Hydrostannation of 1,1-bis(trimethylstannyl)ethylene and some related olefins: First steps toward constructing a karplus-type curve for 3J(Sn-Sn)

Article abstract of DOI:10.1021/om00125a015

Four trimethylstannyl-substituted alkenes, Me₃SnCR=CH₂ (R = Ph, t-Bu, Me₃Si, Me₃Sn), were hydrostannated by trimethyltin hydride. Though all four olefins reacted, that with R = t-Bu was consumed only very slowly. The major product was, as expected, the 1,2-distannylalkane RCHSnMe₃CH₂SnMe₃; however, for R = Me₃Sn 40% of the regioisomer (Me₃Sn)₂CRCH₃ was obtained compared with at most 5% in the other cases. On the basis of NMR data (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn) for distannylalkanes and for Me₃SnCH₂CH₂SiMe₃ the preferred rotamers in solution (CDCl₃) at room temperature have been determined. The value of ³J(Sn-Sn) corresponding to a dihedral angle of 180° is ca. 1100 Hz, while an angle of 90° apparently corresponds to a value near zero: values of this magnitude are shown by allene-hexamethylditin adducts. First results on bromodemethylated derivatives show that the effect of increasing the electronegativity of the tin moiety is not straightforward.