Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(A) Diels–Alder mechanism for the reaction between 3 and 4c. (B) Retro Diels–Alder step of the addition/N2 elimination/cyclization pathway between 3 and 4c. (C) Electrocyclization step of the addition/elimination/cyclization pathway between 3 and 4c. Lowest energy pathways and 3D geometries of key structures are shown. Energies are in kcal/mol relative to starting materials. *Barrier height was corrected to account for tunneling.
