Cooperative Photoredox- and Nickel-Catalyzed Alkylative Cyclization Reactions of Alkynes with 4-Alkyl-1,4-dihydropyridines

Interplay of diruthenium catalyst in controlling enantioselective propargylic substitution reactions with visible light-generated alkyl radicals

Transition metal-catalyzed enantioselective free radical substitution reactions have recently attracted attention as convenient and important building tools in synthetic chemistry, although construction of stereogenic carbon centers at the propargylic position of propargylic alcohols by reactions with free radicals remains unchallenged. Here we present a strategy to control enantioselective propargylic substitution reactions with alkyl radicals under photoredox conditions by applying dual photoredox and diruthenium catalytic system, where the photoredox catalyst generates alkyl radicals from 4-alkyl-1,4-dihydropyridines, and the diruthenium core with a chiral ligand traps propargylic alcohols and alkyl radicals to guide enantioselective alkylation at the propargylic position, leading to high yields of propargylic alkylated products containing a quaternary stereogenic carbon center at the propargylic position with a high enantioselectivity. The result described in this paper provides the successful example of transition metal-catalyzed enantioselective propargylic substitution reactions with free alkyl radicals.

Theoretical Study for Evaluating and Discovering Organic Hydride Compounds as Potential Novel Methylation Reagents

Methylation reaction is a fundamental chemical reaction that plays an important role in the modification of drug molecules, DNA, as well as proteins. This work focuses on seeking potential novel methylation reagents through a systematic investigation of the thermodynamics and reactivity of methyl-substituted organic hydride radical cations (XH^•+s). In this work, 45 classical and important XH^•+s were designed to investigate the relationship between their structure and reactivity, to find excellent or potential methylation reagents. The Gibbs free energy and activation free energy of XH^•+ to release the methyl radical in MeCN at 298.15 and 355 K are calculated with the density functional theory (DFT) method to quantitatively measure the reactivity of XH^•+ as a methylation reagent in this work. The relationships between structures and reactivities on XH^•+s as methylation reagents are well examined. Since we have calculated the Gibbs free energy and activation free energy of trifluoromethyl-substituted organic hydride compound radical cations (X'H^•+) releasing trifluoromethyl radicals in MeCN with the DFT method in our previous work, accordingly, the relationship of thermodynamics and reactivity between X'H^•+ releasing trifluoromethyl radical and XH^•+ releasing methyl radical is discussed in detail. Excitingly, 4 XH^•+s (1H^•+, 3H^•+∼4H^•+, and 44H^•+) are found to be excellent methyl radical reagents, while 9 XH^•+s (5H^•+, 6H^•+, 9H^•+, 10H^•+, 12H^•+, 13H^•+, 15H^•+, 43H^•+, and 45H^•+) are found to be potential methyl radical reagents in chemical synthesis. The molecular library and reactivity database of novel methylation reagents could be established for synthetic chemists to query and use. Our work may offer a theoretical basis and reference experience for screening different substituted organic hydride compounds (YRHs) as alkylation reagents.

Cyclic vs. acyclic alkyne towards Hg2+ ion detection: combined experimental and theoretical studies

Comparison between the alkynes in terminal and internally conjugated 1,3-diyne systems produces differences in molecular recognition, maintaining the HSAB principle.

Selective Fluoromethyl Couplings of Alkynes via Nickel Catalysis*

We describe here a Ni-catalyzed intermolecular carbo-fluoromethylation of alkynes with aliphatic halides and fluoromethyl halides (BrCF 2 H and ICH 2 F) in the presence of zinc, enabling the facile and selective access to a diverse range of biologically valuable CF 2 H/CH 2 F-incorporated alkenes with excellent regio- and stereo-selectivity. Notably, merging intramolecular radical cyclization with fluoromethyl coupling enables the expedient constructions of CF 2 H/CH 2 F-incorporated lactones and lactams with high efficiency and selectivity. Mechanistic studies disclose that this catalytic protocol proceeds via a radical addition to an alkyne followed by selective coupling with the fluoromethyl unit.