The positional isomerization of alkenes is a well-known process mediated by various transition metal complexes. Nevertheless, systems which isomerize alkenes with complete regio- and stereoselectivity are rare. Most reported cases proceed through 1,3-hydrogen shift (allyl) mechanisms, rather than the generally more common 1,2-hydride shift (alkyl) mechanism, provoking consideration of the unique opportunities the former mechanism offers. Accordingly, the first part of this Perspective article will cover stereoselective alkene isomerization systems operating through 1,3-hydrogen shift mechanisms, with an emphasis on the origin of stereocontrol. Next, examples where these systems are employed in tandem with subsequent transformations to rapidly form complex molecular architecture will be discussed, illustrating the potential of alkene isomerization as a strategic tool in stereoselective synthesis.

An in situ generated cationic Ir‐catalyst isomerizes simple allylic silyl ethers into valuable, fully substituted aldehyde‐derived silyl enol ethers. Importantly, by judicious choice of substrate, either of the two possible stereoisomers of a given enolate derivative is accessible with complete stereoselectivity. One‐pot isomerization‐aldol and isomerization‐allylation processes illustrate the synthetic utility of this method.

The Cope rearrangement of 2,3-divinyloxiranes, a rare example of epoxide C-C bond cleavage, results in 4,5-dihydrooxepines which are amenable to hydrolysis, furnishing 1,6-dicarbonyl compounds containing two contiguous stereocenters at the 3- and 4- positions. We employ...

Facile and modular access to stereodefined disubstituted aldehyde-derived silyl enol ethers allowed their successful application in a stereoselective aldol reaction affording the products with excellent yields and diastereomeric ratios. The counter-intuitive stereochemical behavior of this Mukaiyama-aldol reaction is accounted for by a non-classical open transition state.Scheme 1. Stereoselective preparation of disubstituted enolate derivatives of aldehydes.