Spectroscopic and theoretical studies of derivatives of 1,6- and 1,7-naphthyridines

The solvatochromism in 8-hydroxy-1,6-naphthyridin-5(6H)-one-7-carboxylic acid methyl ester (1), 5-hydroxy-1,7-naphthyridin-8(7H)-one-6-carboxylic acid methyl ester (2), and 4-hydroxy-2-methyl-1(2H)-isoquinolone-3-carboxylic acid methyl ester (3), has been studied in solvents of different polarity and hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) ability. The relative stabilities of isomers for these naphthyridine derivatives and their interaction with the solvent are reported. Two intramolecular hydrogen-bonded structures contribute to the ground state of compound 1. Temperature effects on the absorption bands were recorded to analyse the possible equilibrium between covalent and zwitterionic forms. The formation of zwitterionic species was observed only in HBD solvents, from which is inferred the solvent assistance in the proton transference. AM1 and PM3 semi-empirical calculations were used in support of the proposed interpretations.     

Pyrrolo[2,3-d] pyrimidines. I. 5-hydroxypyrrolo[2,3-d] pyrimidines

5-Hydroxy-7-alkyl-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbonitriles (VIIb-d) and 5-hydroxy-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid, ethyl ester (VIIa) were prepared from 5-carbethoxy-4-chloro-2-phenylpyrimidine (IV) via 4-[(cyanomethyl)alkylamino[-2-phenyl-5-pyrimidinecarboxylic acid, ethyl esters (Vb-d) and 4-[(carboxymethyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid, diethyl ester (Va), respectively. The hydroxy group of the pyrrolo-[2,3-d]pyrimidines could be methylated, acetylated and tosylated. Hydrolysis of 5-methoxy-7-methyl-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbonitrile (IX) afforded the corresponding amide (X).     

Efficient synthesis of 2,6-disubstituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters

A general procedure is described for the preparation of 6-substituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters (6-substituted-5-hydroxy-3(2H)-pyridazinone-4-carboxylic acid ethyl esters). These compounds are shown to undergo selective alkylation at the 2-position in moderate to good yields (19-77%) to afford 2,6-disubstituted-5-hydroxy-3-oxo-2,3-dihydro-pyridazine-4-carboxylic acid ethyl esters (2,6-disubstituted-5-hydroxy-3(2H)-pyridazinone-4-carboxylic acid ethyl esters).     

Synthesis of the (Z) and (E) isomers of 1,2-diaryl-3-methyl-4,5-dioxo-3-pyrrolidinecarboxylic acid esters. Structural assignment by nmr and mass spectroscopy

Reaction of N-benzylideneaniline, 1a , with 3-methyl-2-oxobutanedioic acid diethyl ester, 2a , produced isomeric 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid ethyl esters, 3a and 3b . The higher melting isomer, 3a , was shown to have the (Z) configuration by nmr spectroscopy. The (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid methyl esters, 3c and 3d , were prepared from 1a and 3-methyl-2-oxobutanedioic acid dimethyl ester, 2b . The higher melting isomer, 3c , was shown to have the (Z) configuration. Similarly, N-benzylidene-p-toluidine, 1b , reacted with 2a to form (Z) and (E) isomers of 3-methyl-4,5-dioxo-1-(4-methylphenyl)-2-phenyl-3-pyrrolidinecarboxlic acid ethyl esters, 3e and 3f . Assignment of the ¹³C carbonyl carbon nmr chemical shift was made by preparing 2-methyl-3-oxobutanedioic-1-¹³C acid diethyl ester, 4 , and from it the corresponding (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic ¹³C acid ester, 5a and 5b . The mass spectra of the (Z) isomers exhibit prominent ions corresponding to the masses of the Schiff bases used to make them, and ions corresponding to the loss of ArNCOCO from the parent ion. The (E) isomers 3b, 3d and 5b exhibit a prominent ion of mass 264; 3f gives mass 278, corresponding to the loss of the carboalkoxy group.     

The chemistry of 2H-3,1-benzoxazine-2,4(1H)-dione (isatoic anhydride). 10. Reactions with ester enolates. Synthesis of 4-hydroxy-1-methyl-3-prenyl-2(1H)-quinolinones,Crucial intermediates in the synthesis of quinoline alkaloids

N-Methylisatoic anhydride reacts with the lithium enolates of esters to produce β-ketoesters 4 in nearly quantitative yield. Thermal cyclization of these relatively unstable intermediates afford the corresponding 3-substituted-4-hydroxy-1-methyl-2(1H)-quinolinones (5) in good yields. The reaction of the lithium enolate of 5-methyl-4-hexenoic acid ethyl ester ( 14 ) with various nuclear substituted isatoic anhydrides gives 4-hydroxyl-methyl-3-prenyl-2(1H)-quinolinones 8, 9 , and 18 which are highly desirable intermediates in the synthesis of a variety of quinoline alkaloids. Treatment of 18 with DDQ furnishes oricine in 73% yield.     

Synthesis and antibacterial activity of 1-(substituted-benzyl)-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acids and their 6,8-difluoro analogs

Alkylation of 6,7-difluoro-4-hydroxyquinoline-3-carboxylic acid ethyl ester with substituted-benzyl chlorides gave 1-(substituted-benzyl)-6,7-difluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ethyl esters. Their treatment with piperazine or N-methylpiperazine in pyridine yielded 1-(substituted-benzyl)-6-fluoro-1,4-dihydro-4-oxo-7-(l-piperazinyl)quinoline-3-carboxylic acid ethyl esters which were hydrolyzed with aqueous sodium hydroxide and then acidified with hydrochloric acid afforded the desired 1-(substituted-benzyl)-6-fluoro-1,4-dihydro-4-oxo-7-(1-iperazinyl)quinoline-3-carboxylic acids. The 6,8-difluoro analogs were prepared similarly using 6,7,8-trifluoro-4-hydroxyquinoline-3-carboxylic acid ethyl ester as a starting material. Some of these quinolones demonstrated fairly good antibacterial activities. Among them, 6-fluoro-1-(4-fluorophenylmethyl)-1,4-dihydro-7-(1-iperazinyl)-4-oxoquinoline-3-carboxylic acid ( 7d ) and 6,8-difluoro-1-(3-fluorophenylmethyl)-1,4-dihydro-7-(1-piperazinyl)-4-oxoquinoline-3-carboxylic acid ( 8c ) are two of the best.     

Synthesis and cytotoxic activity of derivatives of the <Emphasis Type="Italic">tert</Emphasis>-butyl ester of 7<Emphasis Type="Italic">Z</Emphasis>-acetylmethylene-3-methyl-3-cephem-4-carboxylic acid

The condensation of the acetylmethylene group in the tert-butyl esters of 7Z-acetylmethylene-3-methyl-3-cephem-4-carboxylic acid and 7Z-acetylmethylene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid and in 7Z-acetylmethylene-3-methylene-1,1-dioxo-3-cephem with arylmethoxyamines and O-alkylation of the tert-butyl ester of 7Z-(2-hydroxyimino)propylidene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid using substituted benzyl bromides as well as pyridylmethyl chlorides gave arylmethoxyimino and pyridylmethoxyimino derivatives of these compounds in the syn and anti isomeric forms. The Vilsmaier reagent was used to introduce the N,N-dimethylaminomethylene group at C-2 of the cephem system in the tert-butyl esters of 7Z-[2-(arylmethoxyimino)propylidene]-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid. Subsequent transformation of the N,N-dimethylaminomethylene cephems using hydroxylamine led to 3Z-[2-(anti-arylmethoxyimino)propylidene]-tert-butoxycarbonylmethyl-4-(5-methyl-4-isoxazolylsulfonyl)- azetidin-2-ones. Condensation of the acetyl group in the tert-butyl ester of 7Z-acetylmethylene- 3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid with 4-bromophenylhydrazine gave a cephem with a 2-(4-bromophenylhydrazono)propylidene group at C-7. Acylation of the tert-butyl ester of 7Z-(2-hydroxyimino)propylidene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid by 2-bromobenzoyl chloride gave a cephem with a 2-(2-bromo-benzoyloxyimino)propylidene group at C-7. Biological screening of these products towards to malignant and normal cells in vitro showed that their antitumor activity and cytotoxic selectivity towards to malignant and normal cells depend on the structure and configuration of the arylmethoxyimino and pyridylmethoxyimino groups in the 7-alkylidene substituent as well as on the presence or absence of N,N-dimethylaminomethylene and carboxyl groups, respectively, at C-2 and C-4 of the cephem system.     

Synthesis of some 3-substituted quino[3,2-c][1,8]naphtyridines. A new heterocyclic ring system

Isatoic acid reacts with 7-mcthyl-2,3-dihydro-1,8-naphthyridin-4(1H) one ( 8 ) to give 3-methyl-5,6-dihvdroquino[3,2-c][1,8]naphthyriclin-7-carboxylic acid ( 9a ), which was transformed into the 3-methylquino[3,2-c][1,8]naphthyridine ( 7a ) by refluxing with copper chromite in quinoline. The same product ( 7a ) was also obtained by aromatization of the 3-methyl-5,6-dihydroquino-[3,2-c][1.8]naphthvridine ( 10a ), prepared by condensation of the ketone ( 8 ) and o-aminobenzaldehyde. Other 3-substituted quino[3,2-c][1,8]naphthyridines ( 7b,c,d,e ), which contain a new heterocyclic, ring structure, have been prepared using o-aminobenzaldehyde and 7-sub-stituted-2,3-dihv dro-1,8-naphthyridin-4(1H) ones ( 12 and 13 ) as starting materials. Also, the preparation of the parent nucleus ( 7f ) is described.     

Reactions of 3-chloro-6-hydrazinopyridazine with michael-retro-michael reagents

Although pyrazole formation results from treatment of 3-chloro-6-hydrazinopyridazine ( 2 ) with both ethoxymethylenemalononitrile and ethyl (ethoxymethylene)cyanoacetate, 6-chlorotriazolo[4,3-b]pyridazine ( 5 ) was produced (75% yield) when 2 was treated with diethyl ethoxymethylenemalonate. Treatment of 2 with diethyl acetylmalonate ( 8 ) gave both 6-chloro-3-methyltriazolo[4,3-b]pyridazine ( 10 ) and 5-hydroxy-3-methyl-1-(6-chloro-3-pyridazinyl)-1H-pyrazole-4-carboxylic acid ethyl ester ( 12 ). Pyrazole 12 was initially isolated as a salt of triazolopyridazine 10 .     

A facile and novel synthesis of 1,6-naphthyridin-2(1H)-ones

A new and convenient procedure for the synthesis of 1,6-naphthyridin-2(1H)-ones and their derivatives is described. In the first scheme 5-acetyl-6-[2-(dimethylamino)ethenyl]-1,2-dihydro-2-oxo-3-pyridinecarbonitrile ( 4 ) obtained by the reaction of N,N-dimethylformamide dimethyl acetal with 5-acetyl-1,2-dihydro-6-methyl-2-oxo-3-pyridinecarbonitrile ( 3 ) was cyclized to 1,2-dihydro-5-methyl-2-oxo-1,6-naphthyridine-3-carbonitrile ( 5 ) by the action of ammonium acetate. Thermal decarboxylation of acid 7 obtained from the hydrolysis of nitrile 5 led to a mixture of 5-methyl-1,6-naphthyridin-2(1H)-one ( 8 ) and its dimer 9 . Hydrazide 11 obtained from nitrile 5 in two steps was converted to 3-amino-5-methyl-1,6-naphthyridin-2(1H)-one ( 12 ) by the Curtius rearrangement. The amino group of 12 was readily replaced by treatment with aqueous sodium hydroxide to yield 3-hydroxy-5-methyl-1,6-naphthyridin-2(1H)-one ( 13 ). In the second scheme, Michael reaction of enamines of type 20 with methyl propiolate, followed by ring closure gave 5-acyl(aroyl)-6-methyl-2(1H)-pyridinones ( 21 ) which in turn were treated with Bredereck's reagent to produce 5-acyl(aroyl)-6-[2-(dimethylamino)ethenyl]-2(1H)-pyridinones ( 22 ). Treatment of 22 with ammonium acetate led to the formation of 1,6-naphthyridin-2(1H)-ones 23 .     

1,5-Hydride shift in products of Stevens 3,2-rearrangement of methyl(alkyl)(alkoxycarbonylmethyl)-(3-phenyl-2- propynyl)ammonium bromides

The products of the Stevens 3,2-rearrangement of ammonium salts containing methyl and other (ethyl, propyl, butyl) alkyl groups along with 3-phenylprop-2-ynyl, under the reaction conditions undergo, roughly by half, intramolecular hydride shift with intermediate formation of immonium salts. The latter convert into enamino esters whose hydrolysis involving alkyl groups at the nitrogen atom gives rise to lower aliphatic aldehydes and the corresponding amino esters. Treatment with dilute hydrochloric acid of the reaction mixture containing enamino esters results in formation of hydrogenated and nonhydrogenated alkyl esters of -keto acids. This mixture was reacted with concentrated hydrochloric acid to obtain 3-hydroxy-5-methyl-4-phenylfuran-2(5H)-one from the nonhydrogenated keto ester and to isolate pure the hydrogenated keto ester.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1484–1490.Original Russian Text Copyright © 2004 by Ovsepyan, Babakhanyan, Manukyan, Kocharyan.This revised version was published online in April 2005 with a corrected cover date.     

Applying density functional theory on tautomerism in 3,4-dihydropyrimidin-2(1H)-ones

In the present study, the density functional theory (DFT) and Gibbs free energy calculations were performed to investigate the stability and tautomerism of C4-substituted-3,4-dihydropyrimidin-2(1H)-ones. Three different forms are possible for the ethyl 3,4-dihydropyrimidinones (ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1H)-one-5-carboxylates, ethyl 4-aryl-2-hydroxy-6-methyl-1,4-dihydropyrimidine-5-carboxylates and ethyl 4-aryl-2-hydroxy-6-methyl-3,4-dihydropyrimidine-5-carboxylates) forms that the most stable form is ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2 (1H)-one-5-carboxylates (keto-form). The obtained data showed that the substitution on the C4-substitut position can be effective on the equilibrium constant (K _eq).     

Indole esters as heterocyclic synthons. III. Preparation and reactions of furo[3,2-b]indoles

The preparation of furo[3,2-b]indoles via Dieckmann cyclization is described. The precursor diesters were obtained from 3-hydroxy-1H-indole-2-carboxylic acid esters and methyl or ethyl bromoacetate. Reactions of the furo[3,2-b]indole enolic esters prepared are discussed.     

Reaction of 2-dimethylaminomethylene-1,3-diones with dinucleophiles. VI. Synthesis of ethyl or methyl 1,5-disubstituted 1H-pyrazole-4-carboxylates

Reaction of ethyl or methyl 3-oxoalkanoates with N,N-dimethylformamide dimethyl acetal gave, generally in excellent yields, a series of ethyl or methyl 2-dimethylaminomethylene-3-oxoalkanoates II which reacted with phenylhydrazine to afford the esters of 5-substituted 1-phenyl-1H-pyrazole-4-carboxylic acids III in high yields. Esters III were hydrolyzed to the relative 5-substituted 1-phenyl-1H-pyrazole-4-carboxylic acids which were converted by heating to 5-substituted 1-phenyl-1H-pyrazoles in excellent yields. Reaction of II with methylhydrazine afforded in general a mixture of 3- and 5-substituted ethyl 1-methyl-1H-pyrazole-4-carboxylates with the exception of IIg , which gave in high yield methyl 5-benzyl-1-methyl-1H-pyrazole-4-carboxylate, which was hydrolyzed to the relative pyrazolecarboxylic acid. This afforded by heating 5-benzyl-1-methyl-1H-pyrazole in quantitative yield.     

3-Oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide derivatives. I. Reaction of esters with alkoxides

Reaction of 3-oxo-1,2-benzoisothiazoline-2-acetic acid alkyl esters 1,1-dioxide ( 1a-d ) with alkaline alkoxides was carried out under various conditions. Under mild conditions, o-(N-carboxymethylsulfamyl)benzoic acids dialkyl esters ( 2a-d ) were obtained with good yields. Reaction of 1a-d or 2a-d with sodium alkoxides under drastic conditions afforded 4-hydroxy-2H-1,2-benzothiazine-3-carboxylic acid alkyl esters 1,1-dioxide ( 3a-d ). Transesterification was observed when esters 1b-d were treated with sodium methoxide in methanol. Esters 3a-d were hydrolyzed in concentrated aqueous sodium hydroxide affording the acid 6 . Attempts to recrystallize 6 from water resulted in its decarboxylation to give 2H-1,2-benzothiazine-4-(3H)one 1,1-dioxide (7). Compound 6 could not be obtained by acid hydrolysis of esters 3a-d or by rearrangement of 3-oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide ( 8 ). Different experimental evidence supports the suggestion that rearrangement took place by ethanolysis of the carboxamide linkage affording the open sulfonamides (fast step) followed by a Dieckmann cyclization (slow step). It was demonstrated that transesterification took place in the open sulfonamides 2 .     

3-Oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide derivatives. II. Reaction of amides with alkoxides

Reaction of some 3-oxo-1,2-benzoisothiazoline-2-acetamide 1,1-dioxides ( 1a-f ) with alkaline alkoxides was carried out under various conditions. Under mild conditions, 1a-f with sodium methoxide gave o-(N-carbox-amidomethylsulfamyl)benzoic acid methyl esters ( 2a-f, R = CH3 ). Compounds 1a or 2a reacted with sodium alkoxides under drastic conditions affording only ester 5 . Under the same conditions, 1b-d or 2b-d gave 4-hydroxy-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxides ( 3b-d ), while 1e-f or 2e-f afforded the acid 6 in variable amounts, together with the expected benzothiazines 3e-f . Isolation of ethyl ether as another product in the reaction of 1e-f with sodium ethoxide supports the suggestion that the formation of 6 involves the O-alkyl fission on the alkyl carbon of the esters 2e-f . An explanation of these results may be related to the acidic character of the amide hydrogen in compounds 2e-f .     

Synthesis of New Fused Pirano[4,3-b]pyridine Derivatives

A method was developed for the synthesis of pyrano[4,3-b]thieno[3,2-e]pyridine derivatives based on the reaction of 3-amino-7-ethyl-7-methyl-7,8-dihydro-5H-pyrano[4,3-b]thieno[3,2-e]pyridine-2-carboxylic acid ethyl ester with chloroacetic acid chloride, triethyl orthoformate, hydrazine hydrate, and also phenyl chloroformate. The synthesis of various new representatives of pyrano[2″,3″:5′,6′]pyrido[3′,2′:4,5]thieno[3,2-dl-pyrimidine series was carried out.

     

Methyl 3-cyclopropyl-3-oxopropanoate in the synthesis of heterocycles having a cyclopropyl substituent

Reactions of methyl 3-cyclopropyl-3-oxopropanoate with chloroacetone and ammonia, benzaldehyde and ammonia, and benzoquinone gave, respectively, methyl 2-cyclopropyl-5-methyl-1H-pyrrole-3-carboxylate, dimethyl 2,6-dicyclopropyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate, and methyl 2-cyclopropyl-5-hydroxy-1-benzofuran-3-carboxylate. Cyclization of methyl 3-cyclopropyl-3-oxopropanoate with ethyl chloro(arylhydrazono)ethanoates and other halohydrazones led to the formation of 3-substituted 1-aryl-5-cyclopropyl-1H-pyrazole-4-carboxylic acids, and 5-cyclopropyl-1-(quinolin-5-yl)-1H-1,2,3-triazole-4-carboxylic acid was obtained by reaction of the title compound with 5-azidoquinolines.     

Reaction of the Reformatskii reagent obtained from bromotetrahydrofuran-2-one with 2-oxochromene-3-carboxylic or 3-oxo-3<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">f</Emphasis>]chromene-2-carboxylic acid derivatives

The Reformatskii reagent obtained from 3-bromotetrahydrofuran-2-one reacts with alkyl esters of 6-bromo- and 6,8-dibromo-2-oxochromene-3-carboxylic acid or alkyl esters and N-benzylamide of 3-oxo-3H-benzo[f]chromene-2-carboxylic acid to form alkyl esters of 6-bromo- and 6,8-dibromo-2-oxo-4-(2-oxotetrahydrofuran-3-yl)chroman-3-carboxylic acid or alkyl esters and N-benzylamide of 2,3- dihydro-3-oxo-1-(2-oxotetrahdrofuran-3-yl)-1H-benzo[f]chromene-2-carboxylic acid as a mixture of two diastereomers.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1513–1515.Original Russian Text Copyright © 2004 by Shchepin, Fotin, Shurov.This revised version was published online in April 2005 with a corrected cover date.     

The Synthesis of 4-Amino-2-methyl-3-(1-oxo) Pent-4-ynyl-5,6,7,8-tetrahydrobenzo[b]thieno[2,3-b]pyridine

The synthesis of ketone 1 from the ethyl ester of 4-amino-2-methyl-5,6,7,8-tetrahydrobenzo[b]thieno[2,3-b]pyridine-3-carboxylic acid using β-ketosulfone methodology is described.