Regioselective [3 + 2] cycloaddition of diazo reagents and internal alkynes: Accessing regiosomers of highly substituted trifluoromethylpyrazoles

We herein descript a metal-free and highly regioselective [3 + 2] cycloaddition reaction between diazo compounds and internal alkynes, accessing to a series of trifluoromethylated pyrazoles. Using different combination of starting materails, both regioisomers can be obtained under this protocal. The developed cycloaddition reaction provides a valuable tool for future medicinal chemistry research on highly substituted trifluoromethyl pyrazoles.