Reaction with thiourea

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

II. Thiazoles from -Halocarbonyl Compounds and Derivatives 213 3. Reaction with Thiourea... 

Because of the structural requirements of the bielectrophile, fully aromatized heterocycles are usually not readily available by this procedure. The dithiocarbamate (159) reacted with oxalyl chloride to give the substituted thiazolidine-4,5-dione (160) (see Chapter 4.19), and the same reagent reacted with iV-alkylbenzamidine (161) at 100-140 °C to give the 1 -alkyl-2-phenylimidazole-4,5-dione (162) (see Chapter 4.08). Iminochlorides of oxalic acid also react with iV,iV-disubstituted thioureas in this case the 2-dialkylaminothiazolidine-2,4-dione bis-imides are obtained. Thiobenzamide generally forms linear adducts, but 2-thiazolines will form under suitable conditions (70TL3781). Phenyliminooxalic acid dichloride, prepared from oxalic acid, phosphorus pentachloride and aniline in benzene, likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

Claisen condensation, 6, 156 reactions, S, 92 IsothiazoIe-3-carboxyIic acids decarboxylation, 6, 156 Isothiazole-4-carboxylic acids decarboxylation, 6, 156 Isothiazole-5-carboxylic acids decarboxylation, S, 92 6, 156 IR spectroscopy, 6, 142 Isothiazole-3-diazonium borofluoride decomposition, 6, 158 IsothiazoIe-4-diazonium chloride, 3-methyl-reactions with thiourea, 6, 158 Isothiazole-5-diazonium chloride, 4-bromo-3-methyl-halogen exchange, 6, 163 Isothiazole-5-diazonium chloride, 3-methyl-reactions... 

The isomeric thiazolo[5,4-g]quinoline skeleton was prepared from 6-chloro-quinoline-5,8-dione hydrochloride by reaction with thiourea, resulting in the 2-amino-4,9-dioxo-4,9-dihydroderivative 42 (91CCC1919). 

The reaction of chloromethyl aryl ethers with nucleophilic reagents has been described by Barber et al Thus, by reaction with thiourea, potassium thiocyanate, or sodium cyanide, there arc obtained aryloxyalkylisothiouronium salts, aryloxyalkyl thiocyanates, and aryloxyalkylacetonitriles, respectively. The reaction of chloromethyl aryl ethers with butyllithium leads to an aryloxycarbene which on reaction with olefins gives aryloxy-cyclopropanes. The ethers react with triphenylphosphine and a base to give phcnoxymethylene ylides which arc useful in con-... 

Another type of cyclization reaction with thioureas has been observed by Ueno et Here l,3-thiazetidin-3-ylium salts (179) are obtained in good yields by treatment of chloromethylsulfoxide with substituted thioureas followed by treatment of the resulting isothiuronium chlorides with coned H2SO4 and NaBPh. The methanesullinyl unit acts as the leaving group in this cyclic nucleophilic substitution reaction. 

Thioureas react readily with /3-diketones, and reactions with thioureas in many cases give higher yields than ureas in pyrimidine cyclizations. d -Alkylisothioureas are frequently used instead of thioureas, as demonstrated by the reaction of A-methylthiuronium sulfate 654 with mucochloric acid (2,3-dichloromalealdehydic acid) 653 which represents an example of reaction with a masked ketoaldehyde where the ketone is protected as a vinyl chloride <2002SC153>. 

Spirocyclic 2,4-oxazolidinedione analogues have been prepared and evaluated as cholinergic agents by Japanese workers (Scheme 6.52). For example, condensation of the a-hydroxy ester 226 with urea produced 227a quantitatively, whereas reaction with thiourea afforded 227b in poor yield together with 228. 

Reaction with thiourea results in salt-like crystallized from boiling acetone. Further treatment with alkalis or excess thiourea results in their degradation to the thiol (305).169... 

Phenyliminooxalic acid dichloride likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

Cyclohexanones have been employed in reactions with thioureas to give quinazolines with varying degrees of saturation. For example, octahydroquinazolinedithiones (182) have been prepared from cyclohexanone and symmetrical313 315 or unsymmetrical314 disubstituted... 

Fused oxygen and nitrogen-containing rings may also be prepared in reactions with thioureas thus, dihydrobenzoxazine products are obtained on treatment of salicyloyl chloride with thioureas371 or on fusion of salicylate esters with thiopseudoureas.320 When the thio-pseudoureas are treated with o-aminophenol, the products are benzoxa-zoles.320 A naphthyl analog of a benzoxazole is produced on treatment of l-(2-hydroxy-l-naphthyl)-2-thiourea with dimethyl sulfate.372... 

Other ring types prepared from thioureas include those of Petersen and Hcitzer, who prepared the naphthoxathiolones 233 (X = 0, Y = OH)411 from 2-(2-methylpropanal-2-yl)-l,4-naphthoquinone and 233 (X = NH, Y = H)412 starting with a tctrahydrobenz[gr]indol-5-one, each through reaction with thiourea in hydrochloric acid. Kaushal and Narang413 prepared a series of dihydrothiazolo[4,5-c]cinnolines... 

Thiols may be prepared from the corresponding alkyl halide by reaction with thiourea followed by treatment of the isothiouronium salt with base. 

A base-promoted cleavage of the hetero ring of the 4-oxo-3,4-dihydro-2/7-thiochromenium salt 299 results in the formation of an ethylsulfanylaryl vinyl ketone, while reaction with thiourea produces the thiochroman-4-one (Scheme 45) <1998T5599>. 

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