Table 2. ωB97X-D/6-31+G** Relative Gibbs Free Energies in kcal·mol–1, Computed at 298 K in Toluene, of the Stationary Points Involved in the Diels–Alder Reaction of 4-Alkenyl-2-dimethylaminothiazoles 1b,e with Nitroethylenes 2a,b.
| path | 1b+2a | 1b+2b | 1e+2a | 1e+2b | |
|---|---|---|---|---|---|
| endo-A | TS1xy-endoA | 26.6 | 23.6 | 24.7 | 22.0 |
| INTxy-endoA | 10.8 | 5.4 | |||
| TS2xy-endoA | 22.5 | 17.5 | |||
| 3′xy-endoA | –18.1 | –22.6 | –11.4 | –16.1 | |
| 3xy-endoA | –30.8 | –34.7 | –24.1 | –28.6 | |
| exo-A | TS1xy-exoA | 23.7 | 22.5 | 20.3 | 20.7 |
| 9xy-exoA | 21.1 | 16.4 | |||
| TS2xy-exoA | 21.8 | a | |||
| 3′xy-exoA | –18.3 | –24.8 | –13.1 | –19.8 | |
| 3xy-exoA | –31.0 | –36.2 | –26.8 | –31.2 | |
| endo-B | TS1xy-endoB | 29.9 | 25.7 | 29.6 | 27.2 |
| 3′xy-endoB | –14.9 | –20.0 | –11.4 | –13.8 | |
| 3xy-endoB | –25.1 | –34.5 | –25.4 | –30.0 | |
| exo-B | TS1xy-exoB | 28.3 | 25.5 | 28.8 | 27.2 |
| 3′xy-exoB | –17.0 | –22.9 | –12.6 | –18.1 | |
| 3xy-exoB | –29.1 | –35.7 | –25.5 | –31.5 |
a
We have not been able to optimize this transition state.