Suzuki-Miyaura and related cross-couplings in aqueous solvents catalyzed by di(2-pyridyl)methylamine-palladium dichloride complexes

Article abstract of DOI:10.1002/adsc.200404195

Di(2-pyridyl)methylamine-based palladium dichloride complexes 4 are versatile catalysts for different types of cross-coupling reactions in water or aqueous solvents under aerobic conditions. The Suzuki-Miyaura reaction of arylboronic acids can be performed with bromoarenes under water reflux using K₂CO₃ as base or at room temperature or 60°C in aqueous methanol using KOH as base. For aryl chlorides the corresponding cross-couplings with arylboronic acids can be carried out in refluxing water with K₂CO₃ as base and TBAB as additive to provide biaryls and heterobiaryls. Arylboronic acids react with benzylic chlorides and allylic substrates such as chlorides, acetates or carbonates also in refluxing water with K₂CO₃ as base or at room temperature in aqueous acetone and KOH as base, to give diarylmethanes and arylpropenes. Trimethylboroxine and alkylboronic acids are coupled with bromo- and chloroarenes under water at reflux with K₂CO₃ as base and TBAB as additive to furnish methyl- and butylarenes. These cross-couplings have also been performed in shorter times under microwave irradiation. Several important intermediates such as, 4′-methylbiphenyl-2-carbonitrile, 4-biphenylacetic acid, 3-(3-methylphenyl)benzoic acid, 4,5-diphenyl-2-methyl- 3(2H)pyridazinone and 2-(4′-fluorobenzyl)thiophene have been prepared under aqueous and aerobic conditions in good yields.