Novel access to 2-substituted quinolin-4-ones by nickel boride-mediated reductive ring transformation of 5-(2-nitrophenyl)isoxazoles
作者:Bernhard Lohrer、Franz Bracher
DOI:10.1016/j.tetlet.2019.151327
日期:2019.12
Reductive ring transformation of 3-substituted 5-(2-nitrophenyl)isoxazoles, readily accessible via 1,3-dipolar cycloaddition of 2-ethinylnitrobenzene with nitriles oxides, opens a novel access to 2-substituted quinolin-4-ones. Nickel boride, generated in situ from nickel chloride and sodium borohydride, allows, via simultaneous reduction of the nitro group and reductive cleavage of the isoxazole ring, the
3取代的5-(2-硝基苯基)异恶唑的还原环转化很容易通过2-乙炔基硝基苯与腈的氧化物进行1,3-偶极环加成而获得,为2取代的喹啉-4-酮的开发提供了一种新途径。由氯化镍和硼氢化钠原位生成的硼化镍可以通过同时还原硝基和异恶唑环的还原性裂解,一步一步转化为目标喹啉-4-酮。该方案耐受除烯烃以外的各种官能团,因此与铁/乙酸的还原环转化互补,铁/乙酸主要耐受烯烃。