse heterocycles on their basis. The highlights of reactions utilizing acyl(imidoyl)ketenes are high yields, short reaction time (about several minutes), high selectivity, atom economy, and simple purification procedures, which benefits the drug discovery. The present review focuses on the approaches to thermal generation of acyl(imidoyl)ketenes, patterns of their immediate transformations via intra- and intermolecular reactions, including the reactions of cyclodimerization, in which either symmetric or dissymmetric heterocycles can be formed. Recent advances in investigations on mechanisms, identifications of intermediates, and chemo- and regioselectivity of reactions with participation of acyl(imidoyl)ketenes are also covered.
This review summarizes a series of studies on the reactions of 1H-pyrrole-2,3-diones, fused at the C 5 -N 1 bond to nitrogen-containing heterocycles, with nucleophiles, leading to the formation of C-C bonds. Reactions of pyrrolobenzoxazinetrione and pyrroloquinoxalinetrione with CH,OH-, CH,NH-binucleophiles, and dienophiles are discussed.
Data on methods for the synthesis of 2,3-dihydro-2,3-pyrrolediones condensed with azaheterocycles on the [a] side are reviewed. Their reactions with nucleophilic reagents, allylboronation, reduction, and thermal transformations are discussed.The chemistry of 2,3-dihydro-2,3-pyrrolediones condensed with azaheterocycles on the [a] side first evolved in the seventies, when the application of 2,3-dihydro-2,3-pyrroledione derivatives as synthetic blocks for the construction of alkaloid molecules was first demonstrated [1][2][3][4][5][6][7].It should be mentioned that up to the beginning of the nineties these annelated dihydropyrrolediones were studied almost exclusively as subjects for photoreduction and photocyclization or as dienophiles in DielsAlder reactions (for the production of intermediate compounds in the synthesis of alkaloids). A large part of these papers belong to certain groups of investigators [1][2][3][4][5]. Single reports on reactions with nucleophilic reagents, allylboronation, reduction, and thermal transformations of 2,3-dihydro-2,3-pyrrolediones annelated with azaheterocycles on the [a] side have only begun to appear comparatively recently. This region of their chemical behavior has been studied little in spite of the fact that they exhibit high reactivity toward various nucleophiles (particularly with the presence of several electron-withdrawing substituents in the rings) and generate imidoylketenes during thermolysis.In the present review we examine publications existing up to March, 2002, on methods for the production of dihydropyrrolediones condensed with azaheterocycles and their chemical transformations. The review does not include data on the chemistry of isatins and their aza analogs, which were described in [8], or data on the cycloaddition of these pyrrolediones, which have been discussed before [1][2][3][4][5][6][7][9][10][11] and were reviewed in [11].
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