The [3 + 2] Annulation of In Situ Formed Trifluorodiazoethane with 4-Nitroisoxazoles: Access to Trifluoromethylpyrazolo[3,4-d]isoxazoles

A general and practical K2CO3 promoted [3 + 2] annulation between trifluoroacetaldehyde N-triftosylhydrazone (TFHZ-Tfs) and 4-nitroisoxazoles has been developed to access structurally diverse trifluoromethylpyrazolo[3,4-d]isoxazoles. Mechanistically, CF3CHN2 is formed in situ...