Table 6.
Effect of the type of added base on the yield of the reduction products 3a and 4a.
| Entry | Base | Yield of 3a (%)c |
Yield of 4 (%)c |
|
|
| ||||
| Type (pKa of conjugated acid of baseb) |
equiv | |||
|
| ||||
| 1 | pyridine (5.33) | 0.5 | 33 | 19 |
| 2 | 2,6-lutidine (6.7) | 0.5 | 38 | 30 |
| 3 | piperidine (11.1) | 0.5 | 31 | 28 |
| 4 | DBU (12.0) | 0.5 | 61 | 25 |
| 5 | DBU (12.0) | 1.0 | 78 | 11 |
| 6 | DBU (12.0) | 1.5 | 77 | 17 |
aExperimental conditions: cathode, GC plate; anode, Pt plate; electricity, 2.15 F mol−1; current density, 12.7 mA cm−2; electrode distance, 40 μm; solvent, THF; substrate, 0.06 M benzylideneaniline (1) and 0.12 M 1,4-dibromobutane (2a); base added, 0.06 M DBU; supporting electrolyte, 0.14 M n-Bu4N∙ClO4; flow rate, 11 mL h−1 (residence time, 3.9 s). bLiterature data according to ref. [37–41]. cDetermined by HPLC.