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Cheng, Shee Chau
(1984).
DOI: https://doi.org/10.21954/ou.ro.000100fc
Abstract
Two methods of synthesising l-aryl-3-hydroxymethyl-3- methyltriazenes have been examined. The method of Vernin's et.al. was found to be erroneous yielding bistriazenes instead. A mechanism for the formation of hydroxymethyltriazenes and bistriazenes has been proposed. Furthermore, modification of Steven's procedure enabled the synthesis of 4-chlorophenyl- hydroxymethyltriazene.
Hydroxymethyltriazenes were shown to decompose in the presence of metal ion in non-agueous solutions to give the corresponding arylamines. This reaction was shown to follow a consecutive pseudo-first-order mechanism with the intermediacy of monomethyltriazene. Moreover, the reaction was found to be metal ion and not proton catalysed. Compared to hydroxymethyltriazenes, monomethyltriazenes are more reactive towards metal ions. This is believed to be due to the higher nucleophilicity of the triazene group in monomethyltriazenes. A salient feature of this study was the stabilising effect of a heteroaryl ring in the decomposition of hydroxymethyltriazenes. The ability of the heteroaryl ring to interact with metal ion is thought to be responsible for this stabilising effect. This was confirmed by the lanthanide shift reagent study.
Lanthanide induced chemical shifts are reported for hydroxymethyltriazenes and related compounds. The induced shifts for both Eu(fod)3 and Pr(thd)3 reveal that the hydroxymethyltriazenes bind to the Mn+ ion via the hydroxymethyl oxygen atom and that the binding ability of this atom is lowered when the hydroxyl proton is replaced with a bulky group.
The presence of bases was also found to promote the decomposition of hydroxymethyltriazenes. In this instance, however, monomethyltriazenes are stable enough to exist as the product. The base requires an X-H bond for catalytic activity.
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