A visible‐light‐induced radical difluoromethylation of alkynoates using [bis(difluoroacetoxy)iodo]benzene as the CF2H radical precursor was developed for the first time. 3‐Difluoromethyl‐substituted coumarins were synthesized via a radical difluoromethylation/cyclization/ester migration cascade. The mild and catalyst‐free conditions, as well as the good functional group tolerance, render this protocol an alternative and green strategy for the synthesis of 3‐difluoromethyl‐substituted coumarins.

Background G-quadruplexes (G4s) are unique noncanonical nucleic acid secondary structures, which have been proposed to physically interact with transcription factors and chromatin remodelers to regulate cell type-specific transcriptome and shape chromatin landscapes. Results Based on the direct interaction between G4 and natural porphyrins, we establish genome-wide approaches to profile where the iron-liganded porphyrin hemin can bind in the chromatin. Hemin promotes genome-wide G4 formation, impairs transcription initiation, and alters chromatin landscapes, including decreased H3K27ac and H3K4me3 modifications at promoters. Interestingly, G4 status is not involved in the canonical hemin-BACH1-NRF2-mediated enhancer activation process, highlighting an unprecedented G4-dependent mechanism for metabolic regulation of transcription. Furthermore, hemin treatment induces specific gene expression profiles in hepatocytes, underscoring the in vivo potential for metabolic control of gene transcription by porphyrins. Conclusions These studies demonstrate that G4 functions as a sensor for natural porphyrin metabolites in cells, revealing a G4-dependent mechanism for metabolic regulation of gene transcription and chromatin landscapes, which will deepen our knowledge of G4 biology and the contribution of cellular metabolites to gene regulation.

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