Preparation of Triethylammonium Tetra-Arylborates (TEATABs): Coupling Partners for the Suzuki Reaction

Abstract

Six triethylammonium tetra-arylborates (TEATABs) were synthesized via a convenient reproducible procedure and characterized by spectroscopic methods (¹H, ¹³C, ¹¹B NMR and electrospray ionization–high-resolution mass spectrometry). The compounds could be stored at ambient temperature and were useful as reactants in the Suzuki reaction in aqueous conditions when using commercially available catalysts.

Keywords:

• Carboxybiphenyls
• organoboron reagents
• Suzuki reaction
• tetra-arylborates

ACKNOWLEDGMENTS

This work was supported by the National Graduate School of Organic Chemistry and Chemical Biology. We thank also the Academy of Finland for financial support (No. 110043) and Markku Reunanen (Åbo Akademi, Finland) for mass spectral measurements.

Notes

^a Isolated yield after recrystallization. No attempts was made to find the best recrystallization solvents.

^b Preparation started from commercially available Ph₄BNa, and only cation exchange was used.

^a Reaction conditions: tetra-arylborate (0.27 mmol), 4-iodonitrobenzene (1 mmol), Pd(OAc)₂ (1 mol%), Na₂CO₃ (1 mmol), and solvent (5.3 ml).

^b 10 mol% of catalyst was used.

^a Reaction conditions: TEATAB 1 (0.068 mmol), 4-bromobenzoic acid (0.25 mmol), base (0.5 mmol), and solvent (1 ml).

^b Same results were also obtained when 5 mol% catalyst was used.

^a Reaction conditions: tetra-arylborate (0.068 mmol), 4-bromobenzoic acid (0.25 mmol), base (0.5 mmol), and EtOH/H₂O (1 ml).

^a Reaction conditions: TEATAB (0.18 mmol), 4-bromobenzoic acid (0.60 mmol), Pd(PPh₃)₄ (0.030 mmol, 5 mol%), Na₂CO₃(aq) (1.19 mmol), and EtOH/H₂O (1:1) (0.5 ml) at 85 °C, 2 h.

^b Reaction time was 18 h.

^c NMR analysis indicated that traces of desired compound were formed as well as many side products. Isolation was not attempted.

^d After 48 h, the product was not observed.