Remarkable Reactivity Difference in Oxygen-Substituted versus Non-Oxygen-Substituted Bromoalkynes in Cu(I)-Catalyzed Cross-Coupling Reactions: Total Synthesis of (−)-<i>S</i>-18-Hydroxyminquartynoic Acid
作者:Benjamin W. Gung、Godwin Kumi
DOI:10.1021/jo0344900
日期:2003.7.1
three-component Cadiot-Chodkiewicz reaction affording the tetrayne unit. The oxygen-substituted bromoalkyne 10 was found to react at a much faster rate than the non-oxygen-substituted bromoalkyne 6 in the key step. The undesired symmetric cross-coupling by 10 generates a symmetric tetrayne intermediate, which undergoes a nucleophilic addition by 1 equiv of ethylamine. This side reaction is suppressed by controlling
共轭四乙炔天然产物(S)-18-羟基Minquartynoicic酸(2)由五个线性步骤合成,总收率从可商购的1,2,5,6-O-二异亚丙基甘露糖醇中获得17.7%。关键步骤是提供四炔单元的一锅三组分Cadiot-Chodkiewicz反应。在关键步骤中,发现氧取代的溴炔烃10的反应速率比非氧取代的溴炔烃6快得多。不需要的10的对称交叉偶联产生了对称的四炔中间体,该中间体通过1当量的乙胺进行亲核加成。通过控制各组分的加入顺序和速率以及减少乙胺的量,可以抑制该副反应。