Copper‐Catalyzed Enantioselective Allylboration of Alkynes: Synthesis of Highly Versatile Multifunctional Building Blocks

Rivera‐Chao, Eva; Mitxelena, Maider; Varela, J.; Fañanás‐Mastral, Martín

doi:10.1002/ange.201910707

Cited by 38 publications

(2 citation statements)

References 69 publications

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“…[22] Based on this result, we questioned whether it would be possible to employ C(sp 3 )-based electrophiles in lieu of a proton to develop a three-component carboboration, with regioselectivity and product substitution patterns that would complement existing methodology. [23][24][25][26][27][28][29][30][31][32] Of relevance to this proposal, Xiao and Fu disclosed an important study in which the combination of CuCl (10 mol%) as precatalyst, DMAP (24 mol%) as ligand, and B2pai2 (pai = (+)-pinanediolato) as bis-boron reagent leads to branched-selective carboboration, though in this case yields and regioselectivity were variable (30-70% yield, 64:36-95:5 r.r.). The less common and more expensive B2pai2 nucleophile was employed to maximize regioselectivity, and some synthetically useful carbogenic groups were incompatible with this protocol (e.g., allyl electrophiles).…”

Section: Terminal (β)-Selective (Well-developed)mentioning

confidence: 99%

“…The former was selected because allyl electrophiles have not been previously employed in α-selective carboboration of alkynes, despite being used in several reports of linear selectivity. [30][31][32]34] The latter was selected because it was found to be low-yielding under previously published conditions (one example, 87:13 r.r., 32% yield). [33] Table 1.…”

Section: Terminal (β)-Selective (Well-developed)mentioning

confidence: 99%

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(CAAC)Copper Catalysis Enables Regioselective Three-Component Carboboration of Terminal Alkynes

Gao

Kim

Yazdani

et al. 2022

Preprint

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Cyclic(alkyl)(amino)carbene (CAAC) ligands are found to perturb regioselectivity of the copper-catalyzed carboboration of terminal alkynes, favoring the less commonly observed internal alkenylboron regiosomer through an α-selective borylcupration step. A variety of carbon electrophiles participate in the reaction, including allyl alcohols derivatives and alkyl halides. The method provides a straightforward and selective route to versatile tri-substituted alkenylboron compounds that are otherwise challenging to access.

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Section: Terminal (β)-Selective (Well-developed)mentioning

confidence: 99%

Section: Terminal (β)-Selective (Well-developed)mentioning

confidence: 99%

(CAAC)Copper Catalysis Enables Regioselective Three-Component Carboboration of Terminal Alkynes

Gao

Kim

Yazdani

et al. 2022

Preprint

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Sulfonate N‐Heterocyclic Carbene–Copper Complexes: Uniquely Effective Catalysts for Enantioselective Synthesis of C−C, C−B, C−H, and C−Si Bonds

et al. 2020

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…I believe that every militant chemist can confirm it:that one must distrust the almost-the-same…, the practically identical, the approximate, the or-even, all surrogates and all patchwork. The differences can be small, but they can lead to radically different consequences…; the chemist's trade consists in good part in being aware of these differences, knowing them close up, and foreseeing their effects. "

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C−Boron Enolates Enable Palladium Catalyzed Carboboration of Internal 1,3‐Enynes

Wang

Lamine

et al. 2021

Angewandte Chemie

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A new family of carbon-bound boron enolates, generated by a kinetically controlled halogen exchange between chlorocatecholborane and silylketene acetals, is described. These CÀboron enolates are demonstrated to activate 1,3-enyne substrates in the presence of a Pd 0 /Senphos ligand complex, resulting in the first examples of a carboboration reaction of an alkyne with enolate-equivalent nucleophiles. Highly substituted dienyl boron building blocks are produced in excellent site-, regio-, and diastereoselectivity by the described catalytic cis-carboboration reaction.Alkenyl boronates are versatile building blocks in synthetic chemistry. [1] The ability of organoboron compounds to engage in Suzuki-Miyaura cross couplings [2] and to transform into various derivatives [3] have made alkenyl boronates highly appealing in organic synthesis. In this context, numerous approaches [4] have been developed to synthesize di- [5] and tri- [6] substituted alkenyl boronates. The synthesis of tetrasubstituted alkenyl [7] boronates on the other hand, particularly in regioselective and stereoselective fashion, has been more challenging. [8] Pioneering work by Suginome et al. (Scheme 1 a) established the nickel-or palladium catalyzed intramolecular boryl migration approach using alkyne substrates tethered with boryl moiety. [9] Similarly, nickel and palladium catalyzed intermolecular carboboration of alkynes with various carbon sources (Scheme 1 b) was reported. [10] More recently, copper-catalyzed three-component coupling of an alkyne, B 2 pin 2 , and an electrophile (Scheme 1 c) has received attention. [11] Despite these advances, carboboration reactions are still relatively limited in substrate scope and generality. In particular, stereoselective carboborations to produce tetrasubstituted alkenes often face regio-and dia-stereoselectivity issues for internal unsymmetrical alkynes. [11a-e] We recently reported the trans-hydroboration and trans-cyanoboration of 1,3-enynes catalyzed by a 1,4-azaborine biaryl phosphine (Senphos)-Pd complex. [12] An unusual outer-sphere oxidative addition mechanism [13] (a cooperative activation of the 1,3-Scheme 1. Regio-and stereoselective synthesis of tetrasubstituted alkenyl boronates.

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Copper‐Catalyzed Enantioselective Allylboration of Alkynes: Synthesis of Highly Versatile Multifunctional Building Blocks

Cited by 38 publications

References 69 publications

(CAAC)Copper Catalysis Enables Regioselective Three-Component Carboboration of Terminal Alkynes

(CAAC)Copper Catalysis Enables Regioselective Three-Component Carboboration of Terminal Alkynes

Sulfonate N‐Heterocyclic Carbene–Copper Complexes: Uniquely Effective Catalysts for Enantioselective Synthesis of C−C, C−B, C−H, and C−Si Bonds

C−Boron Enolates Enable Palladium Catalyzed Carboboration of Internal 1,3‐Enynes

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