Palladium-catalysed annulation of β-chloro-α,β-unsaturated esters with internal alkynes leading to 2H-pyran-2-ones

Abstract

Heteroannulation of β-chloro-α,β-unsaturated esters with internal alkynes proceeded in the presence of triethylamine and palladium complexes, bis(triphenylphosphine)palladium species in particular, to afford to 2H-pyran-2-ones. Treatment of methyl (Z)-3-chloro-2-heptenoate with Pd(PPh3)4 generates [(Z)-1-butyl-2-methoxycarbonylethenyl]chlorobis(triphenylphosphine)palladium via oxidative addition, which gives the corresponding 2H-pyran-2-one upon addition of 4-octyne. Terminal alkynes also reacted with β-chloro-α,β-unsaturated esters, but the major products were β-alkynylated α,β-unsaturated esters.