Isothiouronium salt, from thiourea

The evidence available suggests that, in a general way, steric factors affect the course of the reaction. Increase in the size of substituents at positions 5 or 7 or in the size of the nucleophile appears to favor protode-bromination over nucleophilic substitution, Furthermore it appears that 6-iododihydrodiazepines undergo protodeiodination rather than nucleophilic substitution irrespective of the size of the nucleophile or of 5(7)-substituents, whereas 6-chlorodihydrodiazepines are less susceptible to protodchalogenation.64 Thus with thiourea 6-bromodihydrodiazepines undergo protodebromination, whereas 6-chlorodihydrodiazepines form 6-isothiouronium salts, in contrast to the normally more ready formation of isothiouronium salts from bromo compounds than from chloro compounds. It is not unreasonable that protodehalogenation should be favored for more bulky dihydrodiazepines or nucleophiles since this reaction has less steric demands than nucleophilic substitution. Similarly, both for... 

Aminopropanols, when reacted with cyanogen bromide, also afford 2-amino-(or imino)-dihydro-1,3-oxazines (Scheme 90) (64ZOB3427), and related thiazines are formed when allylic isothiouronium salts (207) are cyclized with trifluoroacetic acid and stannic chloride. The necessary starting materials are synthesized from aldehydes or ketones by the action of vinylmagnesium chloride and subsequent treatment of the product allyl alcohols (206) first with hydrogen chloride and then with a thiourea (Scheme 91) (77JHC717). 

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

Cyanomethyl isothiouronium salt, as acyclic intermediate in reaction of thiourea with o-halonitrile, 297 Cyanothiazoles, from dehydration of amides, 530, 531... 

The mercapto group can also be formed via the isothiouronium salt (Andriska et al., 1962b Kniisli et al., 1962). With thiourea 2-chloro-4,6-bis(alkylamino)-5-triazines give isothiouronium salt in a practically quantitative yield this is then decomposed by alkali to the corresponding mercapto compound and dicyano diamide. From this, the 2-mercapto-4,6-bis(alkylamino)-s-triazinc derivative is obtained with a methylating agent. The reaction scheme is as follows ... 

Quinoxaline-2-thione (2) is prepared from 2-chloroquinoxaline by treatment with thiourea in methanol, followed by hydrolysis of the resulting isothiouronium salt (1) with 2.5 M sodium hydroxide. A number of other quinoxaline-2-thiones have been prepared by this method, in most cases without the isolation of the intermediate isothiouronium salt. 3-Hydrazinoquinoxaline-2-thiones are obtained from the corresponding 2-chloro-3-hydrazinoquinoxalines by treatment with an aqueous solution of alkali sulfide or alkali hydrogen sulphide.3-Amino-quinoxaline-2-thione has been prepared similarly by treating 2-amino-3-chloroquinoxaline with methanolic potassium hydrogen sulfide in an... 

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