Epr Evidence For Alpha-Triphenylstannylvinyl Radicals In The O-Directed Hydrostannation Of Dialkylacetylenes With Ph3snh/Cat. Et3b/O-2

Here we provide definitive EPR evidence for the existence of alpha-triphenylstannylvinyl radicals in the low temperature O-directed free radical hydrostannation of dialkyl propargylic alcohols with Ph3SnH/cat. Et3B and O-2 in PhMe. Isotropic hyperfine splitting patterns and spectral simulations confirm the assignments made. In the case of the alpha-triphenylstannylvinyl radical (Z)-2, an isotopic Sn-119/117 hyperfine coupling constant of 9.5 mT (95 G) was measured along with a H-1(beta) hyperfine coupling constant of 1.1 mT.