An Efficient Catalyst System for Palladium-Catalyzed Borylation of Aryl Halides with Pinacolborane

Abstract

The combination of Pd(dba)₂ and bis(2-di-tert-butyl­phosphinophenyl)ether has proven to be efficient for the cross-­coupling of pinacolborane with aryl bromides and chlorides. The substrate scope is broad and the present system enables the synthesis of ortho-, meta-, and para-substituted electron-rich and -deficient arylboronates.

Key words

boron - palladium - catalysis - cross-coupling - ligands

References and Notes

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• 11 t-Bu-DPEphos (L8) was prepared from diphenylether and (t-Bu)₂PCl by a similar procedure for the preparation of DPEphos. See: Kranenburg M. Vanderburgt YEM. Kamer PCJ. van Leeuwen PWNM. Goubitz K. Fraanje J. Organometallics  1995,  14:  3081 
• 12 For a review of the palladium-catalyzed couplings of aryl chlorides, see: Littke AF. Fu GC. Angew. Chem. Int. Ed.  2002,  41:  4176 

13

Compound 3d: ¹H NMR (CDCl₃): δ = 1.35 (s, 12 H), 7.47 (t, J = 7.9 Hz, 1 H), 7.73 (d, J = 7.9 Hz, 1 H), 8.01 (d, J = 7.9 Hz, 1 H), 8.09 (s, 1 H). ¹³C NMR (CDCl₃): δ = 24.81, 84.46, 111.95, 118.79, 128.36, 134.37, 138.37, 138.73. HRMS (EI): m/z calcd for C₁₃H₁₆BNO₂ [M⁺]: 229.1274; found: 229.1312. IR (KBr): 2228 cm^-1.
Compound 3f: ¹H NMR (CDCl₃): δ = 1.36 (s, 12 H), 7.61 (d, J = 7.9 Hz, 2 H), 7.92 (d, J = 7.9 Hz, 2 H). ¹³C NMR (CDCl₃): δ = 24.98, 84.25, 124.29 (q, J = 4 Hz), 124.13 (q, J = 272 Hz), 132.80 (q, J = 32 Hz), 135.21. HRMS (EI): m/z calcd for C₁₃H₁₆BF₃O₂ [M⁺]: 272.1196; found: 272.1229.
Compound 3g: ¹H NMR (CDCl₃): δ = 1.21 (s, 12 H), 7.30-7.50 (m, 8 H), 7.71 (d, J = 7.8 Hz, 1 H). ¹³C NMR (CDCl₃): δ = 24.55, 83.69, 126.23, 126.79, 127.74, 128.92, 129.08, 130.03, 134.40, 143.19, 147.46. HRMS (EI): m/z calcd for C₁₈H₂₁BO₂ [M⁺]: 280.1635; found: 280.1629.
Compound 3i: ¹H NMR (CDCl₃): δ = 1.21 (d, J = 6.7 Hz, 6 H), 1.25 (d, J = 6.7 Hz, 12 H), 1.37 (s, 12 H), 2.84 (sept, J = 6.7 Hz, 1 H), 2.98 (sept, J = 6.7 Hz, 2 H), 6.93 (s, 2 H). ¹³C NMR (CDCl₃): δ = 24.01, 24.55, 24.98, 34.00, 34.49, 83.61, 119.63, 149.72, 151.86. HRMS (EI): m/z calcd for C₂₁H₃₅BO₂ [M⁺]: 330.2730; found: 330.2773.
Compound 3j: ¹H NMR (CDCl₃): δ = 1.32 (s, 12 H), 2.86 (d, J = 5.5 Hz, 3 H), 3.92 (br s, 1 H), 6.58 (d, J = 8.5 Hz, 2 H), 7.65 (d, J = 8.5 Hz, 2 H). ¹³C NMR (CDCl₃): δ = 24.79, 30.22, 83.13, 111.38, 136.26, 151.74. HRMS (EI): m/z calcd for C₁₃H₂₀BNO₂ [M⁺]: 233.1587; found: 233.1611.
IR (KBr): 3425, 3401, 3375 cm^-1.