Photoclick and Release for Spatiotemporally Localized Theranostics of Single Cells via In Situ Generation of 1,3-Diaryl-1H-benzo[f]indazole-4,9-dione

Bioorthogonal click-release chemistry is a cutting-edge tool for exploring and manipulating biomolecule functions in native biological systems. However, it is challenging to achieve the precise regulation or therapy of individual cells via click-release strategies driven by proximity and thermodynamics. Herein, we propose a novel photoclick-release approach based on a photo-induced cycloaddition between 4,4'-bis(N-arylsydnone) or C-bithienyl-diarylsydnone and 2-arylamino-naphthoquinone via irradiation with 405 or 485 nm light. It constructs 1,3-diaryl-1H-benzo[f]indazole-4,9-dione (BIZON) as a pharmacophore while releases an arylamine for fluorescence turn-on probing. Both photoclick reagents were tailored by connecting to the triphenyl phosphonium delivery motif for enrichment in the mitochondria of live cells. This enables an intracellular photoclick and release under the control of 405 or 485 nm light. We then discovered that the in situ photo-generated BIZON is capable of photosensitizing upon 485 or 520 nm light to produce singlet oxygen inside the mitochondria under aerobic conditions. Therefore, we realized wash-free fluorescence tracking and subsequent anti-cancer efficacy at single-cell resolution using global illumination, which provides a foundation for wavelength-gated single-cell theranostics.

Visible light-driven and substrate-promoted alkenyltrifluoromethylation of alkenes to synthesize CF3-functionalized 1,4-naphthoquinones

The first example of the visible light-driven and substrate-promoted three-component alkenyltrifluoromethylation of alkenes is developed. This approach uses easily available alkenes, 2-arylamino-1,4-naphthoquinones and Togni reagent as the reactants, and describes good functionality tolerance. The reaction offers a precise synthesis of valuable CF3-functionalized 1,4-naphthoquinones and can be applied in late-stage modification of natural products and pharmaceuticals. Experimental results imply that bifunctional 2-arylamino-1,4-naphthoquinones serve as both substrates and catalysts. In terms of this autocatalytic system, the protocol enables a straightforward intermolecular difunctionalization of alkenes under visible light irradiation without external catalysts.

Oxidative Aminotrifluoromethylation of 1,4-Naphthoquinone

A strategy for convenient and precise oxidative aminotrifluoromethylation of 1,4-naphthoquinone with the Togni reagent and amines has been demonstrated via a radical process. This method allows efficient access for the preparation of a wide range of CF3-functionalized 1,4-naphthoquinones under mild conditions, and its application in late-stage modification of drug molecules is achieved. Mechanistic studies indicate that 1,4-naphthoquinone serves as both a substrate and a catalyst and that the Togni reagent plays a dual role of a substrate and an oxidant. As a result, the title reaction can take place in the dark without external catalysts and oxidants.

Practice of green chemistry strategies in synthetic organic chemistry: a glimpse of our sincere efforts in green chemistry research

This feature article summarises our recent contributions (2019-2023) in designing and developing a handful of promising organic transformations for accessing several diversely functionalised biologically relevant organic scaffolds, following the green chemistry principles, particularly focusing on the application of low-energy visible light, electrochemistry, ball-milling, ultrasound, and catalyst- and additive-free synthetic strategies.

Visible-Light-Triggered Synthesis of N-α-Ketoacylated Sulfoximines by Denitrogenative and Oxidative Functionalization of Vinyl Azides

We have introduced a sulfoximidation reaction initiated by visible light between α-phenyl vinyl azides and NH-sulfoximines. The cost-effective and readily accessible hypervalent iodine reagent (PIDA) easily promoted the oxidative sulfoximidation process to afford N-α-ketoacylated sulfoximines in good to high yields, involving the formation of two new C-O bonds and one C-N bond. Additionally, the protocol offers noteworthy advantages, including its metal-free and photocatalyst-free reaction and its broad substrate compatibility.

Visible-Light-Promoted Metal- and Photocatalyst-Free Reactions between Arylglyoxylic Acids and Tetraalkylthiuram Disulfides: Synthesis of α-Ketoamides

A convenient and new synthetic approach has been developed for the oxidative cross-coupling of the C-N bond through the reaction between arylglyoxylic acids and tetraalkylthiuram disulfides. The reaction proceeds under ambient air at room temperature in the presence of visible light. This reaction offers a metal-, base-, photocatalyst-, and solvent-free synthesis of various α-ketoamides with moderate to excellent yields via the radical pathway. In addition, this protocol demonstrates the potential application of a gram-scale synthesis.

Copper-catalysed chemoselective C-OH bond activation of N-benzoyl cytosine: facile access to 2-(dimethylamino)pyrimidine

A novel method for the direct amination of N-benzoyl cytosine has been developed, giving access to 2-(dimethylamino)pyrimidine derivatives. A copper(II) catalyst and tert-butyl hydroperoxide easily promote the selective amination process that proceeds via C-OH bond activation. This practical approach can utilize different formamide molecules, N,N-dimethylformamide and N,N-diethylformamide, as efficient amino (-NMe₂, -NEt₂) sources. Moreover, the facile nature of the procedure, its broad tolerance of aliphatic and aromatic substrates, the high yields and ease of separation of the products, and the fact that it can be conducted under aerobic conditions are all notable advantages of the present protocol.

Copper catalysed oxidative cascade deamination/cyclization of vinyl azide and benzylamine for the synthesis of 2,4,6-triarylpyridines

A highly efficient one-pot method for the synthesis of 2,4,6-triaryl pyridines has been developed via cascade deamination and annulation. Copper triflate and molecular iodine easily promoted the oxidative cyclization reaction of vinyl azide and benzylamine to access a wide variety of substituted pyridine substrates under an oxygen atmosphere. The presence of benzyl amine enables the cyclization process by providing the aryl functionality and the nitrogen source. Moreover, a broad range of substrates with good functional group tolerance, avoidance of external oxidants, excellent product yields, operational simplicity and mild conditions are the notable advantages of the present protocol.

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)-H and N-H Bonds: Amination of Naphthoquinones with Amines

Herein, we report a blue-light-driven amination of C(sp²)-H bond of naphthoquinones and quinones with the N-H bond of primary and secondary amines for the synthesis of 2-amino-naphthoquinones and 2-amino-quinones. The coupling of naphthoquinones with a wide array of aliphatic, aromatic, chiral, primary, and secondary amines having electron donating (-CH₃, -OCH₃, -SCH₃), withdrawing (-F, -Cl, -Br, -I), and CO₂H, -OH, -NH₂ groups with acidic protons selectively occurred to afford C-N coupled 2-amino-naphthoquinones in 60-99% yields and hydrogen gas as a byproduct in methanol solvent without using any additional reagents, additives, and oxidant under the blue light irradiation. Mechanistic insight by DFT computation, controlled experiments, kinetic isotopic effect, and substitution effect of the substrates suggest that the reaction proceeds by radical pathway in which naphthoquinone forms a highly oxidizing naphthoquinonyl biradical upon irradiation of blue light (457 nm). Consequently, electron transfer from electron-rich amine to an oxidizing naphthoquinonyl biradical leads to a naphthoquinonyl radical anion and aminyl radical cation, followed by proton transfer and delocalization leading to a carbon-centered naphthoquinonyl radical. The cross-coupling of naphthoquinonyl carbon-centered and aminyl nitrogen radicals forms a C-N bond, with subsequent elimination of hydrogen gas (which was also confirmed by GC-TCD), affording 2-amino-1,4-naphthoquinone under metal-, reagent-, base-, and oxidant-free conditions.

Electrochemical Regioselective C(sp2)-H Selenylation and Sulfenylation of Substituted 2-Amino-1,4-naphthoquinones

A straightforward and efficient electrochemical method for regioselective C(sp²)-H selenylation and sulfenylation of substituted 2-amino-1,4-naphthoquinones has been unearthed. This oxidative cross-coupling reaction avoids using transition metal catalysts, oxidants, and high temperatures. The other notable advantages of this protocol are the tolerance of diverse functional groups, mild reaction conditions at ambient temperature, energy efficiency, good to excellent yields, short reaction times (in minutes), gram-scale applicability, and eco-friendliness.

Silver-Catalyzed, One-Pot, Three-Component Difunctionalization of Quinones: Synthesis of Indole-Functionalized p-Iminoquinone Derivatives

A one-pot, three-component difunctionalization of quinones with indoles and arylamines has been developed to synthesize indole functionalized p-iminoquinones derivatives. The approach employed AgOAc as the catalyst in the presence of 3-chlorophenylboronic acid, giving a series of indole functionalized p-iminoquinones derivatives in moderate to good yields. This catalytic approach represents a step-economic and convenient strategy for the difunctionalization of quinones. A plausible reaction pathway has been proposed based on a series of control experiments.

Iodine-TBHP mediated efficient synthesis of α-ketoamides from vinyl azides and amines under mild conditions

A convenient and practical synthetic approach for α-ketoamides has been developed under mild conditions. The facile synthesis of α-ketoamides has been accomplished using aryl vinyl azides and secondary amines at room temperature. The inexpensive and readily available iodine and TBHP easily promoted the oxidative amidation process to afford diketoamide derivatives in high yields. This method involves the synthesis of ketoamide compounds via sequential C-O and C-N bond formation. Moreover, metal-free and aerobic conditions and wide substrate scope are the notable advantages of this protocol.

Updates on hypervalent-iodine reagents in metal-free organic synthesis

Hypervalent iodine (HVI) chemistry is a rapidly growing subdomain of contemporary organic chemistry because of its enormous synthetic applications. The high nucleofugality of the phenyliodonio group (I+Ph) and their radical...