Synthesis of 2,2′-dithiobis- and 2,2′-trithiobis-3-pyridinecarboxylic acid derivatives as new potential radiosensitizers/radioprotectors

This paper reports the synthesis of dithio and trithio derivatives of 1,2-dihydro-2-thioxopyridine, starting with 1,2-dihydro-2-thioxo-3-pyridine carboxylic acid 1 . This compound reacted with thionyl chloride to give the respective dithiobis (acyl chloride) 2 , which hydrolyzed to the corresponding dithio acid 3 . On the other hand, 1 reacted with sulfur dichloride to give trithio acid 4 , which on treatment with thionyl chloride gave the trithiobis (acyl chloride) 5 . Treatment of 2 and 5 with ethanol/pyridine, gave 8 and 12 respectively. Compounds 2–5, 8 and 12 were unstable in alkaline medium and they were degraded to 1 . The bis(acyl chloride) 2 and 5 reacted with ammonia and primary and secondary amines to give the respective bis(amide) 9 and 13 . Most of these amides (R = H, alkyl, aryl, R' = H) were found to be unstable in the presence of bases such as triethylamines, pyridine or excess of the starting amine, which promotes disproportion to give (see Scheme 3) the respective N-substituted (R) 1,2-dihydro-2-thioxo-3-pyridinecarboxamide 10 and the respective 2-substituted (R)-3-oxo-isothiazolo[5,4-b]pyridine 11 . On the other hand, compounds 11 were unstable to strong bases and they were transformed into the respective compounds 10 by an unknown mechanism. Boiling 11f with sodium hydroxide in ethanol gave 10f (50%). According to these last results, boiling 9h or 13d with sodium hydroxide in ethanol 10h (68%) and 10d (70%) were obtained.     

An alternative synthesis of piritrexim,a lipophilic inhibitor of human dihydrofolate-reductase

An alternative synthesis of the lipophilic antifolate piritrexim ( 1 ) is outlined. Starting from ketone 2 , treatment with phosphorus oxychloride and dimethylformamide gave the β-chlorocrotonaldehydes 3E/Z , which were reacted with cyanoacetamide ( 6 ) in the presence of sodium hydride to yield a 3-cyano-2-pyridone derivative 7 . Chlorination of 7 with thionyl chloride and subsequent reaction with guanidine ( 9 ) gave rise to piritrexim ( 1 ). The reaction of β-chlorocrotonaldehydes 3E/Z , with 2,4,6-triaminopyrimidine ( 4 ) yielded iso-piritrexim ( 5 ).     

Synthesis via pummerer intermediates. III. Rearrangements of 3-(methylsulfinyl)quinolinones, 3-(methylsulfinyl)cinnolinones, 3-(methylsulfinyl)chromanones and 3-(methylsulfinyl)chromones with acetic anhydride and with thionyl chloride

The reaction of 1-methyl-3-(methylsulfinyl)-4(1H)quinolinone ( 1 ) with acetic anhydride and thionyl chloride gave 3-[[(acetyloxy)methyl]thio]]-1-methyl-4(1H)quinolinone ( 2 ) and 3-[(chloromethyl)thio]-1-methyl-4(1H)quinolinone ( 3 ) respectively. 3-(Methylsulfinyl)-4(1H)cinnolinone ( 4 ) gave the corresponding products when treated under similar conditions. Treatment of 8-methoxy-3-(methylsulfinyl)-4H-1-benzopyran-4-one ( 11 ) with acetic anhydride and thionyl chloride gave bis addition vinyl Pummerer products 2,3-bis(acetyloxy)-2,3-dihydro-8-methoxy-3-(methylthio)-4H-1-benzopyran-4-one ( 12 ) and 2,3-dichloro-2,3-dihydro-8-methoxy-3-(methylthio)-4H-1-benzopyran-4-one ( 13 ), respectively.     

The chemistry of 1,2,5-thiadiazoles,IV. Benzo[1,2-c:3,4-c′:5,6-c″] tris [1,2,5] thiadiazole

Benzo [1,2-c:3,4-c′:5,6-c″] tris [1,2,5] thiadiazole (1) was synthesized from benzo [1,2-c:3,4-c′] - bis [1,2,5] thiadiazole (11) . Nitration of 11 gave compound 15 , which on direct amination gave nitroamine 17 . Reduction of 17 gave diamine 18 , and cyclization of 18 with thionyl chloride gave 1 . Diamine 18 was also cyclized with selenium oxychloride, glyoxal, 9,10-phenanthrene-quinone, and formic acid to give the compounds 4, 5, 19 , and 6 , respectively. A new procedure for the preparation of 2,1,3-benzothiadiazole (7) from o-phenylenediamine was used.     

Synthesis of novel 1-phenyl-1H-indole-2-carboxylic acids. II. Preparation of 3-dialkylamino, 3-alkylthio, 3-alkylsulfinyl,and 3-alkylsulfonyl derivatives

The synthesis of novel indole-2-carboxylic acids with amino- and sulfur-containing substituents in the indole 3-position is described. An Ullmann reaction with bromobenzene converted 1H-indoles with 3-(acetylamino)- and 3-(diethylamino)-substituents into 1-phenyl-1H-indoles. Reaction of 3-unsubstituted indoles with thionyl chloride provided indole 3-sulfinyl chlorides, which reacted with alkyl and aryl Grignard reagents to form the corresponding sulfoxides. The indole sulfoxides thus obtained were reduced to sulfides or oxidized to sulfones.     

Studies on organophosphorus compounds: Synthesis and reactions of [1,2,4,3]triaza‐phospholo[4,5‐a]quinoxaline derivative

2,4‐Bis‐(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide (Lawesson's reagent) ( 1 ) reacted with 2‐hydrazino‐3‐methyl‐quinoxaline ( 2 ) to give [1,2,4,3]‐triazaphospholo[4,5‐a]quinoxaline derivative 3 . The Mannich reaction using different amines on compound 3 gave Mannich bases 4a–d . Also, compound 3 reacted with formaldehyde to give the corresponding 2‐hydroxymethyl derivative 5 , which upon reaction with thionyl chloride gave the corresponding chloromethyl derivative 6 . Treatment of compound 6 with some thiols yielded the corresponding sulfides 7a–d . Acylation of compound 3 gave acylated compounds 8a,b . Compound 9 , which was prepared through the reaction of compound 3 with ethyl cyanoacetate, was investigated as a starting material for the synthesis of some new heterocyclic systems 10–13 . Also, reaction of compound 9 with carbon disulfide and 2 equivalents of methyl iodide in a one‐pot reaction yielded the corresponding ketene‐S,S‐acetal 14 , which in turn reacted with bidentates to give some new heterocycles 15–17 . © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:520–529, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20473     

Condensed thiophenes and selenophenes: thionyl chloride and selenium oxychloride as sulfur and selenium transfer reagents

3,4-Cyanomethyl substituted thiophenes reacted with thionyl chloride in the presence of base to give dicyano substituted thieno(3,4-c)thiophenes. The use of selenium oxychloride furnished the corresponding cyano substituted seleno(3,4-c)thiophene. 1,2-Phenylenediacetonitriles gave the corresponding cyano substituted benzo(c)thiophenes and benzo(c)selenenophenes, respectively, upon reaction with thionyl chloride and selenium oxychloride in the presence of base.     

Selenium heterocycles. XLI . Syntheses of substituted thiazolo,selenazolo, 1,2,3-thiadiazolo and 1,2,3-selenadiazoloquinolines

The reaction of thionyl chloride with the semicarbazone 2 gave 4,5-dihydro[1,2,3]thiadiazolo[4,5-f]quinoline. Selenium dioxide oxidaion of compound 2 gave 4,5-dihydro[1,2,3]selenadiazolo[4,5-f]quinoline ( 4 ) and the aromatic analog 5 . Thermolysis of compound 5 yielded [1,4]diselenino[2,3-f:5,6-f′]diquinoline ( 6 ). Reaction of selenourea with α-bromoketone 7 gave 2-amino-4,5-dihydroselenazolo[4,5-f]quinoline ( 8 ). Compounds 9 and 10 were prepared from the reaction of selenobenzamide and thiobenzamide with compound 7 .     

The Synthesis and Application of Novel Nitrating and Nitrosating Agents

Alcohols and phenols are efficiently nitrated with thionyl chloride nitrate or thionyl nitrate, even in the presence of an aromatic moiety. While thionyl chloride nitrate is suitable for nitration of primary OH-groups in carbohydrates, thionyl nitrate is reactive enough to react with secondary OH-groups as well. These reagents permit the highly selective nitration of the 5′-,2′5′- and 3′, 5′-OH-groups of ribonucleosides to produce either mono-or diprotected nitro derivatives in high yields. Carbon acids and the enol form of some ketones are efficiently nitrated with trifluoromethanesulfonyl nitrate/potassium tert-butoxide. Lutidine N-oxide (2,6-(CH₃)₂C₅H₃N O) was found to have a marked effect on nitration reactions. Similarly, thionyl chloride nitrite and thionyl nitrite exhibit an excellent capacity for nitrosation of the aforementioned substrates.     

Reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride leading to purine,thiazolo[4,5-d]pyrimidine,pyrimido[4,5-e][1,3,4]thiadiazine,pyrazolo[3,4-d]pyrimidine,and [1,2,3]thiadiazolo[4,5-d]pyrimidine derivativese

The reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride in benzene afforded purine, thiazolo[4,5-d]pyrimidine, pyrimido[4,5-e][1,3,4]thiadiazine, pyrazolo[3,4-d]pyrimidine, and [1,2,3]thiadiazolo[4,5-d]pyrimidine derivatives, while the treatment of 6-(benzylidene-1′-methylhydrazino)-1,3-dimethyluracil with thionyl chloride in benzene gave 4-methylpyrimido[4,5-e][1,3,4]thiadiazine and 1-methylpyrazolo-[3,4-d]pyrimidine derivatives. Plausible mechanisms for the formation of these fused pyrimidines are also described.     

An Efficient Synthesis of Pyrazolyl‐1,2,3‐thiadiazoles via Hurd–Mori Reaction

An efficient synthetic strategy has been developed for the synthesis of pyrazolyl‐1,2,3‐thiadiazoles via Hurd–Mori cyclization reaction. The reaction of various pyrazolyl‐phenylethanones with semicarbazide hydrochloride in the presence of sodium acetate/methanol gave the corresponding semicarbazones ( 3a – i ). These semicarbazones were further reacted with thionyl chloride via the Hurd–Mori cyclization conditions to accomplish the title products ( 4a – i ). The present protocol favored for the formation of both pyrazolyl semicarbazone derivatives and pyrazolyl‐1,2,3‐thiadiazole derivatives by forming C─S, N─S, and C═N bonds in excellent yields with variety of substrates. The final compounds were characterized by analytical and spectral studies.     

9,9′-Thiobis-(1,2,3,4,7,8-hexahydro-7-methyl-6H-pyrimido[1,6-a]pyrimidine-6,8-dione)

The 6-(3-hydroxypropylamino)-3-methylpyrimidine-2,4-dione (1) did not afford the expected 6-(3-chloro-propylamino)- derivative on reaction with thionyl chloride, but, instead, the pyrimidine rings were joined via a sulfur bridge to give 9,9′-thiobis(1,2,3,4,7,8-hexahydro-7-melnyl-6H-pyrimido[1,6-a]pyrirnidine-6,8-dione) ( 3 ). An identical 9,9′-thiobis- derivative 3 was obtained when reacting thionyl chloride with 1,2,3,4,7,8-hexahydro-7-methyl-6H-pyrimido[1,6-a]pyrimidine-6,8-dione ( 4 ). We suppose the sulfoxide- derivative 2 to be the intermediate of both routes: it underwent reduction to the final sulfide 3 in excess thionyl chloride.     

The synthesis of unusual isocoumarin derivatives: the chemistry of homophthalic acid

Homophthalic acid was reacted with thionyl chloride/DMF and ethyl chloroformate/NEt₃ in the presence and absence of NaN₃. In all cases completely different isocoumarin derivatives were obtained. These unusual isocoumarin derivatives were characterized and their mechanism of formation is discussed.     

Naphth[1,2-d]oxazole intermediates in the preparation of 3-hydroxy-4-(1-alkyl-3-methyl-5-hydroxy-4-pyrazolyl)-azo-1-naphthalenesulfonamide dyes

Acylation of 4-amino-3-hydroxy-1-naphthalenesulfonic acid ( 3 ) with benzoyl chloride in pyridine gave pyridinium 3-hydroxy-4-(N-benzoylamino)-1-naphthalenesulfonate ( 12 ) which was converted by thionyl chloride followed by diethylamine into N,N-diethyl-2-phenylnaphth[1,2-d]oxazole-5-sulfonamide ( 14 ). The naphthoxazole moiety was hydrolyzed with potassium hydroxide and the resulting N,N-diethyl-4-amino-3-hydroxy-1-naphthalenesulfonamide ( 11 ) coupled with 1-alkyl-3-methyl-5-pyrazolones. The 2-phenylnaphth[1,2-d]oxazole intermediates and various by-products were investigated.     

C(6)N(7)-cyclized purines

By reaction of 6-[N-(2-hydroxyethyl)-N-methyl]aminopurine ( 2a ) and of the corresponding 3-hydroxypropyl derivative 2b with thionyl chloride a bridge to N(1) is formed yielding 5 and 6 , respectively, whereas from 6-[N-(4-hydroxybutyl)-N-methyl]aminopurine ( 2c ) the 4-chlorobutyl compound 4 is obtained, which cyclizes in alkaline medium to the C(6)-N(7) bridged compound 7 . A related cyclization to 11a–11f is observed when 6-chloropurines are reacted with 3-alkyl-1,3-oxazolidines or 3-methyl-1,3-thiazolidine.     

Synthesis and identification of new thieno[3,2-b] benzothiophenes

The reaction of 2-lithiobenzo[b]thiophenes with ketones produced 2-hydroxyalkylbenzo[b]thiophenes which were cyclized in thionyl chloride to give novel thieno[3,2-b][1]benzothiophenes. Oxidation with peroxyacetic acid gave the S,S-dioxides whose regiochemistry was identified from ¹H nmr model studies using substituted benzo[b]thiophenes and their corresponding-1,1-dioxides [1].     

5,5-Bis(alkoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Synthesis and X-ray diffraction study

2,2-Bis(alkoxy-NNO-azoxy)propane-1,3-diols reacted with thionyl chloride to give previously unknown 5,5-bis(methoxy-NNO-azoxy)- and 5,5-bis(ethoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Replacement of the hydroxy groups by chlorine is a minor reaction path. According to the X-ray diffraction data, the heteroring in the molecule of 5,5-bis(methoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxide adopts a chair conformation with axial orientation of the S=O bond.     

Synthesis of hindered hydrazones and their reaction with thionyl chloride

Hydrazones 12a–c and ketazines 13a–c were prepared by the reaction of ketones 11a–c with hydrazine hydrate depending on the temperature and the reaction time. Some ketone (aryl)hydrazone derivatives 14a,c,e reacted with thionyl chloride to afford the chlorothiadiazoline derivatives 15a–c . Surprisingly, the chlorine atom in the latter compounds was found to undergo smooth nucleophilic substitution, and by boiling these compounds in absolute ethanol gave the corresponding ethoxythiadiazoline derivatives 16a–c . The structure of the ethoxythiadiazoline 16b was confirmed by single crystal X‐ray determination. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:223–228, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10125     

Cobalt Porphyrazines with Heterocyclic Substituents

Reactions of 4,5-diaminophthalodinitrile with thionyl chloride, sodium nitrite in concentrated sulfuric acid, and phenanthrenequinone gave, respectively, 5,6-dicyano-2,1,3-benzothiadiazole, 5,6-dicyano- 1H-benzotriazole, and 6,7-dicyano-2,3-(9,10-phenanthro)quinoxaline, from which the corresponding cobalt porphyrazines were prepared. The effect of the heterocyclic moiety on the physicochemical and spectral properties of porphyrazines was elucidated.     

Synthesis of 5,6,7,8-tetrahydro-5-oxopyrido[2,3-d]pyrimidine-6-carbonitriles and -6-carboxylic acid esters

Dieckmann ring closure reactions of 4-[(2-cyanoethyl)substituted amino]-2-phenyl-5-pyrimidinecarboxylates (Ha-f) afforded several 5,6,7,8-tetrahydro-5-oxo-2-phenylpyrido[2,3-d]pyrimidine-6- carbonitriles (IIIa-f). The open-chain intermediates (IIa-f) were prepared by dechloroamination of 5-carbethoxy-4-chloro-2-phenylpyrimidine (1a) with several 3-substituted amino- propionitriles. Alkylation of the sodium salt of 5,6,7,8-tetrahydro-8-methyl-5-oxo-2-phenyl-pyrido[2,3-d]pyrimidine-6- carbonitrile (IIIa) with methyl iodide in DMF resulted in methylation at C-6 to afford IV. Tosylation of IIIa in pyridine gave the corresponding tosyl ester (V) of the enolic form. Oxidative dehydrogenation at the 6,7-position resulted when IIIa reacted with thionyl chloride, affording 5,8-dihydro-8-methyl-5-oxo-2-phenylpyrido[2,3-d]pyrimidine-6- carbonitrile (VII). Dechloroamination of la or 5-carbethoxy-4-chloro-2-methylthiopyrimidine (Ib) with ethyl 3-ethylaminopropionate followed by Dieckmann cyclization of the resulting open-chain intermediates gave the corresponding ethyl 5,6,7,8-tetrahydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxylates IX'a and IX'b, respectively. These exist predominately in the enol form and undergo alkylation and oxidation reactions similar to IIIa.