Palladium-Catalyzed Heck Alkynylation of Benzyl Chlorides

Abstract

An efficient and general protocol for the palladium-catalyzed Heck alkynylation of benzyl chlorides was developed. A ­catalyst system comprised of PdCl₂(CH₃CN)₂ and 2-dicyclohexyl­phosphino-2′,4′,6′-triisopropylbiphenyl (XPhos), with Cs₂CO₃ as the base, efficiently couples a wide range of functionalized terminal alkynes and substituted benzyl chlorides at 65 °C. We have also demonstrated that the corresponding aryl allene product can be ­selected for using an excess amount of base and higher reaction temperatures (80 °C) in a one-pot procedure.

Key words

palladium - alkynes - Heck alkynylation - benzyl chlorides - allene

References and Notes

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13

Reaction of (1-chloroethyl)benzene and 1-decyne resulted in a reproducible yield of 54%; however, the product was unstable and decomposed rapidly.