Table 1a.
entry | donor | solvent | yield (%) | (α/β) |
---|---|---|---|---|
1 | 22 | CH2Cl2 | 85 (24) | α only |
2 | 23 | PhMe/CH2Cl2 (3:1) | 99 (25) | 3:2 |
3 | 23 | CHCl3 | 96 (25) | 1:3 |
Reagents and conditions: (a) Ph2SO, Tf2O, TBP; add 20.
entry | donor | solvent | yield (%) | (α/β) |
---|---|---|---|---|
1 | 22 | CH2Cl2 | 85 (24) | α only |
2 | 23 | PhMe/CH2Cl2 (3:1) | 99 (25) | 3:2 |
3 | 23 | CHCl3 | 96 (25) | 1:3 |
Reagents and conditions: (a) Ph2SO, Tf2O, TBP; add 20.