Leveraging Metallotropism-Enabled Substrate Activation in Cobalt-Catalyzed Annulation Chemistry: Protic NHC Template Is the Key

This
study introduces the access of protic NHC
(pNHC) complexes with Cp*Co­(III) species via metallotropism-triggered
activation of ubiquitous azole substrates. These “CoIII-pNHC” templates were further explored in
catalytic annulative functionalization of azoles with internal alkynes,
providing a variety of π-extended polycyclic heteroarene compounds.
Mechanistic investigations via isolation and structure elucidation
of the key pNHC-Co intermediates followed by control
stoichiometric and catalytic reactions highlighted the crucial electronic
control on the azole C–H activation, alkyne insertion, and
regiodivergent annulation steps involved in this catalytic protocol.
These results demonstrate that the cobalt-based metallotropism can
act as a potentially useful platform toward earth-abundant first-row
transition metal-catalyzed C–H functionalization, complementary
to the dominant noble metal-based strategies.

本研究引入了通过金属亲合作用触发的普遍唑类底物活化，实现对质子化N-杂环化合物（pNHC）复合物与Cp*Co(III)物种的接入。这些所谓的‘CoIII-pNHC’模板在催化唑类内炔烃的环化功能性化方面进行了进一步探索，从而提供了一系列π-扩展的多环杂芳烃化合物。通过分离和结构阐明关键pNHC-Co中间体，随后进行控制化学计量和催化反应，对催化机理进行了深入研究。这些结果证实，基于钴的金属亲合作用可作为向地球丰富的一行过渡金属催化的C-H功能化提供潜在有用平台的策略，与主流的贵金属基策略相辅相成。