Nickel/Zinc Iodide Co-catalytic Asymmetric [2+2] Cycloaddition Reactions of Azabenzonorbornadienes with Terminal Alkynes

Amino alcohol-derived chiral stationary phases

An updated minireview of chiral stationary phases (CSPs) based on amino alcohols is presented. In this minireview, we focused on amino alcohols as starting materials in preparation of chiral catalysts for asymmetric organic synthesis and CSPs for chiral separations. Among the various CSPs, we summarized the important developments and applications of the amino alcohol-based Pirkle-type CSPs, ligand exchange CSPs, α-amino acid-derived amino alcohol CSPs, and symmetric CSPs from their first appearance to the present day to propose ideas for the development of new CSPs with improved performance.

Nickel-catalyzed cyclization of 1,7-enynes for the selective synthesis of dihydrocyclobuta[c]quinolin-3-ones and benzo[b]azocin-2-ones

We herein described a nickel-catalyzed cyclization of N-(o-ethynylaryl)acrylamides for the selective synthesis of dihydrocyclobuta[c]quinolin-3-ones and benzo[b]azocin-2-ones. The two varied products could be easily obtained by tuning the reaction temperature. This reaction features easy temperature-control, high efficiency, and gram-scale synthesis.

Asymmetric Reduction of Aromatic α-Dehydroamino Acid Esters with Water as Hydrogen Source

The asymmetric reduction of aromatic α-dehydroamino acid esters with water as the hydrogen source was developed by a Rh/Cu co-catalytic system. The reaction tolerates various functional groups, providing a valuable synthetic tool to access chiral α-amino acid esters readily. Moreover, the present methodology also was applied in the cost-effective and easy to handle preparation of chiral deuterated α-amino esters by using D₂O.

Ruthenium-Catalyzed [2 + 2] versus Homo Diels-Alder [2 + 2 + 2] Cycloadditions of Norbornadiene and Disubstituted Alkynes: A DFT Study

The ruthenium-catalyzed [2 + 2] and homo Diels-Alder [2 + 2 + 2] cycloadditions of norbornadiene with disubstituted alkynes are investigated using density functional theory (DFT). These DFT calculations provide a mechanistic explanation for observed reactivity trends with different functional groups. Alkynyl phosphonates and norbornadiene form the [2 + 2 + 2] cycloadduct, while other functionalized alkynes afford the respective [2 + 2] cycloadduct, in excellent agreement with experimental results. The computational studies on the potential energy profiles of the cycloadditions show that the rate-determining step for the [2 + 2] cycloaddition is the final reductive elimination step, but the overall rate for the [2 + 2 + 2] cycloaddition is controlled by the initial oxidative cyclization. Two distinct mechanistic pathways for the [2 + 2 + 2] cycloaddition, cationic and neutral, are characterized and reveal that Cp*RuCl(COD) energetically prefers the cationic pathway.

Catalytic asymmetric transformations of oxa- and azabicyclic alkenes

This review provides an overview of the fundamental concepts and recent developments in a wide range of enantioselective transformations involving oxa- and azabicyclic alkenes.

Chiral Stationary Phases for Liquid Chromatography: Recent Developments

The planning and development of new chiral stationary phases (CSPs) for liquid chromatography (LC) are considered as continuous and evolutionary issues since the introduction of the first CSP in 1938. The main objectives of the development strategies were to attempt the improvement of the chromatographic enantioresolution performance of the CSPs as well as enlarge their versatility and range of applications. Additionally, the transition to ultra-high-performance LC were underscored. The most recent strategies have comprised the introduction of new chiral selectors, the use of new materials as chromatographic supports or the reduction of its particle size, and the application of different synthetic approaches for preparation of CSPs. This review gathered the most recent developments associated to the different types of CSPs providing an overview of the relevant advances that are arising on LC.

Nickel-Catalyzed Asymmetric [2+2] Cycloaddition Reaction of Hetero-Bicyclic Alkenes with Internal Alkynes

Enantioselective [2+2] cycloaddition reaction of azabenzonorbornadienes and oxabenzonorbornadienes with internal alkynes has been enabled by a catalyst system comprising Ni(COD)₂ and (R)-SIPHOS-Ph-Mor. This transformation represents the first asymmetric [2+2] cycloaddition reaction of azabenzonorbornadienes with internal alkynes, providing a straightforward method to prepare four-membered carbocycles.