Mislow-Evans sulfoxide rearrangement

During the final stages of the total synthesis of (-)-subergorgic acid by L.A. Paquette and co-workers, the transposition of a tricyclic enone was needed. The enone was exposed to the Luche conditions and an 85 15 mixture of diastereomers was obtained. In order to achieve this level of diastereoselectivity, the reaction temperature had to be lowered to -50 °C instead of the usual 0 °C. The major product was formed via the exo attack of the carbonyl group by the hydride. The allylic alcohol was later converted to the corresponding sulfoxide followed by a Mislow-Evans rearrangement to the isomeric allylic alcohol. 

The first asymmetric total synthesis of the macrocyclic lactone metabolite (+)-pyrenolide D was accomplished in the laboratory of D.Y. Gin. The natural product has a densely functionalized polycyclic structure and its absolute configuration had to be established. The key step of the synthesis was a stereoselective oxidative ring-contraction of a 6-deoxy-D-gulal, which was prepared from anomeric allylic sulfoxide via the Mislow-Evans rearrangement. 

Masaki, Y., Sakuma, K., Kaji, K. Facile synthesis of (E)-allylic alcohols by acid-catalyzed modification of the Mislow-Evans rearrangement of allylic sulfoxides. Chem. Pharm. Bull. 1985, 33, 2531-2534. 

Jones-Hertzog, D. K., Jorgensen, W. L. Elucidation of Transition Structures and Solvent Effects for the Mislow-Evans Rearrangement of Allylic Sulfoxides. J. Am. Chem. Soc. 1995, 117, 9077-9078. 

The sulfoxide-sulfenate ester rearrangement (Mislow/Evans rearrangement) where the X-Y fragment is a sulfoxide. 

Scheme 18.5 Under non-polar conditions at least part of sulfoxide interconversion is due to Mislow-Evans rearrangement. ...

Scheme 18.S2 Tandem Claisen-type r3.31/Mislow-Evans rearrangement of sulfoxide-substituted propargyl ketene acetals.—...

Scheme 18.SB Condensation of a chiral bis-sulfoxide with cyclopentanone followed by a double Mislow-Evans rearrangement and ketones.—...

Scheme 18.60 Isomerization/Mislow-Evans rearrangement of vinyl sulfoxides generated by addition of enolates to alkynyl sulfoxides.—...

Finally, calculations show that the transition state for the Mislow-Evans rearrangement is sulfenate-like. This was consistent with the fact that the reaction rate in the sulfoxide-to-sulfenate direction slowed in solvents of increasing polarity, presumably because a polar solvent stabilizes the sulfoxide starting material more than the sulfenate-like transition state. Indeed, Jorgensen s calculations indicated that the sulfoxide forms a stronger hydrogen bond to water ( 10 kcal/mol) than does the sulfenate ( 6 kcal/mol). Nevertheless, in a calculation that included methanol solvation, the Mislow-Evans transition state maintained a sulfoxide-like hydrogen bond to methanol. 

In general, diastereoface selectivity in the allylic sulfoxide-to-sulfenate Mislow-Evans rearrangement is possible in cases such as 74 (Scheme 18.19). having the sulfoxide attached to a chiral center, or with substrates of type 75, where the alkene faces are rendered diastereotopic by a structural element distal from the allyl sulfoxide. These diastereoselective... 

Scheme 18.27 Only one sulfoxide diastereomer undergoes Mislow-Evans rearrangement in modular approach to tetracycline analogue synthesis. ...

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