Dehydration-type Ti-Claisen Condensation (Carbonhomologation) of α-Heteroatom-substituted Acetates with Alkyl Formates: Utilization as (<i>Z</i>
)-Stereodefined Cross-coupling Partners and Application to Concise Synthesis of Strobilurin A
作者:Hidefumi Nakatsuji、Risa Kamada、Hideya Kitaguchi、Yoo Tanabe
DOI:10.1002/adsc.201700879
日期:2017.11.10
homologation (dehydration type Ti-Claisen condensation) of alkyl α-heteroatom (halo and sulfonyloxy)-substituted acetates (XCH2CO2R) with alkyl formates (HCO2R) to afford various alkyl β-alkoxy-α-halo or sulfonyloxy-substituted acrylates (24 examples; 51%–91% yield). Stereoretentive Suzuki-Miyaura, Negishi, and Sonogashira cross-couplings using the obtained methyl β-methoxy-α-halo or sulfonyloxy-substituted
的TiCl 4 -Et 3 Ñ或-Bu 3 ñ试剂进行的高度(ż烷基α-杂原子(卤和磺酰氧基)的)-stereoselective碳同系化(脱水型Ti克莱森缩合)取代的乙酸盐(XCH 2 CO 2 R)用烷基甲酸酯(HCO 2 R)得到各种烷基β-烷氧基-α-卤代或磺酰氧基取代的丙烯酸酯(24个实例; 51%–91%的收率)。使用获得的甲基β-甲氧基-α-卤代或磺酰氧基取代的丙烯酸酯的立体定向Suzuki-Miyaura,Negishi和Sonogashira交叉偶联反应顺利进行,以中等至高收率生产了多种β-烷氧基-α-取代的丙烯酸酯(35实例; 29%–99%的收率)。作为一项成功的应用,利用本发明的反应顺序(脱水型Ti-Claisen缩合和Suzuki-Miyaura交叉偶联)进行了3步直接合成的strobilurin A的合成,其中三个连续烯烃的几何构型(2 E,3 Z,5 E)被完全维持。