Achieving Vinylic Selectivity in Mizoroki–Heck Reaction of Cyclic Olefins

Abstract

In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions.

Controlling Olefin Isomerization in the Heck Reaction with Neopentyl Phosphine Ligands

“…5 Cyclic olefins have the added complication of the thermodynamically favored 1-arylcycloalkene product being inaccessible via syn β-hydride elimination after the initial migratory insertion of the olefin into the Pd−Ar bond (Figure 1). 6 Under a large number of conditions, double bond migration is believed to occur via a "chain-walking" mechanism in which the hydridopalladium species does not undergo olefin exchange. 7 As a result, a mixture of allylic and homoallylic products is generally formed with only minor amounts of the vinylic product.…”

Palladium nanoparticles immobilized on amphiphilic and hyperbranched polymer‐functionalized magnetic nanoparticles: An efficient semi‐heterogeneous catalyst for Heck reaction

“…The palladium‐catalysed Heck cross‐coupling reaction between aryl halides and alkenes is a versatile method for carbon–carbon bond formation in synthetic and medicinal chemistry . In this context, various palladium‐based compounds, usually complexes with phosphane ligands, have been utilized for this transformation under homogeneous conditions . Although these catalytic systems exhibit high catalytic activity and selectivity, their separation from the reaction mixture, recovery and reusability are challenging.…”

Selective arylation at the vinylic site of cyclic olefins

“…6 Recently, we conducted DFT calculations on the relative stability of simple arylcyclopentenes and aryl cyclohexenes. 3 The conjugated isomers were more stable than the nonconjugated ones by 4-6 kcal mol À1 due to the conjugation effect.…”

“…1b). 3 Only the dppp ligand gave good yields via a cationic pathway. One drawback was the use of rather expensive aryl triflates.…”