On the Configurational Stability of Chiral Heteroatom-Substituted [D1]Methylpalladium Complexes as Intermediates of Stille and Suzuki-Miyaura Cross-Coupling Reactions

Enantiomerically pure (S)-tributylstannyl[D-1]methanol and (R)- and (S)-tributylstannyl[D-1]methyl benzoates were Stille-coupled with bromobenzene and benzoyl chloride in 1,4-dioxane and toluene using [(Ph3P)(4)Pd] or [(Ph3P)(2)PdCl2] either alone or in combination with CuCN as cocatalyst at temperatures up to 80 degrees C. The products were found to be enantiomerically pure. (R)- and (S)-N-(tributylstannyl[D-1]methyl)phthalimides gave enantiomerically pure products with benzoyl chloride, but with bromobenzene protected phenyl[D-1]methylamines gave products of only 52-69% ee depending on the solvent used. Tributyl(thio[D-1]methyl)stannanes could not be Stille-coupled with benzoyl chloride or with bromobenzene. Similarly, dimethyl phenyl[D-1]methylboronate underwent a Suzuki-Miyaura coupling with bromobenzene to give phenyl[D-1]methylsilane with 99% ee. All couplings followed a retentive course and, except in one case, the intermediate [XCHDPdLn] complexes were found to be microscopically configurationally stable.