期刊
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
卷 21, 期 4, 页码 306-314出版社
WILEY
DOI: 10.1002/poc.1327
关键词
azole-to-azole interconversion; copper salts catalysis; E,Z-isomerization; Lewis-acids-catalysis
A kinetic investigation in methanol of the title reaction has evidenced the occurrence of two processes: the 1-E reversible arrow 1-Z isomerization and the rearrangement of the (Z)-isomer into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (1-Z -> T). The latter reaction is in line with the ability of the (Z)-phenylhydrazones of 3-benzoyl-1,2,4-oxadiazoles to undergo the so called mononuclear rearrangement of heterocycles (MRH). The occurrence of both the examined reactions is dependent on a Lewis-acid-catalysis. The obtained results have shown the possibility of a 'new' type of acid-catalysis (bifunctional catalysis by Lewis salts) in the MRH. This catalysis operates through a completely different mechanism with respect to the one recently observed, and deeply investigated, in the presence of protic acids for the (Z)-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole, in both dioxane/water and toluene, for which the catalytic process was dependent on the protonation of N(4) ring-nitrogen of the 1,2,4-oxadiazole. As a matter of fact, the copper salts seem able to interact with the >C=N-NH-C6Hs moiety, yielding adducts which, in some cases, are prone to both isomerize and rearrange. Therefore, a similar behaviour in some manner parallel to that already observed in benzene in the presence of aliphatic amines (base-catalysis) has been evidenced. Copyright (C) 2008 John Wiley & Sons, Ltd.
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