Silyl-Group-Directed Linear-Selective Allylation of Carbonyl Compounds with Trisubstituted Allylboronates Using a Copper(I) Catalyst

Iwamoto, Hiroaki; Hayashi, Yuta; Ozawa, Yasutomo; Ito, Hajime

doi:10.1021/acscatal.9b05408

Cited by 13 publications

(14 citation statements)

References 36 publications

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“…We were pleased to find that this reaction produced the linear vinyl silane 20 exclusively, with excellent stereocontrol. Such linear selectivity has been previously observed in other metal-catalyzed allylations and provides opportunity for further synthetic elaboration via cross-coupling. , Finally, we demonstrated that other allyl ethers are viable coupling partners in the reaction, using both methyl and phenyl allyl ethers. As expected, allyl acetatethe most common electrophile in transition metal catalyzed allylationsis not applicable likely owing to the reductant involved…”

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confidence: 80%

Stereospecific Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Tosylate and Allyl Alcohol Electrophiles

Tercenio

Alexanian

2021

Org. Lett.

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The stereospecific cross-coupling of easily accessed electrophiles holds significant promise in the construction of C− C bonds. Herein, we report a nickel-catalyzed reductive coupling of allyl alcohols with chiral, nonracemic alkyl tosylates. This crosscoupling delivers valuable allylation products with high levels of stereospecificity across a range of substrates. The catalytic system consists of a simple nickel salt in conjunction with a commercially available reductant and importantly represents a rare example of a cross-coupling involving the C−O bonds of two electrophiles.

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confidence: 80%

Stereospecific Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Tosylate and Allyl Alcohol Electrophiles

Tercenio

Alexanian

2021

Org. Lett.

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“…Moreover, an increased isosurface between the B(pin) moiety and the silyl moiety of ( E )- 1e was observed in the NCIPLOT of TS1′ allyl . In previous studies, the regioselectivity toward the formation of borylcyclopropanes, in which the copper(I) atom must attach to the carbon atom adjacent to the silicon atom in the alkenyl silane substrate, was rationalized in terms of the stabilizing electronic effect of the silyl group on the newly formed Cu–C bond. ,− However, we found that the steric contacts between the substrate and the phosphine substituents of the ligands also crucially affect the regioselectivity.…”

Section: Resultsmentioning

confidence: 77%

Conformationally Fixed Chiral Bisphosphine Ligands by Steric Modulators on the Ligand Backbone: Selective Synthesis of Strained 1,2-Disubstituted Chiral cis-Cyclopropanes

et al. 2022

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A new series of C 1-symmetric P-chirogenic bisphosphine ligands of the type (R)-5,8-Si-Quinox-tBu3 (Silyl = SiMe3, SiEt3, SiMe2Ph) have been developed. The bulky silyl modulators attached to the ligand backbone fix the phosphine substituents to form rigid chiral environments that can be used for substrate recognition. The ligand showed high performances for a copper(I)-catalyzed asymmetric borylative cyclopropanation of bulky silyl-substituted allylic electrophiles to afford higher disfavored 1,2-cis-silyl-boryl-cyclopropanes than the other possible isomers, trans-cyclopropane and allylboronate (up to 97% yield; 98% ee; cis/trans = >99:1; cyclopropane/allylboronate = >99:1). Detailed computational studies suggested that the highly rigid phosphine conformation, which is virtually undisturbed by the steric interactions with the bulky silyl-substituted allyl electrophiles, is key to the high stereo- and product-selectivities. Furthermore, the detailed computational analysis provided insight into the mechanism of the stereoretention or -inversion of the chiral alkylcopper(I) intermediate in the intramolecular cyclization.

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“…Mechanistic studies indicate that isoprene insertion into a Cu–H bond occurs slower than carbonyl allylation, in agreement with theoretical predictions . Our experimental observation of rapid and regioselective formation of branched homoallylic alkoxide products from linear Cu allyl complexes is also consistent with the computed barrier of ∼14–15 kcal/mol for carbonyl allylation by Cu–allyl complexes supported by diphosphine and NHC ligands. , Lastly, consistent with reports of rapid regeneration of Cu–H from the reaction of Cu alkoxide complexes and silanes, the addition of (EtO) 3 SiH to a colorless solution 4 in toluene at 25 °C promptly regenerated a bright yellow solution of [(6Dipp)CuH] 2 based on UV–vis spectroscopy with strong transitions at 360, 440, and 458 nm (Figure S12c). …”

Section: Resultsmentioning

confidence: 99%

“…For CuH-catalyzed carbonyl allylation, the elementary steps of isoprene insertion into Cu−H complexes and formation of the C−C bond by allylation of ketones and aldehydes have been examined computationally. 10,17,19,20 In this work, we employed isolable [(NHC)CuH] 2 (NHC = N-heterocyclic carbene) complexes 18,21,22 to examine these two underlying elementary steps. Tuning the steric properties of NHC ligands is a general strategy to achieve different regioselectivities, 23,24 new reaction pathways, 25,26 and improved rates.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Despite the rapid pace of methodology development for Cu–H catalysis, empirical mechanistic studies and characterization of key intermediates are sparse. For CuH-catalyzed carbonyl allylation, the elementary steps of isoprene insertion into Cu–H complexes and formation of the C–C bond by allylation of ketones and aldehydes have been examined computationally. ,,, …”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Studies of Carbonyl Allylation Mediated by (NHC)CuH: Isoprene Insertion, Allylation, and β-Hydride Elimination

et al. 2022

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The ability of Cu−H complexes to undergo selective insertion of unsaturated hydrocarbons under mild conditions has rendered them valuable, versatile catalysts. The direct formation of Cu allyl intermediates from unfunctionalized 1,3-dienes and transient Cu hydrides is an appealing strategy for upgrading conjugated diene feedstocks. However, empirical mechanistic studies of the underlying elementary steps and characterization of key intermediates in Cu−H catalysis are sparse. Using [(NHC)-CuH] 2 (NHC = N-heterocyclic carbene), we examined the steric effects of NHC ligands on two key elementary steps of CuHcatalyzed carbonyl allylation: the insertion of a diene into the Cu− H bond to produce a Cu−allyl complex, and the formation of C−C bonds from stoichiometric allylations of ketones and aldehydes. The resulting allyl and homoallylic alkoxide complexes have been characterized by NMR spectroscopy and single-crystal X-ray diffraction. Employing isolable (NHC)Cu−allyl complexes, we further evaluated the roles of the ligand size, electronic properties of carbonyl substrates, coordinating groups within the substrate, and solvent on the regioselectivity, diastereoselectivity, and relative rate of the C−C bond formation step. In contrast to the clean allylation of ketones, allylation of aldehydes provided a rare example of a formal β-hydride elimination reaction from a secondary homoallylic alkoxide species. Mechanistic studies of key elementary steps provide insights for a range of catalytic reactions of dienes mediated by hydride complexes.

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Silyl-Group-Directed Linear-Selective Allylation of Carbonyl Compounds with Trisubstituted Allylboronates Using a Copper(I) Catalyst

Cited by 13 publications

References 36 publications

Stereospecific Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Tosylate and Allyl Alcohol Electrophiles

Stereospecific Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Tosylate and Allyl Alcohol Electrophiles

Conformationally Fixed Chiral Bisphosphine Ligands by Steric Modulators on the Ligand Backbone: Selective Synthesis of Strained 1,2-Disubstituted Chiral cis-Cyclopropanes

Mechanistic Studies of Carbonyl Allylation Mediated by (NHC)CuH: Isoprene Insertion, Allylation, and β-Hydride Elimination

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