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Table 1. Oxidative coupling of toluene to DMBP and subsequent isomerization
| DMBP isomer |
2,2´ |
2,3´ |
2,4´ |
3,3´ |
3,4´ |
4,4´ |
| Regioselectivity of oxidative coupling of toluene over Pd(OAc)2a |
Distribution, % |
| 5 |
18 |
14 |
24 |
29 |
10 |
| Isomerization of DMBP isomers at 100 °C, 10 minb |
Isomer distribution, % |
| Acid/substrate mol ratio 5:1 |
0 |
2 |
1 |
39 |
47 |
11 |
| Acid/substrate mol ratio 10:1 |
0 |
1 |
1 |
39 |
51 |
8 |
| Isomerization of DMBP at room temperatureb,c |
Isomer distribution, % |
| Acid/substrate mol ratio 4:1 |
4 |
19 |
14 |
24 |
29 |
10 |
| Acid/substrate mol ratio 180:1 |
0 |
0 |
0 |
30 |
70 |
0 |
| Predictionsd |
0 |
0 |
0 |
22 |
77 |
1 |
For structures of isomers, see Figure 1.
aReaction temp, 150 °C; reaction time, 3 h; turnover rate, 18.5 h–1; O2 partial pressure, 375 psig; 0.1 mol% Pd(OAc)2.
bSubstrate is isomer mixture produced in oxidative coupling reaction.
cToluene solvent, stirred autoclave, 20 h.
dPredictions using AM-1 modeling tool. |
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