Table 1. Selected Optimization for the Zinc-Mediated CAA Reaction.
| entry | reductant | Lewis acid (equiv) | solvent | yield (%)a |
|---|---|---|---|---|
| 1 | Mn | TMSOTf (1) | CH2Cl2 | 2 |
| 2 | In | TMSOTf (1) | CH2Cl2 | 28 |
| 3 | Zn | TMSOTf (1) | CH2Cl2 | 43 |
| 4 | Zn | TMSOTf (2) | CH2Cl2 | 99 |
| 5 | Zn | TMSOTf (2) | EtOAc | 100 |
| 6 | Zn | TBSOTf (2) | EtOAc | 87 |
| 7 | Zn | TMSCl (2) | EtOAc | 93 |
| 8 | Zn | TFA (2) | EtOAc | 45 |
| 9b | Zn | TMSOTf (2) | EtOAc | 65 |
| 10b | Zn | TMSOTf (1) | EtOAc | 84 |
a
Yields of 4a were determined by 1H NMR using 1,1,2,2 tetrachloroethane as an internal standard.
b
Amine hydrochloride salt used.