Cascade bicyclization of triethylammonium thiolates with hydrazines: efficient access to pyrazolo[3,4-c]quinolines.

A new bicyclization strategy has been established, allowing a flexible and practical approach to 33 examples of pyrazolo[3,4-c]quinolines from low-cost and readily accessible triethylammonium thiolates with hydrazines. Notably, the features of this work include broad functional group compatibility, mild reaction conditions and good reaction yields.