Zhang-Pei Chen

4,5-Dihydropyrrolo(1,2‑a)quinoxalines: A Tunable and Regenerable Biomimetic Hydrogen Source

A series of tunable and regenerable biomimetic hydrogen sources, 4,5-dihydropyrrolo[1,2-a]quinoxalines, have been synthesized and applied in biomimetic asymmetric hydrogenation of 3-aryl-2H-benzo[b][1,4]oxazines and 1-alkyl-3-aryl-quinoxalin-2(1H)-ones, providing the chiral amines with up to 92% and 89% ee, respectively.

Enantioselective synthesis of trifluoromethyl substituted piperidines with multiple stereogenic centers via hydrogenation of pyridinium hydrochlorides

An enantioselective iridium-catalyzed hydrogenation of trifluoromethyl substituted pyridinium hydrochlorides is described. Introduction of a trifluoromethyl group increases the reactivity due to the electron-withdrawing effect. Three stereogenic centers could be generated in one operation. This methodology provides a convenient route to chiral poly-substituted piperidines with up to 90% ee.

Synthesis of Chiral Fluorinated Hydrazines via Pd-Catalyzed Asymmetric Hydrogenation.

An enantioselective hydrogenation of fluorinated hydrazones has been achieved by employing [Pd(R)-DTBM-SegPhos(OCOCF3)2] as the catalyst, providing a general and convenient method toward chiral fluorinated hydrazines. A broad substrate scope including β-aryl-, γ-aryl-, and alkyl-chain-substituted hydrazones worked efficiently in high yields and up to 94% of enantioselectivity. The reductive amination between trifluoromethyl-substituted ketones and benzohydrazides could also proceed smoothly.

Synthesis of Chiral Fluorinated Propargylamines via Chemoselective Biomimetic Hydrogenation

A highly enantioselective synthesis of chiral fluorinated propargylamines was developed through phosphoric acid and ruthenium-catalyzed chemoselective biomimetic hydrogenation of the carbon-nitrogen double bond of fluorinated alkynyl ketimines in the presence of a carbon-carbon triple bond. This reaction features high chemoselectivity and slow background reaction. In addition, selective transformations of the chiral fluorinated propargylamines were also reported.

Synthesis of Fluorinated Heteroaromatics through Formal Substitution of a Nitro Group by Fluorine under Transition‐Metal‐Free Conditions

An efficient and transition-metal-free approach was developed to access a series of fluorinated heteroaromatics in moderate to excellent yields. This one-pot procedure features a triple-relay transformation of rapid dearomatization, fluorination, and rearomatization processes, which represents a conceptually novel strategy of combining partial hydrogenation and electrophilic fluorination.