Copper-Catalyzed Hydroalumination of Allenes with Diisobutylaluminum Hydride: Synthesis of Allylic Ketones with α-Quaternary Centers via Tandem Allylation/Oppenauer Oxidation

An efficient and straightforward approach to allylaluminum reagent synthesis through Cu-catalyzed hydroalumination of readily accessible allenes with diisobutylaluminum hydride is described. The N-heterocyclic carbene-based copper complex promotes hydride addition to various functionalized allenes under mild reaction conditions. The catalytic reaction is applied to a highly selective one-pot synthesis of allylic ketones with α-tertiary and α-quaternary centers through tandem nucleophilic addition of in situ-generated allylaluminums to aldehydes/Oppenauer oxidation.

Zn-Catalyzed Multicomponent KA2 Coupling: One-Pot Assembly of Propargylamines Bearing Tetrasubstituted Carbon Centers

Tetrasubstituted propargylamines comprise a unique class of highly useful compounds, which can be accessed through the multicomponent coupling between ketones, amines, and alkynes (KA² coupling), an underexplored transformation. Herein, the development of a novel, highly efficient, and user-friendly catalytic system for the KA² coupling, based on the environmentally benign, inexpensive, and readily available zinc acetate, is described. This system is employed in the multicomponent assembly of unprecedented, tetrasubstituted propargylamines derived from structurally diverse, challenging, and even biorelevant substrates. Notable features of this protocol include the demonstration of the enhancing effect that neat conditions can have on catalytic activity, as well as the expedient functionalization of hindered, prochiral cyclohexanones, linear ketones, and interesting molecular scaffolds such as norcamphor and nornicotine.

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

Alkenes are fundamental functionalities in nature and highly useful intermediates in organic synthesis, medicinal chemistry and material sciences. Transition-metal-catalyzed Heck couplings with organic halides as electrophiles have been established as a powerful protocol for the synthesis of this valuable building block. However, the requirement of organic halides and the generation of stoichiometric hazardous halide wastes may cause significant sustainable concerns. The halide-free oxidative Heck alkenylations involving organometallics or arenes as the coupling partners provide a facile and alternative pathway. Nonetheless, stoichiometric amounts of extra oxidant are essential in most cases. Herein, we present a direct dehydrogenative alkyl Heck-coupling reaction under oxidant-free conditions, liberating hydrogen, nitrogen and water as the side products. Excellent regioselectivity is achieved via neighboring oxygen atom coordination. Broad substrate scope, great functional group (ketone, ester, phenol, free amine, amide etc) tolerance and modification of pharmaceutical candidates and biological molecules exemplified its generality and practicability.

The influence of ZnII coordination sphere and chemical structure over the reactivity of metallo-β-lactamase model compounds

The first coordination sphere influences the reactivity of metallo-β-lactamase monozinc model complexes.

Efficient transformation of CO2 into quinazoline-2,4(1H,3H)-diones at room temperature catalyzed by a ZnI2/NEt3 system

The readily available ZnI₂/NEt₃ system promotes the efficient transformation of CO₂ and 2-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones at room temperature and low CO₂ pressure.

Visible-light-mediated dehydrogenative cross-coupling between terminal alkynes and aldehydes by employing a supramolecular polymeric ensemble of PBI derivative

A supramolecular polymer of PBI derivative and ZnO NPs exhibits remarkable efficiency in direct dehydrogenative cross-coupling reaction for the synthesis of ynones under photocatalytic conditions.

Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes

A general AzePhenol dinuclear zinc catalytic system has been successfully developed and introduced into the asymmetric addition of dimethylzinc and alkynylzinc to aromatic aldehydes.

Oxidative coupling of tetraalkynyltin with aldehydes leading to alkynyl ketones

A small library of acetylenic ketones was synthesized by the reaction of tetraalkynyltin reagents with aldehydes.

Magnesium salt promoted tandem nucleophilic addition-Oppenauer oxidation of aldehydes with organozinc reagents

A magnesium salt promoted synthesis of ketones via tandem nucleophilic addition-Oppenauer oxidation of aldehydes using organozinc chemistry was demonstrated. Magnesium salts concomitantly generated via magnesium metal mediated organohalide zincation exhibit high efficacy for nucleophilic addition of organozinc reagents to aromatic aldehydes and thereafter Oppenauer oxidation whereby ketones are formed in high to excellent yields.

A facile and efficient method for the synthesis of alkynone by carbonylative Sonogashira coupling using CHCl3 as the CO source

A facile and efficient method for the synthesis of alkynones by a Pd-catalyzed carbonylative Sonogashira coupling reaction starting from aryl iodide, terminal alkyne and chloroform (CHCl₃) as the CO source is described.

Isomerizable (E/Z)-alkynyl-O-methyl oximes employing TMSCl–NCS in chlorinative cyclization for the direct synthesis of 4-chloroisoxazoles

For the first time, 4-chloroisoxazoles are directly synthesized in moderate to excellent yields from mixtures of (E)- and (Z)-alkynyl-O-methyl oximes via (E)- to (Z)-oxime isomerization followed by chlorinative cyclization.

Transition-Metal-Free Synthesis of Ynones via Decarboxylative Alkynylation of α-Keto Acids under Mild Conditions

A transition-metal-free synthetic method of various ynones via decarboxylative alkynylation of α-keto acids is described. The reaction is carried out under mild conditions and exhibits remarkable tolerance of functional groups. The mechanism of a radical process is proposed in the reaction.

Metal-free carbonyl C(sp2)–H oxidative alkynylation of aldehydes using hypervalent iodine reagents leading to ynones

The metal-free and facile synthesis of ynones via carbonyl C(sp²)–H oxidative alkynylation of aldehydes with enynyl benziodoxolones is presented.

Dinuclear versus mononuclear pathways in zinc mediated nucleophilic addition: a combined experimental and DFT study

A combined experimental and DFT study was conducted to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition.

Nickel N-heterocyclic carbene-catalyzed cross-coupling reaction of aryl aldehydes with organozinc reagents to produce aryl ketones

The transformation of aromatic aldehydes into aryl ketones by nickel-catalyzed cross-coupling has been developed. This transformation represents an efficient and attractive synthetic utilization of organozinc reagents.