| Entry | Cobalt salt | Lewis acid | Yield/% | Selectivity | |
| 7 | 6 | 7/6 | |||
| 1 | Co(NO3)2∙6H2O | - | 0.0 | 98.0 | 0.0/100.0 |
| 2 | CoCl2 | - | 0.0 | 78.9 | 0.0/100.0 |
| 3 | Co(BF4)2∙6H2O | - | 5.8 | 81.4 | 6.7/93.3 |
| 4 | Co(ClO4)2∙6H2O | - | 1.1 | 95.9 | 1.1/98.9 |
| 5 | - | Sm(OTf)3 | 8.4 | 89.9 | 8.6/91.4 |
| 6 | Co(NO3)2∙6H2O | Sm(OTf)3 | 11.1 | 86.5 | 11.4/88.6 |
| 7 | CoCl2 | Sm(OTf)3 | 47.0 | 31.9 | 59.5/40.5 |
| 8 | Co(BF4)2∙6H2O | Sm(OTf)3 | 89.0 | 8.5 | 91.2/8.8 |
| 9 | Co(ClO4)2∙6H2O | Sm(OTf)3 | 96.6 | 0.0 | 100.0/0.0 |
| 10 | - | Yb(OTf)3 | 36.9 | 62.1 | 37.2/62.8 |
| 11 | Co(NO3)2∙6H2O | Yb(OTf)3 | 57.4 | 28.4 | 66.9/33.1 |
| 12 | CoCl2 | Yb(OTf)3 | 71.6 | 26.0 | 73.4/26.6 |
| 13 | Co(BF4)2∙6H2O | Yb(OTf)3 | 76.8 | 15.7 | 83.1/16.9 |
| 14 | Co(ClO4)2∙6H2O | Yb(OTf)3 | 63.1 | 22.9 | 73.4/26.6 |