A new convinient synthesis of 3(2H)-furanones

A selective oxidative fission of the heterocyclic nucleus of 5-methyl-2-(acylmethyl)furans or 2-(5-methyl-2-furyl)-1,3-dicarbonyl compounds by m-chloroperbenzoic acid allows the easy synthesis of the 3(2H)-furanone system.     

A convenient synthesis of optically active 5,5-disubstituted 4-amino- and 4-hydroxy-2(5H)-furanones from (S)-ketone cyanohydrins

(S)-Ketone cyanohydrins (S)-2 are accessible by enantioselective HCN addition to ketones 1 by using hydroxynitrile lyase from Manihot esculenta ((S)-MeHNL) as a biocatalyst. Acylation of (S)-2 gave the corresponding (S)-acyloxynitriles (S)-3, which can be cyclized by LHMDS to give 5,5-disubstituted (S)-4-amino-2(5H)-furanones (S)-4 and (S)-5. Different substituents (H. Me, OBn, OH) in the 3-position of the furanones were introduced by selecting the appropriate acylating agent, which in the case of benzyloxyacetyl chloride led to the novel structure type of 4-amino-3-hydroxyfuranones (S)-5. For the synthesis of 5,5-disubstituted (S)-tetronic acids (S)-8, ketone cyanohydrins (S)-2 were first transformed into the corresponding 2-hydroxy esters (S)-6. Acylation of (S)-6 gave 2-acyloxy esters (S)-7, which, by treatment with LHMDS or LDA, afforded tetronic acids (S)-8 in high yields and enantiomeric excesses. By debenzylation of benzyloxy acetoxy derivatives (S)-8e,f, the new vitamin C analogues (S)-9a,b were generated. All the described tetronic acid and aminofuranone derivatives were obtained in good chemical yields and without racemization with respect to the starting cyanohydrins (S)-2. In many cases the enantiomeric purity could be enriched by simple recrystallization (e.g. (S)-4a from 69% ee to > 99% ee).     

Reactions of 2(3H)-furanones

This review article presents a systematic overview of approaches and reactivity data for 2(3H)-furanones, published from 1999 until 2018.     

A catalytic asymmetric protocol for the enantioselective synthesis of 3(2H)-furanones

3(2H)-Furanones can be prepared by a catalytic asymmetric protocol from enynones, which, if electron-rich, require only one reagent and involve two reactions in a single operation--a domino process.     

A new synthesis of 3(2H)-furanones from acetylenic β-diketones

Thermal cyclization of 1,5-diarylpent-1-yne-3,5-diones led to the formation of 2-benzyliden-5-aryl-3(2H) furanones as well as 2,6-diaryl-4H-pyran-4-ones as minor products. The structure of the furanones was established from their ir, ¹H nmr and mass spectral data. Their reaction with hydrazine hydrate gave pyrazole derivatives.     

A new and facile synthesis of 3(2H)-furanones via carboxylation- decarboxylation sequence

One-pot synthesis of 3(2H)-furanones from α-ethynyl tertiary alcohols and acyl halides has been achieved in the presence of a palladium complex under CO₂ pressure.     

Cycloisomerization of bifunctionalized allenes: synthesis of 3(2H)-furanones in water

A simple protocol for the efficient synthesis of 3(2H)-furanones by cycloisomerization of allenic hydroxyketones is described. This transformation is achieved in water and in the absence of any expensive metal catalysts.     

A convenient synthesis of 1,4-disubstituted imidazoles

An efficient method for the regioselective protection of 4-alkyl-, 4-iodo, 4-vinylimidazoles has been developed via an alkylation-isomerization sequence with various imidazole-protecting groups. The initially formed mixture of 4/5-alkyl-, 4/5-iodo, and 4/5-vinylimidazoles are isomerized to the corresponding 4-isomers on treatment of a DMF solution with a small amount of RX and heating at 75 °C.     

Asymmetric synthesis of 1,4-disubstituted 3-methylidenedihydroquinolin-2(1H)-ones

A series of enantiomerically pure or highly enriched (R)- or (S)-3-methylidenetetrahydroquinolin-2-ones was readily prepared by highly diastereoselective Michael additions of various Grignard reagents to quinolin-2(1H)-ones, containing an (R,R)- or (S,S)-di(1-phenylethylamino)phosphoryl group as chiral auxiliary, followed by Horner-Wadsworth-Emmons olefination of formaldehyde. An efficient synthesis of the starting (R,R)- and (S,S)-3-({di[(1-phenylethyl)amino]}phosphoryl)-1-alkyl-quinolin-2(1H)-ones is also described. The relative and absolute configurations of the intermediate adducts and final methylidenequinolinones were established by NMR and X-ray analysis.     

A highly enantioselective synthesis of 5-(l-menthyloxy )-4-substituted-3-chloro-2(5H )-furanones

In this paper, stereocontrolled tandem Michael addition-elimination reaction of the novel chiral source, 5-(l-menthyloxy)-3,4-dichloro-2(5H)-furanone, with various thiols and amines has been investigated. A series of new enantiomerically pure compounds, 5–(l-menthyloxy)-4-substituted-3-chloro-2(5H)-furanones, were obtained in good yields with d. e. ? 98% under mild conditions.     

A novel rearrangement of 2(5H)-furanones

A novel rearrangement of 2(5H)-furanones is described. When refluxed in aq. Ethanolic solution in the presence of excess KOH, the 2,5-dihydro-2-oxofuran-3-carboxamides 6 underwent a novel rearrangement to the corresponding 4,5-dihydro-4-oxo-2-(phenylamino)-3-furancarboxylic acids 1 in moderate-to-excellent yields.     

A convenient synthesis of nitro-substituted 1,2-benzisothiazol-3(2H)-one 1,1-dioxides (nitrosaccharins)

Nitro-substituted 1,2-benzisothiazol-3(2H)-one 1,1-dioxides (nitrosaccharins) have been synthesized by amminolysis of nitro 2-chlorosulfonylbenzoate esters. This method appears to have advantages over the original procedure of oxidation of an ortho-toluenesulfonamide.     

Synthesis of 2(3H)-furanones via electrophilic cyclization

A variety of highly substituted 2(3H)-furanones are readily prepared from 3-alkynoate esters and the corresponding acids via electrophilic cyclization. Successful electrophiles in this process include I2, ICl, and PhSeCl. This highly efficient process proceeds under mild conditions, tolerates various functional groups, and generally provides substituted 2(3H)-furanones in good to excellent yields.     

A simple synthesis of 2,2-disubstituted tetrahydrothiophenes

Treatment of diethyl 2-(3-mesyloxypropyl) malonate with KSCOCH₃/DMF at room temperature gave 2,2-dicarbethoxytetrahydrothiophene. The reaction can be used to prepare isopenams in good yield.

     

A convenient synthesis of 5-acyl-6-substituted 3-cyano-2(1H)-pyridinones

2-Dimethylaminomethylidene-1,3-diketones are useful synthons for the construction of 5-acyl-6-substituted-3-cyano-2(1H)-pyridinones. The reaction of these 1,3-diketones and the anion of cyanoacetamide gave the title compounds. When the 1,3 diketone contained different alkyl or aryl groups, mixtures of regioisomers were formed. To circumvent this problem, dimethylaminomethylidene hydrazones, regioselectively prepared from dimethylhydrazino enones and dimethylformamide dimethyl acetal were reacted with cyanoacetamide anion followed by acid hydrolysis to give the title compounds.     

A facile solid-phase synthesis of substituted 2(5H)-furanones from polymer-supported alpha-selenocarboxylic acids

The synthesis of polystyrene-supported alpha-selenoacetic acid, alpha-selenopropionic acid, and alpha-selenophenylacetic acid is described. The reaction of the dilithio derivatives of polymer-supported alpha-selenocarboxylic acids with racemic epoxides or optically active styrene oxide afforded polystyrene-supported gamma-substituted alpha-selenobutyrolactones. The alpha-alkylation reaction of gamma-substituted polystyrene-supported alpha-selenobutyrolactones provided another route for the synthesis of polystyrene-supported alpha,gamma-disubstituted alpha-selenobutyrolactones. Subsequent oxidation-elimination with an excess of 30% hydrogen peroxide at room temperature afforded substituted (3- and 5-mono-; 3,4- and 3,5-di) 2(5H)-furanones in high yields and good purities.     

Photochemistry of 5-aryl-2(3H)-furanones. : A new route to the synthesis of chromones

The photochemistry of 5-phenyl-, 5-(2',5'-dimethoxyphenyl)-, 5-(2'-acetoxy-5'-methoxyphenyl)- and 5- (2',5'-diacetoxyphenyl)- 2(3H)-furanone (1a-d) has been investigated. Compound 1a yields phenyl vinyl ketone as expected. Similarly, 1b affords the corresponding aryl vinyl ketone but, in this case, photodimerization also occurs. Irradiation of the two o-acetoxyaryl furanones 1c and 1d gives rise to the formation of chromones as the main products. This interesting result can be accounted for in terms of a photochemical opening of the lactonic ring followed by radical addition to the acetoxy group.     

A convenient preparation of 2-thioxo-4(3H)-quinazolinones

A simple method is described for the preparation of 3-aryl-2-thioxo-4(3H)-quinazolinones (4) by the reaction of anthranilic acids and ammonium or triethylammonium N-aryl-dithiocarbamates in ethanol. The method is also applicable to the preparation of 3-ethyl-2-thioxo-4(3H)-quinazolinone.