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submitted on 10.04.2019 and posted on 11.04.2019by Elena Prigorchenko, Sandra Kaabel, Triin Narva, Anastassia Baškir, Maria Fomitšenko, Jasper Adamson, Ivar Järving, Kari Rissanen, Toomas Tamm, Riina Aav
of a thermodynamically unfavoured macrocyclic product through the directed
shift of the equilibrium between dynamic covalent chemistry library members is
difficult to achieve. We show for the first time that during condensation of
formaldehyde and cis-N,N'-cyclohexa-1,2-diylurea formation of inverted-cis-cyclohexanohemicucurbituril
(i-cis-cycHC) can be induced at
the expense of thermodynamically favoured cis-cyclohexanohemicucurbituril
(cis-cycHC). The formation of i-cis-cycHC is enhanced in low
concentration of the templating chloride anion and suppressed in excess of this
template. We found that reaction selectivity is governed by the solution-based template-aided
dynamic combinatorial chemistry and continuous removal of the formed cycHC macrocycles
from the equilibrating solution by precipitation. Notably, the i-cis-cycHC was isolated with 33%
yield. Different binding affinities of three diastereomeric i-cis-, cis-cycHC and their chiral isomer (R,R)-cycHC for trifluoroacetic acid demonstrate the influence of
macrocycle geometry on complex formation.