Bro̷nsted Acid-Catalyzed Reduction of Furans

Bioderived furans play a pivotal role in advancing defossilized
chemical pathways. The complete reduction of furans currently relies
on impractical metal-catalyzed hydrogenations at high pressures and
temperatures. In addition, the Birch reduction of unbiased furans
to 2,5-dihydrofurans remains an unsolved synthetic challenge. Herein,
we report a mild Bro̷nsted acid-catalyzed reduction of furans
to 2,5-dihydro- and/or tetrahydrofuran derivatives using silanes as
reducing agents. In particular, the first formal Birch reduction of
furan itself is achieved. Mechanistic investigations reveal an intricate
behavior of HFIP as the crucial solvent, preventing the intrinsic
polymerization behavior of furans under acidic conditions and introducing
additional driving force by specific product binding.