Aqueous and Visible-Light-Promoted C-H (Hetero)arylation of Uracil Derivatives with Diazoniums

Development of a Divergent Synthesis Strategy for 5-Sulfonyl-Substituted Uracil Derivatives

An efficient, diversity-orientated synthesis of 5-sulfone-substituted uracils was established. The use of protecting groups to synthesize sulfones from N-heterocycles was avoided. Various heterocycles were synthesized for the first time from favorable, easily accessible starting materials. Diversity-orientated syntheses are important for the medicinal chemistry of virostatics and chemotherapeutics. This approach provides a broad substrate tolerance and excellent yields of up to 98%.

Eosin Y Catalyzed Photochemical Synthesis of Arylated Phenothiazones

In the presence of Eosin Y (EY), the synthesis of substituted phenothiazones was carried out efficiently using various substituted 2-aminothiophenol, diazonium salts, and 1,4-napthaquinones (1,4-NQ) at room temperature (RT) (condition: green LED of 525 nm, 44 W; reaction time: 8 h, isolated yield: 68-90%). A fluorescence quenching experiment and density functional theory (DFT) calculations suggested that the triplet photoexcited state of EY (EY*; τT = 320 ± 10 ns) converts to EY+• via oxidative quenching by ArN2 + (-1.11 V vs SCE for EY* to EY+•) initially. Thiyl and aryl radicals were captured as TEMPO adducts in high-resolution mass spectroscopy (HRMS). The reaction was not inhibited by the addition of a singlet oxygen quencher such as 1,4-diazobicyclo [2.2.2] octane (DABCO), which suggests that singlet oxygen is not participated.

Generation and Application of Aryl Radicals Under Photoinduced Conditions

Photoinduced aryl radical generation is a powerful strategy in organic synthesis that facilitates the formation of diverse carbon-carbon and carbon-heteroatom bonds. The synthetic applications of photoinduced aryl radical formation in the synthesis of complex organic compounds, including natural products, physiologically significant molecules, and functional materials, have received immense attention. An overview of current developments in photoinduced aryl radical production methods and their uses in organic synthesis is given in this article. A generalized idea of how to choose the reagents and approach for the generation of aryl radicals is described, along with photoinduced techniques and associated mechanistic insights. Overall, this article offers a critical assessment of the mechanistic results as well as the selection of reaction parameters for specific reagents in the context of radical cascades, cross-coupling reactions, aryl radical functionalization, and selective C-H functionalization of aryl substrates.

Selective Methylation of Nucleosides via an In Situ Generated Methyl Oxonium

A very mild and efficient procedure has been developed for the preparation of N-methylated uridine, pseudouridine, guanosine and inosine derivatives. This process was compatible with free hydroxyls within the ribose and did not require precautions on the protection or deprotection of other functionalities. The key to this extremely mild methylation without protection relied on the in situ generated methyl oxonium from the Wittig reagent and methanol. A putative mechanism for the selective methylation was also proposed.

Azo Coupling of Indoles Revisited: Synthesis of Biindolyl Photoswitches via the Azo-Coupling/C-H Functionalization Domino Approach

When azo coupling of aryldiazonium salts with indoles was carried out in aprotic nonpolar solvent on air, a pseudo-three-component reaction has been discovered. Azo coupling is followed by a nucleophilic addition of a second indole unit to the indolium intermediate; aromatization and oxidation are achieved under air.

Characterization of the Nonpolar and Polar Extractable Components of Glanded Cottonseed for Its Valorization

Cottonseed is the second major product of cotton (Gossypium spp.) crops after fiber. Thus, the characterization and valorization of cottonseed are important parts of cotton utilization research. In this work, the nonpolar and polar fractions of glanded (Gd) cottonseed were sequentially extracted by 100% hexane and 80% ethanol aqueous solutions and subjected to ¹³C and ¹H nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. The nonpolar (crude oil) extracts showed the characteristic NMR peak features of edible plant oils with the absence of ω-3 linolenic acid. Quantitative analysis revealed the percentage of polyunsaturated, monounsaturated, and saturated fatty acids as 48.7%, 16.9%, and 34.4%, respectively. Both general unsaturated fatty acid features and some specific olefinic compounds (e.g., oleic, linolenic, and gondonic acids) were found in the nonpolar fraction. In the polar extracts, FT-ICR MS detected 1673 formulas, with approximately 1/3 being potential phenolic compounds. Both the total and phenolic formulas fell mainly in the categories of lipid, peptide-like, carbohydrate, and lignin. A literature search and comparison further identifies some of these formulas as potential bioactive compounds. For example, one compound [2,5-dihydroxy-N'-(2,3,4-trihydroxybenzylidene) benzohydrazide] identified in the polar extracts is likely responsible for the anticancer function observed when used on human breast cancer cell lines. The chemical profile of the polar extracts provides a formulary for the exploration of bioactive component candidates derived from cottonseed for nutritive, health, and medical applications.

Palladium-catalyzed C-H olefination of uridine, deoxyuridine, uridine monophosphate and uridine analogues

The palladium-catalyzed oxidative C-H olefinations of uridine, deoxyuridine, uridine monophosphate and uridine analogues are reported herein. This protocol provides an efficient, atom-economic and environmentally friendly approach to the synthesis of biologically important C5-alkene modified uracil/uridine-containing derivatives and pharmaceutical candidates.