Mercuric oxide with thioureas

The earliest preparations of carbodiimides involved the reaction of mercuric or lead oxide with thioureas [6-10]. 

Guanidines have been prepared by the reaction between an amine, or an amine salt, and a host of other reagents, such as a thiourea in the presence of lead or mercuric oxide [83, 157, 158], carbodi-imides [140, 174, 175],calcium cyanamide [176, 177], isonitrile dichlorides [178—180], chloroformamidines [181], dialkyl imidocarbonates [182], orthocarbonate esters [183], trichloro-methanesulphenyl chloride [184], and nitro- or nitroso-guanidines [185-188]. Substituted ureas can furnish guanidines, either by treatment with amines and phosphorus oxychloride [189], or by reaction with phenylisocyanate [190] or phosgene [191]. 

Thiourea is tbimed by heating ammonium thiocyanate at 170°C. After about an hour, 25% conversion is achieved. With HQ, thiourea forms thiourea hydrochloride with mercuric oxide, thiourea forms a salt and with silver chloride, it forms a complex salt. 

If the reaction, say, with cyanogen chloride, is carried out in ether solution, ammonium chloride precipitates and is filtered off, and the cyanamide is procured as a syrup by allowing the ether solution to evaporate spontaneously and later as crystals by allowing the syrup to stand over sulfuric acid in a desiccator. Cyanamide may also be prepared by removing the component atoms of hydrogen sulfide from thiourea by means of mercuric oxide. Thionyl chloride effects the corresponding removal of water from urea. 

Condensation of 258 with isothiocyanate 7 gave thiourea 417 (80%), which could be cyclized in 70% yield to aminooxazoline 418 using yellow mercuric oxide. Deprotection of 418 by hydrogenolysis afforded (+)-416 (82%) (Scheme 56).106,107... 

Hydrolysis of the oxazolidinone 236 gave the corresponding amino alcohol, which without isolation was coupled with the sugar 4-isothiocyanate 2653 to provide the thiourea 452 (Scheme 67).105 Cyclization of 452 to the isourea 453 was carried out with yellow mercuric oxide, and the resulting oxazoline 453 was debenzylated to give... 

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. ... 

This procedure for the preparation of l-ethyl-3-(3-dimethyl-amino)propylcarbodiimide and its salts is a modification of one that has been published. Unsymmetrical carbodiimides have also been prepared by desulfurization of the corresponding thioureas with mercuric oxide or by dehydration of the corresponding ureas with -toluenesulfonyl chloride in pyridine. Unsymmetrical 1,3-disubstituted ureas are best prepared by the reaction... 

Phenyl mercuric nitrate, iodoacetate, thiourea, and ammonium sulfate stimulated arsenite-oxidizing activity, whereas cupric ion, and p-chloromercuriben-zoate inhibited it significantly. Legge (8) showed that cytochromes associated with the solid fraction from broken cells of P. arsenoxydans-quinque played a role in aerobic oxidation of arsenite. 

Forms unstable explosive products in reaction with acetaldehyde + desiccants (forms polyethyUdine peroxide) acetic acid (forms peracetic acid) acetic + 3-thietanol acetic anhydride acetone (forms explosive peroxides) alcohols (products are shock-and heat-sensitive) carboxylic acids (e.g., formic acid, acetic acid, tartaric acid), diethyl ether, ethyl acetate, formic acid -f- metaboric acid, ketene (forms diacetyl peroxide) mercur f(II) oxide + nitric acid (forms mercur f(II) peroxide) thiourea -f- nitric acid polyacetoxyacryUc acid lactone + poly(2-hydroxyacrylic acid) + sodium hydroxide. 

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