La(OTf)3‑Catalyzed [3+2] Cycloaddition Reactions for the Synthesis of Benzo[d]oxazoles/Benzofurans

The La­(OTf)3-catalyzed [3+2] cycloaddition reactions for the synthesis of benzo­[d]­oxazoles/benzofurans via quinones and 1,2-di-tert-butyl-3-(cyanimino)­diaziridine (1,3-di-tert-butyl-2-cyanoguanidine)/vinyl azides have been explored. A series of 5-hydroxybenzofuran-4-carboxylic acid derivatives and 5-hydroxybenzo­[d]­oxazole-4-carboxylic acid derivatives were conveniently obtained with high yields and good stereoselectivities, which could be used for further transformations to valuable compounds.