1. Govt. P.G. college Rajouri
Pericyclic Reactions
Dr.Amita Sharma
Dept. Of Chemistry
Govt. P.G. college Rajouri

2. Pericyclic Reactions Electrocyclic react.
Polar react. (nucleophiles and electrophiles)
Radical react.
Pericyclic react. (concerted, cyclic TS#)
Electrocyclic react.
Cycloadditions (i.e. Diels Alder)
Sigmatropic rearrangement
Rearrangement of polyene
Termal (react. in ground state)
or photochemical
(react of exited state)

3. Symmetry Allowed React.
Woodward Hoffmann rules
Symmetry in reactants are preserved during pericyclic react.
Results can generally be predicted just by looking at Front Orbitals
(FMO; HOMO and LUMO) - Fukui

4. Molecular orbitals 1,3-butadiene Stereospesific react. S: Symmetric
A: Antisym.

5. Molecular orbitals
hexatriene
Symmetry allowed react

6. Photochemical electrocyclic react.

7. Cycloadditions (i.e. Diels Alder)
Stereospesific react.

8. endo - exo selectivity
Normal electron demand DA - Electron poor dienophile (Michael accept.)
Ethene etc, very low react.
Michael accept.
Lower LUMO

9. [2+2] Cycloadditions

10. Carbene Cycloadditions

11. Sigmatropic Rearrangements
[3,3] Rearrangements; Claisen rearrang. etc.

12. [1,5] Rearrangement (H-shift)