Novel Synthesis of 4-Fluoropyridines Based on 2-Fluoroallylic Alcohols by Succeeding Ireland-Claisen and Aza-Cope Rearrangements as Key Steps
作者:Günter Haufe、Ulrich Wittmann、Frank Tranel、Roland Fröhlich
DOI:10.1055/s-2006-942411
日期:2006.7
were transformed to give 4-(2-fluoroallyl)oxazol-5(4H)-ones in a Steglich-type, Ireland-Claisen rearrangement. The latter compounds gave either N-aroyl-substituted 2-amino-4-fluoro-2-methyl- or 2-amino-4-fluoro-2-phenylalk-4-enoic acids in excellent yields by hydrolysis or substituted 2-aryl-4-fluoro-6-phenylpy-ridines in a cascade reaction initiated by an aza-Cope rearrangement to form thermally unstable
一种新的合成途径导致 4-氟吡啶在 2 位和 6 位带有芳基取代基,并可能在 3 位带有额外的烷基。2-氟烯丙醇用 N-苯甲酰丙氨酸或 N-芳酰基苯基甘氨酸酯化,所得酯转化为 4 -(2-fluoroallyl)oxazol-5(4H)-ones 在 Steglich 型,Ireland-Claisen 重排中。后一种化合物通过水解或取代的 2-芳基-以优异的收率得到 N-芳酰基取代的 2-氨基-4-氟-2-甲基-或 2-氨基-4-氟-2-苯基烷-4-烯酸由 aza-Cope 重排引发的级联反应中的 4-fluoro-6-phenylpyridines 形成热不稳定的 2-(2-fluoroallyl)oxazol-5(2H)-ones。随后二氧化碳的挤出,氟化双键与形成的卡宾的分子内环丙烷化,