Thioureas reaction with chlorine compounds

Another useful method to convert thioureas into carbodiimides involves their reaction with reactive chlorine compounds, such as SOCI2, SO2CI2, SCI2 or S2CI2, The use of the sulfur chlorides involves chloroformamidines as intermediates (see Section 2.2.6). The reaction of thioureas 11 with methanesulfonyl chloride in methylene chloride in the presence of triethylamine/DMAP (4-dimethylaminopyridine) at room temperature produces carbodiimides 12 in 85-100% yield... 

The direct replacement of chlorine in 2-chlorotetrahydrothiophene by means of MeSH leads to low yields of (339). However, reaction with diphenylacetic acid and EtjN gives the diphenylacetic ester which can be converted to (339) in excellent yield by MeSH. Alternatively, 2-mercaptotetra-hydrothiophene can be prepared by the thiourea method (CHEC-I) and methylated to give (339) <92CB1641>. Deprotonation of (339) with Bu"Li at —30°C gives the 2-lithio derivative this reacts with a variety of electrophiles (alkyl halides, carbonyl compounds) to form (340) (Scheme 69). 

The synthesis of 38 began with 39. Acetal formation and chlorination adjacent to sulfur provided 40. Thiourea was used to introduce sulfur. Hydrolysis of 41 provided the free thiol and a ketal exchange (hydrolysis-protection) gave 42. This compound was configurationally stable at the anomeric center and thus, was resolved via the thioester derived from reaction with (-)-camphanyl chloride. The absolute configuration of the proper enantiomer was established by X-ray crystallography of this thioester. S-Alkylation of 43 with racemic mesylate 46 provided a mixture of diastereomers 47 (Erythronolide-6). 

With sulfur and triethylamine in dimethylformamide, compounds (86) give (89) (Equation (21)) <89JPR243>. With thiols or KjS, sulfides are produced (e.g., (90) and (91)), which show spasmolytic activity in vitro <86MI 404-01 >. Smooth 5N2-displacements of chlorine occur with phenol, thiophenol, SCN, and thiourea in dimethylsulfoxide. However, with K2CO3 or sodium cyanide, (86) (Ar = Ph) affords the trimers (92) or (93) (Scheme 32). With electron-deficient trans alkenes, stereoselective formation of cyclopropanes (94) was observed (Scheme 32). No reactions occur with maleates <66HCA412>. 

Of all the methods described for the synthesis of thiazole compounds, the most efficient involves the condensation of equimolar quantities of thiourea and a-halo ketones or aldehydes to yield the corresponding 2-aminothiazoles (Scheme 167) (l888LA(249)3l). The reaction occurs more readily than that of thioamides and can be carried out in aqueous or alcoholic solution, even in a distinctly acid medium, an advantage not shared by thioamides which are often unstable in acids. The yields are usually excellent. A derived method condenses the thiourea (2 mol) with the non-halogenated methylene ketone (1 mol) in the presence of iodine (1 mol) or another oxidizing agent (chlorine, bromine, sulfuryl chloride, chlorosulfonic acid or sulfur monochloride) (Scheme 168) (45JA2242). 

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. 

Chloro-l,3-dimethylimidazolium chloride (DMC) [26] (R =R = Me, L = H in 11, Scheme 4.8a) not only acts as a powerful dehydration agent but also has unique and versatile abilities to chlorinate primary alcohols, to oxidize primary and secondary alcohols and to reduce sulfoxides and so on. In addition, DMC easily reacts with amines to yield the corresponding guanidines. Thus, methods of preparing monocyclic and bicyclic systems by application of DMC chemistry in the key steps have been developed [27] the reaction of DMC-type chloroamidine compounds with amines for trisubstituted mono-cyclic guanidines [27a] (Scheme 4.8a), the intramolecular cyclization of thiourea derivatives after activation with DMC for monosubstituted or disubstituted monocyclic and bicyclic guanidines [27b] (Scheme 4.8b), and the DMC mediated cyclization of... 

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