Solvent-Driven Switchable Annulation of Cyclopropanols with 1,2-Diaminoarenes Enables Divergent Synthesis of 1,5-Benzodiazepines and Quinoxaline-2-carbaldehydes.

Synthetic strategies enabling the divergent synthesis of various product types from identical substrates are greatly favored in organic synthesis. In this work, we develop a switchable, metal-free strategy for the controllable synthesis of 1,5-benzodiazepines and quinoxaline-2-carbaldehydes via selective [4+3] and [4+2] cyclization of cyclopropanols with 1,2-diaminoarenes. Tunable product selectivity can be attributed to solvents that mediate divergent reaction pathways. The formation and stabilization of 1,5-benzodiazepines are promoted by HFIP, whereas further oxidation and isomerization into quinoxaline-2-carbaldehydes are facilitated by DMSO. Notably, this strategy not only provides a facile route to controllably synthesize valuable nitrogen heterocycles but also realizes diversified ring-opening transformations of cyclopropanols.