TY - JOUR
T1 - Enantiomer recognition of asymmetric catalysts. Thermodynamic properties of homochiral and heterochiral dimers of the methylzinc alkoxide formed from dimethylzinc and enantiomeric 3-exo-(dimethylamino)isoborneol
AU - Kitamura, Masato
AU - Suga, Seiji
AU - Niwa, Makoto
AU - Noyori, Ryoji
AU - Zhai, Zong Xi
AU - Suga, Hiroshi
PY - 1994/1/1
Y1 - 1994/1/1
N2 - Reaction of dimethylzinc and (2S)- or (2R)-3-exo-(dimethylamino)isoborneol forms methylzinc alkoxide 1, which forms a dimeric structure 2 in a reversible manner. Depending on the chirality of the monomer 1, three stereoisomeric dinuclear complexes are formed; the homochiral dimerization of 1 leads to (S,S)- or (R,R)-2, whereas the heterochiral interaction forms (S,R)-2. The heterochiral dimer is thermodynamically favored over the homochiral dimer in both toluene solution and crystalline states. The vapor pressure osmometry method has revealed that the stereoisomeric dimers 2 in toluene are in equilibrium with the monomer 1 with dissociation constants Khomo = (3.0 ± 1.0) × 10-2 and Khetero ≅ 1 × 10-5 at 40°C, respectively. Calorimetric determination of the enthalpies of solution of the crystalline compounds indicates that the S,R heterochiral dimer is more stable than the S,S or R,R homochiral dimer by 3.4 ± 0.8 kJ mol-1 in the solid state.
AB - Reaction of dimethylzinc and (2S)- or (2R)-3-exo-(dimethylamino)isoborneol forms methylzinc alkoxide 1, which forms a dimeric structure 2 in a reversible manner. Depending on the chirality of the monomer 1, three stereoisomeric dinuclear complexes are formed; the homochiral dimerization of 1 leads to (S,S)- or (R,R)-2, whereas the heterochiral interaction forms (S,R)-2. The heterochiral dimer is thermodynamically favored over the homochiral dimer in both toluene solution and crystalline states. The vapor pressure osmometry method has revealed that the stereoisomeric dimers 2 in toluene are in equilibrium with the monomer 1 with dissociation constants Khomo = (3.0 ± 1.0) × 10-2 and Khetero ≅ 1 × 10-5 at 40°C, respectively. Calorimetric determination of the enthalpies of solution of the crystalline compounds indicates that the S,R heterochiral dimer is more stable than the S,S or R,R homochiral dimer by 3.4 ± 0.8 kJ mol-1 in the solid state.
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U2 - 10.1021/j100099a048
DO - 10.1021/j100099a048
M3 - Article
AN - SCOPUS:0000736403
VL - 98
SP - 12776
EP - 12781
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
SN - 0022-3654
IS - 48
ER -