Geminal Bond Participation in the Sigmatropic [1,5]-Hydrogen Shifts: Relative Reactivities of <i>Z</i>- and <i>E</i>-1-Substituted 1,3-Pentadienes

Abstract

Abstract The analysis of the bond interactions at the transition states of the sigmatropic [1,5]-hydrogen shift of 1,3-pentadiene showed the significant participation of the σ bonds geminal to the reacting centers. The electron-donating σ bonds at the Z-positions in the 1-substituted 1,3-pentadienes were predicted to enhance the reactivities rather than those at the E-positions. The predictions of the relative reactivities of the Z- and E-isomers were confirmed by the calculated activation energies by the density functional theory calculations.