(Z)-(E) Interconversion of Olefins by the Addition-Elimination Sequence of the (TMS)3Si(.) Radical

Article abstract of DOI:10.1021/jo00117a038

Tris(trimethylsilyl) radical is effective inisomerizing either acyclic or cyclic olefins by an addition-elimination sequence.The E/Z ratio after equilibration generally reflects the thermodynamic stability of (Z)- and (E)-alkenes.It has been shown for (E)- and (Z)-hexen-1-ol that equilibration (Z/E = 18/82) is reached with the (TMS)3Si(.) radical in 10 h at 80 deg C, whereas with PhS(.) and Bu3Sn(.) radicals the same isomeric composition is reached in 1 and 4 h, respectively.In cyclic systems like (Z)-cyclododecene the ratio of Z/E = 46/54 is reached in 8 h, while with PhS(.) and Bu3Sn(.) it is much slower.An explanation of this phenomenon has been advanced.Additional information on the impact of this addition-elimination methodology in organic synthesis is given.