A New Model of Light‐Powered Chiral Molecular Motor with Higher Speed of Rotation, Part 1 – Synthesis and Absolute Stereostructure

Abstract

AbstractTo develop a molecular motor with a higher speed of rotation, a new model light‐powered chiral molecular motor 2 of five‐membered ring type was designed, and the motor rotation isomers (–)‐2a and (–)‐2c were directly synthesized in enantiopure forms for the first time from the ketone (+)‐8. The precursor alcohols 9 and 10 were enantioresolved by the camphorsultam‐dichlorophthalic acid (CSDP acid; 3) method, and their absolute configurations were determined by X‐ray crystallographic analysis of the CSDP ester (–)‐11b and chemical correlations. The enantiopure ketone (S)‐(+)‐8 formed from (1S,2S)‐(+)‐9 or (1R,2S)‐(–)‐10 was subjected to the McMurry reaction with TiCl3/LiAlH4, yielding the motor rotation isomers [CD(–)257.8]‐(2S,2′S)‐(M,M)‐(E)‐(–)‐2a and [CD(–)270.0]‐(2S,2′S)‐(M,M)‐(Z)‐(–)‐2c. These studies enabled us unambiguously to determine the absolute stereostructure of the motor 2, which is of critical importance for control over the direction of motor rotation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)