Enantiodifferentiating photoisomerization of (Z )-cyclooctene and (Z,Z )-cycloocta-1,3-diene sensitized by chiral aromatic amides

Abstract

Optically active benzene(poly)carboxamides with C₂-symmetric pyrrolidine moieties have been employed as chiral sensitizers for the geometrical photoisomerizations of (Z )-cyclooctene (1Z ) and (Z,Z )-cycloocta-1,3-diene (1ZZ ) in some solvents at varying temperatures. ortho-Substituted di- and tetra-amides used as chiral sensitizers give enantiomeric excesses (ee) up to 14% for both 1Z and 1ZZ in pentane at low temperatures. The use of polar solvents dramatically diminishes the product’s ee, due to the intervention of a free or solvent-separated radical ion pair between 1 and the chiral sensitizer.

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