Benzazoles. 4. Synthesis and chemical reactions of 6-chlorosulfonylbenzoxazolin-2-ones

The corresponding 6-chlorosulfonyl derivatives were synthesized from benzoxazolin-2-one and its 3-methyl derivative by treatment with chlorosulfonic acid. By treatment of the compounds obtained with water and other nucleophilic reagents (aliphatic and heterocyclic amines) 2-oxobenzoxazoline-6-sulfonic acids and a series of their amides were obtained, while reduction with SnCl₂·2H₂O gave 6-mercaptobenzoxazolin-2-ones.     

Synthesis and coordinating properties of 5-phenyl- and 5-pyridylmethylidene-substituted 2-selenohydantoines and 2-selenoimidazol-4-ones

2-Selenoimidazolidin-4-ones and 2-selenoimidazol-4-ones containing phenylor pyridylmethylidene substituent at position 5 were synthesized. The structure of 3-benzyl-2-selenohydantoine was confirmed by X-ray crystallography. A series of 2-(methylseleno)imidazol-4-ones was obtained by alkylation of 3,5-disubstituted selenohydantoines with methyl iodide. The synthesized selenohydantoines and 3-benzyl-5-pyridylmethylidene-2-(methylseleno)imidazol-4-ones were examined in the complexation reactions with CoCl₂, NiCl₂, CuCl₂, and Cu^I(CH₃CN)₄ClO₄; electrochemical investigations showed that reduced forms of the copper-containing complexes were stable     

Mild Nitration of Pyrazolin-5-ones by a Combination of Fe(NO3)3 and NaNO2: Discovery of a New Readily Available Class of Fungicides, 4-Nitropyrazolin-5-ones

4-Nitropyrazolin-5-ones have been synthesized by the nitration of pyrazolin-5-ones at room temperature by employing the Fe(NO₃)₃/NaNO₂ system. The method demonstrated selectivity towards the 4-position of pyrazolin-5-ones even in the presence of NPh and allyl substituents, which are sensitive to nitration. It was shown that other systems containing Fe^III and nitrites, namely Fe(NO₃)₃/tBuONO, Fe(ClO₄)₃/NaNO₂, and Fe(ClO₄)₃/tBuONO, were also effective. Presumably, Fe^III oxidizes the nitrite (NaNO₂ or tBuONO) to form the NO₂ free radical, which serves as the nitrating agent for pyrazolin-5-ones. The synthesized 4-nitropyrazolin-5-ones were discovered to be a new class of fungicides. Their in vitro activities against phytopathogenic fungi were found comparable or even superior to those of commercial fungicides (fluconazole, clotrimazole, triadimefon, and kresoxim-methyl). These results represent a promising starting point for the development of a new type of plant protection agents that can be easily synthesized from widely available reagents.     

Biomimetic synthesis of 4-acetylbenzoxazolin-2(3H)-one isolated from Zea mays

4-Acetylbenzoxazolin-2(3H)-one has been prepared biomimetically during attempts to synthesize the hemiacetalic hydroxamic acid 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one by the immediate degradation of this unstable compound generated as an intermediate. Thus, 4-acetylbenzoxazolin-2(3H)-one recently isolated from Zea mays kernels, and similar to other benzoxazolin-2(3H)-ones known from plant sources, is assumed to have originated from the degradation of natural 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one which in turn could have been enzymatically released by a β-glucosidase from the corresponding 2-β-D-glucoside.     

Efficient synthesis of functionalized spiro-2,5-dihydro-1,2-λ-oxaphospholes

The reaction of ethyl propiolate with triphenylphosphine (Ph₃P) in the presence of N-alkylisatins led to ethyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ⁵-oxaphosphole-4-carboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones in good yield. The reaction of dialkyl acetylenedicarboxylates with Ph₃P in the presence of N-alkylisatins led to dialkyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ⁵-oxaphosphole-3,4-dicarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones and alkyl 4-(alkoxy)-5-oxo-2,5-dihydro-3-furancarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones.     

Oxidation of 3,4-dihydropyrimidin-2（1H）-ones with nitrosonium （NO^＋）

3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) were oxidized with 1.2 equiv. of nitrosonium tetrafluoroborate (NO⁺BF₄⁻) to pyrimidin-2(1H)-ones in acetonitrile at room temperature in high yields.     

New derivatives of benzoxazolinones and benzoxazolinethiones

N-(Aryloxycarbonyl)benzoxazolin-2-ones have been obtained from benzoxazolinones and aryl chloroformates and from N-(chlorocarbonyl) benzoxazolinones and phenols. These compounds possess acylating properties and with phenols in the presence of phenoxide ions they give diaryl carbonates.     

Reduction of 6/7-substituted 3-phenyltrop-3-en-2-ones: stereoselectivity and conformational analysis of the products

Reduction of 6/7-carboethoxy-3-phenyltrop-3-en-2-ones with H₂/Pd/C and NaBH₄ was studied in order to find a stereoselective route to the corresponding 3-phenyltropan-2-ones and 2α/2β-hydroxy-3-phenyltropanes. The 6/7-exo-carboethoxy-3-phenyltrop-3-en-2-ones were selectively reduced by Pd/C to 3β-phenyltropan-2-ones and 2α-hydroxy-3β-phenyltropanes. The corresponding 2β-hydroxy-3β-phenyl analogues were synthesized using NaBH₄, with a yield of 40%. Reduction of 6-endo-carboethoxy-3-phenyltrop-3-en-2-one yielded several products. The corresponding 7-endo-substituted analogue was selectively reduced with both Pd/C and NaBH₄ to 7-endo-carboethoxy-3β-phenyltropin-2-one. Analysis of stereochemically important ¹H NMR spectroscopy parameters was performed for all the products and used for conformational analysis in solution. X-ray analysis was performed for selected compounds.     

A comparison of electron impact mass spectrometry of isomeric pyranocoumarins (pyrano[3,2-c][1]benzopyran-5-ones) and pyranochromones (pyrano[2,3-b][1]benzopyran-5-ones)

The mass spectrometric behaviour of two pairs of isomeric 2,2-dimethylpyrano[3,2-c][1]benzopyran-5-ones (pyranocoumarins) and 2,2-dimethylpyrano[2,3-b][1]benzopyran-5-ones (pyranochromones) and four pairs of isomeric 2-hydroxymethyl-2-methylpyrano[3,2-c][1]benzopyran-5-ones (pyranocoumarins) and 2-hydroxymethyl-2-methylpyrano[2,3-b][1] benzopyran-5-ones (pyranochromones) has been studied in detail with the aid of exact mass measurements, linked scans, collisionally activated decompositions and deuterium labelling experiments. The presence in both series of compounds of the same ions derived by structural interconversion of both molecular ions is emphasized, and structural information on the ions [C₇H₅O₂]⁺ (m/z 121), highly characteristic for these classes of compounds, as for 4-hydroxycoumarins, is reported.     

Acid-Base Properties and Prototropic Tautomerism of Isomeric 1,2,4-Triazin-3- and -5-ones

The acidity and basicity constants of isomeric phenyl(aryl)-1,2,4-triazin-3- and -5-ones in aqueous solution were determined by spectrophotometry: pK _a = 7.3–6.2; pK _BH+= 0.1 to –2.2. 1,2,4-Triazin-3-ones are weaker bases than the corresponding 1,2,4-triazin-5-ones. According to the AM1 calculations, the most thermodynamically favorable tautomer in the gas phase is the oxo form: namely, 2H-tautomers of the neutral bases and 2,4-H,H ⁺-tautomers of the conjugate acids.     

Collision-induced dissociation study of cyclization of α-diazo-ω-arylsulphonylaminoalkan-2-ones

The collision-induced dissociation mass-analysed ion kinetic energy (CID MIKE) spectra (electron impact and chemical ionization) of five α-diazo-ω-arylsulphonylaminoalkan-2-ones and corresponding N-arylsulphonylazetidin-3-ones and N-arylsulphonylpyrrolidin-3-ones were studied. The [M ? N₂]⁺˙ and [MH ? N₂]⁺ ions of two types of the diazo ketones provide CID MIKE spectra similar to those of the corresponding M⁺˙ and MH⁺ of the heterocyclic compounds, i.e. a cyclization analogous to that in solution takes place. For the other three types of diazo compounds the Wolff rearrangement prevails in both the gas and liquid phases. The effect of the substituents on the cyclization process was studied. The data obtained permit the results of acid-catalysed cyclization of similar diazo ketones to be predicted on the basis of their CID MIKE spectra. Chemical ionization provides a closer similarity with reactions in solution than electron impact ionization, which can be rationalized by the protonation of the diazo ketone molecule being the driving force of the cyclization reaction either in solution or in the ion source of a mass spectrometer.     

Reactivity of 5-<Emphasis Type="Italic">endo</Emphasis>-hydroxy-4-azatricyclo[5.2.1.0<Superscript>2,6</Superscript>]dec-8-en-3-ones and their isomerization initiated by acids and bases

Study of isomerization of 5-endo-hydroxy-4-azatricyclo[5.2.1.0^2,6]dec-8-en-3-ones under the action of Lewis acids (MgBr₂, AlCl₃), CF₃COOH, and NaH showed that the optimum catalyst of the process was trifluoroacetic acid. In reaction of 4-benzyl-5-endo-hydroxy-4-azatricyclo-[5.2.1.0^2,6]dec-8-en-3-one with anhydrous AlCl₃ in benzene was unexpectedly isolated N-benzyl-3-(diphenylmethyl)bicyclo[2.2.1]hept-5-ene-2-carboxamide. A convenient method was developed for the preparation of 5-exo-alkoxy-4-alkyl(aryl)-4-azatricyclo[5.2.1.0^2,6]dec- 8-en-3-ones.     

New derivatives of benzoxazolinones and benzoxazolinethiones

N-(Aryloxycarbonyl)benzoxazolin-2-ones have been obtained from benzoxazolinones and aryl chloroformates and from N-(chlorocarbonyl) benzoxazolinones and phenols. These compounds possess acylating properties and with phenols in the presence of phenoxide ions they give diaryl carbonates.     

Rearrangement during halogenation of 2-hydroxy-1,2-diphenylpropan-1-one (α-methylbenzoin)

The reaction of 2-hydroxy-1,2-diphenylpropan-1-one 1 with SOCl₂ or PBr₃ gives, respectively, the 3-chloro- and 3-bromo-1,2-diphenylpropan-1-ones 4 and 6. The expected 2-chloro- and 2-bromo-1,2-diphenylpropan-1-ones 2 and 5 can, however, be formed by treatment of 1,2-diphenylpropan-1-one 8 with Cl₂ or Br₂/AlCl₃. The four halogenated products are characterised by ¹H and ¹³C NMR spectroscopy for the first time.     

Reactions of 4-acyl-1-alkoxyaryl-5-aryl-3-hydroxy-2,5-dihydro-1H-pyrrol-2-ones with nucleophilic reagents

4-Acetyl-1-alkoxyaryl-5-aryl-3-hydroxy-2,5-dihydro-1H-pyrrol-2-ones reacted with amines to give 1-alkoxyaryl-5-aryl-4-(1-R-aminoethylidene)pyrrolidine-2,3-diones. Reactions of amines with 4-benzoyl-substituted analogs involve nucleophilic attack on the C³ atom in the heteroring to produce the corresponding 3-R-amino-1-alkoxyaryl-5-aryl-4-benzoyl-2,5-dihydro-1H-pyrrol-2-ones. Reactions of the title compounds with hydrazine hydrate, regardless on the substituent on C₄, afforded 4-aryl-3-methyl(phenyl)-5-[2(4)-methoxyphenyl]-4,6-dihydropyrrolo[3,4-c]pyrazol-6-ones.     

First Example of 1,3-Dipolar Cycloaddition of Carbonyl Ylides to Cyclopropenes

Carbonyl ylide generated from 1-diazo-5-phenylpentane-2,5-dione in the presence of Rh₂(OAc)₄ reacts with 3-substituted cyclopropenes following the 1,3-dipolar cycloaddition pattern to afford substituted 9-oxatricyclo[3.3.1.0^2,4]nonan-6-ones.     

Thermal and spectroscopic studies of terbium(III) and dysprosium(III) complexes with piperidin-4-ones

Terbium(III) and dysprosium(III) nitrate complexes with variously substituted 2,6-diphenylpiperidin-4-ones (L¹)-(L¹⁰) of general formula [Ln(L)(NO₃)₂(H₂O)₂]NO₃ have been synthesized. These complexes have been characterized by analytical, spectral and thermal studies. Molar conductance data show that these complexes are 1:1 electrolytes. The presence of two coordinated water molecules is confirmed by thermal and infrared spectral studies. IR spectral data indicate that piperidin-4-ones, in spite of having two coordinating sites, are monodentate, coordinating only through ring nitrogen. The IR and conductance data reveal the presence of two bidentate and one ionic nitrate groups. The nephelauxetic ratio (β), covalency factor (b^1/2) and Sinha’s parameter (δ) evaluated from electronic spectral data of dysprosium(III) complexes indicate a little covalency in metal-ligand bonding.     

Isoquinolin-1(2H)-ones and 1,6-naphthyridin-5(6H)-ones by an N-acylation-SNAr sequence

A new synthesis of 2,3-dialkyl-4-carbomethoxyisoquinolin-1(2H)-ones and 6,7-dialkyl-8-carbomethoxy-1,6-naphthyridin-5(6H)-ones is reported. The process involves treatment of a β-enaminoester with 2-fluoro-5-nitrobenzoyl chloride, 2-fluorobenzoyl chloride or 2-chloronicotinoyl chloride followed by heating in the presence of base. The conversion, which proceeds by an N-acylation-S_NAr reaction sequence, affords 50–86% yields when R¹ is n-alkyl but ≤30% yields when R¹ is α-branched.     

Mass-spectrometric study of the cyclization of diazo ketones. 4. Cyclization of N'-phenyl-3-ureido- and N'-phenyl-3-thioureido-1-diazoalkan-2-ones. 2-Anilino-5,6-dihydro-4H-1,3-thiazin-5-ones

A comparison of the mass spectra of N'-phenyl-3-thioureido-1-diazo-alkan-2-ones (I) with the mass spectra of 2-anilino-5,6-dihydro-4H-1,3-thiazin-5-ones (II) and N'-phenyl-3-ureido-1-diazoalkan-2-ones (III) makes it possible to conclude that under the influence of electron impact the molecular ions of the diazo ketones, through the loss of a molecule of nitrogen, undergo only partial cyclization to the corresponding thiazinones (oxazinones in the case of III). In the case of diazo ketones III virtually all of the [M-N₂]⁺ ions undergo fragmentation without cyclization. Under chemical-ionization conditions (with isobutane as the gas-reactant) the principal fragmentation of the protonated ions of I and III entails cleavage of the C-N bonds. Only a small part of these ions lose a molecule of nitrogen, but it is impossible to establish the structures of the resulting [MH-N₂]⁺ ions from the mass-spectrometric data.See [1], for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 473–480, April, 1983.     

Synthesis of benzo[c][2,7]naphthyridine-6-ones via cascade aromatization/C(sp2)–H amidation of 1,4-dihydropyridines

A K₂S₂O₈-mediated cascade dehydrogenative aromatization/intramolecular C(sp²)–H amidation of 1,4-dihydropyridines is described. This method provides an efficient access to multisubstituted benzo[c][2,7]naphthyridine-6-ones in 38–74% yields.