3,4-Di:hydro-alpha-pyrone prodn. - from di:hydro-5-bromo:methyl-3m-furanone, useful as intermediate for pharmaceuticals, plant protection agents and dyes

摘要

The patent DE2952068 describes the prepn. of alpha-pyrone cpds. (I) (R1, R2 and R3 are H or 1-10C alkyl, at least one being alkyl) by reacting a 3- and/or 4-substd. dihydro-5-bromomethyl-3H-furanone with a base to give the corresp. 4,5-epoxypentanoic acid deriv. This is treated with acid to form a substd. dihydro-5-hydroxy-methyl-3H-furanone which is converted to (I) by heating at 200-500 deg.C. This invention describes prodn. of (I) in which R1, R2 and R3 are all H (cpd. (Ia) by a similar process using an unsubstd. dihydro-5 bromo-methyl-3H-furanone (II) as starting material. (Ia) is an intermediate for plant-protecting agents, pharmaceuticals and dyes.