The reaction of 4,5-dichloro-1,2,3-dithiazolium chloride with DMSO: an improved synthesis of 4-chloro-1,2,3-dithiazol-5H-one

4,5-Dichloro-1,2,3-dithiazolium chloride 2 (Appel salt) reacts with either DMSO, diphenylsulfoxide 11 or methylphenylsulfoxide 12 to give 4-chloro-5H-1,2,3-dithiazol-5-one 1 in excellent yields. The use of catalytic amounts of DMSO (1 mol %) in MeCN in the presence of water (1 equiv) transforms Appel salt 2 into dithiazolone 1 in near quantitative yields (92%). Rational mechanisms are proposed to explain the catalytic nature of these reactions.     

The degradation of 4,5-dichloro-1,2,3-dithiazolium chloride in wet solvents

4,5-Dichloro-1,2,3-dithiazolium chloride 1 (Appel salt) reacts in wet DCM, THF or MeCN to give elemental sulfur, dithiazole-5-thione 4, dithiazol-5-one 5 and thiazol-5-one 6. Furthermore the reaction of 2-phenylthiazol-5(4H)-one 12 with Appel salt 1 at ca. 20 °C gives 4-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-2-phenylthiazol-5(4H)-one 13 (26%) while at ca. 82 °C a new product 2,2′-diphenyl-4,4′-bithiazol-ylidene-5,5′-dione 14 (36%) is additionally isolated. Finally, 4,4′-bithiazolylidene-5,5′-dione 14 is prepared directly by treating 2-phenylthiazol-5(4H)-one 12 with N-chlorosuccinimide. All new compounds are fully characterised and rational mechanisms are proposed for the formation of all key compounds.     

Unusual regioselective reaction of 2,6-dichloro-4-methylnicotinonitrile with malononitrile dimer

Russian Chemical Bulletin - The reaction of 2,6-dichloro-4-methylnicotinonitrile with malononitrile dimer in the presence of triethylamine leads to regioselective nucleophilic substitution of the...     

The preparation and characterization of 5-substituted-4-chloro-1,2,3-dithiazolium salts and their conversion into 4-substituted-3-chloro-1,2,5-thiadiazoles

A series of monosubstituted acetonitriles were treated with disulfur dichloride at room temperature in CH2Cl2 to afford 5-substituted-4-chloro-1,2,3-dithiazolium chlorides 1.Where the 5-substituent was not a good leaving group the chloride salts were converted into the corresponding perchlorate salts 2 which were sufficiently stable and soluble to provide both (1)H- and (13)C-NMR and cyclic voltammetry data. Several of the dithiazolium chlorides were converted into their corresponding 4-substituted-3-chloro-1,2,5-thiadiazoles 13 on treatment with aqueous ammonia. Mechanisms for all reactions are proposed.     

Novel synthesis of 4-chloro-3-hydroxy-2-pyrone by the reaction of acetonide protected 4,5-dihydroxy-2-chloroglycidic ester with magnesium chloride

Treatment of acetonide protected 4,5-dihydroxy-2-chloroglycidic ester with magnesium chloride gave 4-chloro-3-hydroxy-2-pyrone in excellent to good yields.     

New cascade reaction of azides with malononitrile dimer to polyfunctional [1,2,3]triazolo[4,5-b]pyridine

A new cascade reaction of azides with malononitrile dimer yielding polyfunctional [1,2,3]triazolo[4,5-b]pyridine was found. It was established that during the reaction of aryl azides with malononitrile dimer, under base catalysis, the formed intermediate triazole underwent spontaneous cyclization leading to the pyridine ring annulation. The obtained products have provided a new entry to [1,2,3]triazolo[4,5-b]pyridine.     

The reaction of 2-substituted-4,5-dichloro-3(2H)-pyridazinones with alkoxides and alkylthiolates

The reaction of 2-substituted-4,5-dichloro-3(2H)-pyridazinones 1a-b with alkoxides and alkylthiolates was investigated. Regiospecific displacement of either the 4 or 5 chlorine atom could be achieved in most cases by appropriate selection of the reaction solvent.     

Regioselective synthesis of 1-(2,6-dichloro-4-trifluoromethylphenyl)- 4-alkyl-1H-[1,2,3]-triazoles

A new and efficient method for the synthesis of 1-(2,6-dichloro-4-trifluoromethylphenyl)-4-alkyl-1H-[1,2,3]-triazoles by the room temperature 1,3-dipolar cycloaddition of (2-azido-1,3-dichloro-5-trifluoromethyl)benzene with terminal alkynes in the presence of Cu (I) salt as catalyst is reported. All the reactions gave 1,4-disubstituted products with high regioselectivity, as no 1,5-disubstituted product was formed. The structures of all the title compounds have been confirmed by elemental analysis, 1H- and 13C-NMR and in addition, the structure of compound 5a was investigated by X-ray crystallography.     

4-Aryl(benzyl)sulfonyl-2-chloro-5-polyfluoroalkyl-1,2,3-triazoles. The first monocyclic N-chloro-1,2,3-triazoles

Treatment of 4-aryl(benzyl)sulfonyl-5-polyfluoroalkyl-v-triazoles with NaOCl gave the 4-aryl(benzyl)-sulfonyl-2-chloro-5-polyfluoroalkyl-v-triazole derivatives which contain a chlorine atom only on the N₍₂₎ atom of the heterocycle. The structure of 2-chloro-5-(1,1,2,2,3,3-hexafluoropropyl)-4-(p-tolyl-sulfonyl)-2H-[1,2,3]triazole has been established by X-ray structural investigation. The presence of a highly polarized N—Cl bond with a positive halogen atom causes the N-chlorotriazoles to react with KCN and KF as strong acids to form the potassium salts of the triazoles and to form 4-arylsulfonyl-2-(2-chloro-1-ethoxyethyl)-5-polyfluoroalkyl-2H-[1,2,3]triazoles with vinyl ethyl ether. It was found that chlorination of 4-arylsulfonyl-5-polyfluoroalkyl-v-triazoles in the presence of KF gives 4-chloro-5-polyfluoroalkyl-2H-[1,2,3]triazoles. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1342–1352, September, 2007.     

One step cascade synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles

A Lewis base-catalyzed three-component cascade reaction was developed for the synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles. More than 25 new (NH)-triazoles were prepared in good to excellent yields under mild conditions. The availability of the C-4 vinyl group allows easy conversion into other triazole derivatives.     

新试剂4，4'-(2-氯-4-硝基重氮氨基)联苯与氯化十六烷基吡啶显色反应的研究

研究了4,4'-(2-氯-4-硝基重氮氨基)联苯与阳离子表面活性剂氯化十六烷基吡啶发生显色反应,提出了光度法测定氯化十六烷基吡啶的新方法。实验结果表明,在碱性介质中,4,4'-(2-氯-4-硝基重氮氨基)联苯与氯化十六烷基吡啶形成1：2紫红色离子缔合物,最大吸收波长位于570 nm处,表观摩尔吸光系数为2.16×104...     

Efficient synthesis of 3H-imidazo[4,5-b]pyridines from malononitrile and 5-amino-4-(cyanoformimidoyl)imidazoles

1-Aryl-5-amino-4-(cyanoformimidoyl)imidazoles 2 were reacted with malononitrile under mild experimental conditions and led to 3-aryl-5,7-diamino-6-cyano-3H-imidazo[4,5-b]pyridines 5, when the reaction was carried out in the presence of DBU, or to 3-aryl-5-amino-6,7-dicyano-3H-imidazo[4,5-b]pyridines 3, in its absence. Both reactions evolved from the adduct formed by nucleophilic attack of the malononitrile anion to the carbon of the cyanoformimidoyl substituent. A 5-amino-1-aryl-4-(1-amino-2,2-dicyanovinyl)imidazole 4 was isolated when this reaction was carried out in the presence of DBU. The structure of compound 4 was confirmed by spectroscopic methods and by reaction with triethyl orthoformate and with acetic anhydride, leading respectively to 9-aryl-6-(cyanomethylidene)purines 11 and 12. Imidazole 2b was also reacted with ethyl acetoacetate, a carbon acid with a pK(a) comparable to that of malononitrile. Similar reaction conditions were used and the product isolated was a 6-carbamoyl-1,2-dihydropurine 10, showing that a different mechanism was operating in this case.     

An improved synthesis of fused 1,2,3-benzothiadiphospholes and a proposed reaction pathway

A fresh look has been taken at the reaction of PCl₃ with thioanisole 1b and AlCl₃ that gives, after treatment with water, the title compounds cis- 2b in 38% yield together with small amounts of the isomeric cis- 3b (2%). The course of this reaction has been studied by ³¹P-NMR spectroscopy. A multistep pathway, governed by the formation of several AlCl₃ complexes with sulfur and phosphorus containing intermediates, has been proposed. The crucial step of this reaction is very reasonably an intramolecular electrocyclic ring closure of a diphosphane intermediate. From this plausible mechanism, an improved procedure that gives only the cis- 2b isomer in 42% yield has been realized. In addition, an alternative synthesis using p-thiocresol that gives compounds cis- 2b and cis- 3b in a ratio of about 2:1 has been effected. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 551–556, 1997     

The unprecedented reaction of dimethylsulfonium methylide with Michael acceptors: synthesis of 1-substituted vinyl silanes and styrenes

Rather than the usual cyclopropanation, conditions for an unprecedented elimination reaction from the adduct of dimethylsulfonium methylide and various Michael acceptors have been established leading to functionalized 1-substituted alkenes. In silyl substituted substrates (2a and 2h), where a facile Peterson-type olefination is possible from the adduct; elimination took place instead to give functionalized 1-substituted vinyl silanes. Aryl substituted Michael acceptors (2b-e, 2g and 2i-k) also underwent a similar kind of olefination to give 1-substituted styrene derivatives with moderate yields along with a side product, which arose by nucleophilic demethylation from the adduct of dimethylsulfonium methylide and arylidene malonates. Hammett studies revealed that selectivity for olefination vs. demethylation increases as the aryl substituent becomes more electron deficient. Alkylidene malonates (2f and 2l) with a beta-alkyl substituent did not favour the olefination process. Sequential addition of Michael acceptors and alkyl halides to a mixture of dimethylsulfonium methylide and sodium dimsylate provided olefination followed by alkylation on the active methine group. A mechanistic pathway has been formulated from the studies of a few sulfonium methylides.     

Synthesis and reaction of N-butyl-N-isobutenyl-aminotrimethylsilane with 4,5-benzo-2-chloro-1,3,2-dioxaphospholane

The reaction of N-butylisobutyraldimine with trimethyliodosilane obtained in situ proceeds to give N-butyl-N-isobutenylaminotrimethylsilane, which reacts with 4,5-benzo-2-chloro-1,3,2-dioxaphospholane to yield 2-(N-butyl-N-isobutenylamino)-4,5-benzo-1,3,2-dioxaphospholane.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, 420083 Kazan. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1923–1924, August, 1992.     

One-pot synthesis of 2-aminobenzimidazoles using 2-chloro-1,3-dimethylimidazolinium chloride (DMC)

2-Chloro-1,3-dimethylimidazolinium chloride (DMC or DMC-Cl) has been found to effectively and rapidly generate 2-aminobenzimidazoles from 1,2-diaminoarenes and isothiocyanates in moderate to good yields at room temperature in a one-pot operation.