An easy-to-perform evaluation of steric properties of Lewis acids

Chemical Science, Journal Year: 2023, Volume and Issue: 14(9), P. 2275 - 2288

Published: Jan. 1, 2023

An easy-to-perform approach to assess and quantify steric properties of Lewis acids is reported. The novel LAB-Rep model (Lewis acid/base repulsion model) introduced, which judges in pairs.

Language: Английский

---

Unlocking Diverse π-Bond Enrichment Frameworks by the Synthesis and Conversion of Boronated Phenyldiethynylethylenes

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(14), P. 10167 - 10176

Published: March 27, 2024

The π-bond enrichment frameworks not only serve as a crucial building block in organic synthesis but also assume pivotal role the fields of materials science, biomedicine, photochemistry, and other related disciplines owing to their distinctive structural characteristics. incorporation various substituents into C═C double bonds tetrasubstituted alkenes is currently highly significant research area. However, with diverse on poses challenge achieving stereoselectivity. Here, we reported an efficient convergent route Cu-catalyzed borylalkynylation both symmetrical unsymmetrical 1,3-diynes, B2pin2, acetylene bromide construction boronated phenyldiethynylethylene (BPDEE) derivatives excellent chemo-, stereo-, regioselectivities. BPDEE could transform novel π-conjugated gem-diphenyldiethynylethylene (DPDEE), vinylphenyldiethynylethylene (VPDEE), phenyltriethynylethylene (PTEE) by stepwise process, which provides flexible platform for complex that were difficult synthesize previous methods. initial optical characterization revealed synthesized molecules exhibited aggregation-induced emission (AIE) properties, further establishes groundwork future applications enriches advances field functional research.

Language: Английский

---

Nickel boryl complexes and nickel-catalyzed alkyne borylation

Chemical Science, Journal Year: 2023, Volume and Issue: 14(8), P. 2215 - 2228

Published: Jan. 1, 2023

The first nickel bis-boryl complexes cis-[Ni( i Pr2ImMe)2(Bcat)2], Pr2ImMe)2(Bpin)2] and Pr2ImMe)2(Beg)2] are reported, which were prepared via the reaction of a source [Ni( Pr2ImMe)2] with diboron(4) compounds B2cat2, B2pin2 B2eg2 ( Pr2ImMe = 1,3-di-iso-propyl-4,5-dimethylimidazolin-2-ylidene; B2cat2 bis(catecholato)diboron; bis(pinacolato)diboron; bis(ethylene glycolato)diboron). X-ray diffraction DFT calculations strongly suggest that delocalized, multicenter bonding scheme dictates situation NiB2 moiety in these square planar complexes, reminiscent "non-classical" H2 complexes. also efficiently catalyzes diboration alkynes using as boron under mild conditions. In contrast to known platinum-catalyzed diboration, system follows different mechanistic pathway, not only provides 1,2-borylation product excellent yields, but an efficient approach other products such C-C coupled borylation or rare tetra-borylated compounds. mechanism nickel-catalyzed alkyne was examined by means stoichiometric reactions calculations. Oxidative addition diboron reagent is dominant; steps catalytic cycle coordination subsequent at coordinated and, thus, activated yield type [Ni(NHC)2(η2-cis-(Bcat)(R)C[double bond, length m-dash]C(R)(Bcat))], exemplified isolation structural characterization Pr2ImMe)2(η2-cis-(Bcat)(Me)C[double m-dash]C(Me)(Bcat))] Pr2ImMe)2(η2-cis-(Bcat)(H7C3)C[double m-dash]C(C3H7)(Bcat))].

Language: Английский

---

Mechanism of Pd/Senphos-Catalyzed trans-Hydroboration of 1,3-Enynes: Experimental and Computational Evidence in Support of the Unusual Outer-Sphere Oxidative Addition Pathway

The Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 88(4), P. 2415 - 2424

Published: Feb. 8, 2023

The reaction mechanism of the Pd/Senphos-catalyzed trans-hydroboration 1,3-enynes was investigated using various experimental techniques, including deuterium and double crossover labeling experiments, X-ray crystallographic characterization model intermediates, progress kinetic analysis. Our data are in support an unusual outer-sphere oxidative addition where catecholborane serves as a suitable electrophile to activate Pd0-bound 1,3-enyne substrate form Pd-η3-π-allyl species, which has been determined be likely resting state catalytic cycle. Double points toward second role played by borane hydride delivery shuttle. Density functional theory calculations reveal that rate-limiting transition is abstraction shuttle, consistent with experimentally rate law: = k[enyne]0[borane]1[catalyst]1. computed activation free energy ΔG‡ 17.7 kcal/mol KIE (kH/kD 1.3) also line observations. Overall, this work establishes Lewis acids such viable electrophilic activators engage underutilized general approach unsaturated substrates.

Language: Английский

---

Transition Metal‐Free Regio‐ and Stereo‐Selective trans Hydroboration of 1,3‐Diynes: A Phosphine‐Catalyzed Access to (E)‐1‐Boryl‐1,3‐Enynes

Chemistry - A European Journal, Journal Year: 2022, Volume and Issue: 28(63)

Published: Aug. 2, 2022

We report a transition metal-free, regio- and stereo-selective, phosphine-catalyzed method for the trans hydroboration of 1,3-diynes with pinacolborane that affords (E)-1-boryl-1,3-enynes. The reaction proceeds excellent selectivity boron addition to external carbon 1,3-diyne framework as unambiguously established by NMR X-ray crystallographic studies. displays broad substrate scope including unsymmetrical diynes generate products in high yield (up 95 %). Experimental theoretical studies suggest phosphine attack on alkyne is key process catalytic cycle.

Language: Английский

---

How to Break the Law: trans‐Hydroboration and gem‐Hydroboration of Alkynes

Israel Journal of Chemistry, Journal Year: 2023, Volume and Issue: 63(7-8)

Published: March 9, 2023

Abstract Classical hydroboration is the textbook example of an organometallic reaction under rigorous frontier orbital control: a synergetic bonding mode between substrate and reagent evolves into four‐membered transition state that enforces syn /suprafacial delivery H−BR 2 to π‐system. This strict stereochemical “law” remained valid for decades, even after advent metal‐catalyzed hydroboration. During last decade, however, numerous possibilities emerged allow this paradigm be challenged. Thus, direct trans ‐hydroboration terminal as well internal alkynes was achieved through radical, ionic, organocatalytic, manifolds, which are summarized in review. Among them, pathways involving either metal vinylidenes (Rh, Ir, Ru, Fe) derived from or metallacyclopropenes (η ‐vinylmetal complexes) triple bond [Cp X Ru]‐based catalyst represent currently most widely applicable solutions. The latter type intermediates also accountable equally perplexing gem alkynes: geminal borane has no precedent classical canon. only forerunner ‐hydrogenation, represents unconventional yet highly useful entry discrete ruthenium carbene complexes. close mechanistic ties these transformations outlined, brief reference made remotely related reactions such ‐diboration ‐carboboration.

Language: Английский

---

Ligand-controlled regiodivergent Ni-catalyzed trans-hydroboration/carboboration of internal alkynes with B₂pin₂

Chemical Science, Journal Year: 2024, Volume and Issue: 15(6), P. 2236 - 2242

Published: Jan. 1, 2024

With the aid of directing group strategy, an approach for synthesis alkenyl and 1-naphthyl boronates with stereo- regioselectivity via ligand-controlled Ni-catalyzed trans -hydroboration/carboboration internal alkynes was developed.

Language: Английский

---

Regio- and Stereoselective Copper-Catalyzed Borylation–Protodeboronation of 1,3-Diynes: Access to (Z)-1,3-Enynes

Organic Letters, Journal Year: 2023, Volume and Issue: 25(15), P. 2652 - 2656

Published: April 6, 2023

A facile method to access (Z)-1,3-enynes is realized via sequential copper-catalyzed regio- and stereoselective borylation-protodeboronation of 1,3-diynes. Pinacolborane, copper(II) acetate, Xantphos as the ligand efficiently install hydrogen Bpin in a cis fashion, which followed by rapid hydrolysis with water. The reaction has wide substrate scope occurs chemoselective fashion.

Language: Английский

---

Visible-Light-Induced trans-Hydroboration of Diaryl Alkynes Utilizing Excited State of Borate Complexes

Organic Letters, Journal Year: 2024, Volume and Issue: 26(11), P. 2180 - 2185

Published: March 11, 2024

We have developed visible-light-induced trans-hydroboration of diaryl alkynes via direct photoexcitation in-situ-generated diboron complexes, affording previously elusive (E)-1,2-diaryl-vinylboronates with high stereoselectivity. Experimental, spectroscopic, and theoretical mechanistic studies revealed that the triplet-state borate complex facilitates B–B bond cleavage desired C–B formation. This methodology does not require any catalyst is operationally simple. The highly borylated 1,2-diaryl alkenes [1-(2-borylphenyl)vinyl)boronates] are shown to be useful as building blocks.

Language: Английский

---

Chemo-, Regio-, and Stereoselective cis-Hydroboration of 1,3-Enynes: Copper-Catalyzed Access to (Z,Z)- and (Z,E)-2-Boryl-1,3-dienes

Organic Letters, Journal Year: 2024, Volume and Issue: 26(29), P. 6136 - 6141

Published: July 17, 2024

A copper-catalyzed alkyne-selective hydroboration of 1,3-enynes is disclosed, providing access to the previously elusive 2-boryl-1,3-dienes. Using CuOAc, Xantphos, and HBpin, Bpin was installed on internal carbon a series symmetric nonsymmetric 1,3-enynes, affording products with excellent Z:E selectivity. The utility 2-boryl-1,3-diene demonstrated by transformation useful functional groups.

Language: Английский

---