Jung-Chih Wan

Bio: Jung-Chih Wan is an academic researcher from Tamkang University. The author has contributed to research in topics: Nitrile & Palladium. The author has an hindex of 1, co-authored 2 publications receiving 80 citations.

Novel Syntheses of Fluorenones via Nitrile-Directed Palladium-Catalyzed C—H and Dual C—H Bond Activation.

Abstract: Novel procedures for the [Pd]/[Ag]/TFA system catalyzed cascade reactions of nitrile directed remote C-H and dual C-H bond activation with insertion of nitrile were developed, which afforded variously polysubstituted fluorenones in moderate to good yields with tolerance of a wide variety of substrates.

Palladium-catalyzed meta-selective C-H bond activation with a nitrile-containing template: computational study on mechanism and origins of selectivity.

Abstract: Density functional theory investigations have elucidated the mechanism and origins of meta-regioselectivity of Pd(II)-catalyzed C–H olefinations of toluene derivatives that employ a nitrile-containing template. The reaction proceeds through four major steps: C–H activation, alkene insertion, β-hydride elimination, and reductive elimination. The C–H activation step, which proceeds via a concerted metalation–deprotonation (CMD) pathway, is found to be the rate- and regioselectivity-determining step. For the crucial C–H activation, four possible active catalytic species—monomeric Pd(OAc)2, dimeric Pd2(OAc)4, heterodimeric PdAg(OAc)3, and trimeric Pd3(OAc)6—have been investigated. The computations indicated that the C–H activation with the nitrile-containing template occurs via a Pd–Ag heterodimeric transition state. The nitrile directing group coordinates with Ag while the Pd is placed adjacent to the meta-C–H bond in the transition state, leading to the observed high meta-selectivity. The Pd2(OAc)4 dimeric ...

Transition-metal-catalyzed π-bond-assisted C - H bond functionalization: an emerging trend in organic synthesis.

Abstract: Transition-metal-catalyzed C - H activation is considered to be an important tool in organic synthesis and has been accepted and widely used by chemists because it is straightforward, cost-effective, and environmentally friendly. A variety of functional groups have been used to direct metal complexes and achieve regioselective C - H activation. Most directing is achieved through the σ-bond coordination of functional groups to the metal catalyst, followed by ortho-selective C - H bond cleavage. However, recent work has demonstrated that π-coordinating functional groups can also assist in guiding metal complexes for site-selective C - H bond activation. This emerging approach significantly expands the scope of C - H activation reactions in organic synthesis. Herein, recent developments in this field are summarized.

Pd(ii)-catalyzed remote regiodivergent ortho- and meta-C–H functionalizations of phenylethylamines

Abstract: Site selectivity control is of vital importance in the direct functionalization of inert C–H bonds. Reported here is a novel example of remote regiodivergent ortho- and meta-C–H bond functionalizations of phenylethylamine derivatives by using a novel 2-cyanobenzoyl group as the original directing functionality, where the regioselectivity was adjusted by a methylation. The potential of the method was exemplified by sequential functionalizations of both ortho- and meta-C–H bonds of a phenylethylamine derivative in a streamlined manner.