Synthesis and Comprehensive Structural and Chiroptical Characterization of Enones Derived from (-)-α-Santonin by Experiment and Theory.
The aim of the present work is to explain the causes of the observed deviations from sector and helicity rules to determine the absolute configuration of optically active α,β-unsaturated ketones by means of electronic circular dichroism (ECD). To this end, a series of model compounds with a common decahydronaphthalene skeleton representing both cisoid and transoid enones were synthesized. In the framework of this work, detailed dichroic studies supported by single crystal X-ray analysis were performed where possible. To assist the achievement of the desired objectives the conformational flexibility of the selected cis-enones through the dependence of solvent and temperature on the ECD spectra were examined. All experimental studies were supplemented by detailed DFT calculations. A notable result of the study is assessing the applicability of the enone sector and helicity rules in dichroic studies and potential restrictions. To this end, a number of factors that could determine the signs of the individual Cotton effects has been considered. Among these nonminimum structure effects, i.e., twisting of the enone chromophore and nonplanarity of the enone double bond can be mentioned.
Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
Marek
M
Masnyk
Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
Aleksandra
A
Butkiewicz
Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
Marcin
M
Górecki
Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
Roman
R
Luboradzki
Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn , Beringstr. 4, 53115 Bonn, Germany.
Christoph
C
Bannwarth
Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn , Beringstr. 4, 53115 Bonn, Germany.
Stefan
S
Grimme
Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
Jadwiga
J
Frelek