Switching engineered Vitreoscilla hemoglobin into carbene transferase for enantioselective SH insertion

An attractive strategy for efficiently forming CS bonds is through the use of diazo compounds SH insertion. However, achieving good enantioselective control in this reaction within a biocatalytic system has proven to be challenging. This study aimed to enhance the activity and enantioselectivity of to enable asymmetric SH insertion. The researchers conducted site-saturation mutagenesis (SSM) on 5 amino acid residues located around the iron carbenoid intermediate within a distance of 5 Å, followed by iterative saturation mutagenesis (ISM) of beneficial mutants. Through this process, the beneficial variant VHbSH(P54R/V98W) was identified through screening with 4-(methylmercapto) phenol as the substrate. This variant exhibited up to 4-fold higher catalytic efficiency and 6-fold higher enantioselectivity compared to the wild-type VHb. Computational studies were also conducted to elucidate the detailed mechanism of this asymmetric SH insertion, explaining how active-site residues accelerate this transformation and provide stereocontrol.

Scandium-catalyzed chemoselective carbene insertion into N-H over S-H: access to o-alkylamine-diaryl disulfides

Herein, we report a scandium-catalyzed chemoselective carbene insertion into a N-H bond over a S-H bond with disulfide formation. This reaction represents the first example of the synthesis of o-alkylamine-diaryl disulfides through the N-alkylation of o-aminobenzenethiol, while also undergoing oxidative coupling to form a S-S bond. Control experiments explain the chemo-selectivity of this rare-earth-metal Lewis acid-induced catalysis by a carbene outer-sphere nucleophilic addition mechanism. This method holds tremendous potential as a valuable tool for functionalizing advanced-synthetic-intermediates, offering numerous applications in medicinal and materials chemistry.

O-H Insertion of Hydrogenphosphate Derivatives and α-Diazo Compounds

An efficient O-H insertion of hydrogenphosphate derivatives and α-diazo compounds has been developed to construct α-phosphoryloxy scaffolds. Diverse α-phosphoryloxy skeletons could be obtained under mild and catalyst-free conditions in good yields. The control experiments suggest a protonation and nucleophilic addition process of α-diazo compounds via a diazonium ion pair for this 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.

Carboxylic Acid O-H Insertion Reaction of β-Ester Diazos Enabling Synthesis of β-Acyloxy Esters

Generation of non-stabilized β-ester diazos and their applications in carboxylic acid O-H insertion reactions have been reported, which afford β-acyloxy esters in excellent yield. Varieties of aryl- and alkyl-substituted diazos are well tolerated in this insertion reaction under mild and convenient conditions. Moreover, structural modification of the natural product and molecular drug can also be achieved in this reaction. This protocol not only realizes the reaction involving unstable β-ester diazos but also provides an efficient strategy for the synthesis of β-acyloxy esters.

Synthesis of functionalized S-benzyl dithiocarbamates from diazo-compounds via multi-component reactions with carbon disulfide and secondary amines

Triflic acid promoted multi-component synthesis of functionalized S-benzyl dithiocarbamates from diazo compounds, carbon disulfide and secondary amines is reported. The reactions proceeded at room temperature and gave the desired dithiocarbamates in good yields. Wide-substrate scope and easy operation are the important features of this methodology.

TBAI-Catalyzed S-H and N-H Insertion Reactions of α-Diazoesters with Thiophenols and Amines under Metal-Free Conditions

Mild, convenient, and effective TBAI-catalyzed S-H and N-H insertion reactions of α-diazoesters with thiophenols and aromatic amines under metal-free conditions have been described, furnishing a straightforward and general platform for the synthesis of various thioethers and 2-amino-2-oxoacetates in moderate to excellent yields. Moreover, this strategy features simple operation, mild conditions, broad substrate scope, and easy scale-up.

Domino assembly of dithiocarbamates via Cu-catalyzed denitrogenative thiolation of iodotriazole-based diazo precursors

An efficient domino approach to assemble benzoxazoles and anthranilamides bearing dithiocarbamate moieties has been developed. The proposed route represents a Cu-catalyzed three-component reaction between readily available 5-iodo-1,2,3-triazoles, amines, and CS₂. The cascade transformation is based on a denitrogenative coupling of in situ formed dithiocarbamic acids with diazo intermediates, generated via annulation-triggered triazole ring-opening. This method is applicable to nucleophilic secondary amines and features good functional group compatibility.

Solvent-free, B(C6 F5 )3 -Catalyzed S-H Insertion of Thiophenols and Thiols with α-Diazoesters

Described herein is a B(C₆ F₅ )₃ -catalyzed S-H insertion reaction of thiophenols and thiols with α-diazoesters to access valuable α-thioesters. With the established protocol, an array of α-thioester products are generated in moderate to good yields with broad scope and functional group tolerance. In addition, this reaction maintains its high efficiency on gram scale and the product can be easily transformed into other useful motifs. This reaction proceeds under solvent-free conditions at room temperature, and generally finishes in twenty minutes upon magnet stirring, which offers an expedient way for synthesis of thioether-containing compounds.

TfOH-catalyzed regioselective N2-alkylation of indazoles with diazo compounds

Selective alkylation of indazoles is still a highly challenging topic in chemistry and the synthesis of important molecules. Herein, a novel highly selective N²-alkylation of indazoles with diazo compounds is described in the presence of TfOH. Unlike the traditional metal- and base-catalysed version, this protocol highlights the regioselectivity of alkylation of indazoles and a metal-free catalysis system, affording N²-alkylated products in good to excellent yields with high regioselectivity (N²/N¹ up to 100/0) and excellent functional group tolerance. Furthermore, a gram scale synthesis was conducted successfully to give rise to the corresponding products. Mechanistic studies through control experiments provide plausible mechanistic proposals.

A solvent controlled three-component reaction of diazo compounds for the synthesis of hydrazone compounds under Brønsted acid catalysis

A novel Brønsted acid catalyzed three-component reaction of diazo compounds has been achieved from α-diazo ester, N-aminophthalimide and a solvent.

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

Two visible-light-mediated O-H insertion protocols involving oximes and aryldiazoacetates leading to different products depending on the solvent employed are reported. In DCM, direct O-H insertion takes place. In THF, there is the additional incorporation of the ring-opened form of this solvent into the structure of the product. These metal-free protocols are mild and tolerant to air and moisture. The preparation of an acaricide has been developed as an example of synthetic application.

Chemodivergent Synthesis of Oxazoles and Oxime Ethers Initiated by Selective C-N/C-O Formation of Oximes and Diazo Esters

Chemodivergent reactions of oximes and diazo esters involving Rh-catalyzed [3+2] annulation and photodriven O-H insertion have been developed to generate oxazoles and oxime ethers. A range of aldehyde and ketone oximes reacted with α-diazocarbonyl compounds in a controllable manner in which functional groups, including ketone, ester, amide, ether, thiol ether, silane, alkene, allene, and alkyne groups, were well tolerated.

Oxime Ether Synthesis through O-H Functionalization of Oximes with Diazo Esters under Blue LED Irradiation

A green and sustainable oxime ether formation method via the visible-light-promoted O-H functionalization of oximes with diazo esters is described. The reaction occurs under very mild conditions (catalyst- and additive-free) with a high yield and a high functional group tolerance. When the reaction was performed with a cyclic ether as the solvent (e.g., THF, 1,4-dioxane, tetrahydropyran, ect.), an interesting photochemical three-component reaction product was obtained in good yields.

B(C6F5)3-catalyzed O-H insertion reactions of diazoalkanes with phosphinic acids

A highly efficient base-, metal-, and oxidant-free catalytic O-H insertion reaction of diazoalkanes and phosphinic acids in the presence of B(C6F5)3 has been developed. This powerful methodology provides a green approach towards the synthesis of a broad spectrum of α-phosphoryloxy carbonyl compounds with good to excellent yields (up to 99% yield). The protocol features the advantages of operational simplicity, high atom economy, practicality, easy scalability and environmental friendliness.