Ag-Catalyzed ring-opening of tertiary cycloalkanols for C-H functionalization of cyclic aldimines

Silver-catalyzed generation of acyl radicals from α-imino-oxy acids: access to acylated 3-CF3-2-oxindoles

A unified strategy to generate acyl radicals from α-imino-oxy acids via selective C-C bond activation is reported. In the presence of a silver catalyst, α-imino-oxy acids could undergo decarboxylation and N-O and C-C bond homolysis to deliver the acyl radicals, which were subsequently captured by N-alkyl-N-aryl-2-(trifluoromethyl)acrylamides to access acylated 3-CF3-2-oxindoles.

Solvent-controlled silver catalyzed radical transformation of α-imino-oxy acids with cyclic aldimines

A silver-catalyzed cross coupling of cyclic aldimines and α-imino-oxy acids has been developed. The solvent-dependent reaction could selectively deliver either cyclic imine moiety retained nitriles or ring-opened oxonitriles in moderate yields. The mechanistic studies show that the reaction undergoes a radical pathway.

Electro-catalyzed, solvent-controlled divergent decarboxylative annulation and hydroaminomethylation of cyclic aldimines with N-arylglycines

Herein, we reported a sustainable and simple method involving electrochemical-catalyzed decarboxylative annulation and hydroaminomethylation of cyclic aldimines with N-arylglycines by switching the reaction solvents. When the reaction was carried out in MeCN/H2O or H2O, the resulting products included imidazolidine-fused sulfamidates and C4-aminomethylated cyclic aldimines, obtained in moderate to good yields, respectively. Mechanistically, a radical pathway was proposed to be involved in this approach.

CeCl3-Catalyzed C-H Alkylation of N-Sulfonyl Ketimines with Alkanes and Ether via Photoinduced Ligand-to-Metal Charge Transfer

A cerium-catalyzed C-H alkylation of N-sulfonyl ketimines with low-cost and readily available alkanes as alkyl sources was developed. This transformation proceeded through the synergy of photoinitiated ligand-to-metal charge transfer (LMCT) using a chlorine radical as an HAT reagent and air as a green oxidant. A series of alkylated N-sulfonyl ketimines were synthesized with moderate to good yields in a highly atom-economic manner under chemical oxidant-free conditions.

Organophotocatalytic Remote Thiocyanation Reaction via Ring-Opening Functionalization of Cycloalkanols

The remote C(sp3)-SCN bond formation via ring-opening functionalization of cycloalkanols with N-thiocyanatosaccharin as the precursor of SCN radicals and pyrylium salt as the organic photocatalyst under visible light has been developed. Thus, various terminal keto thiocyanates were prepared without transition metals and oxidants in moderate to good yields. The simplicity, wide substrate scope and mild conditions feature its synthetic application capability.

Ring-Opening Coupling of Cyclopropanol with 1,2,3-Triazole for the Synthesis of Fused Triazoles

A radical ring-opening arylation of cyclopropanol with 1,2,3-triazole has been achieved. This synthetic protocol provides straightforward access to a wide range of structurally diverse and chiral 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyridines with high efficiency from readily available chiral cyclopropanols.

Divergent Synthesis of β-Fluoroamides via Silver-Catalyzed Oxidative Deconstruction of Cyclopropanone Hemiaminals

An expedient approach for the synthesis of challenging β-fluoroamides from readily accessible cyclopropanone equivalents is reported. Following the addition of pyrazole used here as a transient leaving group, silver-catalyzed regiospecific ring-opening fluorination of the resulting hemiaminal leads to a β-fluorinated N-acylpyrazole intermediate reactive to substitution with amines, ultimately affording β-fluoroamides. The process could also be extended to the synthesis of β-fluoroesters and γ-fluoroalcohols via the addition of alcohols or hydrides as terminal nucleophiles, respectively.

Silver-catalyzed cyclization of α-imino-oxy acids to fused tetralone derivatives

A silver-catalyzed intramolecular radical relay cyclization of α-imino-oxy acids under mild conditions has been described. This reaction offers facile access to a diverse range of fused tetralone derivatives with exquisite stereoselectivity in moderate to good yields (40-98%). Experimental studies show that the reaction undergoes a decarboxylation and acetone fragmentation/1,5-hydrogen atom transfer (HAT)/cyclization process.

Swapping Copper-Catalytic Process: Selective Access to Pyrazoles and Conjugated Ketimines from Oxime Acetates and Cyclic Sulfamidate Imines

A powerful CuCl-catalyzed sequential one-pot reaction of aryl methyl ketoxime acetates with cyclic N-sulfonyl imines followed by elimination in the presence of base is reported. This hydrazine-free method conveniently makes C-C and N-N bonds via a radical cleavage of the N-O bond, delivering a special class of C3-hydroxyarylated pyrazoles in good yields. Surprisingly, while employing CuI as a catalyst instead of CuCl, the reaction proceeds through a non-radical pathway which embodies a new tactic for the high-yielding access to value-added conjugated N-unsubstituted ketimines. Moreover, additive-free approach to sulfamidate-fused-pyrazoles was achieved by successfully catalyzing addition and oxidative N-N bond-making reactions by CuI and CuCl, respectively. Significantly, our novel technique could convert the prepared ketimines into the pharmacologically recognized 6H-benzo[c]chromene frameworks.

Selective C3-nitrosation of imidazopyridines using AgNO3 as the NO source

We developed a novel method for selective radical nitrosation of imidazo[1, 2-a]pyridine derivatives using AgNO3 as a NO source.

Lewis-Acid-Catalyzed Tandem Cyclization by Ring Expansion of Tertiary Cycloalkanols with Propargyl Alcohols

A new method for the efficient synthesis of hexahydro-1H-fluorene and octahydrobenzo[a]azulene derivatives through a ring-expansion strategy is reported. With an appropriate combination of thulium(III) trifluoromethanesulfonate and 13X molecular sieves, a range of unsaturated polycyclic compounds were obtained in good yields. Mechanism studies reveal that the reaction is more likely to undergo Meyer-Schuster rearrangement, ring expansion, and Friedel-Crafts-type pathways, which provide a conceptually different strategy for the ring opening of tertiary cycloalkanols.

Iron-Catalyzed Ring Opening of Cyclopropanols and Their 1,6-Conjugate Addition to p-Quinone Methides

A novel iron-catalyzed ring opening of cyclopropanols and their 1,6-conjugate addition to p-quinone methides for accessing substituted phenols is disclosed. In this protocol, various cyclopropanols are converted to alkyl radicals and undergo 1,6-conjugate addition to p-quinone methides toward C-C bond formation. The salient features of this methodology include operationally simple and mild reaction conditions, environmentally benign protocol, high efficiency, inexpensive catalyst, good to excellent yield, and a wide range of substrate scope.

An organophotoredox-catalyzed C(sp2)-N cross coupling reaction of cyclic aldimines with cyclic aliphatic amines

An organophotocatalyzed C(sp2)-H/N-H cross-dehydrogenative coupling of cyclic aldimines with aliphatic amines has been developed, which represents the first example of visible-light-induced C-H amination of N-sulfonylated imines. This methodology enables the streamline assembly of amine derivatives via radical mediated C-N bond formation. The current protocol features transition-metal-free, mild conditions, good functional group tolerance and good yields.