Suzuki Cross-Coupling Reactionof Benzylic Halides with Arylboronic Acids in the Presence of aTetraphosphine/Palladium Catalyst

Abstract

The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane-[PdCl(C₃H₅)]₂ systemcatalyses efficiently the Suzuki cross-coupling reaction of benzylichalides with arylboronic acids. A wide variety of benzylic bromidesor chlorides and functionalised arylboronic acids lead selectivelyto the corresponding diarylmethane adducts in good yields. Furthermore,this catalyst can be used at low loading in many cases.

catalysis - palladium - tetraphosphine - arylboronicacids - benzylic halides

References

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<A NAME="RG11903ST-10">10</A>

As a typical experiment, the reactionof 4-cyanobenzyl bromide (1.00 g, 5.1 mmol), 4-methoxyphenylboronicacid (1.55 g, 10.2 mmol) and K₂CO₃ (1.4 g,10.2 mmol) at 130 °C during 20 h in anhydrous xylene (10mL) in the presence of cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane-[PdCl(C₃H₅)]₂ complex(0.0051 mmol) under argon affords the corresponding adduct afterextraction with ether, evaporation and filtration on silica gel(dichloro-methane) in 81% (0.92 g) isolated yield. 4-(4-Methoxy-phenylmethyl)benzonitrile: ¹HNMR (300 MHz, CDCl₃): δ = 7.59(d, J = 8.3 Hz, 2 H, Ar), 7.29(d, J = 8.3 Hz, 2 H, Ar), 7.11(d, J = 8.6 Hz, 2 H, Ar), 6.88(d, J = 8.6 Hz, 2 H, Ar), 4.00(s, 2 H, CH2), 3.82 (s, 3 H, OMe).

<A NAME="RG11903ST-11">11</A>

Analytical data of selected products:Table [1] (entry11): δ = 7.71 (s, 1 H, Ar), 7.62 (s, 2 H, Ar),7.35-7.10 (m, 5 H, Ph), 4.09 (s, 2 H, CH₂);Table [1] (entry16): δ = 7.30-7.00 (m, 5 H, Ph), 7.08(m, 1 H, Ar), 6.80 (m, 2 H, Ar), 3.94 (s, 2 H, CH₂); C₁₃H₁₀F₂ (204.2):calcd. C 76.46, H 4.94; found C 76.62, H 4.71; MS (EI, 70 eV) m/z (%): 204(100) [M⁺];Table [1] (entry 18): δ = 7.25-7.10(m, 3 H, Ph), 7.01 (d, J = 7.2Hz, 2 H, Ph), 6.89 (s, 2 H, Ar), 4.02 (s, 2 H, CH₂),2.29 (s, 3 H, Me), 2.20 (s, 6 H, Me); Table [1] (entry 25): δ = 9.96(s, 1 H, CHO), 8.14 (d, J = 8.7Hz, 2 H, Ar), 7.85-7.35 (m, 4 H, Ar), 7.33 (d, J = 8.7 Hz, 2 H, Ar), 4.14 (s,2 H, CH₂); C₁₄H₁₁NO₃ (214.2): calcd.C 69.70, H 4.60; found C 70.01, H 4.72; MS (EI, 70 eV) m/z (%): 241(100) [M⁺];Table [1] (entry26): δ = 8.12 (d, J = 8.7Hz, 2 H, Ar), 7.34 (d, J = 8.7Hz, 2 H, Ar), 7.11 (m, 1 H, Ar), 6.82 (m, 2 H, Ar), 4.03 (s, 2 H,CH₂); C₁₃H₉F₂NO₂ (249.2):calcd. C 62.65, H 3.64; found C 62.52, H 3.74; MS (EI, 70 eV) m/z (%): 249(100) [M⁺];Table [1] (entry28): δ = 8.08 (d, J = 8.6Hz, 2 H, Ar), 7.32 (d, J = 8.6Hz, 2 H, Ar), 7.25 (m, 1 H, Ar), 7.09 (d, J = 7.3Hz, 1 H, Ar), 6.89 (m, 2 H, Ar), 4.03 (s, 2 H, CH₂),3.77 (s, 3 H, Me); Table [1] (entry 35): δ = 7.60(d, J = 7.8 Hz, 2 H, Ar), 7.29(d, J = 7.8 Hz, 2 H, Ar), 7.10(d, J = 8.5 Hz, 2 H, Ar), 6.88(d, J = 8.5 Hz, 2 H, Ar), 4.00(s, 2 H, CH2), 3.82 (s, 3 H, Me); Table [1] (entry 39): δ = 7.53(d, J = 7.3 Hz, 2 H, Ar), 7.28(d, J = 7.3 Hz, 2 H, Ar), 7.23(m, 1 H, Ar), 7.07 (d, J = 7.4Hz, 1 H, Ar), 6.87 (m, 2 H, Ar), 4.00 (s, 2 H, CH₂),3.78 (s, 3 H, Me); Table [1] (entry43): δ = 7.83 (m, 1 H, Ar), 7.79 (s, 1 H, Ar),7.67 (d, J = 7.6 Hz, 1 H, Ar),7.39 (t, J = 7.6 Hz, 1 H, Ar),7.30 (m, 3 H, Ar), 7.20 (d, J = 7.6Hz, 1 H, Ar), 4.31 (s, 2 H, CH2), 3.86 (s, 3 H, Me), 2.46 (s, 3H, Me); C₁₇H₁₆O₃ (268.3): calcd.C 76.10, H 6.01; found C 75.87, H 6.21; MS (EI, 70 eV); m/z (%): 268(36) [M⁺].