Oxidative Coupling of Diazo and NH4I: A Route to Primary Oxamates and α-Ketoamides.

A simple and efficient method has been developed for the preparation of primary oxamates and α-ketoamides through the oxidative coupling of diazo compounds and NH4I. Under the optimized reaction conditions, a range of diazoesters and α-diazoketones was explored, and the corresponding products were obtained in moderate to good yields. This protocol is metal-free, is performed under mild conditions, has a wide substrate scope, and offers operational simplicity.

Cross coupling of sulfonyl radicals with silver-based carbenes: a simple approach to ß-carbonyl arylsulfones.

A coupling reaction between sulfonyl radicals and silver-based carbenes has been well established. This simple radical-carbene coupling (RCC) process provided an efficient approach to a variety of ß-carbonyl arylsulfones from sodium arylsulfinates and diazo compounds, and was characterized by wide substrate scope, easy scale-up, simple manipulation, accessible starting materials, and mild reaction conditions.

Mn-Catalysed photoredox hydroxytrifluoromethylation of aliphatic alkenes using CF3SO2Na.

This work demonstrated the photoinduced hydroxytrifluoromethylation of aliphatic alkenes catalysed by Mn(acac)3. The synthesis uses an inexpensive catalyst under mild reaction conditions, and exhibits a wide substrate scope and excellent functional group tolerance.

Visible-Light-Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2.

This work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2-dichloride compounds using an inexpensive, low-molecular-weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C-Cl bonds in this synthetic process.

Rapid Interception of Cn F2n+1 (O)SO. Radical with Copper-Based Carbene: A Novel Access to Perfluoroalkanesulfinate Ester.

In this communication, an unprecedented interception of Cn F2n+1 (O)SO. radical with a copper-based carbene has been established. Distinguished by wide substrate scopes and mild reaction conditions, this novel radical-carbene coupling reaction (RCC reaction) provides a fundamentally different and mechanistically interesting strategy for the synthesis of perfluoroalkanesulfinate esters.

Combination of Tetrabutylammonium Iodide (TBAI) with tert-Butyl Hydroperoxide (TBHP): An Efficient Transition-Metal-Free System to Construct Various Chemical Bonds.

In this account, we describe our recent progress on transition-metal-free-catalyzed cross-coupling reactions using tetrabutylammonium iodide (TBAI) as the catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant. A rich variety of important organic compounds including α-acyloxy ethers, tert-butyl peresters, allylic esters, amides, α-amino nitriles, fully substituted pyrazoles, N-sulfonyl formamidines, α-amino acid esters, cyanomethyl esters, N-nitrosamines, and 3-acyloxy-2,3-dihydrobenzofurans have been successfully achieved in high chemoselectivity. Mechanistic studies suggested that TBAI could decompose TBHP to t BuO. and t BuOO. or be oxdized to (hypo)iodite by TBHP.

In situ generation of nitrile oxides from copper carbene and tert-butyl nitrite: synthesis of fully substituted isoxazoles.

Herein, we present a novel [3 + 2] cycloaddition reaction of ß-keto esters with nitrile oxides, which were generated in situ from copper carbene and tert-butyl nitrite. This three-component reaction provides new methodology for the direct synthesis of fully substituted isoxazole derivatives, featuring mild reaction conditions, readily accessible starting materials and simple operation. The experimental studies and DFT calculations suggest that the reaction starts with the generation of the key intermediate nitrile oxides, followed by a [3 + 2] cycloaddition reaction of ß-keto esters to give the final isoxazole products.

In Situ Generation of Quinolinium Ylides from Diazo Compounds: Copper-Catalyzed Synthesis of Indolizine.

The Cu-catalyzed three-component reaction between quinolines, diazo compounds, and alkenes has been established for direct construction of indolizine derivatives via quinolinium ylides. This methodology is distinguished by the use of a commercially inexpensive catalyst and readily available starting materials, wide substrate scope, and operational simplicity.

Difunctionalization of Styrenes with Perfluoroalkyl and tert-Butylperoxy Radicals: Room Temperature Synthesis of (1-(tert-Butylperoxy)-2-perfluoroalkyl)-ethylbenzene.

A novel strategy for the difunctionalization of styrenes was developed. This synthesis includes the use of electrophilic perfluoroalkyl and tert-butylperoxy radicals and produces (1-(tert-butylperoxy)-2-perfluoroalkyl)ethylbenzene at room temperature, which has been traditionally difficult to synthesize. With at least four radical species included in the transformation, its high chemoselectivity was extraordinary; the results were further elucidated using computational studies. The methodology also holds a good potential for application as a result of its mild reaction conditions, ease of further modification, and insensitivity to moisture and air.

Cu-Catalyzed Multicomponent Reaction of Styrenes, Perfluoroalkyl Halide, Alcohol, and tert-Butyl Hydroperoxide: One-Pot Synthesis of (Z)-ß-Alkoxyperfluoroalkenone.

An efficient synthesis of Z-perfluoroalkyl-substituted enones by a multicomponent reaction strategy has been described. A variety of elusive perfluoroalkylated enones are furnished under mild reaction conditions in good yields with unique chemo- and stereoselectivity. A sequence of radical-mediated Kornblum-DeLaMare reaction, Michael addition, and HF elimination is proposed for the mechanism.

In situ generation of nitrilium from nitrile ylide and the subsequent Mumm rearrangement: copper-catalyzed synthesis of unsymmetrical diacylglycine esters.

A novel in situ generation of nitrilium from a nitrile ylide and the subsequent Mumm rearrangement of carboxylic acid, nitrile, and diazo compounds gave various unsymmetrical diacylglycine esters in moderate to high yields. This copper-catalyzed cascade reaction enables one-pot generation of two C-N bonds, one C[double bond, length as m-dash]O bond, and one C-H bond, with nitrogen as the only byproduct. The reaction has a broad functional-group tolerance, is rapid, easily scales up to the 100 mmol scale, and is insensitive to air and moisture.

[3 + 2] cycloaddition and subsequent oxidative dehydrogenation between alkenes and diazo compounds: a simple and direct approach to pyrazoles using TBAI/TBHP.

A novel Bu4NI-catalyzed pyrazole formation reaction is well described via sequential [3 + 2] cycloaddition and oxidative dehydrogenation reactions using TBHP as the primary oxidant. In comparison with previous cases toward pyrazoles from alkenes and diazo compounds, alkenes without a pre-organized leaving group were applied in this transformation. In addition, this methodology was distinguished by its broad substrate scope, commercially available inexpensive starting materials, high atom economy and operational simplicity.

A Cu-catalyzed four-component cascade reaction to construct ß-ester-γ-amino ketones.

Herein, a novel Cu-catalyzed four-component cascade reaction, which encompasses styrenes, diazo compounds, amines, and tert-butyl hydroperoxide (TBHP), was developed for the synthesis of ß-ester-γ-amino ketones. Mechanistically, this transformation was initiated by the interception of an electrophilic Cu-based carbene with nucleophilic α-aminoalkyl radicals, followed by a radical cascade process and an ionic Kornblum-DeLaMare reaction. The methodology was also distinguished by its wide substrate scope, easily available starting materials, and operational simplicity.

Cyanoacetic Acid as a Masked Electrophile: Transition-Metal-Free Cyanomethylation of Amines and Carboxylic Acids.

Using cyanoacetic acid as a masked electrophile, a new cyanomethylation reaction of amines and carboxylic acids was developed, producing a variety of α-aminonitriles and cyanomethyl esters with good yields and excellent functionality tolerance. This protocol features simple manipulation, inexpensive reagents, and a wide substrate scope. Iodoacetonitrile was generated in situ from the iodination-decarboxylation of cyanoacetic acid in this transformation.

Metal-Free Coupling of 2-Vinylphenols and Carboxylic Acids: An Access to 3-Acyloxy-2,3-dihydrobenzofurans.

A new coupling reaction between 2-vinylphenols and carboxylic acids was developed to synthesize 3-acyloxy-2,3-dihydrobenzofurans using Bu4NI as a catalyst and t-BuOOH as an oxidant. This simple and practical methodology is notable due to the ability to complete it under metal-free conditions, with easily available precursors, resulting in a product with high atom economy and high functional group tolerance. Upon the basis of experimental observations and literature, a plausible mechanism is proposed.

Transition-metal-free decarboxylation of dimethyl malonate: an efficient construction of α-amino acid esters using TBAI/TBHP.

A transition-metal-free decarboxylation coupling process for the preparation of α-amino acid esters, which succeeded in merging hydrolysis/decarboxylation/nucleophilic substitution, is well described. This strategy uses commercially available inexpensive starting materials, catalysts and oxidants and has a wide substrate scope and operational simplicity.

Interception of cobalt-based carbene radicals with α-aminoalkyl radicals: a tandem reaction for the construction of ß-ester-γ-amino ketones.

The interception of cobalt-based carbene radicals with α-aminoalkyl radicals was combined with the Kornblum-DeLaMare reaction and provides ß-ester-γ-amino ketones, which are otherwise difficult to obtain in high chemoselectivity. Mechanistically, this transformation is an interplay of cobalt-based carbene radicals, organoradicals, and ionic intermediates and involves the construction of two C-C bonds and one C=O bond in a one-pot process. The reaction also features a wide substrate scope and is highly efficient and insensitive to moisture and air.

Nucleophilic attack of α-aminoalkyl radicals on carbon-nitrogen triple bonds to construct α-amino nitriles: an experimental and computational study.

A new reactivity pattern of α-aminoalkyl radicals, involving nucleophilic attack on C≡N triple bonds under thermal conditions, has been developed to construct α-amino nitriles. In contrast to previous C-H functionalization of tertiary amines involving α-aminoalkyl radicals, this methodology does not require the use of photocatalytic conditions or a transition-metal catalyst. Inexpensive and nontoxic phenylacetonitrile was chosen as cyano source for this α-aminonitrile forming reaction. A plausible mechanism is proposed based upon experimental and computational results. An α-aminoalkyl radical intermediate and benzoyl cyanide have been shown to be key intermediates in this green and mild radical process. Nucleophilic attack of the α-aminoalkyl radical on the C≡N bond of PhCOCN followed by an elimination step forms the desired α-aminonitrile and an acyl radical.

Iodide-catalyzed synthesis of N-nitrosamines via C-N cleavage of nitromethane.

An iodide-catalyzed process to synthesize N-nitrosamines has been developed using TBHP as the oxidant. The mild catalytic system succeeded in cleaving the carbon-nitrogen bond in nitromethane. This methodology uses commercially available, inexpensive catalysts and oxidants and has a wide substrate scope and operational simplicity.

Reacting Molecular Oxygen with Butanone under Visible Light Irradiation: A General Aerobic Oxidation of Alkenes, Sulfides, Phosphines, and Silanes.

Here, we present a novel oxidation technique by reacting molecular oxygen with butanone under visible light irradiation. This method enables the mild oxidation of various functionalized compounds, including olefins, sulfides, phosphines, and silanes. Preliminary mechanistic experiments and theoretical calculations suggest that visible light triggers molecular oxygen to produce singlet oxygen in butanone. This singlet oxygen then reacts with butanone, producing an active oxidizing species.