Synthesis of 2,4,5-Trisubstituted Oxazoles via Pd-Catalyzed C–H Addition to Nitriles/Cyclization Sequences
作者:Di Zhang、Hao Song、Na Cheng、Wei-Wei Liao
DOI:10.1021/acs.orglett.9b00700
日期:2019.4.19
A practical and flexible intermolecular protocol for the diverse synthesis of trisubstituted oxazole derivatives via a Pd-catalyzed direct C–H addition of electronic-rich heteroarenes to O-acyl cyanohydrins bearing an α-hydrogen/cyclization sequence is described. A wide range of trisubstituted oxazoles can be prepared from readily available starting materials in good to high yields with high efficiency
A palladium‐catalyzed tandem reaction of cyanomethyl benzoates with arylboronic acids has been achieved. Substitution at the 2‐position of cyanomethyl benzoates was found to be crucial for the selective synthesis of oxazoles and isocoumarins. Cyanomethyl benzoates afforded 2,4‐diaryloxazoles as products, while 2‐benzoyl‐substituted cyanomethyl benzoates delivered 3‐benzoyl‐4‐aryl‐isocoumarins selectively
Pd(II)-catalyzed addition of sp2 C–H to nitrile/aerobic oxidation sequences for the preparation of functionalized α-imino ketones is described in which readily available heteroarenes and O-acyl cyanohydrins were employed. Various functionalized targeted molecules can be prepared in good yields with high atom and step economy. Moreover, a broad substrate scope and the ready manipulation and availability