Microwave-Promoted Palladium(II)-Catalyzed C-P Bond Formation by Using Arylboronic Acids or Aryltrifluoroborates

The first Pd-II-catalyzed P arylation has been performed by using palladium acetate, the rigid bidentate ligand dmphen (dmphen=2,9-dimethyl-1,10-phenanthroline), and without the addition of base or acid. Couplings of arylboronic acids or aryl trifluoroborates with H-phosphonate dialkyl esters were conducted in 30 min with controlled microwave (MW) heating under non-inert conditions. Aryl phosphites were also synthesized at room temperature with atmospheric air as the sole reoxidant. The arylated phosphonates were isolated in 44-90% yields. The excellent chemoselectivity of the method was illustrated in the synthesis of a Mycobacterium tuberculosis glutamine synthetase (MTB-GS) inhibitor. Online ESIMS was used to detect cationic palladium species in ongoing reactions directly, and a catalytic cycle has been proposed based on these results.