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 regioand 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.

Automated summary

The palladium-promoted vinylation of cyclohexenes using a directing group strategy resulted in coupled vinyl cyclohexenes with excellent regio- and stereoselectivity. Reaction of 2-(cyclohex-2-en-1-yl)-N-tosylacetamide (1a) with (Z)-styryl bromides (2) produced cis-2-[(E)-styryl]cyclopent-3-en-1-yl-N-tosylacetamides in good to excellent yields, with the (Z)-styryl moiety inverted into (E)-form in the products. However, (E)-styryl bromide substrates were not suitable for this reaction. Further studies on norbornene system showed that the palladium-catalyzed reaction of endo-N-tosylbicyclo[2.2.1]hept-5-ene-2-carboxamide (6) with styryl bromides resulted in Aza-Heck type products.