Coordination‐Driven Direct C─H Metalation of <i>N</i> ‐Heterocycles With a Superbasic Co(II) Amide Co(TMP) ₂

Abstract

ABSTRACT Metalation of N ‐heterocycles such as pyridines or diazines with conventional alkali metal bases is particularly challenging due to the limited activation of their C─H bonds coupled with the thermal fragility of the resulting organometallic intermediates. Building upon previous work in this area, we demonstrate that the superbasic cobalt(II) amide Co(TMP) 2 (TMP = 2,2,6,6‐tetramethylpiperidide) enables high‐yielding and highly regioselective C─H metalation of a broad range of N ‐heterocycles via direct, redox‐neutral Co(II)–H exchange. This reactivity extends beyond single‐site activation, with controlled di‐cobaltation of non‐activated substrates such as pyrimidine and pyrazine. Via a combination of NMR reaction monitoring, isolation and characterisation of key organometallic intermediates, and density functional theory calculations, we establish that regioselectivity is dictated by coordination effects at positions α to nitrogen, overriding conventional trends based solely on C─H acidity. Exploiting cobalt's redox flexibility, oxidative treatment of the metalated intermediates with iodine enables selective C─N bond formation, giving sterically demanding TMP‐substituted heterocycles. Collectively, these findings establish Co(TMP) 2 as a mechanistically distinct and versatile reagent for the selective functionalisation of N ‐heterocycles.