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

Heteroannulation of beta -chloro-alpha,beta -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 beta -chloro-alpha,beta -unsaturated esters, but the major products were beta -alkynylated alpha,beta -unsaturated esters.