Comparing the anome ric effect in Į-halo ether and Į-halo-O-oxime eth er com pounds; DFT and NBO stud ies

The a nomeric effe ct is descri bed as the p reference of an electron egative substituent at C-l of a pyran osides ring to undertake the axial rather than equatorial orie ntation [۱]. Two explan ation have b een propos ed to be resp onsible for the anomeric effect; unf avorable interaction between lone pairs of the oxygen and the dipole of the C–X bond of a pyranoside, and an other explan ation, the overlap bet ween a nonbonding electron pair o n the oxygen atom and the vacant ı* orbital of the C–X bond [۲]. The anomeric effect ma y also be extended to th e so-called "generalized anomeric effect" which defines the preference for the g auche conf ormer over the anti conf ormer in an R–Y–CH۲– X (Y=O, N or S; X=O, N, halogen, etc) fragme nt [۳]. In the present study, using density fun ctional theory (DFT), the anomeric effects in Į- chloro ether (ACE) and Į-chloro-O-oxime (AC OE) ether compounds (Fig. ۱), as representatives for their all halo-substitute d analogue, have been c ompared. D ifferent R groups with different electronic pr operties suc h as elect ron-withdra wing, electr on-donating and electr on-supplyin g have been employed for studying their influe nces on interactions that are respon sible for anomeric effec t.

کلیدواژه ها:

anomeric effect ، Į -haloether ، Į-halo-O-ox ime ether ، DFT ، NBO