Isothiouronium salt, from

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... 

Condensation of the isothiouronium salt, obtained from the vinyl alcohol (413), with 2-methyl-cyclopentane-1,3-dione has led to a series of A-nor-3-oxa-steroids and similar condensation of the thia-analogue (408) with 2-methyl-cyclopentane-1,3-dione afforded the thia-oestrane (410), which was reduced catalytically to a mixture of 14a- and 14/S-H-dihydro-epimers. Reduction of the remaining conjugated 8,9-unsaturation was less easy than in the carbocyclic analogue metal-ammonia afforded thiols, and catalytic reduction was slow and led to a mixture of, presumably, 8a,9a- and 8, 9jS-epimers. The former isomer (416) which has its 9 -H favourably disposed for hydride abstraction with DDQ readily dehydrogenated to the 9(ll)-olefin which, on subsequent catalytic reduction, gave 6-thia-oestrone methyl ether. Condensation of the same thia-... 

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... 

The tetrakis-bromomethyl derivatives, apart from themselves being useful m-terphenyl base synthons for the construction of thia- and aza- cuppedophanes and cappedophanes (see Sects. 4.1 and 4.5), are also precursors to other useful molecular base synthons. Tetrakis-mercaptomethyl derivative 90 [9], tetrakis-aminomethyl derivatives 92 [11] and tetrakis-p-toluenesulfonylmethyl derivative 93 [11] are three new m-terphenyl templates easily accessed from 8 (Scheme 11). While the mercaptomethyl derivative was prepared via the isothiouronium salt 89, the tetrakis-aminomethyl derivatives 92 and 93 were prepared via the phthalimido derivative 91 [11]. 

A simple route to prepare A,A-dlsubstituted 2,4-diaminothiazoles used a modified Hantzsch synthesis. The isothiouronium salt (49), prepared from the... 

Dihydro-l,3-dithiepins (218) have usually been obtained from (Z)-l,4-dichloro-2-butene (214) via the isothiouronium salt (215) (Scheme 36). For the preparation of the 2-unsubstituted 4,7-dihydro-l,3-dithiepin, the isothiouronium salt can be reacted directly with dibromomethane and potassium hydroxide in methanol <76TL1251,780PP133), but isolation of the dithiol (217) and acid-catalyzed reaction with an aldehyde or ketone in a second step is preferred for the preparation of 2-substituted 4,7-dihydro-1,3-dithiepins <93JCS(P2)87l>. 

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