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Thermal and Photochemical Switching of Chiral Sugar Azoalkenes: A Mechanistic Interrogation
Author(s) -
SánchezLeón Ana María,
Cintas Pedro,
Light Mark E.,
Palacios Juan Carlos
Publication year - 2020
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202000029
Subject(s) - isomerization , chemistry , photochemistry , chirality (physics) , monosaccharide , combinatorial chemistry , organic chemistry , catalysis , chiral symmetry breaking , physics , quantum mechanics , nambu–jona lasinio model , quark
This manuscript describes a thorough study on the thermal and photochemical evolution of carbohydrate‐based azoalkenes, which have been proposed as putative intermediates en route to other heterocyclic derivatives and nucleoside analogues. These substances represent new protagonists in the azo chemical space , under intense study due to reversible photoswitching of this functional group suitable for designing artificial nanomachines and responsive materials. Although structurally simple azadienes derived from monosaccharides have long been known, the dynamics of such species in solution and solid phase remains poorly characterized. Herein, we show that such azoalkenes undergo 3 E →3 Z thermal isomerization, which is accelerated by the presence of Brönsted acids. On the other hand, they undergo 1 E →1 Z isomerization when irradiated by sunlight, while the reverse 1 Z →1 E isomerization occurs thermally in the dark or under acid catalysis. As a result, sugar monoazadienes not only exhibit inherent chirality, but also dual on‐off isomerization under external stimuli. Both experiments and DFT‐based computational analyses provide a consistent and unifying mechanistic picture of these transformations.