A highly efficient BF3路Et2O catalysed intramolecular [3+2] cycloaddition of tosylhydrazone with alkyne has been developed, and a variety of potentially bioactive 1,8-disubstituted-3,4-dihydrobenzopyrano[3,4-c]pyrazoles 7 were obtained with good to excellent yields of up to 93%.
![Graphical abstract: A highly efficient BF3·Et2O-catalysed intramolecular [3+2] cycloaddition for the synthesis of 3,4-dihydrobenzopyrano[3,4-c]pyrazoles](http://hg.y866.cn/compound/lib/scimg/usr/1/C2RA22025C.jpg)
