Alkylations ofN4-(4-Pyridyl)-3,5-di(2-pyridyl)-1,2,4-triazole: first observation of room-temperature rearrangement of anN4-substituted triazole to the N1 analogue

Attempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4-pyridyl ring in the bis(bidentate) triazole ligand N-4-(4-pyridyl)-3,5-di(2-pyridy1)-1,2,4-triazole (pydpt) were made to ascertain what effect a strongly electron-withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N-4 substituent moves to the NI position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N4 substituent is obtained. Heating a pure sample of N-4-Bzpydpt center dot 3r to reflux in MeCN resulted in clean conversion to N-1-Bzpydpt center dot Br. This is consistent with AP-Bzpydpf Br being the kinetic product whereas N-1-Bzpydpt.Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N-4 to N-1 rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N-4 to N-1 rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested.

alkylation, iron, n ligands, structure elucidation, triazoles

10.1002/asia.200900485

1861-471X

910-918

Kitchen, Jonathan A.

3999f5cb-d53e-4c51-b750-627bd2a1b9b6

Larsen, David S.

b0f13c30-43dc-4796-a3a8-5a87cbf1a80d

Brooker, Sally

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