Lewis Base Adducts of Phosphine-Stabilized Pb(II) Cations: Synthesis and Catalytic Hydroamination of Alkynes

Phosphine-stabilized Pb(II) cations, generated by chloride abstraction from chloroplumbylene 1, readily react with Lewis bases (L) such as phosphines and amines to give the corresponding donor-acceptor complexes 3. These complexes 3 react with phenylacetlylene via alkyne insertion into the Pb-L bond to afford the corresponding vinylplumbylenes 4. Of particular interest, the stable complex 4-HNiPr₂ (with a secondary amine) can be used as a hydroamination catalyst of phenylacetylene.

Metal-free synthesis of β-aminoketones by the reductive hydroamination of ynones

This study describes a cascade method for the synthesis of β-aminoketones through the reductive hydroamination of alkynes under very mild metal-free conditions. It allows for the rapid conversion of ynones and amines into corresponding β-aminoketones with a broad substrate scope and diverse functionalities. This straightforward and easy-to-handle reaction process can be successfully applied for the synthesis of Proroxan and Propipocaine, offering a potential option for the synthesis of drug molecules with the β-aminoketone skeleton.

Recent progress in the chemistry of β-aminoketones

The current study highlighted the significance of β-aminoketones as privileged biologically active molecules, recent synthetic strategies, and synthetic applications.

Pd-catalyzed cross-coupling of arabinogalactan propargyl ethers with 5-bromosalicylic acid

New salicylate derivatives of arabinogalactan have been synthesized in up to 90% yield by cross-coupling of propargyl ethers of arabinogalactan with 5-bromosalicylic acid salts. The reaction proceeds in the presence of the catalytic system Pd(PPh₃)₄/PPh₃ with CuBr (CuI), and piperidine or 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) as a base in DMSO at 70-95 °С. The propargyl groups of the starting arabinogalactan ethers are converted into propinylsalicylate ones with 35 and 50% conversion depending on the nature of the base used. Degree of arabinogalactan substitution with propynyl salicylate fragments reaches 1.0 and 0.7 in the reactions with piperidine and DBU, respectively. In the case of piperidine, along with the main process, intensive unprecedented (for Sonogashira reaction) hydroamination of propargyl groups is also observed, followed by hydrolysis of unstable enamines. The products have been characterized by IR, ¹Н and ¹³С NMR, UV spectroscopy as well as elemental analysis and gel permeation chromatography. Salicylate derivatives of arabinogalactan show high activity in prolonging the activated partial thromboplastin time (APTT), whereas neither the arabinogalactan nor propargyl ethers of arabinogalactan nor salicylic acid salts have obvious effects.

2:1 versus 1:1 Coupling of Alkylacetylenes with Secondary Amines: Selectivity Switching in 8-Quinolinolato Rhodium Catalysis

Both 2:1 and 1:1 couplings of alkylacetylenes with secondary amines were achieved using 8-quinolinolato rhodium catalysts and CsF. The 2:1/1:1 selectivity was switched by choosing the reaction solvent. In DMA, an unprecedented 2:1 coupling reaction of alkylacetylenes with amines proceeded to give 2-aminodiene products. One-pot 2:1 coupling/reduction provided rapid access to various allylamines, while one-pot coupling/hydrolysis gave enones as products. In toluene, anti-Markovnikov hydroamination occurred under relatively mild conditions to give 1:1 coupling products.

Synthesis of Arylethylamines via C(sp3)-C(sp3) Palladium-Catalyzed Cross-Coupling

Substituted arylethylamines represent a key structural motif in natural, pharmaceutical, and agrochemical compounds. Access to such scaffolds has been the subject of long-standing synthetic interest. Herein, we report the synthesis of such scaffolds via a palladium-catalyzed C(sp³)-C(sp³) coupling between (chloromethyl)aryls and air-/moisture-stable N,N-dialkylaminomethyltrifluoroborate salts. Rapid hit identification was achieved using microscale high-throughput experimentation and was followed by millimolar-scale reaction parameter optimization. A range of structurally and electronically varied arylethylamine products were obtained in moderate to excellent yields (27-96%, >60 examples). The reaction mechanism is proposed to proceed via formation of a trialkylbenzylammonium species prior to oxidative addition.

Catalysis and regioselectivity in hydrofunctionalization reactions of unsaturated carbon bonds. Part II. Hydroamination

This review continues consideration of the regioselectivity problem in the catalyzed hydrofunctionalization of unsaturated organic compounds and addresses hydroamination of unsaturated hydrocarbons. Particular parts of the review deal with reactions of alkenes, alkynes, allenes and dienes. It is shown that the selectivity of hydroamination depends on the natures of the reactants and the catalyst. Conditions of the reactions are described; in some cases, reaction mechanisms are discussed. Reactions for which divergent regioselectivity is possible are noted.

The bibliography includes 249 references.

Dedicated to the memory of V.V.Markovnikov.

Silica Surface Modification and Its Application in Permanent Link with Nucleic Acids

In this paper, the Pt-catalyzed hydrosilylation of hydroxyl ethers is described. Various bifunctional alkoxysilanes were obtained and applied in O-silylation of free hydroxyl groups on the silica surface. These modified solid materials have been used as excellent supports for linking synthetic nucleic acids. Nucleic acids permanently attached to the solid surface were tested in hybridization with complementary fluorescence-labeled sequences. Detection of nucleic acids anchored to the solid support was performed by fluorescence microscopy after hybridization.

Regio- and Stereoselective Copper-Catalyzed Allylation of 1,3-Dicarbonyl Compounds with Terminal Allenes

Simple ligand-free copper systems were found as efficient catalysts for the addition of 1,3-dicarbonyl compounds to N-allenyl derivatives. This highly regio- and stereoselective reaction has been accomplished in the presence of malonates, 1,3-ketoesters, and 1,3-diketones with good to excellent yields under mild conditions. This methodology represents the first allylation of 1,3-dicarbonyl compounds with allenes catalyzed by copper.

Mechanism of Zn(OTf)2catalyzed hydroamination–hydrogenation of alkynes with amines: insight from theory

Zn(OTf)₂catalyzed hydroamination of alkynes with amines proceeds through an outer sphere mechanism which is contrary to other late transition metals.

Cyclopentadienyl-based Mg complexes in the intramolecular hydroamination of aminoalkenes: mechanistic evidence for cationic versus neutral magnesium derivatives

Mechanistic evidence in the catalytic hydroamination of aminoalkenes for a cationic magnesium derivative.