Photochemical Transformation of <i>O</i>
-(β-Arylethyl) Arylimidates into 2,4-Diaryl-5-iodoxazoles with 1,3-Diiodo-5,5-dimethylhydantoin
作者:Aya Saito、Hideo Togo
DOI:10.1002/ejoc.202000383
日期:2020.6.16
2,4‐Diaryl‐5‐iodoxazoles could be obtained by the treatment of O ‐(β‐arylethyl) arylimidates with 1,3‐diiodo‐5,5‐dimethylhydantoin (DIH) under irradiation with a tungsten lamp. This reaction proceeds through multiple stets, i.e., formation of N ‐iodoimidate, iminyl radical, 1,5‐H shift, 5‐exo‐tet cyclization to oxazoline, oxidation to oxazole, and iodination to 5‐iodoxazole.
A reaction sequence involving halogenation and replacement of the halo substituent by a nitro group using dinitrogen tetraoxide has led to a general, convenient route to 5-nitrooxazoles. Reaction schemes employing both bromine and iodine as the halo substituent have been investigated; however, the method using iodine preceded by a mercuration step affords a better overall yield in the range of 20–50%
A new and efficient method for the synthesis of 4-aryl-2-phenyloxazoles is described which is based upon the reaction of α-[(2,4-dinitrobenzene)sulfonyl]oxy ketone intermediates with benzamide in ionicliquid.
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