| 摘要 |
4- beta , beta -dichlorovinyl (or dibromovinyl)-3,3-dimethylbutyrolactones are prepared from 1,1-dichloro (or dibromo)-4-methylpenta-1,3-diene by reacting with an acid of formula CH2R.CO2H in presence of a salt of a metal in one of its higher valency states, especially manganese (III), cerium (IV), or vanadium (V). Higher yields are obtained in the presence of the anhydride of the acid and of the sodium or potassium salt of the acid. Treatment of the lactones with an inorganic acid halide opens the lactone ring with formation of the corresponding 4-haloacid halide, which with alcohols affords the corresponding 4-haloacid ester, cyclised by bases to a 3- beta , beta -dichloro (or dibromo)vinyl-2,2-dimethylcyclopropanecarboxylic ester, intermediate for insecticides such as the m-phenoxybenzyl ester. |
