chapter 2 palladium catalysts in suzuki cross- coupling reaction

Table 5.9. Pd(NH3)4 2+ -loaded NaY type zeolite catalyzed Suzuki reaction of 4-
R
substituted aryl bromides with arylboronic acid
+
Br
Entry Aryl Halide
0.005 - 0.001% [Pd(NH3) 4] +2 B(OH) 2
-Y
1g NaY, 20 mmol Na 2CO 3
20 mL DMA/water (1:1)
100 ºC, in air
Isolated
Yield%
Pd%
(mmol)
Time
R
(min) TOF -1a TON a
1 4-COCH3C6H4Br 95 0.005 15 76,000 19,000
2 4-COCH3C6H4Br 97 b 0.001 30 194,000 97,000
3 4-COCH3C6H4Br 30 b 0.0001 120 150,000 300,000
4 4-NO2C6H4Br 97 0.001 30 194,000 97,000
5 4-CNC6H4Br 91 0.001 105 52,000 91,000
6 4-CHOC6H4Br 100 0.001 30 200,000 100,000
7 4-OCH3C6H4Br 92 0.005 30 36,800 18,400
8 4-CH3C6H4Br 93 b
0.005 15 74,400 18,600
9 4-CH3C6H4Br 76 b 0.001 15 304,000 76,000
10 4-NH2C6H4Br 94 0.005 45 25,067 18,800
11 C6H6Br 90 b 0.001 45 120,000 90,000
12 c 4-COCH3C6H4Br 99 0.001 45 132,000 990,000
a TOF = TON/h, TON = [yield]/[Pd]. b GC yield. c 4-methoxyphenylboronic acid was used.
The optimization of reaction conditions was determined at the Pd concentration
of 0.005%. In the case of the activated aryl bromides, we were able to perform the
reaction even at 0.001% Pd (Table 5.9, entries 2, 4-6). Unfortunately, product formation
was not good at much lower (0.0001%) Pd concentration (entry 3). However, the
catalyst showed high activity for the reactions of the inactivated aryl bromides (Table
5.9, entries 7, 8, 10) and also nonactivated bromobenzene (entry 11) at 0.005% Pd and
0.001% of Pd concentrations, respectively. Moderate yield was obtained in the presence
of 0.001% Pd concentration for 4-bromotoluene (entry 9). 4-Bromoacetophenone also
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