Thiourea diaryl

Symmetrical dialkyl and diaryl thioureas have been prepared in generally good yield (60-90%) from the reaction of the amine with thiophosgene, formed in situ from the catalysed reaction of carbon tetrachloride with sodium sulphide [5], Reaction with diamines yields cyclic ureas. 

The thioureas were prepared by boiling an alcoholic solution of the aniline, carbon disulfide, and sodium hydroxide for 14 hr. The product, diaryl thioureas, were recrystallized from benzene. 

Keywords aryl isothiocyanate, aromatic primary amine, diaryl thiourea... 

The simplest synthesis of pseudothiohydantoins (8) is by condensation of thiourea (6) with substituted a-chloroacetates (7)3 5 [Eq. (1)]. Synthons6 of 7, epoxyacids,7 a-chloroacetic anhydrides,8 and dialkyl acetylenedi-carboxylate,9 have been successfully substituted for 7. Symmetrical diaryl-thioureas (9), conveniently synthesized from the corresponding arylamine and carbon disulfide, react with a-haloacetic acid derivatives to give a single thiazolidinone 108,10,11 [Eq. (2)]. 

Several recent papers deal with the restricted C—N rotations in monosubstituted, NN -disubstituted, and NNN -trisubstituted thioureas, together with the conformational aspects involved. N-Alkyl-thioureas were found to exist both in the cis- and the trans-form, but N-arylthioureas appeared to exist solely in the intramolecularly hydrogen-bonded form (363). A similar form (364) was found to be predominant in l-alkyl-3-aryl- and 1,3-diaryl-thioureas, whereas both of the isomers (365) and (366), but not the sterically unfavourable form (367), were detectable in the case of l,3-dialkylthioureas. Reeves and his coworkers, by means of a total n.m.r, line-shape fitting, have evaluated the... 

Takemoto et al. disclosed the catalytic cyanation of nitrones promoted by a diaryl thiourea [70]. Semicatalytic amount of thiourea was employed to activate the nitrone by hydrogen bonding. 

Diaryl-l,3,4-oxadiazoles 163 react with thiourea to give 2,5-diaryl-l,3,4-thiadiazoles 165 (Table 9) <1998SC4611>. The proposed mechanism proceeds via ring contraction of an intermediate oxathiadiazepine 164 to give the thiadiazole 165 (Scheme 15). 

Table 9 Preparation of 2,5-diaryl-1,3,4-thiadiazoles from 2,5-diaryl-1,3,4-oxadiazoles using thiourea...

Heterocyclic rings can be produced from the reaction of a chalcone 203 under basic conditions with urea or thiourea, generating the corresponding diaryl guanidinium structure 204a or 204b as displayed in Scheme 56 by Kidwai and... 

The reaction between l,3-diaryl-2-thioureas and phosgene or thio-phosgene has been reported to yield 2-arylimino-3-aryl-l,3-thiazetidin-4-ones (5)9 or thiones (6).10 Recent studies on the reaction between... 

Unsubstituted imidazolidine-2-thione, also known as ethylene thiourea, was one of the reported products (along with aniline, 2-anilino-2-imidazoline, and hydrogen sulfide) which resulted from thermolysis of 1-(2-aminoethyl)-3-phenyl-2-thiourea.31Cherbuliez etal.32 found that l,3-diarylimidazolidine-2-thiones (20) were formed by treatment of the l,3-diaryl-l-(2-hydroxyethyl)-2-thioureas (19) with concentrated hydrochloric acid. 

In a reaction first reported by Will in 1881, l,3-diaryl-2-thioureas heated with ethylene bromide yield 2-iminothiazolidines (54).113,114... 

Aryl cyanides react with the anion of urea (or thiourea) to give the 2,4-diaryl-l,3,5-triazinone (164) in good to excellent yields except when o-chloroaryl isocyanates are used (76JHC917). 

Thiourea dioxide (aminoiminomethanesulfinic acid) reduced diaryl ditellurium and divinyl ditellurium derivatives in tetrahydrofuran, to which an ammonium salt such as cetyltrimethylammonium chloride, serving as a phase-transfer catalyst, and 50% aqueous sodium hydroxide had been added4,5. 

Dialkyl and diaryl ditellurium compounds are easily reduced to tellurols and tellurolates. Alkali metals in liquid ammonia or in an inert organic solvent, sodium borohydride in methanol, ethanol, alcohol/benzene, THF, DMF, or in a basic aqueous medium, lithium aluminum hydride in dioxane or THF/hexamethylphosphoric triamide, and thiourea dioxide in THF/50% aqueous sodium hydroxide have been used as reducing agents (p. 164). The tellurolates are easily oxidized in air. For this reason they are almost always used in situ. 

Elemental chlorine, bromine, and iodine, sulfuryl chloride and thionyl chloride convert diorgano ditellurium compounds to organo tellurium trihalides (p. 314). The reactions are carried out in inert organic solvents with stoichiometrically required amounts of reagents. Dialkyl ditellurium compounds may lose alkyl halides if the halogenolysis is not performed under mild conditions at low temperatures. When equimolar amounts of halogens and diaryl ditellurium derivatives are combined in appropriate solvents, aryl tellurium halides are formed (p. 239). The formation of aryl tellurium halides is facilitated by stabilizing substituents in the orf/to-position to the tellurium atom or by the presence of thioureas or selenoureas in the reaction mixture. 

Alkyl Aryl Telluriums2 (Reduction with Thiourea Dioxide) To a solution of 1.0 mmol diaryl ditellurium in 7.5 ml tetrahydrofuran are added 0.108 g (1.0 mmol) thiourea dioxide, 30 mg 2HT (phase transfer reagent), and 2.0 mmol of the alkyl bromide. To this mixture are added 7.5 ml of a 50% aqueous solution of sodium hydroxide. The mixture is stirred for several hours at 20°. The organic phase is separated. The aqueous phase is extracted three times with 20 ml ethyl acetate. The organic phase and the ethyl acetate extracts are combined and dried with anhydrous magnesium sulfate. The mixture is filtered and the solvents evaporated from the filtrate. The residue is chromatographed on silica gel with ethyl acetate as mobile phase. 

Commonly employed reducing agents are sodium borohydride, sodium sulfide nonahy-drate, potassium sulfide, sodium or potassium hydrogen sulfite (Vol. IX, p. 1068), sodium disulfite, hydrazine hydrate, and thiourea dioxide. Lithium diethylamide1 has been found to reduce diaryl tellurium dichlorides. Methyl magnesium iodide is recommended in the older literature as a reducing agent (Vol. IX, p. 1069). 

Dialkyl, alkyl aryl, and diaryl tellurium dichlorides were reduced by thiourea dioxide in a 2 molar aqueous solution of sodium hydroxide to the corresponding diorgano tellurium compounds4,5. The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

Diaryl tellurium arenesufonimides are reduced to the diaryl tellurium by thiourea in acetonitrile solution3, by 1,3-diphenylthiourea in methanol4, by thiobenzamide in methanol4, by thiols in chloroform4, and by diphenyl ditellurium in chloroform5. These reductions proceed in yields of 95%. 

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