Visible-Light-Mediated Strategies for the Preparation of Oxime Ethers Derived from O-H Insertions of Oximes into Aryldiazoacetates

Visible-Light-Induced Multi-Component Nitrooxylation Reactions of α-Diazoesters, Cyclic Ethers, and Tert-Butyl Nitrite Leading to Organic Nitrate Esters

A simple and efficient strategy has been developed for the synthesis of organic nitrate esters via visible-light-induced multi-component nitrooxylation reactions of α-diazoesters, cyclic ethers, and tert-butyl nitrite under open air atmosphere. This transformation could be conducted under mild and metal-free conditions to provide a number of organic nitrate esters in moderate to good yields using air as the green oxidant.

Metal-free visible-light-mediated aerobic nitrooxylation for the synthesis of nitrate esters with t-BuONO

A metal-free and sustainable visible-light-mediated method for the preparation of organic nitrate esters has been developed through the aerobic nitrooxylation reaction of α-diazoesters and cyclic ethers with t-BuONO in the presence of dioxygen. This protocol provides an efficient approach to access nitrate esters with the advantages of clean energy, broad substrate scope, green oxidants, operational simplicity, and mild conditions.

Visible Light-Induced Reactions of Diazo Compounds and Their Precursors

In recent years, visible light-induced reactions of diazo compounds have attracted increasing attention in organic synthesis, leading to improvement of existing reactions, as well as to the discovery of unprecedented transformations. Thus, photochemical or photocatalytic generation of both carbenes and radicals provide milder tools toward these key intermediates for many valuable transformations. However, the vast majority of the transformations represent new reactivity modes of diazo compounds, which are achieved by the photochemical decomposition of diazo compounds and photoredox catalysis. In particular, the use of a redox-active photocatalysts opens the avenue to a plethora of radical reactions. The application of these methods to diazo compounds led to discovery of transformations inaccessible by the classical reactivity associated with carbenes and metal carbenes. In most cases, diazo compounds act as radical sources but can also serve as radical acceptors. Importantly, the described processes operate under mild, practical conditions. This Review describes this subfield of diazo compound chemistry, particularly focusing on recent advancements.

Visible-light-induced three-component reactions of α-diazoesters, quinazolinones and cyclic ethers toward quinazoline-based hybrids

An effective approach for the construction of 4-short-chain ether attached carbonyl group-substituted quinazolines was developed. Visible-light-induced three-component reactions of α-diazoesters, quinazolinones, and cyclic ethers, with a broad substrate scope and excellent functional group tolerance, under extremely mild conditions without the need for any additional additives and catalysts, selectively led to quinazoline-based hybrids in good to excellent yields. The synthesized hybrids, which are a conglomeration of a quinazoline, a short-chain ether, and a carbonyl group in one molecular skeleton, have potential for application in the development of new drugs or drug candidates.

Visible photons as ideal reagents for the activation of coloured organic compounds

In recent decades, the traceless nature of visible photons has been exploited for the development of efficient synthetic strategies for the photoconversion of colourless compounds, namely, photocatalysis, chromophore activation, and the formation of an electron donor/acceptor (EDA) complex. However, the use of photoreactive coloured organic compounds is the optimal strategy to boost visible photons as ideal reagents in synthetic protocols. In view of such premises, the present review aims to provide its readership with a collection of recent photochemical strategies facilitated via direct light absorption by coloured molecules. The protocols have been classified and presented according to the nature of the intermediate/excited state achieved during the transformation.

Synthesis of oxime ethers via a formal reductive O-H bond insertion of oximes to α-keto esters

This study describes an efficient approach to access oxime ethers via P(III)-mediated O-H bond insertion reaction of oximes with α-keto esters. The strategy involves the protonation of in situ generated Kukhtin-Ramirez adducts, followed by SN2-type reaction. Important features include a good functional group tolerance, operational simplicity, and application to gram scale synthesis and the synthesis of an acaricide.

Visible Light-Induced Imide Alkylation of Azauracils with Aryl Diazoesters

A visible light-induced green and sustainable N-H functionalization of (aza)uracils with α-diazo esters leading to imide alkylation is described. The reaction does not require any catalyst or additive and proceeds under mild conditions. Moreover, an intriguing three component coupling was observed when (aza)uracils were allowed to react with α-diazo esters in cyclic ethers (e. g. 1,4-dioxane, THF) as a solvent. Both the insertion and three-component coupling features broad scope with good to excellent yields and appreciable functional group tolerance. Notably, the divergent method enables modification of natural products and pharmaceuticals, thereby facilitates access to potentially biologically active compounds.

Light induced diversity-oriented synthesis (DOS) library of annulated indolizine fluorophores for imaging non-lysosomal lipid droplets (LDs)

We report the design, synthesis, and biological evaluation of a novel class of annulated indolizines as fluorescent probes. The compounds were generated through an eco-friendly, blue LED-induced domino reaction in ethyl acetate. A library of 24 coloured compounds exhibited tuneable emissions. One of the compounds (which we call DASS-fluor) proved to be an excellent polarity sensing probe. It is biocompatible, photostable, and detects specific types of lipid droplets (LDs in response to oleic acid, stress, and drug-induced autophagy in lungs and hepatic carcinoma cells). In comparison to Nile Red (a commercial probe), DASS-fluor can differentiate non-lysosomal LDs from lysosomal LDs and offers an advantage in precisely mapping drug-induced lipidosis caused by increased non-lysosomal LDs in cancerous cells. This unique probe could be a potential fluorescent marker for specific types of lipidosis induced by drugs.

Visible light-induced carbene reactivity of acceptor diazoalkanes: deconstructive difunctionalizations of cyclic ethers with nucleophiles

A visible light-induced carbene reactivity of acceptor diazoalkanes has been developed for the synthesis of difunctionalized ethers from cyclic ethers and various N/O/S nucleophiles.

Visible-Light-Initiated Multicomponent Reactions of α-Diazoesters to Access Organophosphorus Compounds

A simple visible-light-initiated strategy has been established for the construction of organophosphorus compounds via aerobic multicomponent reaction of α-diazoesters, cyclic ethers, and P(O)H compounds under air. A number of phosphonates and phosphinates could be efficiently isolated in moderate to good yields without the use of photosensitizers and metal reagents. This multicomponent reaction has advantages of mild condition, simple operation, eco-friendly energy, good functional-group tolerance, and gram-scale synthesis.

Visible-Light-Induced Imide Synthesis through a Nitrile Ylide Formation/Trapping Cascade

A visible-light-promoted three component reaction of diazo compounds, nitriles, and carboxylic acids is reported. The reaction utilizes acceptor-only diazo compounds as carbene precursors and nitriles as carbene-trapping reagents to form the key nitrile ylides. Under the optimal reaction conditions, a wide range of imide products were obtained in good to excellent yields. The gram-scale synthesis and synthetic application of the imide products to form isoquinoline-1,3(2H,4H)-dione derivatives further proved the value of this method.

A Visible Light-Mediated Three-Component Strategy Based on the Ring-Opening of Cyclic Ethers with Aryldiazoacetates and Nucleophiles

A blue light-promoted reaction between aryldiazoacetates and different nucleophiles has been developed in the presence of THF (and other cyclic ethers) as solvent, allowing the incorporation of these three elements...