Biradical and zwitterionic cyclizations of oxy-substituted enyne-allenes.
[see reaction]. Oxyanion substitution of enyne-allenes causes both Myers-Saito and Schmittel cyclizations to switch their product formation preferences from diradicals to polar, closed-shell singlets. The oxyanion stabilization is larger for the Schmittel products than the Myers-Saito products because the latter must sacrifice aromaticity to maximize interaction. The changing character of the different reaction paths is reflected in their activation energies.
Cramer
C J
CJ
Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431, USA. cramer@dchem.umn.edu
Kormos
B L
BL
Seierstad
M
M
Sherer
E C
EC
Winget
P
P