Kinetics, thermodynamics and stereochemistry of the allyl sulfoxide-sulfenate and selenoxide-selenenate [2,3] sigmatropic rearrangements

Abstract

The thermodynamic relationships between the I1 and IV oxidation states (eq 1, Y = S, Se) play a dominant role in determining

Reaction of selenium and tellurium halides with propargyl alcohols. The regio‐ and stereoselectivity of addition to the triple bond

“…2,5‐Dimethyl‐3‐hexyne‐2,5‐diol reacts with sulfur dichloride under the same reaction conditions in a similar manner 42. Similar saturated γ‐selentines have been prepared recently by Back,43 by a procedure involving the [2,3]sigmatropic rearrangement of allylic selenoxide 44, 45. They were found to have significant biological activity related to oxidative stress 46…”

Organoselenium Chemistry in Stereoselective Reactions

“…[55] The rearrangement of the allylic selenoxides proceeds much faster than that of the corresponding sulfoxides, and detailed kinetic and thermodynamic studies have been carried out. [60] The stereoselective version of these rearrangements can again be performed either by enantioselective oxidation of achiral allylic selenides or by diastereoselective oxidation of allylic selenides bearing a chiral substituent. Several stereoselective syntheses of allylic alcohols have been reported recently.…”

[2,3]‐sigmatropic rearrangements of hydrogen and alkyl 3‐propenyl sulfoxides: A computational study

“…It has been suggested that the thermolysis of sulfenates is the reverse reaction of the photolysis of sulfoxides 7. Computational studies supporting the [2,3]‐sigmatropic shift mechanism 13–15 and the radical pair mechanism 5, 8c have appeared. The thermal racemization of aryl substituted allylic sulfoxides, which can involve achiral sulfenate ester intermediates, may proceed via a [2,3]‐sigmatropic rearrangement, a radical pair mechanism, or pyramidal inversion 1, 2.…”

“…Although it has been generally accepted that the mild thermal interconversion of allylic sulfoxides to allylic sulfenates proceeds via the ubiquitous [2,3]‐sigmatropic rearrangement 1, 2, 5, more recent studies on the photochemical and thermal sulfenate–sulfoxide rearrangements suggest that the reactions may also proceed via a radical pair mechanism 6–9. For example, ultraviolet (UV) light induces a homolytic α‐cleavage of the CS bond of cinnamyl 4‐nitrobenzenesulfenate; the resulting transient resonance stabilized sulfinyl radical 8c, 11, 12 and resonance stabilized allyl radical combine in the solvent cage to afford the corresponding sulfoxide.…”

“…Although the kinetics, stereochemistry, and thermodynamics of allyl aryl sulfoxide–allyl aryl sulfenate interconversions have been studied 1, 2, 5, there is a paucity of computational and experimental studies on [2,3]‐sigmatropic rearrangements of simple allyl alkyl sulfoxides. In addition, there is a lack of consistency among the few available computational studies on the mechanism of the sulfoxide–sulfenate 13–15 and sulfenate–sulfoxide rearrangements 6, 8c.…”