Furfural-Derived Diacid Prepared by Photoreaction for Sustainable Materials Synthesis

A cis-3,4-di­(furan-2-yl)­cyclobutane-1,2-dicarboxylic
acid (CBDA-2) is readily prepared stereospecifically
from trans-3-(2-furyl)­acrylic acid, a furfural-derived
compound, through a solid-state [2 + 2] photocycloaddition in 95%
isolated yield. The cyclobutane ring in CBDA-2 shows
desired stabilities during thermal, sunlight, and chemical tests.
The single crystal structure of CBDA-2 revealed the geometry
of this molecule and orientation of the two dicarboxylic acid groups
displaying its potential to serve as a unique, semirigid diacid building
block in material science. A preliminary study showed that condensation
of this diacid with glycerol yielded a green polymer with good stability.
The diacid could also be used as a cross-linker for a biobased epoxy
to yield an exceptionally hard and solvent-resistant thermoset.