MODEL STUDIES IN ORGANIC CHEMISTRY: EXPLOITING MOLECULAR RIGIDITY

1
MODEL STUDIES IN ORGANIC CHEMISTRY EXPLOITING
MOLECULAR RIGIDITY
Igor V. Komarova, Anthony J. Kirbyb
a Kiev National Taras Shevchenko University,
Kiev, Ukraine b University Chemical Laboratory,
Cambridge, United Kingdom
Synthesis of model compounds is used in organic
chemistry since the early days of this science.
Analysis of the literature shows that the model
compounds often possess a rigid molecular
framework. Molecular rigidity is exploited in the
design of model molecules, if the strictly
defined spatial disposition of functional groups
and fragments is needed in order to get
structural and functional characteristics of the
model molecules closest to the object of study.
This is exemplified below on different model
studies in bioorganic chemistry, stereochemistry,
physical organic chemistry and catalysis.
1-AZAADAMANTANE SYSTEM STABLE TETRAHEDRAL
INTERMEDIATES
1-AZAADAMANTANE SYSTEM TESTING THE REVERSE
ANOMERIC EFFECT (RAE)
RAE is a conformational preference for a
positively charged substituent at the anomeric
position to be equatorial over and above steric
requirements
- STABLE RIGID MODEL SYSTEM (NO RAE OBSERVED)
SYNTHESIS
X-RAY STUDY

• HIGHLY UNSTABLE, CONFORMATIONALLY FLEXIBLE

BICYCLO2.2.1HEPTANE SYSTEM FUNCTIONALISED
DIPHOSPHINE LIGANDS
1-AZAADAMANTANE SYSTEM TESTING THE REVERSE
ANOMERIC EFFECT (RAE)
DESIGN OF AN ISOMERIC SET
SYNTHESIS OF MODEL COMPOUND
KEMPS TRIACID
HYDROGENATION RESULTS WITH NEW CATALYSTS
SYNTHESIS
ANOTHER RIGID MODEL COMPOUND THE TWISTED AMIDE!
ee 90(R)
90(R) 81(R) 88(R)
1-AZAADAMANTANE SYSTEM THE MOST TWISTED AMIDES
CONCLUSIONS
THE MOLECULAR RIGIDITY IN MODEL STUDIES CAN BE
USED FOR
- ACHIEVING THERMODYNAMIC STABILITY OF MODELS
CHEMICAL PROPERTIES
- BRINGING FUNCTIONAL GROUPS INTO CLOSE VICINITY
TOWARD EACH OTHER
SPECTROSCOPICAL PROPERTIES
- FREESING CONFORMATIONAL MOTIONS