The Construction of Chiral Fused Azabicycles Using a Pd-Catalyzed Allylic Substitution Cascade and Asymmetric Desymmetrization Strategy

A highly enantioselective Pd-catalyzed asymmetric allylic substitution cascade of cyclic <i>N</i>-sulfonylimines with an accompanying asymmetric desymmetrization has been developed for the construction of fused tetrahydroindole derivatives bearing two chiral centers. Mechanistic studies confirmed that the cascade reaction proceeds by initial allylic alkylation and subsequent allylic amination. The first alkylation is a chirality-control step and represents an asymmetric desymmetrization of <i>cis</i>-cyclic allyl diacetates. The reaction has been performed on a gram scale, and the desired products can take part in several transformations

Iridium-Catalyzed Asymmetric Hydrogenation of 2<i>H</i>‑Chromenes: A Highly Enantioselective Approach to Isoflavan Derivatives

A highly efficient (a<i>S</i>)-Ir/In-BiphPHOX-catalyzed asymmetric hydrogenation of substituted 2<i>H</i>-chromenes and substituted benzo­[<i>e</i>]­[1,2]­oxathiine 2,2-dioxides is described. A series of 2<i>H</i>-chromenes and benzo­[<i>e</i>]­[1,2]­oxathiine 2,2-dioxides were hydrogenated to give the target products in high yields (92–99%) with excellent enantioselectivities (up to 99.7% ee) using our catalytic system. This reaction provides a direct and efficient method for the construction of chiral benzo six-membered oxygen-containing compounds

Iridium-Catalyzed Asymmetric Hydrogenation of 2<i>H</i>‑Chromenes: A Highly Enantioselective Approach to Isoflavan Derivatives

A highly efficient (a<i>S</i>)-Ir/In-BiphPHOX-catalyzed asymmetric hydrogenation of substituted 2<i>H</i>-chromenes and substituted benzo­[<i>e</i>]­[1,2]­oxathiine 2,2-dioxides is described. A series of 2<i>H</i>-chromenes and benzo­[<i>e</i>]­[1,2]­oxathiine 2,2-dioxides were hydrogenated to give the target products in high yields (92–99%) with excellent enantioselectivities (up to 99.7% ee) using our catalytic system. This reaction provides a direct and efficient method for the construction of chiral benzo six-membered oxygen-containing compounds

Rh-Catalyzed One-Pot Sequential Asymmetric Hydrogenation of α‑Dehydroamino Ketones for the Synthesis of Chiral Cyclic <i>trans</i>-β-Amino Alcohols

Catalyzed by a rhodium complex of P-stereogenic diphosphine ligand (<i>R</i>)-2-<i>tert</i>-butylmethylphosphino-3-(di-<i>tert</i>-butylphosphino)­quinoxaline ((<i>R</i>)-<b>3H-QuinoxP</b>*), five-membered cyclic α-dehydroamino ketones bearing endocyclic vinyl and endocyclic keto-carbonyl groups were sequentially hydrogenated to give chiral cyclic <i>trans</i>-β-amino alcohols with two contiguous stereocenters in quantitative conversions, excellent enantioselectivities and good diastereoselectivities

Chemoselective Transfer Hydrogenation of α,β-Unsaturated Ketones Catalyzed by Pincer-Pd Complexes Using Alcohol as a Hydrogen Source

A pincer-Pd complex was utilized in the chemoselective transfer hydrogenation of α,β-unsaturated ketones using <i>n-</i>BuOH as a hydrogen source and solvent. Good to excellent yields were obtained for various substrates even with reducible groups. Based on deuterium-labeling experiments, the reaction mechanism is proposed to occur via a pincer-Pd-hydride intermediate

Synthesis and Structural Characterization of Nickel Complexes Possessing P‑Stereogenic Pincer Scaffolds and Their Application in Asymmetric Aza-Michael Reactions

Novel P-stereogenic pincer-Ni complexes {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Me^<i>t</i>BuPCH₂)₂C₆H}­NiCl (<b>3</b>), {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Me^<i>t</i>BuPCH₂)₂C₆H}­NiOTf (<b>4</b>), [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­NiCl]Cl (<b>7</b>), [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­NiCl]­BF₄ (<b>8</b>), and [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­Ni­(NCMe)]­(BF₄)₂ (<b>9</b>) were synthesized in 55–84% yields and characterized by ¹H NMR, ¹³C­{¹H} NMR, ³¹P­{¹H} NMR, ¹⁹F­{¹H} NMR, and/or single-crystal X-ray diffractions. The ORTEP diagrams of complexes <b>3</b>, <b>7</b>, <b>8</b>, and <b>9</b> show that the coordination geometries around the Ni center in all these structures are approximately square planar but have different bond lengths and angles. These complexes were shown to be active catalysts for the asymmetric aza-Michael addition of α,β<i>-</i>unsaturated nitriles. For most examples good to excellent yields (up to 99%) and moderate enantiomeric excesses (up to 46% ee) were obtained. Notably, the PCP complex <b>3</b> exhibited higher catalytic activity in the aza-Michael addition than the PNP complexes <b>7</b>, <b>8</b>, and <b>9</b>. Two achiral PCP-type pincer-Ni complexes, {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(^<i>t</i>Bu₂PCH₂)₂C₆H}­NiCl (<b>11</b>) and {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Ph₂PCH₂)₂C₆H}­NiCl (<b>13</b>), were also synthesized and fully characterized in order to reveal the structural differences between the chiral and achiral complexes

Chemoselective Transfer Hydrogenation of α,β-Unsaturated Ketones Catalyzed by Pincer-Pd Complexes Using Alcohol as a Hydrogen Source

A pincer-Pd complex was utilized in the chemoselective transfer hydrogenation of α,β-unsaturated ketones using <i>n-</i>BuOH as a hydrogen source and solvent. Good to excellent yields were obtained for various substrates even with reducible groups. Based on deuterium-labeling experiments, the reaction mechanism is proposed to occur via a pincer-Pd-hydride intermediate

Chemoselective Transfer Hydrogenation of α,β-Unsaturated Ketones Catalyzed by Pincer-Pd Complexes Using Alcohol as a Hydrogen Source

A pincer-Pd complex was utilized in the chemoselective transfer hydrogenation of α,β-unsaturated ketones using <i>n-</i>BuOH as a hydrogen source and solvent. Good to excellent yields were obtained for various substrates even with reducible groups. Based on deuterium-labeling experiments, the reaction mechanism is proposed to occur via a pincer-Pd-hydride intermediate

Hydrogen-Bond-Activated Palladium-Catalyzed Allylic Alkylation via Allylic Alkyl Ethers: Challenging Leaving Groups

C–O bond cleavage of allylic alkyl ether was realized in a Pd-catalyzed hydrogen-bond-activated allylic alkylation using only alcohol solvents. This procedure does not require any additives and proceeds with high regioselectivity. The applicability of this transformation to a variety of functionalized allylic ether substrates was also investigated. Furthermore, this methodology can be easily extended to the asymmetric synthesis of enantiopure products (99% ee)