Pressure effects upon asymmetric photochemical reactions are discussed in the context of entropy control of these reactions. In the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to chiral (E)-isomer (1E) sensitized by chiral aromatic esters (2-7), the 1E/1Z ratio and the enantiomeric excess (ee) of 1E are critical finctions of the applied pressure, accompanying an unprecedented switching of the product chirality. Furthermore the differential activation parameters (ΔΔH
‡, ΔΔS
‡ and ΔΔV
‡) obtained by changing pressure and temperature cleary indicate that these variants act as independent factors in the enantiodifferentiating process. This opens a new channel to the multidimensional control of not only asymmetric photochemical but also conventional thermo/photo/biochemical reactions in which weak interactions are the principal driving force or determining factor.
抄録全体を表示