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  • Author: Branko Stanovnik x
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Reactions of 1-cyano-4-oxo-4H-quinolizine-3-diazonium tetrafluoroborate (1a) and 4-oxo-4Hpyridino[ 1,2-a]pyrimidine-3-diazonium tetrafluoroborate (1b) with aliphatic amines 2a - g were studied. Treatment of heteroaryldiazonium salts 1 with secondary amines 2a - d afforded the corresponding N-alkyl-N’-heteroaryltriazenes 3a - h in high yields. On the other hand, reactions of 1a with aliphatic primary amines 2e - g resulted in an unexpected rearrangements into the corresponding picolinic acid N-alkylcarboxamides 4a - c.

Various aplysinopsin and β -carboline thiohydantoin analogues were prepared starting from ethyl 3-formyl-1H-indole-2-carboxylate by condensation with the active methylene group of 2-thiohydantoin, rhodanine, or thiobarbituric acid derivatives

Abstract

The thermal metal-free [2+2] cycloadditions of electron-poor acetylenes to some polysubstituted systems with conjugated double bonds (polysubstituted butadienes) are described.

Abstract

Dimethyl 3-oxopentane-1,5-dioate (dimethyl acetone-1,3-dicarboxylate) (1) was transformed first with (hetero)arenediazonium salts 3a - j into dimethyl 2-[(hetero)arylhydrazono]pentane-1,5-dioates 4a - j followed by reaction with N,N-dimethylformamide dimethylacetal (DMFDMA) to afford, without isolation of intermediates 5a - j, dimethyl 1-(hetero)aryl-4-oxo-1,4-dihydropyridazine-3,5- dicarboxylates 6a - j. An alternative method represents transformation of 1 with DMFDMA into dimethyl 2-[(dimethylamino)methylidene]-3-oxopentane-1,5-dioate (7) followed by treatment with (hetero)arenediazonium salts 3a - c, j to give pyridazine derivatives 6a - c,j.

By the condensation of malononitrile (1) with dialkyl acetone-1,3-dicarboxylates 2a, b alkyl (3- cyano-6-alkoxy-2-oxo-1,2-dihydropyridin-4-yl)acetates 6a, b are formed in contrast to an earlier report according to which diethyl 3-(dicyanomethylene)glutarate 3b was obtained in the reaction of 1 and 2a. Compounds 6a, b were transformed with DMFDMA into the corresponding (E)-alkyl 2-(3- cyano-6-alkoxy-2-oxo-1,2-dihydropyridin-4-yl)-3-(dimethylamino)propenoates 7a, b. The structures of 6a and 7a were confirmed by X-ray structural analysis.

Abstract

In this communication, a simple synthesis of dimethyl 2-[(Z)-3-amino-1-oxo-1-(substituted)but-2-en-2-yl]fumarates is described. Methyl ketones were transformed by treatment with N,N-dimethylacetamide dimethyl acetal (DMADMA) into 3-dimethylamino-1-(substituted)but-2-en-1-ones, followed by treatment with ammonium acetate into (Z)-3-amino-1-(substituted)but-2-en-1-ones and addition to dimethyl acetylenedicarboxylate. These novel polysubstituted butadienes are potential intermediates for the metal-free preparation of polysubstituted five- and six-membered heterocycles.

Herein a simple one-pot metal-free synthesis of 2,4,5-trisubstituted pyridines and pyridine Noxides by [2+2] cycloaddition of enaminones, which are prepared in situ from alkyl, aryl and heteroaryl methyl ketones using N,N-dimethylformamide dimethyl acetal (DMFDMA), and propyne iminium salts as electron-poor acetylenes, is described.

Abstract

1,3-Dipolar cycloadditions of (1Z,4R*,5R*)-4-benzamido-3-oxo-5-phenylpyrazolidin-1-ium-2- ides 3a - e to ethyl propiolate (4) were studied. The reactions were carried out in anisole under reflux and in anisole under microwave irradiation at 150°C. All reactions were quite non-selective and furnished mixtures of isomeric cycloadducts, 5, 5′ , 6, and 6′ , with ethyl (1S*,6R*,7R*)-6-benzamido-1- (4-nitrophenyl)-5-oxo-7-phenyl-1,5,6,7-tetrahydropyrazolo[1,2-a]pyrazole-2-carboxylates 5a - e as the major isomers. Pure major isomers 5a - e were obtained in low to moderate yields upon thorough chromatographic workup (CC followed by MPLC). The structures of cycloadducts 5, 5′ , 6, and 6′ were determined by 1H NMR and NOESY spectroscopy.

A library of twelve N(4´)-substituted di-tert-butyl (2S,4E)-4-arylaminomethylidene-5-oxopyrrolidine-1,2-dicarboxylates 6/6´a - l were prepared in 47 - 90% yield by parallel acid-catalysed treatment of di-tert-butyl (2S,4E)-4-[(dimethylamino)methylidene]-5-oxopyrrolidine-1,2-dicarboxylate (4) with anilines 5a - j, ethyl glycinate (5k), and ethyl β -alaninate (3l). Acidolytic deprotection of compounds 6a - c, e - j afforded the corresponding (2S,4E)-4-arylaminomethylidene-5-oxopyrrolidine-2-carboxylic acids 7a - c, e - j in 39 - 99% yield. The configuration around the C=C double bond in the enaminones 6 and 7 was determined by NMR spectroscopy.