A novel entry toward 2-imino-1,3-thiazolidines and 2-imino-1,3-thiazolines by ring transformation of 2-(thiocyanomethyl)aziridines

A new, efficient, and straightforward synthesis of 3-arylmethyl-4-chloromethyl-2-imino-1,3-thiazolidines and 2-(N-acylimino)-3-arylmethyl-4-chloromethyl-1,3-thiazolidines has been developed by ring transformation of 1-arylmethyl-2-(thiocyanomethyl)aziridines upon treatment with a catalytic amount of titanium(IV) chloride in dichloromethane. The latter 2-(thiocyanomethyl)aziridines were prepared in high yields from 1-arylmethyl-2-(bromomethyl)aziridines by reaction with potassium thiocyanate in DMF. The 2-imino-1,3-thiazolidines and 2-(N-acylimino)-1,3-thiazolidines thus obtained can be easily interconverted, either by treatment with an acid chloride and a base in ether toward 2-(N-acylimino)thiazolidines or by treatment with potassium carbonate in methanol toward N-deprotected 2-iminothiazolidines. Dehydrohalogenation of 2-(N-acylimino)-3-arylmethyl-4-chloromethyl-1,3-thiazolidines by means of potassium tert-butoxide in DMSO afforded 2-(N-acylimino)-4-methyl-2,3-dihydro-1,3-thiazolines in good yields.     

REACTIONS OF HYDRAZONOYL HALIDES 371: SYNTHESIS OF TRIAZOLO[4,3-a]PYRIMIDINES, 1,3,4-THIADIAZOLES AND 1,3,4-SELENADIAZOLES

1,2,4-Triazolo[4,3-a]pyrimidines, thiadiazolines and selenadiazolines synthesized via reactions of hydrazonoyl halides with each of ethyl 4-(3,4-dimethoxyphenyl)-6-methyl-2-methylthio-3,4-dihydropyrimidine-5-carboxylate (or ethyl 6-(3,4-dimethylphenyl)-4-methyl-2-thio1,3,6-trihydropyrimidine-5-carboxylate), ethyl 4-(2,3-dimethoxyphenyl)- 6-methyl-2-methylthio-3,4-dihydropyrimidine-5-carboxylate, potassium thiocyanate, potassium selenocyanate, and carbodithioates respectively.     

A new approach to 4,6-disubstituted-3,4-dihydropyran-2-ones by Domino Michael addition-cyclization reaction under PTC conditions

Domino Michael addition-cyclization reactions of α,β-unsaturated carbonyl compounds with activated 1,3-dithiane-2-carbothioate esters under solid-liquid phase transfer catalysis conditions provide 4,6-disubstituted-3,4-dihydropyran-2-one-3,3-dithioacetals in good chemical yield. Desulfurization proceeds chemoselectively under mild conditions affording 3,4-dihydropyran-2-ones in high yields.     

Electrosynthesis of 3-chloro-1,4-disubstituted-2(1H)- quinolinones and 3,3-dichloro-4-hydroxy-1,4-disubstituted- 3,4-dihydro-2(1H)-quinolinones,as well as a new convenient process to dioxindoles

Cathodic reduction of N-(2-acyl(or aroyl)phenyl)-2,2,2,-trichloro-N-alkylacetamide at -1.2 V (vs SCE) under aprotic conditions yields 3-chloro-1,4-disubstituted-2(1H)-quinolinones (1) as the major product. When the reaction is carried out at -0.8 V (vs SCE), 3,3-dichloro-4-hydroxy-1,4-disubstituted-3,4-dihydro-2(1H)-quinolinones (2) and 1,4-disubstituted-1,4-dihydro-quinoline-2,3-dione (3) are formed. Ring contraction of 2 and 3 in aqueous sodium hydroxide resulted in the formation of 3-hydroxy-1,3-dihydroindol-2-ones (5). The most plausible reaction mechanisms are proposed.     

Gallium(III) triflate-catalyzed [4+2+1] cycloadditions for the synthesis of novel 3,4-disubstituted-1,5-benzodiazepines

Gallium(III) triflate-catalyzed [4+2+1] cycloaddition of o-phenylenediamines and 2 equiv of alkynoate under solvent-free and ultrasonic irradiation conditions afforded novel 3,4-disubstituted-1,5-benzodiazepines in 82-90% yields.     

Synthesis of new pyrazolothiazole derivatives from 4-thiazolidinones

The synthesis of new 2,3,5,6-aryl substituted tetrahydro-2H-pyrazolo[3,4-d]- thiazoles 4a-j as potential biologically active compounds by the cyclocondensation of phenyl hydrazine with new 5-arylidene derivatives 2a-j of 2,3-disubstituted-1,3- thiazolidin-4-ones 1a-e is reported.     

One-pot approach to 2,3-disubstituted-2,3-dihydro-4-quinolones from 2-alkynylbenzamides

Concise and efficient syntheses of various trans-2,3-disubstituted-2,3-dihydro-4-quinolones have been achieved via tandem Hofmann-type rearrangement of 2-alkynylbenzamides, nucleophilic addition of alcohols to the isocyanate intermediates, intermolecular [2+2]-cycloaddition with carbon-carbon triple bonds and aldehydes, and intramolecular aminocyclization of nitrogen of carbamates to the α,β-unsaturated ketones.     

Facile synthesis of fluorine-containing [4-aryl-4,5-dihydro-5-imino-1,3,4-thiadiazol-2-ylaryl]methanone, 2-amino-4-aryl-5-arylazothiazoles and 3-aroyl-4-acetyl/benzoyl-5-methyl-1-phenylpyrazoles through N-aryl-α-oxo-α-arylethanehydrazonoyl bromide

N-Aryl-α-oxo-α-arylethanehydrazonoyl bromides 2 react with potassium thiocyanate in ethanol leading to the formation of [4-aryl-4,5-dihydro-5-imino-1,3,4-thiadiazol-2-ylaryl]methanone 5 in quantitative yield. Treatment of 2 with thiourea and β-diketones affords 2-amino-4-aryl-5-arylazothiazoles 4 and 3-aroyl-4-acetyl/benzoyl-5-methyl-1-phenylpyrazoles 6 in 65–70 and 60–70% yields respectively. Compound 5 has also been subjected to acetylation and chloroacetylation. All the compounds are characterized by their analytical and spectral (ir, ¹H-nmr and ms) data. Mass fragmentation patterns of these compounds are discussed.     

Synthesis of Some Novel 5-(Arylidene)-2-imino-3(pyridin-2-yl)thiazolidin-4-one Derivatives

Treatment of 2-aminopyridine ( 1 ) with chloroacetyl chloride in dry benzene gave 2-chloro-N-(pyridin-2-yl)acetamide ( 3 ), which on further reaction with potassium thiocyanate gave 2-imino-3-(pyridin-2-yl)thiazolidin-4-one ( 4 ) as an intermediate compound for the synthesis of pyridin-2-yl substituted 2-imino-thiazolidine-4-one derivatives. Cyclocondensation reaction of ( 4 ) with a series of aromatic aldehydes gave 5-arylidene derivatives of pyridin-2-yl substituted 2-imino-thiazolidine-4-ones 5a–j . ¹ H and ¹³C NMR spectroscopy, as well as elemental analyses, were used for the identification of these new compounds.     

Synthesis of 1,5-disubstituted 4-haloimidazoles from α-aminonitriles

Synthesis of pharmaceutically important 1,5-disubstituted-4-haloimidazoles starting from α-aminonitriles is described. Some 1D and 2D NMR spectral features of these imidazoles are discussed.     

Reactions of epoxides of the pyran series involving ring expansion. Reaction of 4-methyl-3,4-epoxytetrahydropyran with potassium thiocyanate

The reaction of 4-methyl-3,4-epoxytetrahydropyran with potassium thiocyanate occurs with expansion of the oxirane ring and leads to 6-methyl-8-amino-3,7-dioxa-9-thiabicyclo[4,3,0]nonane, the formation of which has been proven by the fact that products of its acylation by acid chlorides of 2-R-cinchonic acids are obtained, and also by the formation of Mannich bases when it is treated with formaldehyde and secondary amines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1039–1042, August, 1992.     

Halovinylsulfones 4 . Synthesis and some reactions of 2-phenylsulfonyl-2-propenyl isothiocyanate

The title compound, isothiocyanate 2 , was obtained in good yield from the reaction of α-chloromethylvinyl-sulfone 1 with lead thiocyanate. The isothiocyanate 2 was reacted with aromatic amines to give 2-amino-5,6-dihydro-4H-1,3-thiazines 3 in good to moderate yields. The formation pathways are discussed.     

Synthesis and recyclization of 6-benzyl-3a,4,5,6,7,7a-hexahydro-3a-hydroxy-7a-methyl-2-thioxo-5-phenyloxazolo[5,4-c]pyridines

The corresponding oxazolo[5,4-c]pyridines were obtained in the reaction of stereoisomeric 1-benzyl-3-hydroxy-3-methyl-6-phenyl-4-piperidines with potassium thiocyanate in acetic acid and rearranged into 6-benzyl-5,6,7,8-tetrahydro-1-methyl-3-thioxo-7-phenyloxazolo[3,4-c]pyrimidine by boiling in o-xylene. It was shown that the rearrangement is reversible.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1262–1265, September, 1992.     

A convenient method for the synthesis of 2-[(5-benzyl-1,3-thiazol-2-yl)imino]-1,3-thiazolidin-4-one derivatives

It was found that the reaction of 2-chloroacetamido/chloropropioamido-5-benzylthiazole with potassium thiocyanate gave, via rearrangement, 2-[(5-benzyl-1,3-thiazol-2-yl)imino]-1,3-thiazolidin-4-ones.     

Preparation of compounds in the new dipyrrolo[3,4-b:3′,4′-e]-pyridine series from 1-benzylidene-2,3-dioxopyrrolidines. A variation of the hantzsch synthesis

Treatment of easily prepared l-substituted-4-benzylidene-2,3-dioxopyrrolidines with ammonium formate produces 1,2,4,6,7,8-hexahydro-2,6-disubstituted-8-aryldipyrrolo [3,4-b:3′,4′-e]pyridine-3,5-diones (II), usually in yields of 50 to 60%. Aromatization of the dihydropyridine ring of the hexahydroderivatives II yields corresponding 1,2,6,7-tetrahydro-2,6-disubstituted-8-aryldipyrrolo[3,4-b:3′,4′-e]pyridine-3,5-diones (III). These compounds appear to be the first to incorporate the dipyrrolo[3,4-b:3′,4′-e]pyridine ring system.     

Synthesis of 4,4-dimethyl-3,4-dihydro-3,3,5-trisubstituted-2H-pyrazoles and N-benzoyl derivatives: Method for “Hydrolysis” of unreactive amides and carbamates

Addition of organolithium reagents to 4,4-dimethyl-3,5-disubstituted-4H-pyrazoles produced a series of 4,4-dimethyl-3,4-dihydro-3,3,5-trisubstituted-2H-pyrazoles, 2–6 , in good yield. The reaction was stereoselective: addition of organolithium compounds occurred only to carbon-3 of 4,4-dimethyl-3-alkyl-5-aryl-4H-pyrazoles. The 3,4-dihydro-2H-pyrazoles were found to be of high sensitivity to oxygen. For long term storage and ease of handling, N-benzoyl derivatives were synthesized. Removal of the protecting group could not be accomplished by use of many standard sets of conditions. Deprotection was accomplished in high yield by reaction of the N-benzoyl-4,4-dimethyl-3,4-dihydro-3,3,5-trisubstituted-2H-pyrazoles with anhydrous potassium t-butoxide in toluene [heated under reflux (ultra-pure argon)] in the presence of a phase transfer catalyst (18-Crown-6). Cleavage of a N-carbamate derivative was also achieved by this phase transfer approach. This methodology should be applicable to the hydrolysis of unreactive amides and carbamates in general.     

Synthesis of [4,5-Bis(hydroxymethyl)-1,3-dithiolan-2-yl]nucleosides as Potential Inhibitors of HIV(1)

The synthesis of [4,5-bis(hydroxymethyl)-1,3-dithiolan-2-yl]nucleosides is described. (2S,3S)-1,2:3,4-Diepoxybutane (13) was reacted with potassium thiocyanate to give (2R,3R)-1,2:3,4-diepithiobutane (14). Thiiranering opening with acetate followed by deacetylation gave (2R,3R)-2,3-dithiothreitol (19) which was silylated and treated with trimethyl orthoformate to give the 2-methoxy-1,3-dithiolane 20. Condensation of 20 with silylated thymine, uracil, N(4)-benzoylcytosine and 6-chloropurine using a modified Vorbrüggen procedure, followed by deprotection, gave the nucleoside analogues. Compounds 26, 28, and 30 were found to be inactive when tested for anti-HIV activity in vitro.     

Synthesis of 4-Substituted N-Alkyl-1,3-dithiolan-2-imines

Russian Journal of Organic Chemistry - S-(2-Thiocyanatopropyl) N-alkyl-N-methylcarbamothioates were synthesized from N-alkyl-1,3-oxathiolan-2-imines by reaction with potassium thiocyanate, and...     

Synthesis and molecular structure of 1-(pyrimidin-2-yl)-2-(4-aryl-1,3-thiazol-2-yl)hydrazines

Reactions of some 2-hydrazinopyrimidine hydrochlorides with potassium thiocyanate gave 1-(pyrimidin-2-yl)thiosemicarbazides which underwent Hantzsch condensation with aryl chloromethyl ketones to produce 1-(pyrimidin-2-yl)-2-(4-aryl-1,3-thiazol-2-yl)hydrazine hydrochlorides. The protonation was accompanied by mutually dependent tautomeric rearrangements of heterocyclic fragments.     

Low-valent titanium induced reductive cyclization of nitro compounds and aliphatic ketones:facile synthesis of 3,4-dihydro-(2H) -1,2,4-benzothiadiazine-1,1-dioxides

The intermolecular reductive cyclization of o-nitrobenzene-sulfonamides with aliphatic ketones induced by TiCl4/Sm system was studied and a series of 3,3-disubstituted-3,4-dihydro-(2H)-1,2,4-benzothiadiazine-1,1-dioxides were synthesized in moderate to high yields under mild and neutral conditions.