Tetronic acids and derivatives. Part V. Synthesis of 5-hydroxy-1H-pyrazoles via 4-hydrazino-5H-furan-2-ones. Reaction of hydrazines on tetronic acids

The conversion of tetronic acids 1 to 3(1-hydroxy alkyl)-5-hydroxy-1H-pyrazole derivatives 3, 5, 7 and 12 is described. The formation is shown to proceed via base-catalyzed rearrangement of the intermediate 4-hydrazino-5H-furan-2-one derivatives.     

Chemistry of iminofuran: VIII. Recyclization of 5-aryl-3-arylimino-3H-furan-2-ones effected by cyanoacetic acid derivatives

The recyclization of 5-aryl-3-arylimino-3H-furan-2-ones under the action of esters, nitriles, and amides of cycnoacetic acids resulted in the corresponding esters, nitriles, and amides of (5E)-2-amino-1-aryl-4-oxo-5-(2-oxoethylidene)-1H-4,5-dihydropyrrole-3-carboxylic acids.     

The application of (Z)-3-aryl-3-haloenoic acids to the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones

Studies directed at the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones from (Z)-3-aryl-3-haloenoic acids are described. The successful strategy relies on the preparation of (Z)-3-aryl-3-haloenoic acids from acetophenones through the corresponding (Z)-3-aryl-3-haloenals and the conversion of the (Z)-3-aryl-3-haloenoic acids to (Z)-5-benzylidene-4-aryl-5H-furan-2-ones. The furanones were subsequently treated with primary amines and dehydrated to the corresponding (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones.     

Phase-transfer catalysis in reactions of 5-alkyl-3H-furan-2-ones with dichlorocarbene

Treatment of 5-alkyl-3H-furan-2-ones and 5-alkyl-3H-thiophen-2-ones with dichlorocarbene under conditions of phase-transfer catalysis at 20–90 °C results in insertion of the carbene at the C=C bond followed by skeletal rearrangement.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1995–1997, October, 1995.     

Palladium-catalyzed polyhetero-claisen rearrangement of 4-allylthiopyrimidin-2(1h)-ones and 5-allylthio-1,2,4-triazin-3(2h)-ones

The S → N allylic transposition of 4-allylthiopyrimidin-2(lH)-ones 4 and 5-allylthio-1,2,4-triazin-3(2H)-ones 5 has been performed successfully by catalysis of palladium(II) salts. In both cases the N-alkylated products (6 and 7) are obtained with no traces of the C-alkylated products.     

Addition reactions of thiazol-5(4H)-ones—IV : Synthesis,tautomerism and addition reactions of 2-phenylthiazole-5-thiols

4-Substituted 2-phenylthiazole-5-thiols 3 undergo addition reactions of a different type from those of their oxygen analogues, the oxazol- and thiazol-5(4$\text{H}$)-ones, since they exist in solution entirely in the thioenol tautomeric form. Their addition reactions involve only the exocyclic sulphur atom, and they behave as typical heteroaromatic thiols towards unsaturated systems, giving sulphides. A mesoionic thiazole-5-thiol, however, is shown to possess cycloaddition reactivity, undergoing cycloaddition-extrusion reactions with unsaturated systems comparable with well-established reactions of oxygen analogues.     

Reaction of 3-arylhydrazono-3H-furan-2-ones with o-phenylenediamine

Depending on the conditions, 3-arylhydrazono-3H-furan-2-ones reacted with o-phenylenediamine along two pathways with formation of 2-hydrazonotetrahydrobenzopyrrolo[1,2-a]imidazol-1-ones and 2-(1-aryl-1H-pyrazol-3-yl)benzimidazoles.     

Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

Iminofuran chemistry: VII. Intramolecular cyclization of 2-N-aryl-substituted derivatives of 2-amino-4-aryl-4-oxobut-2-enoic and 2-amino-5,5-dimethyl4-oxohex-2-enoic acids

The cyclization at the treatment of acetic anhydride of 4-aryl-2-arylamino-4-oxobut-2-enoic and 2-arylamino-5,5-dimethyl-4-oxohex-2-enoic acids was investigated furnishing derivatives of 5-aryl-3-aryl-imino-3H-furan-2-ones and 4-arylamino-2-tert-butyl-2,5-dihydro-5-oxofuran-2-yl acetate respectively. 2-N²-Methylenesubstituted 4-aryl-2-hydrazino-4-oxobut-2-enoic and 5,5-dimethyl-2-hydrazino-4-oxohex-2-enoic acids cleanly underwent cyclization under the effect of acetic anhydride into 5-aryl-3-hydrazono-3H-furan-2-ones and 5-tert-butyl-3-hydrazono-3H-furan-2-ones.     

Tetronic Acids and Derivatives Part VIII (1) o-Alkylation of 3-Unsubstituted Tetronic Acids

4-methoxy-(5H)-furan-2-ones 1 are useful starting materials for the synthesis of naturally occuring lactones². In a previous communication we have described an efficient entry to 4-alkoxy-(5H)-furan-2-ones 1–3 (alkyl tetronates) by lactonization of ethyl 4-acetoxy 3-ketoesters 4 using hydrochloric acid in several alcohols¹. The detection of 4-hydroxy-(5H)-furan-2-ones 5 (tetronic acids) during the reaction course³ allowed us to postulate them as intermediates which were subsequently etherified to the products 1–3. In a very recent communication⁴, it was claimed that attempted alkylation of tetronic acids 5 using HC1 in an alcohol or alkyl halides on tetronic acids sodium salts are unsuccessful; moreover, the structure of our compounds 1–3 was questionned by arguing that isomeric 2-alkylated materials     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Tetronic acids and derivatives-IV: Synthesis and lactonization of -γ-acetoxy β-ketoesters

Through our investigation of synthetic routes to tetronic acids, elaboration and cyclization of γ-acetoxy-β-ketoesters were examined. Synthesis of these β-ketoesters 2 has been realized by selective monoacylation of the magnesioenolate of monoethyl malonate. Lactonization of 2 leading to tetronic acids or to 4-alkoxy-furan-2(5H)-ones is reported.     

Cycloaddition reactions of 1,3-benzothiazines—I. : Reactions of 2-phenyl-4-H and 4-phenyl-2H-1,3-benzothiazine derivatives with substituted acetyl chlorides

6,7-Dimethoxy-2-phenyl-4$\text{H}$-1,3-benzothiazine (1) and 6,7-dimethoxy-4-phenyl-2$\text{H}$-1,3-benzothiazine (2) react with substituted acetyl chlorides to give linearly, and new angularly condensed β-lactam derivatives (4,5). Heating of the latter compounds with hydrogen chloride in anhydrous ethanol leads to the formation of the corresponding 4$\text{H}$- and 2$\text{H}$-1,3-benzothiazinium chloride, respectively. The configurations of these compounds (the mutual positions of the substituents relative to the β-lactam ring) were determined by ¹H and ¹³C studies, also making use of the aromatic solvent-induced shifts.     

A short synthesis of (s)-5-hydroxymethyl-(5h)-furan-2-one and derivatives from d-ribonolactone

We describe a short synthesis of ($\text{S}$)-5-hydroxymethyl-(5$\text{H}$-furan-2-one and some 5-O-derivatives, which are being used as key starting products for the synthesis of several antileukaemic lignan lactones, from $\text{D}$-ribonolactone.     

A facile synthesis of novel 3-(aryl/alkyl-2-ylmethyl)-2-thioxothiazolidin-4-ones using microwave heating

(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-(aryl/alkyl-2-ylmethyl)-2-thioxothiazolidin-4-ones (7a–w) have been synthesized by the Knoevenagel condensation reaction of 3-(aryl/alkyl-2-ylmethyl)-2-thioxothiazolidin-4-ones (3a–d) with suitably substituted 2-(1H-indol-3-yl)2-oxoacetaldehydes (6a–g) under microwave conditions. The thioxothiazolidin-4-ones were prepared from the corresponding aryl/alkyl amines (1a–d) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a–g) were synthesized from the corresponding acid chlorides (5a–g) using HsnBu₃.     

Synthesis and Intramolecular Cyclization of N-Substituted 2-Amino-4-aryl-4-oxo-2-butenoic Acids

Treating 4-aryl-2,4-dioxobutanoic acids with aromatic amines, 4-aminoantipyrine, and benzophenone hydrazone furnished N-substituted 2-amino-4-aryl-4-oxo-2-butenoic acids that existed in solutions in enaminoketone and iminoketone forms. The acids obtained underwent in the presence of acetic anhydride cyclization into N-substituted 5-aryl-3-imino-3H-furan-2-ones.     

A new synthesis of 4-methoxy-cyclopent-2-en-1-ones

4-methoxy-cyclopent-2-en-1-ones $\text{6}$ are easily obtained through a simple procedure involving in the key-step the conversion of 2-furylcarbinols $\text{1}$ into 1,1,2-trimethoxy-al-kan-4-ones $\text{3}$, a masked form of 1,4-dicarbonyl compounds, by treatment with Amberlyst H15 in methanolic solution. Then, the regeneration of the aldehydic function and a base-catalysed aldolic condensation lead in high yields to the final products $\text{6}$.     

Photochemistry of N-aryl-2(1H)-pyrimidin-2-ones

Irradiation of N-aryl-2(1H)-pyrimidin-2-ones ($\text{3a}$-$\text{c}$) in a mixed benzene-alcohol solution afforded the products initiated by Type I cleavage, 1-(3-alkoxycarbonylamino-2-propene)-N-arylimines ($\text{4a}$-$\text{c}$, $\text{5}$, and $\text{6}$) in 45–51% yields.     

Tri-component reaction of 2-alkyl-4,5-dichloropyridazin-3(2H)-ones: synthesis of 5-cyano-5-(pyrimidin-2-yl)-2,7-dialkyl-5H-dipyridazino-[4,5-b:4,5-e]-4H-thiopyran-1,6-dione and 2-(4-cyanophenoxy) pyrimidine

Reaction of 2-alkyl-4,5-dichloropyridazin-3(2H)-ones with p-cyanophenol and 2-mercaptopyrimidine in the presence of base gave 2,4,5-trisubstituted-pyridazin-3(2H)-ones 4-9, 2-(4-cyanophenoxy)pyrimidine (10) and 5-cyano-5-(pyrimidin-2-yl)-2,7-dialkyl-5H-dipyridazino[4,5-b:4,5-e]-4H-thiopyran-1,6-diones 11 as a novel heterocycle.