Deprotonation of 3(2H)-Furanone and 3(2H)-Thiophenone by Carbanions in the Gas Phase: Disproportionately High Aromaticity of the Transition State: An Ab Initio Study

作者：Bernasconi Claude F^*; Yamataka Hiroshi; Yoshimura Nobuyoshi; Sato Makoto

来源：Journal of Organic Chemistry, 2009, 74(1): 188-196.

DOI：10.1021/jo8018076

The reversible deprotonation of 3(2H)-furanone (3H-O) and 3(2H)-thiophenone (3H-S) by a series of delocalized carbanions and by CN(-), and the identity proton transfer of 3H-O to its conjugate base (3(-)-O) and of 3H-S to 3(-)-S have been Studied at the MP2//6-31 G** level. The main objective has been to examine to what extent the aromaticity of 3(-)-O and 3--S is expressed at the transition state of these reactions and how the intrinsic barriers are affected by the transition state aromaticity. Aromaticity parameters such as NICS values, HOMA and Bird Indices indicate a disproportionately high degree of aromatic stabilization of the transition state. This stabilization results in a reduction of the ititrinsic barriers which is most clearly manifested in the identity reactions. However, these reductions are relatively modest compared to those reported previously for the identity proton transfers from the benzeniuam ion to benzene and of cyclopentadiene to its conjugate base, reflecting the smaller aromatic stabilization of 3(-)-O and 3--S compared to those of benzene and cyclopentadienyl anion.

• 出版日期2009-1-2