Unusually accelerated silylmethyl transfer from tin in Stille coupling: Implication of coordination-driven transmetalation

The palladium-catalyzed cross-coupling reaction of 2-PYMe2SiCH2SnBu3 with aryl iodide (Ar-I) exclusively produced the 2-PYMe2SiCH2 transferred product 2-PyMe2SiCH2Ar. The relative transfer ability of organic group from tin was found to be 2-PyMe2SiCH2 much greater than Ph > Me > Bu much greater than PhMe2SiCH2, which implies the beneficial pyridyl-to-palladium coordination effect. Thus, the transfer of the silylmethyl group from tin to palladium was remarkably accelerated by simply appending the 2-pyridyl group on silicon. The pyridyl-to-palladium coordination was validated in the palladium(II) complex 2-PyMe2SiCH2PdClPPh3 by H-1 NMR and X-ray crystal structure analysis. The cross-coupling product was used for further transformations. The C-Si oxidation of the cross-coupling product 2-PyMe2SiCH2Ar afforded ArCH2OH in high yield. The fluoride ion-catalyzed 1,2-addition of 2-PYMe2SiCH2Ar to carbonyl compound (RR 'C=O) gave ArCH2C(OH)RR ' in high yield.