Isothiocyanate, aryl-, reaction with

The reaction of 1-amino-1-deoxyketoses, and their N-alkyl and N-aryl derivatives, with alkyl or aryl isothiocyanates (Huber et al, 1960) was studied in more detail, and new 4-(alditol-l-yl)-l-alkyl(aryl)-3-alkyl(aryl)-l,3-dihydro-2H-imidazole-2-thiones were obtained. These compounds were used as starting materials for the synthesis of OL-histidines, DL-histidine-2-thiol, and other imidazole derivatives of biological interest. 

Contrasting with the reported formation of fused [l,3,4]thiadiazole rings in the course of the reaction of 3-substituted-4-amino-5-thio-47/-[l,2,4]triazoles 83 with various isothiocyanates (cf. Section 11.07.8.3, Table 3), the reactions with methyl isothiocyanate and with phenylisocyanate afford 3,7-disubstituted-6,7-dihydro-57/-[l,2,4]triazolo[4,3-f] [l,2,4]triazole-6-thiones 110 and -triazole-6-ones 111, respectively (Equation 29) <1986MI607, 1992IJB167>.The same reaction of 4-amino-l-methyl-3,5-bis(methylthio)[l,2,4]triazolium iodide 112 with aryl isothiocyanates yields the mesoionic compounds 113 (Equation 30) <1984TL5427, 1986T2121>. 

Alkyl and glycosyl isocyanates and isothiocyanates are produced in good yield under phase-transfer catalytic conditions using either conventional soluble catalysts or polymer-supported catalysts [32, 33]. Acyl isothiocyanates are obtained under similar conditions [34]. A-Aryl phosphoramidates are converted via their reaction with carbon disulphide under basic conditions into the corresponding aryl isothiocyanates, when the reaction is catalysed by tetra-n-butylammonium bromide [35]. 

In a different study, anthracene, phenanthrene, perylene 93 (Fig. 31), and 2,7-di-tert-butylpyrene underwent regioselective oxidative-substitution reactions with iodine(III) sulfonate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene, in conjunction with trimethylsilyl isothiocyanate, led to thiocyanation of the PAH nucleus. 

An important prerequisite in these reactions is the nucleophilicity of the imine nitrogen. Indeed, electron-withdrawing substituents in the aryl ring of (159) retard the reaction with isothiocyanates, whereas such substituents in the R group of the isothiocyanates enhance the reaction. No reaction occurs under the above chosen conditions (reflux in chloroform), when the aryl ring of (159) is replaced by a sulfonyl group <88BSB83>. 

Isothiocyanates react much slower with aminothiatriazoles 87 and require the presence of 4-dimethylaminopyr-idine (DMAP) as a basic catalyst <1989JPR115, 1992JOC1671>. In the case of the parent compound 90, trithiadi-azapentalenes 108 are formed. The substituted 5-aminothiatriazoles (R = alkyl or aryl) 87 are more reactive and afford thiourea derivatives 109 in the reaction with 2 equiv of isothiocyanates (Scheme 26). 

Disubstituted iminothiatriazolines may be formed by reaction of alkyl azides and aryl isothiocyanates but the reaction is relatively slow and the thiatriazoline formed undergoes further reaction with the isothiocyanate present (Section 4.28.2.3.l(iii)). 4-Alkyl-5-sulfonyliminothiatriazolines (73) are readily obtained when the more reactive sulfonyl isothiocyanates are treated with alkyl azides at room temperature (equation 47) (73JOC2916, 74JA3973). 

Substituted phenyl isothiocyanates 1 react with (dialkylamino)carbonitriles 2 at 800 MPa to give Af" -aryl-iV, A -dialkylquinazoline-2,4-diamine salts 3 in good to moderate yields. Mechanistically, the reaction probably involves repeated cycloaddition-dectrocyclic ring opening in which carbamimidoyl isothiocyanates are formed as intermediates " (cf. p 57). 

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