Electrochemically Promoted Three-Component Reaction to N-Sulfonyl Amidines

In this study, a multicomponent reaction via the Mannich intermediate was developed using methanol, secondary amine, and sulfonamide as starting materials. This method uses methanol as a green C1 source. The substrate scope is wide, and the yield is good. The mechanistic study shows that methanol generates formaldehyde under electrochemical conditions, and sulfonyl amidine as a nucleophile reacts with Schiff base intermediates to form N-sulfonyl amidine in a single step.

Electrochemical selenocyclization of 2-ethynylanilines with diselenides: facile and efficient access to 3-selenylindoles

An efficient electrochemical selenocyclization strategy for the synthesis of 3-selenylindoles from 2-ethynylanilines and diselenides has been developed in simple tube- or beaker-type undivided cells under ambient conditions. Notably, these sustainable transformations are completed within a short time with low equivalents of charges, diselenides and electrolytes, exhibiting a broad substrate scope with excellent functional group compatibility. Moreover, a gram-scale electrosynthesis and late-stage functionalization of complex molecules further demonstrate the practical synthetic potential of this facile electrochemical system.

Paraformaldehyde as C1 Synthon: Electrochemical Three-Component Synthesis of Tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones in Aqueous Ethanol

A green and practical method for the electrochemical synthesis of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones through the three-component reaction of quinoxalin-2(1H)-ones, N-arylglycines and paraformaldehyde was reported. In this strategy, EtOH played dual roles (eco-friendly solvent and waste-free pre-catalyst) and the in situ generated ethoxide promoted triple sequential deprotonations.

Metal-Free Direct Access to N-Sulfonyl Amidines from Sulfonamides and Secondary Amines Involving Tandem C-N Bond Formations

We report a mild and efficient metal-free one-pot procedure for the synthesis of N-sulfonyl amidines via the direct reaction of sulfonamides with secondary amines without using any additives. A wide range of substrates with variety of functional groups is well tolerated under the reaction conditions. Preliminary mechanistic studies indicate that the secondary amine plays a dual role as a C1 source of the amidine group and an aminating agent. Synthetic utility of this method is shown in the late-stage functionalization of drug molecules on the gram scale.

Electrochemical synthesis of functionalized gem-difluoroalkenes with diverse alkyl sources via a defluorinative alkylation process

An electrochemical defluorinative alkylation of α-trifluoromethyl alkenes is described. This reaction enables the preparation of functionalized gem-difluoroalkenes with diverse alkyl sources including organohalides, NHP esters, and Katritzky salts.

Rapid and efficient synthesis of formamidines in a catalyst-free and solvent-free system

An operationally rapid and efficient synthesis of N-sulfonyl formamidines that proceeds under mild conditions was achieved by reaction of a mixture of an amine, a sulfonyl azide, and a terminal ynone under catalyst-free and solvent-free conditions. Terminal ynones provide the C source to formamidines via complete cleavage of C[triple bond, length as m-dash]C.

Electrochemical synthesis of isobenzofuran-1-imines using oxidative halocyclization of o-alkynylbenzamides

Electrochemical oxidative 5-exo-dig-oxo-halocyclization of o-alkynylbenzamides was achieved using readily available NaX (X = Cl, Br and I) salts under mild reaction conditions. The use of a cheap and highly stable sodium halide as a halide ion source is impressive for the synthesis of a variety of halogenated isobenzofuran-1-imines. This electrochemical protocol shows regioselectivity and excellent conversion to isobenzofuran-1-imines in good yields without the use of stoichiometric amounts of oxidants and transition metal catalysts.

Selective N-Alkylation of Amines with DMC over Biogenic Cu-Zr Bimetallic Nanoparticles

Herein, we report the green synthesis of copper-zirconium bimetallic nanoparticles (Cu-Zr BNPs) from aqueous solutions using Azadirachta indica leaf extract as a reducing and stabilizing agent. The CuO, ZrO2 NP, and Cu-Zr BNP samples were characterized by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and the morphologies of the samples were analyzed by high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction analysis (SAED). The synthesized Cu-Zr BNPs have been employed as efficient catalysts for the selective N-methylation of aromatic and aliphatic amines with dimethyl carbonate. The effect of process conditions on the percentage conversion of benzylamine with dimethyl carbonate as a model reaction has been investigated. The Cu-Zr bimetallic nanoparticle catalytic system in a 1:2 molar ratio was able to convert amines into the corresponding N-methylated amines with a selectivity up to 91% at 180 °C in 4 h. The analysis of catalytic reusability confirmed that the reported heterogeneous catalyst can be used for five consecutive cycles without much loss in activity. Thus, the current protocol can be considered as a simpler, reproducible, and environmentally benign approach for N-methylation of amines.

Visible-light enabled room-temperature dealkylative imidation of secondary and tertiary amines promoted by aerobic ruthenium catalysis

Employing sulfonyl azide as a nitrogen donor, a visible-light-enabled aerobic dealkylative imidation of tertiary and secondary amines involving C(sp³)–C(sp³) bond cleavage with moderate to excellent yields at room temperature is described. It has been demonstrated that this imidation could take place spontaneously upon visible-light irradiation, and could be facilitated considerably by a ruthenium photocatalyst and oxygen. An alternative mechanism to the previous aerobic photoredox pathway has also been proposed.

A photoredox dealkylative imidation of tertiary and secondary amines with sulfonyl azide facilitated by aerobic ruthenium-catalysis to afford sulfonyl amidine at room temperature is reported.

Catalyst-free one-pot, four-component approach for the synthesis of di- and tri-substituted N-sulfonyl formamidines

A straightforward one-pot, multicomponent approach was developed to synthesize di- and tri-substituted N-sulfonyl formamidines from sulfonyl chlorides, NaN3, ethyl propiolate, and primary/secondary amines under mild conditions without catalysts or additives. Structural analysis of the di-substituted sulfonyl formamidines indicated formation of the E-syn/anti isomeric form. Tri-substituted analogues only formed E-isomers.

Reductive Arylation of Aliphatic and Aromatic Aldehydes with Cyanoarenes by Electrolysis for the Synthesis of Alcohols

An electroreductive arylation reaction of aliphatic and aromatic aldehydes as well as ketones with electro-deficient (hetero)arenes is described. A variety of cyano(hetero)arenes and carbonyl compounds, especially aliphatic aldehydes, have been examined, providing secondary and tertiary alcohols in moderate to good yields. Mechanistic studies, including cyclic voltammetry (CV), electron paramagnetic resonance (EPR), and divided-cell experiments, support the generation of aliphatic ketyl radicals and persistent heteroaryl radical anions via cathodic reduction followed by radical-radical cross-coupling.

Electrifying Sustainability on Transition Metal-Free Modes: An Eco-Friendly Approach for the Formation of C-N Bonds

Embracing sustainable green methodologies and techniques in chemical transformations has always been in the limelight to the synthetic community. Electrosynthesis has emerged as a powerful, sustainable synthetic tool for molecular synthesis exploiting inexpensive electricity in place of sacrificial chemical oxidizing/reducing reagents. Herein, recent advances in the incorporation of transition metal-free redox mediators in electrosynthesis for the construction of C-N bonds are outlined. Furthermore, conjugation of this strategy with flow catalysis allows easy scale up of the synthesis of molecular assembly. This comprehensive Review provides an overview of metal-free mediated electro-construction of C-N bonds, focusing on the reaction mechanisms involved and its synthetic applications.

α-C–H functionalization of tertiary amines catalyzed/promoted by molecular iodine/derivatives

A recent review on the α-C–H functionalization of tertiary amines using low-cost and benign I₂ or its derivatives.