Shi Q, Hu H, Du M, Sun Y, Li Y, Li Y. Boron-Assisted Cobalt-Catalyzed C-H Methylation Using CO
2 and H
2.
Org Lett 2023;
25:7100-7104. [PMID:
37767977 DOI:
10.1021/acs.orglett.3c02406]
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Abstract
C-H methylation of heteroarenes (e.g., indoles, pyrroles, etc.) is frequently applied in the synthesis of drug/biorelated compounds. We herein report the use of CO2/H2 as a methylation reagent for selective C-H methylation of indoles and pyrroles in the presence of cobalt/B(C6F5)3 cocatalysts. The Lewis acidic additive B(C6F5)3 is essential to achieving good reactivity for a broad scope of substituted indoles and pyrroles (20 examples, up to 92% yields). The C-H methylation is accomplished via the CO2 reduction/C-C bond formation/reduction sequence. Water is the only byproduct. This system based on the use of non-noble metal catalysts features an environmentally benign alternative for C-H methylation.
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