A method for the preparation of certain difluoromethoxyaromatic compounds useful as intermediates in the preparation of pyrethroid pesticides. The method comprises alkylating a p-substituted phenol with excess chlorodifluoromethane at atmospheric or superatmospheric pressure in the presence of a base, water, and an inert water miscible organic solvent or solvent mixture, alone or in the presence of benzyltriethylammonium chloride, to yield a difluoromethoxyaromatic compound; and, when said difluoroaro- matic compound contains a side chain acetic acid ester having a chiral center, optionally, (a) hydrolyzing said ester to the corresponding racemic acid and thereafter resolving said racemic acid into its dextrorotatory (+) acid and levorotatory (-) acid isomers and recovering said (+) acid isomer, or (b) hydrolyzing said ester to the corresponding racemic acid, resolving said racemic acid into its d(+) acid and I(-) acid isomers, recovering said d(+) acid for use in the preparation of pyrethroid product, esterifying the above-said I(-) acid from the resolution, racemizing the thus-prepared 1(-) ester from said esterification, and hydrolyzing the same to obtain racemic acid which is recycled for admixture with the fresh racemic acid and subsequent resolution.
一种制备某些用作拟
除虫菊酯农药制备中间体的二
氟甲氧基芳香族化合物的方法。该方法包括在常压或超常压下,在碱、
水和惰性
水可混溶有机溶剂或溶剂混合物存在下,单独或在
苄基三乙基氯化铵存在下,用过量的
二氟甲烷将对取代
苯酚烷基化,生成二
氟甲氧基芳香族化合物;当所述二
氟芳香族化合物含有具有手性中心的侧链
乙酸酯时,可选择 (a) 将所述酯
水解为相应的外消旋酸,然后将所述外消旋酸分解为右旋 (+) 酸异构体和左旋 (-) 酸异构体,并回收所述 (+) 酸异构体,或 (b) 将所述酯
水解为相应的外消旋酸、将所述外消旋酸分解成其 d(+)酸和 I(-)酸异构体,回收所述 d(+)酸用于制备拟
除虫菊酯产品,将上述 I(-)酸从分解物中酯化,将由此制备的 1(-)酯从所述酯化物中消旋化,并将其
水解以获得外消旋酸,该外消旋酸被回收用于与新鲜外消旋酸混合和随后的分解。