Fuchibe Kohei, Fushihara Tatsuki, Ichikawa Junji
Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Org Lett. 2020 Mar 20;22(6):2201-2205. doi: 10.1021/acs.orglett.0c00385. Epub 2020 Mar 2.
The treatment of CF-bearing cyclopropanes with EtAlCl generated stabilized difluorocarbocations, which underwent a nucleophilic addition of thiocarboxylic acids or thiols. The sulfur functionality was introduced at the position δ to the fluorine substituents in a regioselective manner (single activation of CF-cyclopropanes). The formed 1,1-difluoro-1-alkenes underwent successive deesterification/5-- cyclization. Intramolecular vinylic substitution proceeded in an aprotic solvent, whereas intramolecular addition proceeded in a protic solvent to afford pharmaceutically and agrochemically promising 2-fluoro-4,5-dihydrothiophene and 2,2-difluorotetrahydrothiophene scaffolds, respectively.
用乙基氯化铝处理含环丙烷的碳氟化合物生成了稳定的二氟碳正离子，这些离子会与硫代羧酸或硫醇发生亲核加成反应。硫官能团以区域选择性方式（碳氟环丙烷的单一活化）引入到氟取代基的δ位。生成的1,1 - 二氟 - 1 - 烯烃会进行连续的脱酯/5 - 环化反应。分子内乙烯基取代在非质子溶剂中进行，而分子内加成在质子溶剂中进行，分别得到在制药和农业化学方面有前景的2 - 氟 - 4,5 - 二氢噻吩和2,2 - 二氟四氢噻吩骨架。
