DMAP-promoted oxidative functionalization of α-amino ketones via oxygen delivery from water/alcohols

This paper shows a novel oxidative functionalization of α-amino ketones to yield the corresponding α-ketoamides and α-acylimidates. The reaction proceeds via oxygen delivery from water/alcohols in conjunction with an electron acceptor and 4-dimethylaminopyridine (DMAP). Mechanistic study indicates that DMAP exhibits a dual function of nucleophilic catalysis and proton abstraction.

Nickel-catalyzed oxidative thiolation of α-amino carbonyl compounds with thiols

An efficient oxidative thiolation of α-amino carbonyl compounds with thiols by the catalysis of an Earth-abundant nickel salt is disclosed for the first time. A variety of alkyl thiols and (hetero)aryl thiols underwent the reaction well with α-amino ketones and an α-amino ester to produce the desired α,α-aminothiocarbonyl compounds in good to excellent yields under ligand- and base-free conditions.

Oxidative Cross-Coupling of α-Amino Ketones with Alcohols Enabled by I2-Catalyzed C-H Hydroxylation

An I2-catalyzed oxidative cross-coupling of α-amino ketones with a wide range of alcohols is described. Using a combination of air and dimethyl sulfoxide (DMSO) as oxidants, the protocol allows an efficient synthesis of α-carbonyl N,O-acetals with high functional group tolerance and enables the late-stage introduction of α-amino ketones into biorelevant alcohols. Moreover, the present method can be used in the coupling of α-amino ketones with other kinds of nucleophiles, which demonstrates great generality for the functionalization of α-amino ketones. A preliminary mechanistic investigation suggests that C-H hydroxylation of α-amino ketones has been recognized as the key step followed by subsequent dehydration coupling.

One-Pot Three-Component Coupling Reaction of α-Amino Aryl Ketones, Indoles, and Perbromomethane Under Mild Conditions

A simple and efficient one-pot three-component cascade reaction of α-amino aryl ketones, indoles, and CBr₄ in moderate to good yields has been developed. This new strategy exhibits excellent mild reaction conditions and step-economy, easily accessible reactants, and simultaneous construction of three different new bonds (C=N, C–C, and N-Br) in a single step. It is worth noting that the protocol developed provides a simple and practical tool for the construction of diverse indole-containing heterocyclic frameworks, indicating its potential applications in medicinal and material chemistry.

Visible-Light-Driven Photoredox-Catalyzed C(sp3)-C(sp3) Cross-Coupling of N-arylamines with Cycloketone Oxime Esters

A novel photoredox-catalyzed C(sp3)-C(sp3) cross-coupling between N-arylamines and cycloketone oxime esters under mild conditions has been accomplished. The redox-neutral reaction proceeds good functional group tolerance and excellent regioselectivity without any...

Preparation and Application of α-Imino Ketones through One-Pot Tandem Reactions Based on Heyns Rearrangement

α-Imino ketone is a useful building block for the preparation of α-amino ketones and α-amino alcohols. However, its preparation has been seldomly seen. Herein, a metal-free and operationally simple strategy has been developed to generate α-imino ketones with high regioselectivity. Meanwhile, the method allowed for the preparation of various N,O-ketals with high regioselectivities and diastereoselectivities through cascade reactions in one pot.

CBr4 Mediated [4 + 1] Dehydrocyclization for the Synthesis of Functionalized Imidazo[1,5-a]heterocycles from Pyridin-2-ylmethanamines and Aldehydes

A CBr₄ mediated [4 + 1] dehydrocyclization was developed for the synthesis of imidazo[1,5-a]heterocycles from pyridin-2-ylmethanamines and aldehydes. This method was highly practical with the advantages of wide substrate scope, functional group tolerance, and mild reaction conditions.

Copper-catalyzed oxidative cyclization of glycine derivatives toward 2-substituted benzoxazoles

A novel and straightforward intramolecular cyclization of glycine derivatives to 2-substituted benzoxazoles through copper-catalyzed oxidative C-H/O-H cross-coupling was described. A variety of glycine derivatives involving short peptides underwent cross-dehydrogenative-coupling readily to afford diverse 2-substituted benzoxazoles. The synthetic method has the advantages of simple operation, broad substrate scope and mild reaction conditions, thus providing an alternative effective approach for benzoxazole construction.

Recent advances in the application of tetrabromomethane in organic synthesis

This review article covers the use of tetrabromomethane as mediator, catalyst and reagents for organic synthesis for the period from 2007 to 2020.

Visible-Light-Induced Dehydrogenative Imidoylation of Imidazo[1,2-a]pyridines with α-Amino Acid Derivatives and α-Amino Ketones

A new and efficient visible-light-promoted dehydrogenative cross-coupling reaction of imidazo[1,2-a]pyridines with α-amino carbonyl compounds toward imidoyl imidazo[1,2-a]pyridines is developed. A diverse range of imidazo[1,2-a]pyridines undergoes the dehydrogenative imidoylation smoothly with α-amino carbonyl compounds to access the corresponding products in satisfactory yields. We have also proposed the possible reaction mechanism based on preliminary mechanistic studies. The synthetic method has the advantages of wide substrate scope, good functional tolerance, and mild reaction conditions, which make this transformation more practical and sustainable.

Thiocyanation of α-amino carbonyl compounds for the synthesis of aromatic thiocyanates

A procedure for K2S2O8-mediated thiocyanation of α-amino carbonyl compounds has been developed for the synthesis of aromatic thiocyanates. A series of α-amino carbonyl compounds have been investigated, and the desired products are obtained in 74%–93% yields. This strategy has the advantages of simple reaction conditions without use of a transition-metal catalyst, high regioselectivity, and high efficiency. Moreover, we found that arylamine thiocyanates can also be obtained from α-amino carbonyl compounds and potassium thiocyanate in the presence of CoCl2·6H2O, I2, and dimethyl sulfoxide through the cleavage of the C–N bond. To explore the reaction mechanism, we designed several control experiments and proposed a possible mechanism using the experimental results and related literature reports.

Direct intramolecular double cross-dehydrogentive-coupling (CDC) cyclization of N-(2-pyridyl)amidines under metal-free conditions

A facile transition-metal-free protocol to form 2-iminoimidazo[1, 2-a]-pyridines bearing a -CHBr₂ group and an aza-quaternary carbon center at the 3 position from N-(2-pyridyl)amidines substrates, in which the new heterocyclic skeletons constructed from amidines via radical reactions or nucleophilic substitution reactions are promoted only by CBr₄ under mild conditions, is demonstrated. The reactions were realized by intramolecular CDC reaction involving C-N and C-C bond formation via the sequential C(sp³)-H bifunctionalization mode on the same carbon atom under mild conditions. Moreover, this work also provides an excellent and representative example for CBr₄ as an efficient reagent to initiate radical reactions under initiator-free conditions or to give rise to nucleophilic substitution reactions only by base.

An efficient synthesis of benzothiazole using tetrabromomethane as a halogen bond donor catalyst

A CBr₄ catalyzed simple, mild, and efficient protocol has been developed for the synthesis of 2-substituted benzothiazole from 2-aminothiophenols and N-methylthioamides under solvent free conditions.