N-Disubstituted Thioureas

The N,N-disubstituted thioureas (135) condensed with a-halocarbonyl compounds give 2-disubstituted aminothiazoies (136) but in lower yields (30 to 70%) (Scheme 65 and Table 11-20) (518). For example, N,N-dialkylthioureas condensed with chloroacetaldehyde or dibromoether lead to Ar,At-dialkyl-2-aminothiazoles in 136, Ri=R2 = methyl (342, 404, 436, 637), ethyl (343, 436), n-propyl (518), n-butyl (518), ally] (518), and benzyl (26, 29). When chloroacetone and dichloroacetone are the carbonyl reactants the corresponding 4-methyl (518) and 4-chloromethyl derivatives (572) were obtained. 

N,N Disubstituted thioureas from secondary amines and silicon tetra-isothiocyanate, 46, 69 N,N-Disubstituted ureas from secondary ammes and silicon tetraiso-cyanate, 46, 69... 

Triazinethiones have been used frequently for the syntheses of triazino-triazines in the literature. Reaction of 6-methyl-5-[substituted styryl]-2/7-[l,2,4]triazine-3-thiones 39 with thiourea or acetylthiourea in dimethylformamide (DMF) led to the formation of N,N -disubstituted thioureas 40. Heating the compound 40b with glacial acetic acid and fused sodium acetate under reflux led to the formation of the compounds 4,7-dimethyl-8-[2-ethenylfuran]-2-thioxo-l,3,5-triazino[5,6- ][l,2,4]triazine 22 (Scheme 6) <2003PS279>. 

The cyclizations to obtain cyclic thioureas have been performed using thiocarbonyldiimidazole.232 Reaction of methyl acetoacetate, thiourea and an aliphatic aldehyde in the presence of the zinc iodide (Znl2) was studied. Under the normal pressure, reaction has not been occurred whereas at high pressure (300 MPa) conditions 3,4-dihydropyrimidine-2-thione was obtained only in 10% yield.233 The same one-pot three-component cyclocondensation reaction in the presence of iodide (I2) provides a variety of 3,4-dihydropyrimi-dine-2-thione in high yields.234 Condensation reaction of thioureas with a,p-unsaturated ketones in the presence of the sodium methoxide in methanol affords 3,4-dihydropyrimidine-2-thione derivatives.235,236 Acylation of N,N -disubstituted thioureas with methyl malonyl chloride followed by base-catalysed cyclization leads in the formation of l,3-disubstituted-2-thiobarbituric acids (Scheme 78).237... 

Dipolar cycloaddition reactions, of nitrones to olefins, 46, 97 of 3-phenylsydnone, 46, 98 Dispiro[5.1.5.1]tetradecane-7,14-dione, photolysis to cyclohexylidene-cyclohexane, 47, 34 preparation from cyclohexanecarbonyl chloride and triethylamine, 47, 34 Displacement of bromine from 1-bromo-2-fluoroheptane to give 2-fluoro-heptyl acetate, 46, 37 N,N -Disubstituted formamidines from triethyl orthoformate and primary amines, 46, 41 N,N-Disubstituted thioureas from secondary amines and silicon tetra-isothiocyanate, 45, 69 N,N-Disubstituted ureas from secondary amines and silicon tetraiso-cyanate, 45, 69... 

N,N-Disubstituted thioureas from secondary amines and silicon tetra-isothiocyanate, 46, 69... 

The Hector s bases (73) undergo a Dimroth rearrangement, presumably via (264), to the symmetrical Dost s bases (84) when heated under alkaline conditions. Oxidation of N -alky 1-iV-arylthioureas affords the symmetrical thiadiazoles (265) directly whereas the products obtained from N,N - disubstituted thioureas (266) depend on the nature of the substituents (80JCR(S)407). 

Reaction of oxalyl chloride with compound 301 gives the thiazolidine-4,5-dione 302 (Scheme 146), and the same reagent with A-alkylbenzamidine 303 at 100-140G affords the l-alkyl-2-phenylimidazole-4,5-dione 304 (Scheme 147). Imi-nochlorides of oxalic acid react with N,N-disubstituted thioureas to give the 2-dialkylaminothiazolidine-4,5-dione bis-imides 305. Phenyliminooxalic acid dichloride likewise yielded thiazolidine derivatives on reaction with thioureas <1971KGS471>. 

The synthesis of carbodiimides by desulfurization of 1,3-disnbstitnted thioureas is the most general method of synthesis because dialkyl-, alkylaryl- anddiarylcarbodiimides with the same or different substituents are obtained. The desnlfurization of N,N -disubstituted thioureas 1 with yellow mercuric oxide is the classical method of synthesis of carbodiimides 2 used by Weith in 1873. ... 

The reaction of N,N -disubstituted thioureas 15 with phosgene (carbonyl chloride) affords aliphatic and aromatic carbodiimides 16 in good yields. For example, addition of phosgene... 

N,N -disubstituted thioureas 20 react with DCC to give a new carbodiimide 21 and N,N -dicyclohexylthiourea. This reaction is an equilibrium reaction ... 

Carbodlimides. Diethyl azodicarboxylate (1) reacts with N,N -disubstituted thioureas (2) in THF at room temperature overnight to form a I I adduct (3) [an N, N -disubstituted-S-(N ,N4-biscarboethoxy)hydrazinoisothiourea], which on treat ment with triphenylphosphine at room temperature affords the corresponding carbo. ... 

In contrast to their reactions with SOCI2 and PCI5 (see Section 6.18.10.2.2.i), N -acy -N, N -disubstituted thioureas (189), on treatment with POCI3 in boiling 1,2-dichloroethane followed by addition of perchloric acid, afford 1,3,5-thiadiazinium perchlorates (190) in 50-98% yield (Equation (12)) <85T5371>. 

N,N -Disubstituted thioureas are converted into carbodiimides by reaction with 1 and 2 equiv. of base (equation IIl). ... 

The elimination of hydrogen chloride from chloroformamidine hydrochlorides is another example illustrating the utility of imidoyl halides. Thermolysis of diarylchloroformamidine hydrochlorides PCIV), obtained from N,N -disubstituted thioureas and phosgene, is the best method of synthesis of unsymmetrical carbodiimides (XV) because the generated... 

Analogous Benzotriazole-mediated syntheses are available, for example, for diaryl-methanes, dieneamines, and N,N-disubstituted thioureas (Katritzky methodology, 1990 for applications in heterocyclic synthesis, cf Ref [510]). 

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