Recent development in the synthesis of pyrrolin-4-ones/pyrrolin-3-ones

Pyrrolin-4-ones/pyrrolin-3-ones and its derivatives are important heterocyclic systems which are observed in vast variety of natural products, pharmaceuticals, and biologically important compounds. Different researchers all across the world have developed different synthetic methodologies for the construction of functionalized pyrrolin-4-ones/pyrrolin-3-one scaffolds such as the transition-metal catalyzed/mediated cycloisomerizations of 1-aminoynones and dimerization of enaminones or α-diazo-β-oxoamides etc. The present review article summarizes various reports on the synthesis of various simple and functionalized pyrrolin-4-ones/pyrrolin-3-ones from 2000 onward.     

Synthesis of imidazolin-2-ones by rearrangement of N-carbamoyliminium salts derived from 4-hydroxyimidazolidin-2-ones

The action of trifluoroacetic acid on 4-hydroxyimidazolidin-2-ones 9a,b,c induces the formation of N-carbamoyliminium salts 10a,b,c which rearrange to imidazolin-2-ones 11a,b,c. The reactions proceed in high yield at ambient temperatures.     

The synthesis of isoindolin-3-ones,Phthalazin-4(3H)-ones and related systems

The reaction between methyl 2-cyanobenzoate and its pyridine analogues gave isoindolin-3-ones, phthalazin-4(3H)-ones and their corresponding aza analogues. Some reactions of 1-benzylaminoiminoisoindolin-3-one 5b were investigated.     

Novel heterocycles derived from substituted aroylthioureas: Synthesis of 3, l-benzothiazin-4-ones,thieno[3,2-d][1,3]thiazin-4-ones and 1,2,4-thiadiazolo[2,3-a][3,1]benzothiazin-5-ones

A series of heterocyclic aroylthioureas has been prepared and investigated as starting materials for ring closure reactions. The formation of several new 3,1-benzothiazin-4-ones and thieno[3,2-d][1,3]thiazin-4-ones (via cyclocondensation reactions) is reported. Oxidative cyclizations were carried out to produce methyl benzothiazole-4-carboxylates (via formation of an S-C bond) as well as 1,2,4-thiadiazolo-[2,3-a][3,1]benzothiazin-5-ones (via formation of an S? N bond).     

The synthesis of methyl 2-(benzyloxycarbonyl)amino-3-dimethylaminopropenoate. The synthesis of trisubstituted pyrroles, 3-amino-2H-pyran-2-ones,fused 2H-pyran-2-ones and 4H-pyridin-4-ones

Methyl 2-(benzyloxycarbonyl)aimno-3-dimemylaminopropenoate ( 2 ) was prepared from methyl N-(benzyloxycarbonyl)glycinate ( 1 ) and t-butoxybis(dimethylamino)methane, and used as a reagent for preparation of substituted 3-(benzyloxycarbonyl)amino-4H-quinolizin-4-ones 5 and 6 , ?2H-pyran-2-ones 17–19 , ?2H-1-benzopyran-2-ones 28–31 , and -naphthopyrans 32–35 , ?2H-pyrano[3,2-c]pyridine-2,5-dione 46 , -pyrano-[4,3-b]pyran-2,5-dione 47 , -pyrano[3,2-c]benzopyran-2,5-dione 48 , -pyrano[2,3-c]pyrazol-6-ones 49 and 50 , -pyrano[2,3-d]pyrirnidin-7-ones 51 and 52 derivatives. In the reaction of 2 with 1,3-diketones trisubsti tuted pyrroles 14–16 were formed. Selective removal of benzyloxycarbonyl group was achieved by cat alytic transfer hydrogenation with Pd/C in the presence of cyclohexene to afford free 3-amino compounds 7 , 8 , 20 , 36–38 and 53–57 in yields better than 80%.     

Reactions of sulfonamides with 4,5-dihydroxyimidazolidin-2-ones

The interaction of sulfonamides with 4,5-dihydroxyimidazolidin-2-ones was studied for the first time. The earlier unknown 4,4′-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-ones) and 4(5)-aryl(alkyl)-sulfonyliminoimidazolidin-2-ones were synthesized. A probable pathway of the reaction was proposed. 1,3-Diethyl-4,5-dihydroxyimidazolidin-2-one was isolated and described. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1604–1607, August, 1998.     

Action of hydrogen peroxide on some 2-aminooxazoles and imidazolin-2-ones. Isolation of hydroperoxyimidazolidin-2-ones

The reaction of some 2-aminooxazoles and imidazolidin-2-ones with hydrogen peroxide afforded stable trans-β-hydroxyhydroperoxy- or dihydroperoxyimidazolidin-2-ones according to the reaction conditions. In the case of 3a-hydroxy-7a-hydroperoxyoctahydro-2H-benzimidazolidin-2-one, the trans isomer is forbidden and cis adduct was isolated. A radical pathway to these hydroperoxides is proposed. From 2-amino-4-methyloxazole and hydrogen peroxide 2-amino-2-hydroxy-4-methyloxazolidin-4-yl peroxyacetate was also isolated.     

Synthesis of 5,6-dihydro-4H-thiopyran-4-ones

The anions of 1,4-diaryl-3-buten-2-ones 1 reacts with arylisothiocyanates, yielding intermediates 4 which can ring close to 5,6-dihydro-4H-thiopyran-4-ones 5 . Under similar reaction conditions ethyl 3-oxo-4-pentenoates 7 gives the 6-spiropyrans 9 . Methylation of 3 gives the S-methylated open form 6 .     

Reactions of 3-hydroxy-1,2-dihydroquinazolin-4-ones with aldehydes

The reactions of 3-hydroxy-2-(2-hydroxyalkyl)- [or (2-hydroxyaryl)]-1,2-dihydro-quinazolin-4-ones with formaldehyde or acetaldehyde afford 1,3-oxazino[3,4-a]quinazolin-4-one derivatives. The reactions with other aldehydes RCHO and 3-hydroxy-2-R′-1,2-dihydroquinazolin-4-ones can give 3-hydroxy-2-R-1,2-dihydroquinazolin-4-ones, 2-substituted quinazolin-4-ones, or dianthranilide. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2523–2526, December, 1998.     

The mass spectra of potential antidiabetics: 4-Arylhydrazono-3-methyl isoxazol-5-ones and pyrazol-5-ones

The mass spectra of variously substituted 4-arylhydrazono-3-methyl isoxazol-5-ones and pyrazol-5-ones have been examined, and the fragmentation pathways elucidated. The spectra of the former compounds differ from previously reported 4-arylidene derivatives and this difference has been attributed to fragmentation involving the ? NH? N?moiety. The investigation has shown up some interesting ‘ortho effects’ as well as the facile loss of HN?C?NH from N-amidino derivatives of the pyrazol-5-ones.     

Synthesis and photophysical properties of 2-styrylquinazolin-4-ones

trans-2-Styryl-substituted 3H-, 3-phenyl-, and 3-naphthylquinazolin-4-ones and their 6,7-difluoro derivatives were synthesized by condensation of appropriate 2-methylquinazolin-4-ones with aromatic aldehydes or by the transformation of the heterocycle of 2-methyl-3,1-benzoxazin-4-one under the action of benzylidenephenylamines.     

Reactions of 3-substituted pyrazolin-5-ones with isocyanates

The reaction sites of 3-substituted pyrazolin-5-ones and their O- and N-blocked analogues toward various isocyanates were investigated. 3-Methyl and 3-ethoxycarbonylpyrazolin-5-ones gave the corresponding 1-carbamoylpyrazolinones, whereas the O-alkylpyrazoles afforded 2-carbamoylpyrazoles. On the other hand, the N-alkylpyrazolinones were carbamoylated at 4-position under drastic conditions.     

Synthetic studies toward 4H-1,3-benzodioxin-2-ones

The investigation into the synthesis of 4H-1,3-benzodioxin-2-ones, utilizing the corresponding 2-(hydroxy-methyl)phenol as the starting diol, is described. The results illustrate that the synthesis of 4H-1,3-benzodi-oxin-2-ones can be achieved utilizing carefully controlled reaction conditions, in a 3–15% yield.     

Facile Approach for the Synthesis of 2,3,4,9-Tetrahydro-1H-xanthen-1-ones and 8,9,10,12-Tetrahydro-11H-benzo[a]xanthen-11-ones via Trapping of o-Quinone Methides

An efficient, simple synthesis of 2,3,4,9-tetrahydro-1H-xanthene-1-ones and 8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-ones is reported by one-pot condensation of 3-dimethylamino-2-cyclohexen-1-ones with hydroxybenzyl alcohols, phenol, and 2-naphthol Mannich bases or their quaternized derivatives. The mechanism of the reaction is believed to involve the formation of the o-quinone methide intermediate.     

Synthesis of arylidene derivatives of N-unsubstituted pyrrolin-2-ones

5-Alkyl(aryl)-3-arylidene-3H-pyrrolin-2-ones were synthesized by ammonolysis of their O-heteroanalogs or by the reactions of 5-alkyl(aryl)-3H-pyrrolin-2-ones with aromatic aldehydes. The structures of the compounds obtained were confirmed by ¹H NMR spectra.     

1,3-Dioxolan-4-ones and 1,3-oxathiolan-5-ones. Configuration of cis and trans isomers

The attempted acid-catalyzed azeotropic removal of water from a mixture containing lactamide and chloral in refluxing toluene lead to the elimination of ammonia; both cis- and trans-5-methyi-2-(trichloromethyl)-1,3-dioxolan-4-one were isolated. A number of 1,3-dioxolan-4-ones and 1,3-oxathiolan-5-ones were obtained by cyclodehydration of aldehydes with α-hydroxy- and α-mercapto-carboxylic acids in the presence of boron trifluoride etherate. Geometric isomers were separated, and their configurations were determined by nuclear magnetic resonance.     

New Dipyrrinonols Derived from 2,3-Dihydro-1H-pyrrol-3-ones

Summary. The reaction of 2-aminomethylene-2,3-dihydropyrrol-3(1H)-ones with ethyl bromoacetate, chloroacetonitrile, or dilute HCl gave rise to a series of methine dyes, namely 1-aryl-2-[3-hydroxy-1-aryl-4,5-diphenyl-1H-pyrrol-2-yl]methylene-4,5-diphenyl-2,3-dihydropyrrol-3(1H)-ones.     

Reactions of Amidines with 5-Methylene-1,3-dioxolan-2-ones

The composition and yields of the products from the reaction of 4,4-dialkyl-5-methylene-1,3-dioxolan-2-ones with amidines depend on the structure of the initial amidine and on the reaction conditions. 2-Aminopyridines lead to 3-substituted 4-hydroxy-4-methyloxazolidin-2-ones and 4-methylene-oxazolidin-2-ones and also to sym-carbamides. 2-Amino-4,6-dimethylpyrimidine leads to the corresponding 4-methyleneoxazolidin-2-one. 3-Aminothiazoles give linear oxourethanes and sym-carbamides.     

Retro-Ene reaction. VI. Functionalization of 4,5-dihalopyridazin-6-ones using 1-acetyloxymethyl-4,5-dihalopyridazin-6-ones as the 1-O, 3-N, 5-O ene-adduct

Functionalization of 1-acetyloxymethyl-4,5-dihalopyridazin-6-ones via retro-ene reaction with some nucleophiles gave regioselectively only 5-halo-4-substitutedpyridazin-6-ones.     

Comparative electron impact mass spectra of new 5-benzylidene-4,5-dihydro-(2H)-pyridazin-3-ones and 4-benzylidene-4,5-dihydrooxazin-6-ones

Electron impact mass spectra are reported for a series of 5-benzylidene-4,5-dihydro-(2H)-pyridazin-3-ones and 4-benzylidene-4,5-dihydrooxazin-6-ones.