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[D1]methanol and (R)‐ and (S)‐tributylstannyl[D1]methyl benzoates were Stille‐coupled with bromobenzene and benzoyl chloride in 1,4‐dioxane and toluene using [(Ph3P)4Pd] or [(Ph3P)2PdCl2] either alone or in combination with CuCN as cocatalyst at temperatures up to 80 °C. The products were found to be enantiomerically pure. (R)‐ and (S)‐N‐(tributylstannyl[D1]methyl)phthalimides gave enantiomerically pure products with benzoyl chloride, but with bromobenzene protected phenyl[D1]methylamines gave products of only 52–69 % ee depending on the solvent used. Tributyl(thio[D1]methyl)stannanes could not be Stille‐coupled with benzoyl chloride or with bromobenzene. Similarly, dimethyl phenyl[D1]methylboronate underwent a Suzuki–Miyaura coupling with bromobenzene to give phenyl[D1]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.