次鹵酸對(duì)烯烴的加成，生成鄰鹵醇，其反應(yīng)本質(zhì)及選擇性相同與鹵素加成反應(yīng)。鹵素正離子首先對(duì)烯烴的雙鍵作親電進(jìn)攻，生成橋鹵三元環(huán)過渡態(tài)，然后，水分子或羥基對(duì)其親核進(jìn)攻，得到鄰鹵醇。按照馬氏規(guī)則，鹵素加成在雙鍵的取代基較少的一端。
應(yīng)用次鹵酸酯（ROX）作為鹵化劑，其機(jī)理相同于次鹵酸的反映，但是可在非水溶液中進(jìn)行反應(yīng)。根據(jù)溶劑的親核基團(tuán)不同，可生成相應(yīng)的-鹵醇β衍生物。
反應(yīng)實(shí)例
Under vigorous agitation andcooling to 0.deg.-5.deg. C., 150 g of chlorine is introduced within 6 hoursinto a solution of 182 g of cis-1,4-dihydroxy-2-butene and 288 g ofcrystallized soda (Na2CO3 *10H2O).. The mixture is stirred for another hour,concentrated under vacuum at 50.deg.-55.deg. C., and diluted with 0.6 l ofethanol.. After standing overnight, the mixture is filtered off from sodiumchloride and thoroughly washed with ethanol. The solution and the filtrate areconcentrated, thus obtaining 3-chloro-1,2,4-butanetriol as a yellow oil. Yield:272 g (97percent of theory) of 3-chloro-1,2,4-butanetriol.
【Patent; SheringAktiengesellschaft; Publ.: US4570007 A1 (1986/02/11), Appl.: US1985-722088(1985/04/11).】
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