A new palladium-dipyridylmethylamine complex is an excellent catalyst for C-C bond-forming processes such as the Heck, Suzuki, and Sonogashira reactions in organic and aqueous solvents under homogeneous conditions. [reaction: see text]

No abstract

The (dipyridin‐2‐ylmethyl)amine‐derived palladium chloride complex 1 and PdCl2 are efficient catalysts for cross‐coupling reactions between terminal alkynes and aryl iodides or bromides under modified Sonogashira–Cassar–Heck conditions. The alkynylation can be performed under copper‐free conditions in water at reflux or at room temperature under air with pyrrolidine as base and tetra‐n‐butylammonium bromide (TBAB) as additive, with TONs of up to 7 × 104 and TOFs(h–1) of up to 6666. Terminal alkynes can be arylated in NMP as well under copper‐ and amine‐free conditions at 110 °C or room temperature, with tetra‐n‐butylammonium acetate (TBAA) acting as base with TONs up to 2 × 105 and TOFs (h–1) up to 66 666. In general, complex 1 displays a slightly higher efficiency than PdCl2 as catalyst and maintains the same activity after five consecutive runs. Alternatively, these alkynylation processes can be carried out under microwave heating conditions. The homocoupling of terminal alkynes to the corresponding 1,3‐diynes proceeds under phosphane‐free conditions with the (dipyridin‐2‐ylmethyl)amine‐derived palladium chloride complex 1 or with PdCl2 as catalysts and with CuI as cocatalyst in NMP with use of either TBAA or pyrrolidine as bases. This Glaser‐type reaction can be performed at 110 °C or at room temp. in the presence of air without the use of a reoxidant. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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 K 2 CO 3 as base or at room temperature or 60 8C 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 K 2 CO 3 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 K 2 CO 3 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 K 2 CO 3 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.