Deprotonative magnesation and cadmation of [1,2,3]triazolo[1,5-a]pyridines
Résumé
[1,2,3]Triazolo[1,5-a]pyridine and 3-substituted derivatives were regioselectively metalated at the 7 position using either Bu3MgLi or (TMP)3CdLi, the former at -10 °C and the latter at room temperature. The lithium arylmagnesates (R = H, Me, Ph) proved to react with iodine (34-75%) or 3,4,5- trimethoxybenzaldehyde (32-51%). Attempts to obtain the cross-couplings products using 2- bromopyridine under palladium catalysis failed, a result attributed to the low stability of these compounds. The corresponding lithium arylzincates reacted in 17 to 60% yield under the same reaction conditions. The lithium arylcadmates were either trapped with iodine (38-76%, R = H, Me, Ph, CN, 2- thienyl) or involved in palladium-catalyzed cross-coupling reactions with 2-bromopyridine (26-67%, R = H, Me, Ph). For R = 2-pyridyl, 3-(6-iodo-2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridine was isolated in 73% yield. (TMP)3CdLi also proved suitable for the clean dideprotonation of two substrates (R = H, 2- thienyl), a result demonstrated by quenching with iodine (66-75%).
Domaines
Chimie organique
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Deprotonative_magnesation_and_cadmation_of_1_2_3_triazolo_1_5-a_pyridines.pdf (368.14 Ko)
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