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 ia 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.
在
三乙胺和
钯络合物(特别是双(
三苯基膦)
钯物种)的存在下,β-
氯-α,β-不饱和酯与内炔进行杂环化反应,生成
2H-吡喃-2-酮。用Pd(PPh3)4处理甲基(Z)-3-
氯-
2-庚烯酸酯,通过氧化加成生成[(Z)-1-丁基-2-甲氧羰基
乙烯基]
氯双(
三苯基膦)
钯,在加入
4-辛炔后得到相应的
2H-吡喃-2-酮。末端
炔烃也能与β-
氯-α,β-不饱和酯反应,但主要产物是β-炔基化的α,β-不饱和酯。