title: "Stereoelectronic umpolung": converting a p-donor into a σ-acceptor via electron injection and a conformational change.
abstract: The para-OMe functional group, usually regarded as a conjugative p-donor, acts as an efficient hyperconjugative σ-acceptor in reductive cycloaromatization reactions. This apparent reversal of electronic properties is associated with a conformational change that aligns the σ*(O-C) orbital with the adjacent aromatic system and provides stabilization to the developing negative charge in the TS of the dianionic cyclization of enediynes. The chameleonic character of the OMe group illustrates the important role of negative hyperconjugation in anionic processes.
authors: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
authors: Paul W
authors: PW
authors: Peterson
authors: Nikolay
authors: N
authors: Shevchenko
authors: Igor V
authors: IV
authors: Alabugin