Isothiuronium salt

By hydrolysis of a phthalocyaninc containing an in situ generated alkyl isothiuronium salt, alkyl thiols as side chains have been obtained.438... 

Reaction of alkyl halides with NaSH cleavage of isothiuronium salts... 

Perfluoroalkyl)ethane thiols have been used as precursors to fluorinated surfactants and products for hydro- and oligophobic finishing of substrates such as textiles and leather (1). The synthesis of 2-(perfluoroalkyl)ethane thiol and a byproduct bis-(-2-perfluoroalkylethane)-disulfide (5-10%) has been practiced via the reaction of 2-(perfluoroalkyl)ethane iodide with thiourea to form an isothiuronium salt which is cleaved with alkali or high molecular weight amine as shown in Equation 1 for 2-(perfluorohexyl)ethane iodide (1). 

Concentration of the filtrate to a volume of about 250 ml. and recrystallization from 95% ethanol of the crude isothiuronium salt which separates gives an additional 130 g. of material. The total yield of the salt is 1234 g. (90%). 

An unexpected reaction occurred when an attempt was made to convert 2-chloromethyl-5-methoxypyran-4-one (512) into its isothiuronium salt. Opening of the pyran ring and recyclization to a benzene ring followed by thiazole ring formation accounts for the formation of 2-amino-5-hydroxy-6 methoxybenzothiazole hydrochloride (513) (80JHC817). 

When the reaction is conducted in the presence of at least an equimolar quantity of acid, the isothiuronium salt (IX) may be obtained in yields up to 80%, The nature of the products obtained on... 

Solid-phase syntheses of triazines (Table 15.32) include the cyclocondensation of polystyrene-bound isothiuronium salts with /V-(cyano)iminodithiocarbonates and the cyclization with simultaneous cleavage from the support of derivatives of a-amino acid hydrazides (Table 15.32). (Benzylthio)triazines, such as those listed in Table 15.32 (Entries 1 and 2), have been cleaved from a support by oxidation to sulfoxides or sul-fones with N-benzenesulfonyl-3-phenyloxaziridine, followed by nucleophilic cleavage with primary or secondary aliphatic amines or with electron-rich anilines (see Section 3.8). 

Thiourea and a-chloropropenoic acid give isothiuronium salts (or their esters) which, when cooled and treated very gradually with aqueous NaOH, lead to the 4-hydroxythiazine 48 or its tautomer 49 (Scheme 29) (51LA140). 

The preparation of 97 was optimized later by Misumi et al. by coupling of the thiolate 94 formed in situ, using the thiocyanate 95 or the isothiuronium salt 96 with the tetrabromide 93 [87], The formation of reactive thiolate groups in the course of the reaction maintains a lower concentration of free thiolate anions and thereby restrains side reactions [87]. 

Using the base CsOH in ethanol/benzene (12 1) as the solvent and the isothiuronium salt 96 increased the yield of the isomeric cyclic compounds 97 to 75 %. The... 

Chloroquinoxaline (1) affords quinoxaline-2(l/f)-thione (16) in 73% yield upon treatment with thiourea in methanol, followed by hydrolysis of the intermediate isothiuronium salt with sodium hydroxide. ... 

A solution of 200 g. (1.0 mole) of the above salt in 800 ml. of water is cooled to 0°, and 500 g. of crushed ice is added. Chlorine gas is introduced into the solution with stirring until decomposition of the isothiuronium salt is complete (see below). The mixture is held at a temperature below 10° during this operation. The sulfonyl chloride separates as an oil and is siphoned off three times during the chlorine addition. The product is dissolved in ether the ethereal solution is washed with water, dried, and distilled. The product boils at 71-72°/20 mm. and is formed in a yield of 110 g. (66%). 

Folkers, Russell, and Bost, J. Am. Chem. Soc., 63, 3530 (1941), report that the above reactions may give explosive mixtures if the chlorination is prolonged or the mixture allowed to stand after completion of the chlorination. The formation of nitrogen trichloride is proposed as an explanation. In the preparation of ethanesulfonyl chloride from 110 g. of the isothiuronium salt, a 10-hour chlorination period allowed formation of an explosive mixture. 

Sodium sulfhydride (NaSH) is a much better reagent for the formation of thiols (mercaptans) from alkyl halides than H2S and is used much more often. It is easily prepared by bubbling H2S into an alkaline solution, but hydrosulfide on a supported polymer resin has also been used. " The reaction is most useful for primary halides. Secondary substrates give much lower yields, and the reaction fails completely for tertiary halides because elimination predominates. Sulfuric and sulfonic esters can be used instead of halides. Thioethers (RSR) are often side products. The conversion can also be accomplished under neutral conditions by treatment of a primary halide with F and a tin sulfide, such as PhsSnSSnPhs. An indirect method for the preparation of a thiol is the reaction of an alkyl halide with thiourea to give an isothiuronium salt (119), and subsequent treatment with alkali or a... 

A problem with the first route is that even with excess of the thiolate, it is difficult to avoid some further reaction leading to formation of the sulfide (R2S). The secondary reaction can be avoided by starting with thiourea (la) and obtaining the thiol via the intermediate S-alkylisothiuronium salt (2) by subsequent hydrolysis (Scheme 2). The formation of the isothiuronium salt (2) depends on the relative instability of the thione ( C=S ) bond in thiourea (la), which therefore exists mainly as the enethiol form isothiourea (lb) which then reacts with the halide. S-Benzylisothiuronium salts are used in organic qualitative analysis for the characterisation of carboxylic acids with which they form nicely crystalline... 

It is clear that effective masking of iron and copper ions would break any destructive chain reaction (oxidative) which they may catalyse. Other substances, all modelled on cysteamine, are available for preventing radiation sickness. An example is 2-mercaptoethylguanidine, generated in the body from 6 -(2-aminoethyl)isothiuronium salts (Doherty, Shapira and Burnett, 1957). 

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