On the [2,3]-sigmatropic rearrangements of sulfenate esters derived from alkenynols: synthesis of vinylallene and vinylacetylene sulfoxides.

A Pericyclic Cascade to the Stereocontrolled Synthesis of 9-cis-Retinoids

“…Among the thermal noncatalyzed mechanisms known to produce double bond isomerization, the first to be considered was a reversible allylic rearrangement of the primary product, i.e., sulfenate ester to allyl sulfoxide, since [2,3] shifts of that nature generally have low activation energies . Indeed, Okamura and van Krutchen had previously isolated the allyl sulfoxide 27 upon treatment of the simple alkenynols 25 (R 1 = R 2 = R 3 = R 4 = H) with PhSCl . Interestingly, although the geometry of the double bond in the primary product 27 is E , heating a benzene solution of ( E )- 27 (R 1 = R 2 = R 3 = R 4 = H) afforded a mixture of ( E )- 27 , ( Z )- 27 and vinylallene sulfoxide 28 .…”

From Allylic Sulfoxides to Allylic Sulfenates: Fifty Years of a Never-Ending [2,3]-Sigmatropic Rearrangement

“…Within this context, Van Kruchten and Okamura designed an interesting study on the chemoselectivity of alkenynols 462 , precursors of alkenyne sulfenates 463 , which underwent sulfenate–sulfoxide rearrangement at −78 °C across the double bond to give 464 or across the triple bond to provide 465 , depending on the substitution of the starting enynol (Scheme ). Further heating in benzene of allylic sulfoxide 464 (R 1 = R 2 = R 3 = H) demonstrated the reversibility of the rearrangement, yielding a 1:20 mixture of allylic sulfoxides ( E / Z ) 464 and allene sulfoxide 465 . Accordingly, 464 formed under kinetic control, and allenyl sulfoxide 465 formed under thermodynamic control.…”