Neighboring-Group Participation by C-2 Acyloxy Groups: Influence of the Nucleophile and Acyl Group on the Stereochemical Outcome of Acetal Substitution Reactions.

ABSTRACT: A single acyloxy group at C-2 can control the outcome of nucleophilic substitution reactions of pyran-derived acetals, but the extent of the neighboring-group participation depends on a number of factors. We show here that neighboring-group participation does not necessarily control the stereochemical outcome of acetal substitution reactions with weak nucleophiles. The 1,2-trans selectivity increased with increasing reactivity of the incoming nucleophile. This trend suggests the intermediacy of both cis-fused dioxolenium ions and oxocarbenium ions in the stereochemistry-determining step. In addition, as the electron-donating ability of the neighboring group decreased, the preference for the 1,2-trans products increased. Computational studies show how the barriers for the ring-opening react

SUBMITTER: Chun Y 

PROVIDER: S-EPMC10592418 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature