Synthesis of 2-aryl-2H-[1,2,4]triazoloquinolin-3-one and 2-aryl-2H-[1,2,4]triazoloisoquinolin-3-one derivatives from α-chloroformylarylhydrazines hydrochloride

The reaction of α-chloroformylarylhydrazines hydrochloride with quinoline under air provided the corresponding 2-aryl-2H-[1,2,4]triazoloquinolin-3-ones 3a-3d in 33-42% yields and unexpected isomeric 2-aryl-2H-[1,2,4]triazoloisoquinolin-3-ones 4a-4d in 30-42% yields. These two isomers were isolated and fully characterized by spectroscopic methods including X-ray crystallography. By employing 3-methylquinoline as the starting material under the same condition, the reaction only gave compound 3e-3h as sole products in 70-82% yields without the formation of isomers. A plausible mechanism was proposed through electrophilic aromatic reaction, the tandem ring cyclization and ring-opening, and oxidation for the generation of 2-aryl-2H-[1,2,4]triazoloisoquinolin-3-ones (4).     

Re-cyclization of 3-(E)-methyl 3-(4-oxo-4H-chromen-3-yl)acrylate with amines and their potential mechanism

The synthesis of 2-pyridone derivatives from different substituted amines and various 3-(E)-methyl 3-(4-oxo-4H-chromen-3-yl)acrylate derivatives was proposed and described. The optimized reaction conditions and the generality of the reaction were investigated, respectively. Moreover, less side products could be formed than the traditional method. Finally, based on the fact that (E)-methyl 2-(7-methoxy-4-oxo-3-((phenylamino)methylene)chroman-2-yl)acetate was separated and determined via X-ray single crystal diffraction, we could propose an interesting and reasonable reaction mechanism for the first time. The reaction could render this method particularly attractive for the efficient preparation of biologically and medicinally interesting molecules.     

Convenient synthesis of O-functionalized mandelic acids via Lewis acid mediated transformation of 1,3-dioxolan-4-ones

An efficient method for the synthesis of O-substituted mandelic acids containing alkenyl, alkynyl, methoxycarbonyl, or phenacyl fragments via the Lewis acid-catalyzed reaction of 1,3-dioxolan-4-ones with different C-nucleophiles is proposed.     

Proline-mediated formation of novel chroman-4-one tetrahydropyrimidines

Novel tricyclic N-benzylated chroman-4-one tetrahydropyrimidine derivatives have been prepared through a multi-component reaction between various 2-substituted chroman-4-one derivatives, N-methylenebenzylamine and a catalytic amount of proline under mild reaction conditions. The tricyclic structure of 1a was determined by NMR spectroscopy and confirmed by X-ray crystallography. An additional product, 2a, was isolated from the reaction mixture and its structure and conformation were determined by a combination of theoretical (Monte Carlo conformational search) and NMR-based (NOE and ³J_HH couplings) conformational analysis. The NMR analysis revealed one preferred geometry for 1a and 2a in CHCl₃ solution.     

A new three-step domino Knoevenagel-hetero-Diels-Alder oxidation reaction

A new catalyst-free domino Knoevenagel-hetero-Diels-Alder oxidation reaction is reported. 6H-Chromeno[4′,3′:4,5]thiopyrano[2,3-d][1,3]thiazol-4-ium-2-olates are formed in good yields via reaction of 2-(2-propynyloxy)benzaldehydes with 4-thioxo-1,3-thiazolidin-2-one.     

Unusual sulfanylation through ring transformation of arene-tethered 2H-pyran-2-ones by in situ built Michael adduct

A novel synthesis of highly functionalized alkylsulfanylmethyl arenes 8a-m through the ring transformation of 6-aryl-4-methyl/ethylsulfanyl-2H-pyran-2-one-3-carbonitriles 1a-j, by reaction with methyl vinyl ketone 2, is delineated and illustrated. To ascertain the course of reaction, 3-arylsulfanylmethyl-2-methyl-6-methylsulfanyl-4-phenylbenzonitriles 8k-m were also prepared from the reaction of 1 with 4-arylsulfanyl-butan-2-ones 7c,d.     

Synthesis of 4-nitromethylene-1,4-dihydropyrimidine derivatives as pyrimidine nucleoside analogues

The synthesis of 4-nitromethylene-1,4-dihydropyrimidine derivatives as pyrimidine nucleoside analogues was developed, starting from 3-nitropyran-2-one N-functionalized amidines. Primary amines were reacted with amidines yielding 4-nitromethylene-1,4-dihydropyrimidine derivatives. In an initial survey, several 4-nitromethylene-1,4-dihydropyrimidines turned into 4-nitromethylene-1,2,3,4-tetrahydropyrimidine derivatives under different reduction conditions. The reduction reaction also induced a change in the exocyclic double bond configuration from (E) to (Z), due to an intramolecular hydrogen bond.     

A novel synthesis and transformations of isothiochroman 2,2-dioxide

A convenient synthesis of isothiochromen-4-one 2,2-dioxide was carried out via cyclisation of o-cyanobenzyl thioacetate by a Thorpe reaction. The reactions of isothiochromen-4-one 2,2-dioxide with nitrogen-containing nucleophilic reagents have been investigated.     

An efficient synthesis of 4,5-dihydronaphtho[2,1-b]furan through a novel ring transformation of 2H-pyran-2-one

An innovative route for the synthesis of substituted naphtho[2,1-b]furan has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 6,7-dihydro-5H-benzofuran-4-one, in good yield.     

Visible-light induced cascade radical cyclization of sulfinic acids and o-(allyloxy)arylaldehydes towards functionalized chroman-4-ones

An efficient method for the synthesis of functionalized chroman-4-ones induced by visible light via the radical cyclization reaction of sulfinic acids and o-(allyloxy)arylaldehydes at room temperature was described. The corresponding products were isolated with moderate to good yields. Radical mechanism was proposed for this transformation. Anti-microbial activity of some desired compounds were screened.     

A facile four-component tandem protocol for the synthesis of novel 2,6-diaryl-2,3-dihydro-1H-pyridin-4-ones

A one-pot, four-component reaction of 1-(phenylsulfinyl)- or 1-(4-chlorophenylsulfinyl)propan-2-one, aromatic aldehydes and ammonium acetate in a 1:2:1 molar ratio affords a series of new 2,6-diaryl-2,3-dihydro-1H-pyridin-4-ones. This reaction proceeds presumably via a double Mannich reaction-elimination tandem sequence.     

Lewis acid-mediated mono- and bis-addition of C-nucleophiles to 1,3-dioxolan-4-ones

The reactions of 1,3-dioxolan-4-ones, readily available from α-hydroxy acids and aldehydes, with C-nucleophiles are described. Two possible reaction pathways resulting in O-substituted acids and tri-(hetero)arylmethanes are shown.     

Nano crystalline ZnO catalyzed one pot multicomponent reaction for an easy access of fully decorated 4H-pyran scaffolds and its rearrangement to 2-pyridone nucleus in aqueous media

A green and highly efficient protocol has been developed for the synthesis of 4H-pyran scaffolds installing a one-pot three-component coupling reaction of an aldehyde, malononitrile, and a 1,3-diketo compound using nano structured ZnO as the catalyst in aqueous alcoholic medium. A greener method to synthesize 3,4-dihydropyridin-2-one has also been developed by rearranging 4H-pyran derivatives in aqueous medium applying p-TSOH as the right catalyst source. A wide spectrum of functional groups was tolerated in both the developed synthetic protocols with good to excellent yield of the targeted molecules.     

Green synthesis of 4,6-bisarylpyrimidin-2(1H)-ones and azo-linked 4-arylpyrimidin-2(1H)-ones using NiFe2O4@SiO2nPr@glucose amine as a mild nano catalyst

The clean, environmentally benign and effective synthesis of novel azo-linked 4-arylpyrimidin-2(1H)-one derivatives and 4,6-bisarylpyrimidin-2(1H)-ones via three-component reaction of various aldehydes or synthetized azo-linked aldehydes, urea, and acetophenone promoted by NiFe₂O₄@SiO₂ⁿPr@glucose amine at room temperature (25 °C) was reported. NiFe₂O₄@SiO₂ⁿPr@glucose amine were synthesized and characterized by transmission electron microscope (TEM), fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), X-ray powder diffraction (XRD) and X-ray spectroscopy (EDX). These compounds were obtained in high yields and short reaction times. The catalyst could be easily recovered and reused for six cycles with almost consistent activity. The structures of the synthesized 4,6-bisarylpyrimidin-2(1H)-one compounds were confirmed by ¹H NMR, ¹³C NMR and FTIR spectral data and elemental analyses.     

Synthesis of new 1-substituted 4-perfluoroalkyl tetrazol-5-ones

1,3-Dipolar cycloaddition of perfluoroalkyl ethyle azides 1 with isocyanates 2 afforded 1-perfluoroalkyl-4-(n-Bu, phenyl or mesitylsulfonyl) tetrazol-5-ones 3 in good yields. The use of perfluoroalkyl ethyl azides extends the reaction to the less reactive n-butyl isocyanate.     

New convenient synthesis of 2,3-diaminothieno[2,3-d]pyrimidin-4(3H)-one derivates from substituted alkyl 2-(1H-tetrazol-1-yl)thiophene-3-carboxylates

4,5-Disubstituted and 4-substituted alkyl 2-amino-thiophene-3-carboxylates react with triethyl orthoformate and sodium azide in acetic acid to yield new 2-(1H-tetrazol-1-yl)-4-R¹-5-R²-thiophene derivates. It was established that the reaction of these tetrazoles with hydrazine generates the insufficiently studied 2,3-diaminothieno[2,3-d]pyrimidin-4(3H)-one system. It is significant that the reaction mentioned above is the unique tetrazole ring cleavage under the action of hydrazine.     

Synthesis of (2,2,2-trifluoroethyl) substituted pyridazin-3(2H)-ones and 1,5-dihydropyrrol-2-ones from α,β-unsaturated γ-lactones and hydrazines

This paper presents the transformation of α,β-unsaturated γ-lactones into 2,2,2-trifluoroethyl substituted pyridazin-3(2H)-ones and 1,5-dihydropyrrol-2-ones starting from various hydrazines. The influence of the γ-lactone substitution (sulfanyl versus sulfonyl moiety) and the nature of the hydrazines (unsubstituted, alkyl- or aryl-substituted) on the outcome of the reaction were studied. All new heterocycles were characterized using 1D NMR, IR, MS and their data was compared with those of two reported X-ray diffraction structures. The two possible competitive pathways leading to pyridazin-3(2H)-ones and/or 1,5-dihydropyrrol-2-ones are discussed. Abinitio DFT calculations were also performed in order to rationalize several experimental results.     

Short synthesis of 4-aryl-3-pyrrolin-2-ones

A three step, convergent synthesis of 4-aryl-3-pyrrolin-2-ones from a tetramic acid has been developed. The key transformation utilized a Suzuki-Miyaura cross-coupling reaction between a 4-tosyloxy-3-pyrrolin-2-one and an arylboronic acid. This work also provides access to 4-arylpyrrolidin-2-ones, cyclic analogs of γ-aminobutyric acid (GABA). Hydrogenation of 4-(4′-chlorophenyl)-3-pyrrolin-2-one proceeded smoothly to give baclofen lactam.     

An innovative synthesis of dibenzofurans through a carbanion-induced ring transformation reaction

An innovative route for the synthesis of substituted dibenzofurans has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 7-methoxybenzofuran-3-one, in high yield. The novelty of the procedure lies in the creation of an aromatic ring from a 2H-pyran-2-one involving the -COCH₂-moiety of the substrate.     

An efficient synthesis of ortho-N-Boc-arylmethyl ketone derivatives

A new and efficient method for the preparation of ortho-N-Boc-arylmethyl ketone derivatives is reported. The reaction involves the intermediacy of a 4-methylene-3,1-benzoaxin-2-one moiety which smoothly converts to the target compounds under acidic conditions. The ortho-N-Boc-arylmethyl ketone derivatives can be formed in a one-pot reaction or alternatively the 4-methylene-3,1-benzoaxin-2-ones can be isolated and subsequently transformed into the desired products.