科研之友
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摘要
Controlled directional displacement of a molecular group has been achieved based on dynamic covalent motions implementing the reactional features of the imine bond. ortho-Carboxybenzaldehyde derivatives are able to form stable adducts with both primary and secondary amines as imines or as amino lactones, respectively, depending on the acidity of the medium. They may thus perform pH-driven intramolecular walking along a non-symmetric polyamine chain, in which an imine serves as the terminus under basic conditions on one end of the chain and a lactone formed on a secondary hydroxylamine nitrogen on the other end serves as the terminal site upon addition of acid. The displacement between the termini occurs stochastically through reversible change in valency at the carbon site of the carbonyl group between imine, aminal, iminium and amino lactone form. On the other hand, the directionality results from the stabilisation of the terminal products under given pH conditions. By its ability to undergo interconversion between CN and O-C-N moieties, the ortho-carboxybenzaldehyde group extends the realm of dynamic covalent chemistry of imines to secondary amines and opens new perspectives in this field. Kovalentne-dynamicky character iminove vazby umonil vyvoj smerove oritentovaneho pohybu na molekulove urovni. Derivaty 2-karboxybenzaldehydu mohou vytvaet stabilni adukty jak s primarnimi, tak sekundarnimi aminy a tvoit odpovidajici iminy i amino-laktony v zavisloti na kyselosti prostedi. Tyto derivaty jsou diky tomu schopny pH-izeneho intramolekularniho achozeni na nesymetrickych polyaminovych drahach, piem v basickem prostedi je stabilni iminova forma na jednom konci drahy, zatimco v kyselem prostedi je stabilizovan lakton utvoeny na sekundarnim dusiku hydroxylaminove skupiny na opanem konci. Pesun mezi opanymi konci drahy probiha diky valenni flexibilite karbonylove skupiny, je reversibilne pechazi mezi formami iminu, aminalu, iminia a amino-laktonu. Pestoe jednotlive kroky probihaji stochasticky, smerove izeni je dano rozdilnou stabilitou aduktu utvoenych na koncich drahy pi danem pH. Samotna schopnost 2-karboxybenzaldehydu reversibilne pechazet mezi CN a O-C-N formami pedstavuje duleite rozieni v oblasti dynamicke kovalentni chemie iminu, jeliko umouje zakomponovat rovne sekundarni aminy a tim otevira nove monosti v teto perspektivni oblasti.
- 出版日期2015-6-22
