Jin-Pei Cheng

Electrocatalytic Water Oxidation by a Dinuclear Copper Complex in a Neutral Aqueous Solution

Electrocatalytic water oxidation using the oxidatively robust 2,7-[bis(2-pyridylmethyl)aminomethyl]-1,8-naphthyridine ligand (BPMAN)-based dinuclear copper(II) complex, [Cu2(BPMAN)(μ-OH)](3+), has been investigated. This catalyst exhibits high reactivity and stability towards water oxidation in neutral aqueous solutions. DFT calculations suggest that the O-O bond formation takes place by an intramolecular direct coupling mechanism rather than by a nucleophilic attack of water on the high-oxidation-state Cu(IV)=O moiety.

Enantioselective Organocatalyzed Vinylogous Michael Reactions of 3-Alkylidene Oxindoles with Enals

An efficient asymmetric vinylogous Michael addition of 3-alkylidene oxindoles and enals has been achieved using a chiral TBS-protected diphenylprolinol catalyst. The γ-substituted alkylidene oxindoles obtained bear a chiral tertiary center and are afforded in moderate to good yields and good to excellent enantioselectivities.

Equilibrium acidities of cinchona alkaloid organocatalysts bearing 6′-hydrogen bonding donors in DMSO

The pKa values of 18 cinchona alkaloid based organocatalysts bearing 6′-hydrogen bonding donors were determined by the overlapping indicator method in DMSO via UV spectrophotometric titrations. The pKa values are in the range of 6.76–20.24.

Equilibrium acidities of BINOL type chiral phenolic hydrogen bonding donors in DMSO

The pKa values of fifteen BINOL type chiral phenolic catalysts were determined by the overlapping indicator method in DMSO via UV spectrophotometric titrations. The acidities cover the range from 9.30 to 16.43. The pKa gap between BINOL and 2-naphthol was explained by IR spectrum data, crystal structure and 1H NMR. The relationship between the pKa values of 3,3′-modified BINOLs and Hammett ortho substituent constants (σo−) was investigated and a good correlation (R2 = 0.984) was obtained. The results may be helpful for the rational design and development of novel BINOL type phenolic catalysts, sensors and ligands.

Computation of standard equilibrium acidity of C–H acids in ionic media: shedding light on predicting changes of chemical behavior by switching solvent system from molecular to ionic

An SMD implicit–explicit approach was developed that allows reproduction of experimental pKa values of various carbon acids in ionic liquids with a mean unsigned error of 1.28 pK units, which is comparable in magnitude to those authentic pKa calculations in conventional molecular solvents. This model may be used for predicting more pKa values in RTILs and may also offer clues for studying other thermodynamic quantities.

Origin of Stereocontrol in Photoredox Organocatalysis of Asymmetric α-Functionalizations of Aldehydes

The merger of the common photoredox catalyst Ru(bpy)3Cl2 with an imidazolidinone organocatalyst by MacMillan et al. has enabled a series of highly enantioselective α-functionalizations of aldehydes, a landmark discovery in photoredox organocatalysis. Herein, we present the theoretical investigation into the origin of enantioselectivity in asymmetric radical additions to the MacMillan imidazolidinone enamines, the key stereocontrolling step in photoredox organocatalysis of asymmetric α-functionalizations of aldehydes. The calculations reveal a hidden but crucial role of E-cis enamine in enantiocontrol. The enantioselectivity in the radical additions is mainly determined by steric effects. A model based on the pseudo C2-symmetric arrangement of the methyl and tert-butyl moieties on the catalyst is proposed. This rationalizes the stereoselective outcome of these reactions and provides a good model to understand MacMillans imidazolidinone/photoredox dual catalysis. The insights obtained from this study should be valuable in future efforts toward the design and development of new enantioselective catalytic radical reactions.

Recent Advances and Advisable Applications of Bond Energetics in Organic Chemistry

Most organic transformation involves cleavage and formation of various covalent bonds, and naturally, can be regarded as a process of bond reorganization, which should be intrinsically related to bond energies (e.g., p Ka, BDE, etc.). However, in many cases such as in C-H bond activation/functionalization, direct correspondence between the bond energy and reaction rate or other relevant properties is only occasionally observed when applying the bond data by simple rules like the Linear Free-Energy Relationships (LFERs) in handling intricate reaction systems. In this Perspective, we present examples to argue that the above-mentioned situation is not a consequence of a diminishing role of the bond energetics in research, but most likely, comes from an improper use of energetic strategy, or simply due to a faulty selection of the data from unsuitable sources. Some advisable applications of bond energies in unscrambling the problems in modern day chemistry are exemplified through representative recent advances of the researches in this connection. Some of the possible directions of future research endeavors in the field of bond energetics and its prudent applications are recommended.