Table 3. Titania-Promoted Reactions of Aryloxyacetic Acids with Maleimides.
| entry | R1 R2 (a–f) | conditionsa | yield (%)b | 6:7 ratio |
|---|---|---|---|---|
| 1 | H Me (a) | P25, 20 h | 75 | 2.38:1.0 |
| 2 | H Me (a) | P25 dd, 45 h | 75c | 10:1 |
| 3 | H Me (a) | coated tube, 22 h | 75c | 0.25:1.0 |
| 4 | H Ph (b) | P25, 11 h | 79 | 1.0:1.0 |
| 5 | H Ph (b) | coated tube, 22 h | 85c | 0.18:1.0 |
| 6 | t-Bu Me (c) | P25, 22 h | 57d | 4.20:1.0 |
| 7 | t-Bu Me (c) | P25 dd, 42 h | 56c | >10:1.0e |
| 8 | t-Bu Ph (d) | P25, 18 h | 74 | 1.64:1.0 |
| 9 | t-Bu Ph (d) | coated tube, 19 h | 51c | 0.82:1.0 |
| 10 | CF3 Me (e) | P25, 16 h | 61 | 1.10:1.0 |
| 11 | CF3 Me (e) | P25 dd, 42 h | 62c | 1.70:1.0 |
| 12 | CF3 Ph (f) | P25, 16 h | 63 | 0.57:1.0 |
| 13 | CF3 Ph (f) | coated tube, 17 h | 93c | 0.38:1.0 |
a
Dispersion of 1 mg mL–1 except for dd = dense dispersion of 5 mg mL–1.
b
mol % isolated products, except as noted.
c
NMR yield.
d
15% 6 was obtained in the absence of P25.
e
Only 6 was observed.