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Enantioselective Noncovalent Synthesis of Hydrogen‐Bonded Double‐Rosette Assemblies
Author(s) -
Prins Leonard J.,
Verhage Jeroen J.,
de Jong Feike,
Timmerman Peter,
Reinhoudt David N.
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020517)8:10<2302::aid-chem2302>3.0.co;2-c
Subject(s) - racemization , enantioselective synthesis , non covalent interactions , chemistry , chirality (physics) , metathesis , supramolecular chirality , dissociation (chemistry) , supramolecular chemistry , hydrogen bond , stereochemistry , photochemistry , catalysis , crystallography , organic chemistry , molecule , polymerization , crystal structure , physics , polymer , quark , nambu–jona lasinio model , chiral symmetry breaking , quantum mechanics
The noncovalent synthesis of enantiomerically pure hydrogen‐bonded assemblies ( M ) ‐ and ( P ) ‐ 1 3 ⋅ (CA) 6 is described. These dynamic assemblies are of one single handedness ( M or P ), but do not contain any chiral components. They are prepared by using the “chiral memory” concept: the induction of supramolecular chirality is achieved through initial assembly with chiral barbiturates, which are subsequently replaced by achiral cyanurates. This exchange process occurs quantitatively and without loss of the M or P handedness of the assemblies. Racemization studies have been used to determine an activation energy for racemization of 105.9±6.4 kJ mol −1 and a half‐life time to racemization of 4.5 days in benzene at 18 °C. Kinetic studies have provided strong evidence that the rate‐determining step in the racemization process is the dissociation of the first dimelamine component 1 from the assembly 1 3 ⋅ (CA) 6 . In addition to this, it was found that the expelled chiral barbiturate ( R BAR or S BAR) acts as a catalyst in the racemization process. Blocking the dissociation process of dimelamines 1 from assembly 1 3 ⋅ (CA) 6 by covalent capture through a ring‐closing metathesis (RCM) reaction produces an increase of more than two orders of magnitude in the half‐life time to racemization.