Catalytic Reactions of Terminal Alkynes Using Rhodium(I) Complexes Bearing 8-Quinolinolate Ligands

Rhodium-NHC-Catalyzed gem-Specific O-Selective Hydropyridonation of Terminal Alkynes

The dinuclear complex [Rh(μ-Cl)(η² -coe)(IPr)]₂ is an efficient catalyst for the O-selective Markovnikov-type addition of 2-pyridones to terminal alkynes. DFT calculations support a hydride-free pathway entailing intramolecular oxidative protonation of a π-alkyne by a κ¹ N-hydroxypyridine ligand. Subsequent O-nucleophilic attack on a metallacyclopropene species affords an O-alkenyl-2-oxypyridine chelate rhodium intermediate as the catalyst resting state. The release of the alkenyl ether is calculated as the rate-determining step.

Rhodium-Catalyzed Anti-Markovnikov Hydroamination of Aliphatic and Aromatic Terminal Alkynes with Aliphatic Primary Amines

Anti-Markovnikov hydroamination of both aliphatic and aromatic terminal alkynes with primary amines was achieved using an 8-quinolinolato rhodium catalyst to form aldimines and enamines in high yields. This catalytic system realized high functional group tolerance including hydroxy, bromo, cyano, and thioester groups.

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.

DFT calculations bring insight to internal alkyne-to-vinylidene transformations at rhodium PNP- and PONOP-pincer complexes

Through DFT calculations, the equilibrium between Rh–alkyne and Rh–vinylidene species of PXNXP pincer ligated Rh cationic complexes is shown to be tuned by the P–Rh–P bite angle, which in turn is dictated by the nature of the X moiety of the pincer ligand.

A Hydroxyquinoline-Based Unnatural Amino Acid for the Design of Novel Artificial Metalloenzymes

We have examined the potential of the noncanonical amino acid (8-hydroxyquinolin-3-yl)alanine (HQAla) for the design of artificial metalloenzymes. HQAla, a versatile chelator of late transition metals, was introduced into the lactococcal multidrug-resistance regulator (LmrR) by stop codon suppression methodology. LmrR_HQAla was shown to complex efficiently with three different metal ions, CuII , ZnII and RhIII to form unique artificial metalloenzymes. The catalytic potential of the CuII -bound LmrR_HQAla enzyme was shown through its ability to catalyse asymmetric Friedel-Craft alkylation and water addition, whereas the ZnII -coupled enzyme was shown to mimic natural Zn hydrolase activity.

A.E.Favorskii’s scientific legacy in modern organic chemistry: prototropic acetylene – allene isomerization and the acetylene zipper reaction

Alexei Evgrafovich Favorskii was an outstanding organic chemist who left a great scientific legacy as a result of long time and fruitful work. Most of the theoretically and practically important discoveries of A.E.Favorskii were made in the chemistry of acetylene and its derivatives. Nowadays, the reactions discovered by him, which include acetylene – allene isomerization, the Favorskii and retro-Favorskii reactions, the Favorskii rearrangement and the vinylation reaction, are widely used in industry and in laboratory synthesis. This review summarizes the main scientific achievements of A.E.Favorskii, as well as their development in modern organic chemistry. Much consideration is given to acetylene – allene isomerization as a convenient method for the synthesis of methyl-substituted acetylenes and to the acetylene zipper reaction as a synthetic tool for obtaining terminal acetylenes. The review presents examples of the application of these reactions in modern organic synthesis of complex molecules, including natural compounds and their analogues.

The bibliography includes 266 references.

Computational and experimental investigation on the BCl3 promoted intramolecular amination of alkenes and alkynes

The BCl₃ promoted aminoboration of alkenes and alkynes was investigated both computationally and experimentally, leading to the discovery of a metal-free hydroamination of alkynes.