Catalyst-Substrate Helical Character Matching Determines the Enantioselectivity in the Ishihara-Type Iodoarenes Catalyzed Asymmetric Kita-Dearomative Spirolactonization

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(13), P. 7301 - 7312

Published: March 20, 2023

Catalyst design has traditionally focused on rigid structural elements to prevent conformational flexibility. Ishihara's elegant of conformationally flexible C2-symmetric iodoarenes, a new class privileged organocatalysts, for the catalytic asymmetric dearomatization (CADA) naphthols is notable exception. Despite widespread use Ishihara catalysts CADAs, reaction mechanism remains subject debate, and mode induction not been well established. Here, we report an in-depth computational investigation three possible mechanisms in literature. Our results, however, reveal that this best rationalized by fourth called "proton-transfer-coupled-dearomatization (PTCD)", which predicted be strongly favored over other competing pathways. The PTCD consistent with control experiment further validated applying it rationalize enantioselectivities. Oxidation I(I) catalyst active I(III) species induces defined helical chiral environment delicate balance between flexibility rigidity. A match/mismatch effect substrate's shape transition states was observed. match allows adapt its conformation maximize attractive noncovalent interactions, including I(III)···O halogen bond, N-H···O hydrogen π···π stacking, stabilize state. stereochemical model capable rationalizing variation enantioselectivities developed. present study enriches our understanding how achieve high stereoinduction may serve as inspiration future exploration designs.

Language: Английский

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Diaryliodonium Tetrachloroplatinates(II): Recognition of a Trifurcated Metal-Involving μ₃-I···(Cl,Cl,Pt) Halogen Bond

Crystal Growth & Design, Journal Year: 2021, Volume and Issue: 21(9), P. 5360 - 5372

Published: Aug. 5, 2021

Synthesis and X-ray characterization of the four diaryliodonium tetrachloroplatinates(II) [Ar1Ar2I]2[PtCl4] (Ar1/Ar2 = Ph/Ph (1), 4-Cl-C6H4/2,4,6-(MeO)3C6H2 (2), 4-Me-C6H4/2,4,6-(MeO)3C6H2 (3), Ph/2,4,6-(MeO)3C6H2 (4)) allowed deterimination several types unconventional halogen-bond (HaB) patterns. The first example a metal-involved trifurcated four-center μ3-X···(X′,X′,M) HaB is represented by metal-involving I···Pt (the structure 4) with iodonium cations acting as donors, which supported two weak I···Cl contacts. structures 1–3 display bifurcated three-center μ2-I···(Cl,Cl) HaBs cations. DFT calculations were used to estimate energetic features Molecular electrostatic potential (MEP) surfaces noncovalent interaction plot index (NCIPlot) computational tools evaluate σ-holes characterize HaBs, respectively, in all structures.

Language: Английский

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N‐Heterocyclic Iod(az)olium Salts – Potent Halogen‐Bond Donors in Organocatalysis

Chemistry - A European Journal, Journal Year: 2021, Volume and Issue: 27(52), P. 13128 - 13134

Published: June 23, 2021

This article describes the application of N-heterocyclic iod(az)olium salts (NHISs) as highly reactive organocatalysts. A variety mono- and dicationic NHISs are described utilized potent XB-donors in halogen-bond catalysis. They were benchmarked seven diverse test reactions which activation carbon- metal-chloride bonds well carbonyl nitro groups was achieved. N-methylated rendered highest reactivity all investigated catalytic applications with reactivities even higher than previously monodentate based on iodine(I) (III) strong Lewis acid BF3 .

Language: Английский

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Dissection of the Origin of π-Holes and the Noncovalent Bonds in Which They Engage

The Journal of Physical Chemistry A, Journal Year: 2021, Volume and Issue: 125(30), P. 6514 - 6528

Published: July 26, 2021

Accompanying the rapidly growing list of σ-hole bonds has come acknowledgment parallel sorts noncovalent which owe their stability in large part to a deficiency electron density area above molecular plane, known as π-hole. The origins these π-holes are probed for wide series molecules, comprising halogen, chalcogen, pnicogen, tetrel, aerogen, and spodium bonds. Much like case counterparts, formation internal covalent π-bond Lewis acid molecule pulls toward bond midpoint away from its extremities. This depletion central atom is amplified by an electron-withdrawing substituent. At same time, amplitude π*-orbital enhanced region density-depleted π-hole, facilitating better overlap with nucleophile's lone pair orbital stabilizing n → π* charge transfer. presence pairs on acts attenuate π-hole shift position somewhat, resulting overall weakening bond. There tendency include higher fraction induction energy than σ-bonds proportionately smaller electrostatic dispersion components, but this distinction less product σ- or π-character more function strength.

Language: Английский

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A Hypervalent Cyclic Dibenzoiodolium Salt as a Halogen‐Bond‐Donor Catalyst for the [4+2] Cycloaddition of 2‐Alkenylindoles

ChemPlusChem, Journal Year: 2021, Volume and Issue: 86(5), P. 741 - 744

Published: April 16, 2021

A stable, hypervalent cyclic dibenzoiodolium salt acted as a strong halogen bonding (XB)-donor catalyst for [4+2] cycloaddition of 2-alkenylindoles, and not an oxidizing agent. The cross-[4+2] 2-vinylindoles with 2-alkenylindoles was catalyzed smoothly by the triflate to give tetrahydrocarbazoles in up 99 % yield 17 : 1 diastereoselectivity. also applicable Povarov reaction 2-vinylindole N-p-methoxyphenyl (PMP) imine indolyl-tetrahydroquinoline 83 yield.

Language: Английский

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