EPR evidence for α-triphenylstannylvinyl radicals in the O-directed hydrostannation of dialkylacetylenes with Ph3SnH/cat. Et3B/O2

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.

Automated summary

This study provides definitive EPR evidence for the existence of alpha-triphenylstannylvinyl radicals in the low-temperature free radical hydrostannation reaction, with isotropic hyperfine splitting patterns and spectral simulations confirming the assignments. The measurement of isotopic Sn-119/117 hyperfine coupling constants and a H-1(beta) hyperfine coupling constant further support the identification of the radical.