Palladium-catalyzed cross-coupling of (hetero)aryl or alkenyl sulfonates with aryl titanium as the multi-functional reagent

Lee, Hang Wai; So, Chau Ming; Yuen, On Ying; Wong, Wing Tak; Kwong, Fuk Yee

doi:10.1039/c9qo01537j

Cited by 18 publications

(10 citation statements)

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“…CM-phos was used in the coupling of ArOMs and Ar′Ti(Oi-Pr) 3 with low yield (Scheme 7C). 24 It is believed that introducing an electrondonating group (i.e., a methoxy or dimethylamino group) at the para position of the −PCy 2 -containing arene of CM-phos would enhance the ligand's ability to support the oxidative addition of the inert C(Ar)−O bond. Using the Pd(OAc) 2 / NMe 2 -CM-phos catalyst system, aryl/alkenyl tosylates and mesylates were successfully coupled with aryl titanium reagents for the first time.…”

Section: Other Cross-couplings and Cyanationmentioning

confidence: 99%

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

2022

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Conspectus This Account presents an overview of a promising collection of phosphine ligands simply made from the modular Fischer indolization process and their applications in modern arylation processes. Using one easily accessible 2-arylindole scaffold, three major phosphino-moiety-positioned ligand series can be readily generated. We have attempted to explore challenging electrophilic and nucleophilic partners for the coupling reaction using the modular ligand tool. For the electrophilic partner study, CM-phos-type ligands, where the phosphino group is located at the 2-arene position of 2-arylindole, allow the successful cross-coupling of aryl mesylates. The CM-phos ligand forms a palladacycle before entering the cross-coupling catalytic cycle. For the nucleophilic partner investigation, the indole C3-positioned phosphines show the first accomplishment of Pd-catalyzed organotitanium nucleophile arylation. Indeed, the aryl-titanium nucleophile undergoes cross-coupling more efficiently than does the organoboron coupling partner in particular cases. Moreover, in the indole C3-positioned phosphine series, the −PPh2-containing ligands perform better in the highly sterically hindered cross-coupling of aryl chlorides than do ligands containing the −PCy2 moiety. The catalyst loading can even be reduced to 0.2 mol % Pd for tetra-ortho-substituted biaryl synthesis. This finding offers a new perspective on the next-generation design of phosphine ligands in which the sterically bulky and electron-rich −PR2 group (R = alkyl) may not be necessary for the cross-coupling of aryl chlorides. In general, we hypothesize that a good balance of steric and electronic properties for entertaining the oxidative addition and reductive elimination steps is crucial to the success of the reaction. For the steric factor, the highly sterically congested −PR2 group normally favors the reductive elimination, yet we conjecture that this sterically bulky group would serve as an obstacle for the incoming aryl halides. For the electronic factor, the electron rich −PR2 group is believed to support the oxidative cleavage of the C(Ar)–Cl bond by donating more electron density to the corresponding σ* orbital. Nevertheless, the high electron richness of the −PR2 group may disfavor the reductive elimination electronically. Overall, an appropriate balance of both electron density and steric bulkiness is suggested to allow the sterically hindered cross-coupling to proceed smoothly. We have found that the −PPh2-containing ligand is a good starting point for this investigation. The formation of aromatic carbon–carbon (C–C) and carbon–heteroatom (C–X) bonds from aryl chlorides was successfully realized using our proprietary phosphines. In addition to the indole-core-bearing ligand skeleton, we also explored the relevant imidazolyl and carbazolyl phosphines for their unique applications. Interestingly, the carbazolyl ligand, having more flexible C–N axial chirality, displays particular interchangeable Pd–N and Pd–arene coordination, which facilitates both oxid...

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Section: Other Cross-couplings and Cyanationmentioning

confidence: 99%

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

2022

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“…19 More recently, organotitanium reagents have been used as organometallic partners in C(sp 2 )–C(sp 2 ) and C(sp 2 )–C(sp 3 ) cross-coupling reactions. 20–28 Organotitanium reagents have lower nucleophilicity, basicity, and better functional group tolerance compared with Grignard reagents. Moreover, compared with organozinc reagents, organotitanium reagents have higher metal transfer rates.…”

Section: Introducementioning

confidence: 99%

“…Interestingly, although many exciting achievements have been made in nucleophilic addition of organotitanium reagents to carbonyl compounds (Scheme 1a), 29,30 by comparison, much less attention has been devoted to the employment of such reagents in C(sp 2 )–C(sp 2 ) cross-coupling transformations (Scheme 1b). 20–28 Furthermore, there is only one successful example of the employment of such reagents in C(sp 2 )–C(sp 3 ) cross-coupling transformations (Scheme 1c). 21 To the best of our knowledge, this is the first example using organotitanium nucleophiles to generate diarylmethane units by C(sp 2 )–C(sp 3 ) cross-coupling reactions (Scheme 1d).…”

Section: Introducementioning

confidence: 99%

A new protocol for synthesizing diarylmethanes using a benzyltitanium reagent as a nucleophile

Zhang

2022

Journal of Chemical Research

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The first palladium-catalyzed cross-coupling of various substituted benzyltitaniums with aryl triflates is presented for the synthesis of diarylmethanes in yields of up to 94% through highly selective C–O bond functionalization. The benzyltitaniums act as nucleophiles to realize the C(sp2)–C(sp3) cross-coupling with high efficiency in short reaction times. The reactions proceed at 60°C and show excellent functional groups tolerance.

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“…In recent years, the pseudohalides (Organomesylates, nonaflates, tosylates, and triflates) have proved as useful substitutes thereby replacing organic halides in cross-coupling reactions [1,2]. There exists interest among scientists worldwide to study the regiospecific control over multiple competing coupling sites [3].…”

Section: Introductionmentioning

confidence: 99%

Regiospecific substitution of the β-vinylic sp2 carbon of cyclohexenones bearing the α-chloro- and β-tosylate-groups: Single crystal XRD/Hirshfeld surface/in-silico studies of three representative compounds

Chakravart

Suresh

2020

Eur J Chem

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2-Chloro-3-tosyl-5,5-dimethyl-2-cyclohexenone was subjected to a series of regiospecific Suzuki-Miyaura cross-coupling reactions in suspensions of nine different substituted boronic acids, Pd(OAc)2, P(Ph3)3, K3PO4 and 1,4-dioxane solvent, under sealed tube conditions. The regiospecific substitution of the tosyl-group by the aryl group in preference over the chloride- group was observed. A comparison between the bromo- and tosylate group’s reactivities is highlighted. Using the methodology, the products: 2-chloro-3-aryl-5,5-dimethyl-2-cyclohexenones were isolated in greater than 85% yields. Good quality crystals of three representative compounds were obtained by slow evaporation technique and subjected to single crystal XRD studies, Hirshfeld surface analysis, 3-D energy framework, and molecular docking studies. Crystal data for compound 3; C15H17ClO4S: monoclinic, space group P21/c (no. 14), a = 8.8687(3) Å, b = 10.5537(4) Å, c = 16.6862(7) Å, β = 89.807(3)°, V = 1561.78(10) Å3, Z = 4, T = 290 K, μ(MoKα) = 0.390 mm-1, Dcalc = 1.398 g/cm3, 13623 reflections measured (6.716° ≤ 2Θ ≤ 54.962°), 3570 unique (Rint = 0.0467, Rsigma = 0.0512) which were used in all calculations. The final R1 was 0.0452 (I > 2σ(I)) and wR2 was 0.1019 (all data). Crystal data for compound 5e; C20H18O2FCl: monoclinic, space group P21/c (no. 14), a = 6.4900(5) Å, b = 18.6070(13) Å, c = 14.2146(11) Å, β = 102.324(2)°, V = 1677.0(2) Å3, Z = 4, T = 296(2) K, μ(MoKα) = 0.239 mm-1, Dcalc = 1.309 g/cm3, 25575 reflections measured (6.262° ≤ 2Θ ≤ 52.224°), 3283 unique (Rint = 0.0494, Rsigma = 0.0307) which were used in all calculations. The final R1 was 0.0875 (I > 2σ(I)) and wR2 was 0.2056 (all data). Crystal data for compound 5h; C12H13OSCl: triclinic, space group P-1 (no. 2), a = 6.7517(6) Å, b = 8.8376(9) Å, c = 12.6049(12) Å, α = 109.538(3)°, β = 98.597(3)°, γ = 90.417(3)°, V = 699.52(12) Å3, Z = 2, T = 290 K, μ(MoKα) = 0.410 mm-1, Dcalc = 1.376 g/cm3, 28754 reflections measured (6.114° ≤ 2Θ ≤ 59.288°), 3898 unique (Rint = 0.0544, Rsigma = 0.0349) which were used in all calculations. The final R1 was 0.1101 (I > 2σ(I)) and wR2 was 0.2481 (all data).

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Palladium-catalyzed cross-coupling of (hetero)aryl or alkenyl sulfonates with aryl titanium as the multi-functional reagent

Abstract: The first palladium-catalyzed cross-coupling reaction of aryl/heteroaryl and alkenyl mesylates and tosylates with aryl titanium as the multi-functional reagent is reported.

Cited by 18 publications

References 72 publications

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

A new protocol for synthesizing diarylmethanes using a benzyltitanium reagent as a nucleophile

Regiospecific substitution of the β-vinylic sp2 carbon of cyclohexenones bearing the α-chloro- and β-tosylate-groups: Single crystal XRD/Hirshfeld surface/in-silico studies of three representative compounds

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