Palladium‐catalyzed vinylation of cyclohexenes using a directing‐group strategy

Palladium‐promoted vinylation of cyclohexenes via employment of a directing‐group strategy to yield the coupled vinyl cyclohexenes with excellent regio‐ and stereoselectivity was studied. Typically, reaction of 2‐(cyclohex‐2‐en‐1‐yl)‐N‐tosylacetamide (1a) with (Z)‐styryl bromides (2) gave cis‐2‐[(E)‐styryl]cyclopent‐3‐en‐1‐yl‐N‐tosylacetamides in good to excellent yields. It is noticed that (Z)‐styryl moiety was inverted into (E)‐form in products. Unfortunately, (E)‐styryl bromide substrates were not suitable for this reaction under the condition investigated. Further studies on norbornene system, we found that palladium‐catalyzed reaction of endo‐N‐tosylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxamide (6) with styryl bromides gave the Aza‐Heck type products. Using a directing‐group strategy, palladium‐catalyzed vinylation of cyclohexene was studied. Reaction of (Z)‐styryl bromides with 2‐(cyclohex‐2‐en‐1‐yl)‐N‐tosylacetamide (1a) gave 2‐[cis‐2‐(E)‐styrylcyclohex‐3‐en‐1‐yl]‐N‐tosylacetamides in good yields. It is noticed that the stereochemistry of styryl group was inverted in this reaction.