Pressure and Temperature-Controlled Enantiodifferentiating[4+4] Photocyclodimerization of 2-Anthracenecarboxylate Mediated by Secondary Face-and Skeleton-Modified gamma-Cyclodextrins

摘要

A series of secondary-face-substituted and skeleton-modified gamma-cyclodextrins(gamma-CDs)were prepared as chiral hosts for enantiodifferentiating[4+4]photocyclodimerization reactions of 2-anthracenecarboxylic acid(AC).These gamma-CD derivatives form stable ternary complexes with ACs,with altroside-bearing gamma-CDs undergoing induced-fit conformational changes upon complexation,and the photocyclodimerization of AC was,thus,dramatically accelerated.The enantiomeric excess(ee)of anti-head-to-head cyclodimer 3 was greatly enhanced in general with altroside-bearing gamma-CDs 7-9.Although mono-altro-gamma-CD 9 and 3~A-azido-3~A-deoxy-altro-gamma-CD 7 gave 2 in ee's smaller than those obtained with native gamma-CD,3~A-amino-3~A-deoxy-altro-gamma-CD 8 yielded 2 in much higher ee's,which is likely to be ascribed to the combined effects of the less-symmetric cavity and the electrostatic interactions.The influence of temperature and high pressure on the supramolecular photochirogenic reaction has been investigated in depth.An ee as high as 71% was obtained for cyclodimer 2 in the photocyclodimerization of AC mediated by 8 at 210 MPa and-21.5 deg C.