Activation energies (ΔG‡, kcal mol−1) and reaction energies (ΔG, kcal mol−1) given in parentheses for conrotatory electrocyclization of 2-substituted (entries 1–7), (3Z)-methyl substituted (entry 8), (3E)-substituted (entries 9–14), (4Z)-methyl substituted (entry 15) and (4E)-substituted (entries 16–21) octatetraenes.
| |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||||
| Entry | R | ΔG‡a | ΔG‡b | Entry | R | ΔG‡a | ΔG‡b | Entry | R | ΔG‡a | ΔG‡b |
| 1 | CH3 | 14.5 (−12.4) | 14.7 (−11.9) | 8 | CH3 | 19.1 (−8.3) | 19.2 (−7.7) | 15 | CH3 | 18.0 (−12.0) | 18.0 (−11.5) |
| 2 | NH2 | 15.7 (−12.5) | 15.7 (−12.1) | 9 | NH2 | 19.4 (−6.3) | 19.5 (−5.7) | 16 | NH2 | 18.5 (−11.1) | 18.6 (−10.5) |
| 3 | OH | 17.8 (−11.6) | 18.3 (−10.7) | 10 | OH | 19.1 (−7.6) | 18.2 (−8.0) | 17 | OH | 17.5 (−11.3) | 18.0 (−10.6) |
| 4 | F | 15.8 (−13.5) | 16.0 (−12.9) | 11 | F | 17.3 (−9.8) | 17.5 (−9.2) | 18 | F | 15.1 (−12.2) | 15.3 (−11.6) |
| 5 | CHO | 11.4 (−16.8) | 11.6 (−16.3) | 12 | CHO | 14.9 (−12.5) | 14.1 (−10.7) | 19 | CHO | 14.1 (−13.7) | 14.2 (−13.2) |
| 6 | CN | 14.2 (−13.3) | 14.4 (−12.6) | 13 | CN | 17.9 (−9.1) | 18.0 (−8.5) | 20 | CN | 15.2 (−12.7) | 15.4 (−12.1) |
| 7 | NO 2 | 10.2 (−17.2) | 10.5 (−16.6) | 14 | NO2 | 12.1 (−15.2) | 12.3 (−14.7) | 21 | NO2 | 14.8 (−13.4) | 14.8 (−12.9) |
a
For computed values using M06-2X/6-31+G(d).
b
For computed values using M06-2X/6-31+G(d,p).