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Biphenyl Bis(amino alcohol) Oxalamide Gelators: Complex Gelation Involving Coupled Equilibria, Central‐to‐Axial Chirality Transfer, Diastereoisomer Interconversion, and Self‐Sorting
Author(s) -
Portada Tomislav,
Molčanov Krešimir,
Šijaković Vujičić Nataša,
Žinić Mladen
Publication year - 2016
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.201501261
Subject(s) - diastereomer , chemistry , chirality (physics) , biphenyl , toluene , kinetics , stereochemistry , crystallography , organic chemistry , chiral symmetry breaking , physics , quantum mechanics , nambu–jona lasinio model , quark
Chiral gelators 3 and 4 , with two valinol‐ or leucinol‐oxalamido arms attached to the 2,2′‐positions of the proatropisomeric biphenyl group, were prepared, and their gels were studied. Compound ( R , R )‐ 3 in the solution and gel states forms a mixture of major [( R , aR , R )‐ 3 ] and minor [( R , aS , R )‐ 3 ] diastereomers due to central‐to‐axial chirality transfer. 1 H NMR studies of its toluene gel provide evidence of diastereomer interconversion and self‐sorting, which results in exclusive incorporation of ( R , aR , R )‐ 3 into the gel network. Gels formed in the 10 –3 M concentration range show an irregular T g /concentration dependence, which is in contrast to those formed in the 10 –2 M concentration range. The peculiar properties of the former gels may be explained by kinetic effects due to the presence of coupled equilibria comprising diastereomer interconversion and ( R , aR , R )‐ 3 self‐assembly where the rate of gelation becomes dependent on the rate of formation of the gelling ( R , aR , R )‐ 3 from the nongelling ( R , aS , R )‐ 3 .