ABSTRACT
Six consecutive Suzuki coupling reactions of aryl bromides were run with a recycled Pd/C catalyst producing yields of 70 - 92 % without apparent loss of activity. On the basis of total palladium in the initial run, the turnover number was 20/cycle or 120 over the entire sequence. Next, a semi-continuous, fixedbed, flow system was built using palladium on 1/8" carbon extrudates. Suzuki coupling reactions of aryl bromides containing electron withdrawing groups were successfully accomplished in reasonable reaction times (2 - 12 h) and levels of conversion (> 98 %) with fresh catalyst. However, subsequent cycles lead to decreasing levels of activity. Nevertheless, turnover numbers for the fixed bed system based on total palladium reached up to 250 after four cycles.
