Thioureas, reaction with carbonyl chloride

The reaction of substituted thioureas with carbonyl chloride is perhaps the most useful synthetic method for chloroformamidines. Thus, alkyl... 

In contrast, the reaction of 1-arenesulfony 1-3-aryIthioureas (V, R = R = aryl), with carbonyl chloride affords the four-membered ring 1,3-thiazetidine-2-ones (IX) almost exclusively ( ). The compounds (IX) are also formed as minor by-products in the reaction of aliphatic and aromatic 1,3-disubstituted thioureas with carbonyl chloride ( ). 

The reaction of thioureas with carbonyl chloride can be conducted at room temperature in an inert diluent, preferentially in a solvent, in which the starting thiourea is soluble. Suitable solvents are benzene, chlorobenzene, ethylene dichloride, dioxane, etc. If by-products are formed, they are easily separated with diethyl ether, in which the salt-like chloroforma-midine hydrochlorides are completely insoluble. Sometimes it is possible to isolate the initial reaction product X, especially if a nonpolar solvent is being used, which retards the elimination of carbonyl sulfide ( ). 

The reaction of thioureas with carbonyl chloride can be extended to cyclic derivatives. Thus, chloroimidazolidine hydrochloride (XII) is obtained in the reaction of ethylene thiourea with carbonyl chloride (see Chapter 8). 

In addition to the activation of carbonyl compounds and imines, Schreiner studied on thiourea-catalyzed acetalization reaction, in which ortho esters were activated by hydrogen bond [19]. Jacobsen has utilized the hydrogen-bond catalysis in reactions with acyliminium ions, wherein hydrogen bond activates the acylim-inium salt through complexation with chloride [20]. 

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... 

The reactions of 2-aminobenzimidazoles have been reviewed <83S86l>. The compounds form Schiffs bases with carbonyl compounds, with isocyanates and isothiocyanates they give ureas and thioureas, they are subject to 1,3-dipolar addition reactions, and to the formation of carbamates on acylation and aroylation. When aminoimidazoles are acylated there is frequently competition between the annular and exocyclic nitrogen (see above). Add chlorides and anhydrides (soft) acylate the amino group chlorocarbonic acid esters (hard) are specific for the heteroatom <84CHE204>. When heated, the A -acyl products isomerize (Scheme 91). 

In general, chloroformamidine hydrochlorides are formed in the reaction of thiourea and urea derivatives with either carbonyl chloride or... 

The use of an excess of carbonyl chloride in the reaction with di-substituted thioureas has to be avoided, because the chloroformamidine hydrochlorides eliminate hydrogen chloride and the generated carbodi-imides add carbonyl chloride to afford chloroformamidine-N-carbonyl chlorides XI... 

Three groups of workers have studied the reactivity of thiourea towards a -unsaturated ketonesThe notable lability in the reaction course was demonstrated by the simultaneous or alternative formation of different open-chain as well as cyclic products, thus clearly indicating the occurrence of nucleophilic attacks of both the sulphur and the nitrogen atoms of thiourea on both the carbonyl carbon and the 3-carbon atom of the a 3-unsaturated ketone. Other papers reporting on the nucleophilic activity of thioureas deal with reactions of the latter with oxirans, oxaziridines," acryloyl chloride," o 3-unsaturated acids," acetylenedicarboxylic acid esters, " ethyl thiocyanoacetate," and isocyanates. ... 

Desulfuration.1 The reaction of K02 with o-nitrobenzenesulfonyl chloride results in a peroxysulfur reagent that converts thioureas, thioamides, and thiocar-bamates in CH3CN at -30° into the corresponding carbonyl compounds. Example ... 

Thioureas such as ethylene thiourea (ETU, NA22) initially react with the primary allylic chloride to yield the thioether. Zinc oxide then reacts at the thio-carbonyl atom. Further reaction at the curing temperature of 160°C eliminates the ethylene nrea and leaves the polymer as the zinc sulfide salt. The sulfide salt reacts with the allylic chloride moiety of a second polymer molecule to generate the thioether-cross-linked polymer (102). 

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