Deprotonative Magnesation and Cadmation of [1,2,3]Triazolo[1,5-<i>a</i>]pyridines

[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-coupling products using 2-bromopyridine under palladium catalysis failed, a result attributed to the low stability of these compounds. The corresponding lithium arylzincates reacted in 17−60% 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%).