posted on 2024-02-21, 14:34authored byCarole Body, Guillaume Wery, Lisa Gubbels, Koen Robeyns, Tom Leyssens
trans-Cinnamic acid and derivatives
can undergo
a [2 + 2] photocycloaddition, resulting in the formation of truxinic
and truxillic acids. These photoproducts are regioisomers, differing
only in the relative arrangement of the acid and phenyl groups on
the cyclobutane ring formed. In this contribution, we show that a
cocrystal engineering approach can direct the outcome of the reaction
(regioisomer) and control the photoreactivity of the compounds in
the solid state. For trans-cinnamic acid, cocrystallization
with 4,6-dichlororesorcinol yields a thermodynamic pathway to β-truxinic
acid. The otherwise photostable para-methoxy-trans-cinnamic acid can be rendered photoactive to also
yield β-truxinic acid using 5-hydroxyisophthalic acid. Finally,
the photoactive para-hydroxy-transcinnamic acid can be rendered photostable by cocrystallization. Cocrystal
engineering is thus a valuable tool not only to control photoreactivity
but also the obtained outcome of a solid-state photoreaction. We expect
to see this approach being applied as a more general procedure for
this type of reaction in the future.