A visible-light-promoted metallophotoredox catalytic system has been developed for the efficient oxidative decarboxylative functionalization of cinnamic acids with aryl iodides, enabling the synthesis of 1,2-diketones through a synergistic combination of perylene bisimide (PDI) dye, copper chloride, tert-butyl hydroperoxide (TBHP), and triethylamine. This method leverages the unique redox properties of PDI under visible light irradiation to facilitate a cascade radical pathway, allowing for the direct transformation of readily available cinnamic acids into valuable 1,2-diketone scaffolds without requiring prefunctionalized substrates or harsh reaction conditions.
The strategy capitalizes on the inherent advantages of carboxylic acids as stable, nontoxic, and easily accessible building blocks in organic synthesis. Cinnamic acids, particularly, are abundant and structurally diverse, making them ideal candidates for such transformations. The key innovation lies in the use of visible light to excite the PDI photocatalyst, which undergoes sequential electron transfer processes involving triethylamine and TBHP. This generates reactive radical species that initiate the decarboxylation of cinnamic acid and subsequent coupling with aryl radicals derived from aryl iodides.
The optimized reaction conditions involve 2 mol % PDI, 20 mol % CuCl, 3 equivalents of TBHP, and 1 equivalent of Et₃N in acetonitrile, irradiated with blue LEDs (470 nm) at room temperature for 24 hours. A broad substrate scope was demonstrated, with both electron-rich and electron-poor substituents on either the cinnamic acid or aryl iodide component yielding the corresponding 1,2-diketones in moderate to excellent yields (up to 89%). Notably, ortho-substituted aryl iodides exhibited slightly reduced reactivity due to steric hindrance, while polycyclic systems like 1-iodonaphthalene performed efficiently, affording the expected product in 68% yield.
Control experiments confirmed the radical nature of the mechanism: the presence of TEMPO or BHT suppressed product formation, and HRMS analysis detected the characteristic adduct 2,2,6,6-tetramethyl-1-phenoxypiperidine, indicating phenyl radical involvement.Nup98 Antibody Biological Activity Additionally, no stilbene intermediate was observed under conditions lacking TBHP, ruling out a classical oxidation route via stilbene.Raf-B Antibody MedChemExpress Instead, the proposed mechanism involves initial formation of a cinnamoyl radical after decarboxylation, followed by addition of a phenyl radical to form an α-aryl ketone intermediate.PMID:35028974 Subsequent oxidation by Cu(II)-OH, hydroxylation, and Kornblum–DeLaMare rearrangement culminate in the formation of the final 1,2-diketone product.
This methodology represents a significant advancement in sustainable synthesis, offering a mild, metal-catalyst-efficient, and operationally simple approach to access biologically relevant 1,2-diketone motifs. Its compatibility with diverse functional groups, low catalyst loading, and use of inexpensive, non-toxic reagents underscore its potential for application in pharmaceutical and natural product synthesis.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com