ChemInform Abstract: Isomerization of N‐(α‐(Alkylthio)alkyl)‐ and N‐(α‐( Arylthio)alkyl)benzotriazoles.

Abstract

The thermal isomerizations of N- [a -(alkylthio)alkyl]-and N- [a -(arylthio)alkyl]benzotriazoles have been investigated under N, atmospheres i ) in toluene, xylene, MeOH, or EtOH, in the presence of acid catalysts and ii) in the absence of solvent. The sulfide isomerization rates depend on the number of H-atoms carried by the C-atom attached to the N-atom of the benzotriazole: tertiary (no hydrogen) > secondary (1 hydrogen) > primary (2 hydrogens). The results support an isomerization mechanism involving a heterolytic N-C bond cleavage with formation of sulfonium/carbonium and benzotriazolate ions.Introduction. -N-[a -(Dialkylamino)alkyl]benzotriazoles usually exist exclusively in the 1 H form in the solid state, while in solution they exist as equilibrium mixtures of the 1H and 2H isomeric forms undergoing rapid interconversion [ 1-31. Extensive investigations [2] [3] have revealed that these isomerizations proceed by intermolecular rearrangements involving an ionic dissociation-recombination mechanism. Recently, we reported similar results on the thermal isomerizations of N-(ary1methyl)benzotriazoles [4] in the absence of solvent. In both series the IH isomer generally predominates over the 2H isomer, but the ratio diminishes with increasing steric bulk of the substituent group.We have recently [5] prepared a number of N-[a-(alkylthio)alkyl]-and N-[a-(arylthio)alkyl]benzotriazoles, which on treatment with Grignard reagents, provide a convenient source for the preparation of tert-alkyl sulfides. We now report our results on the thermal isomerization of N- [a -(arylthio)alkyl]benzotriazoles. Our study, besides elucidating the mechanism of the isomerization process, provides information important to optimising the yields of synthetic transformations.

Structural Diversity and Catalytic Properties in a Family of Ag(I)-Benzotriazole Based Coordination Compounds

“…95−98 Some of these cases include N-arylmethyl-, 99 N-(aminomethyl)-, 100,101 N-(alkoxyalkyl)-, 102 and N-(alkylthioalkyl)-or N-(arylthioalkyl)-benzotriazoles. 103 It has been shown 83,86,95 that the main parameters that affect the position of this equilibrium are (i) solvent polarity, as a more polar solvent shifts the equilibrium toward the more polar 1-isomer, (ii) temperature, as benzotriazole has been found to be stable as the 2-isomer in gas phase, and (iii) the nature of the substituent, as the ratio of the 2-isomer increases in equilibrium when the bulkiness of the substituent is also increased. Interestingly, a search in the literature reveals no similar investigations for bisbenzotriazole substituted compounds.…”

“…Multiple efforts have documented that several types of substituted benzotriazole derivatives exist in solution as an equilibrium mixture of the corresponding 1-and 2-isomers [95][96][97][98] . Some of these cases include N-arylmethyl-benzotriazoles 103 . It has been shown 83,86,95 that the main parameters that affect the position of this equilibrium are i) solvent polarity, as a more polar solvent shifts the equilibrium towards the more polar 1-isomer, ii) temperature, as benzotriazole has been found to be stable as the 2isomer in gas phase, and iii) the nature of the substituent, as the ratio of the 2-isomer increases in equilibrium when the bulkiness of the substituent is also increased.…”