いかにしてフォトクロミック電子環状反応を立体選択的に行うか

Abstract

The development of highly diastereoselective photochromic compounds that our group has carried out in the past 15 years is described here. Observations by 1H NMR of the enantiomeric isomerization of helically chiral hexatriene moiety of a fulgide which undergoes photochemical 6π-electrocyclization are first described, followed by discussions on the optical resolution of a fulgide and diastereoselective photochromism of an (R)-binaphthol-modified fulgide. A new concept of diastereoselective photochromism has also been realized by using diarylethenes as the template. The concept consists of: (i) Allylic 1,3-strain and (ii) electronic and steric repulsions between the oxygen atoms on a substituent on the stereogenic carbon atom attached to the ring-closing carbon atom located at one terminal of the hexatriene moiety and the heteroatom on the second heteroaromatic ring. Finally, a general strategy to achieve extraordinarily high diastereoselectivity of up to 100:0 has been demonstrated by the introduction of dual chiral stereocontrolling substituents to diarylethenes.