Table 2.
Gibbs activation energy for enantiomerization of [n]helicenes (n=3–6) substituted at the inner helix.
|
[n]Helicene |
R1 (A values) |
R1′ (A values) |
ΔG ≠ [kcal mol−1] at (T [K]) |
|---|---|---|---|
|
3 |
OCH2Ph |
Br (0.38) |
11.3 (224)[a,b] |
|
3 |
OCH2Ph |
tBu (>4) |
19.3 (376)[a,b] |
|
3 |
Me (1.7) |
tBu (>4) |
26.6 (353)[a,b] |
|
3 |
CH2OAc |
CH2OAc |
18.1(298)[a,c] |
|
3 |
Me (1.7) |
Me (1.7) |
16.1(298)[a,c] |
|
4 |
OCH2Ph |
H (0) |
14.4 (259)[a,b] |
|
4 |
Me (1.7) |
H (0) |
21.2 (298)[d] |
|
4 |
tBu (>4) |
H (0) |
28.2 (353)[a,b] |
|
4 |
Me (1.7) |
F (0.15) |
30.7 (298)[e,f] |
|
4 |
Me (1.7) |
Me (0.15) |
41.4 (298)[d] |
|
5 |
OMe (0.60) |
H (0) |
32.3 (423)[e,g] |
|
5 |
Me (1.7) |
H (0) |
39.1 (473)[e,g] |
|
5 |
F (0.15) |
F (0.15) |
36.8 (466)[e,h] |
|
5 |
OMe (0.60) |
OMe (0.60) |
41.0 (483)[e,h] |
|
5 |
Me (1.7) |
Me (1.7) |
44.2 (503)[e,h] |
|
6 |
Me (1.7) |
H (0) |
41.4 (298)[e,i] |
|
6 |
Me (1.7) |
Me (1.7) |
43.8 (543)[e,i] |
[a] Originally reported values, the recalculation was not possible because values for the rate constant were not available. [b] See ref. [44]. [c] See ref. [33]. [d] DFT‐calculated values, see ref. [45]. [e] Gibbs activation energy (re)calculated by using the equation ΔG ≠(T)=−RT ln(k e h/κk B T) with κ=0.5. [f] See ref. [42]. [g] See ref. [46]. [h] See ref. [39]. [i] See ref. [47].