Water soluble phosphines: Part XV. Syntheses of multiply functionalized and chiral phosphine ligands by Pd-catalyzed PC and CC coupling reactions

Phosphine ligands containing mono- and multiply substituted aromatic substituents (1–13, 19a and 19b) are accessible in high yields by palladium-catalyzed PC coupling reactions between primary, secondary or disecondary phosphines and iodo- or bromoaromatic compounds. The reaction is of broad applicability and compatible with electron donor or electron acceptor substituents in ortho, meta or para position to the halogen in the aromatic ring systems. It may be performed in protic and aprotic solvents. The chiral spirocyclic boronato complex 15a is formed upon reaction of 3 with boric acid, while with benzeneboronic acid 15c with a peripheral Lewis acid group is obtained. The Pd-mediated PC coupling reaction of primary phosphines proceeds stepwise, tailor-made chiral secondary (16) and tertiary phosphines (17) being formed in high yields. Through combination with Suzuki-type CC coupling reactions, the scope of Pd-catalyzed PC coupling may be extended further, with novel ligands (20a, 20b, 21a, 21b) with biphenylyl substituents being accessible. The X-ray structures of the salicylic acid derivative 3 (space group ) and of ortho-iso-propylphenyl-diphenylphosphine 6 (space group Pbca) have been determined.