PROBLEM TO BE SOLVED: To obtain the subject new compound useful as a raw material for synthesizing medicaments/agrochemicals by synthesis using a readily available halogeno alkenoic ester as the starting material.
SOLUTION: This new compound is an α-pyrone compound of formula I (R1 is a univalent hydrocarbon; X is a halogen; R3 and R4 are each a univalent hydrocarbon, heterocyclic aromatic ring or silyl), e.g. 4-butyl-5,6-dipropyl-2H- pyran-2-one. The compound of formula I is obtained, for example, by reaction of a 3-halogeno-2-alkenoic ester of formula II (R2 is a univalent hydrocarbon; X is a halogen, pref. Cl) with an acetylene compound of formula III in the presence of a group X metal-contg. catalyst, wherein the group X metal in the catalyst is pref. palladium, and the above reaction is carried out pref. in the presence of an organic base (pref. a trialkylamine), thereby efficiently and safety affording the objective compound.