Study on the selectivity in the electrophilic monofluorination of 2,3-allenoates with Selectfluor™: an efficient synthesis of 4-fluoro-2(5H)-furanones and 3-fluoro-4-oxo-2(E)-alkenoates
作者:Bo Lü、Chunling Fu、Shengming Ma
DOI:10.1039/b917793k
日期:——
Different from the reaction of 2,3-allenoic acids with Selectfluorâ¢, 4-fluoro-2(5H)-furanones and (E)-3-fluoro-4-oxo-2-alkenoates were highly selectively generated from 2,4-disubstituted 2,3-allenoates with Selectfluor⢠under different conditions in moderate yields. The reaction of 2,4,4-trisubstituted 2,3-allenoates afforded the corresponding 4-fluoro-2(5H)-furanones highly selectively with up to 95% yield under different conditions. The scope of the substrates has been carefully explored. Due to the more readily availability of 2,3-allenoates as compared to 2,3-allenoic acids, new 4-fluoro-2(5H)-furanones were prepared. Based on the isolation and characterization of the minor fluorohydroxylation product E-5m, a mechanism has been proposed.
与2,3-烯酸与Selectfluorâ¢反应不同,在不同条件下,2,4-取代的2,3-烯酸酯与Selectfluorâ¢反应,能够高选择性地生成4-氟-2(5H)-呋喃酮和(E)-3-氟-4-氧代-2-烯酸酯,产率适中。2,4,4-三取代的2,3-烯酸酯的反应在不同条件下高选择性地生成相应的4-氟-2(5H)-呋喃酮,产率高达95%。对底物的范围进行了仔细探讨。由于与2,3-烯酸相比,2,3-烯酸酯更易获得,因此合成了新的4-氟-2(5H)-呋喃酮。基于小量氟羟基化产物E-5m的分离和表征,提出了一种机制。