Table 1.
Optimization of the reactions conditions.
 | ||||||
| entry | R (x equiv) | MX (y equiv) | solvent | temp. | time | N°, Y, X (yield %)a |
| 1 | Ac (1.2) | LiBr (2.4) | MeCN | 0 °C | 5 min | 2a, Br, Br (91) |
| 2 | C(O)CF3 (1.1) | n-Bu4NBrb (1.2) | MeCN | 0 °C | 15 minc | 3a, OCOCF3, Br (77) |
| 3 | Ac (1.2) | LiBr (2.4) | MeCN/H2O | rt | 5 min | 4a, OH, Br (59)d |
| 4 | Ac (1.2) | LiBre (1.3) | MeCN/H2O | −10 °C | 15 minc | 4a, OH, Br (65)f |
| 5 | Ac (1.4) | LiBre (1.6) | MeCN/H2O | −10 °C | 15 minc | 4a, OH, Br (70) |
| 6 | Ac (1.2) | LiBr (1.2) | EtOH | −10 °C | 105 min | 4a’, OEt, Br (68)g |
| 7 | C(O)CF3 (1.5)h | KI (2.4) | MeCN | 0 °C | 20 min | 5a, OCOCF3, I (70) |
| 8 | C(O)CF3 (1.3)i | n-Bu4NIb (1.5)i | MeCN | 0 °C | 100 min | 5a, OCOCF3, I (44) |
| 9 | C(O)CF3 (1.5) | n-Bu4NIb (1.5) | MeCN | 0 °C | 20 min | 5a, OCOCF3, I (60)j |
| 10 | C(O)CF3 (1.5) | n-Bu4NIb (1.5) | CH2Cl2 | 0 °C | 20 min | 5a, OCOCF3, I (63) |
| 11 | Ac (1.2) | FeCl3 (0.8) | MeCN | rt | 5 min | 6a (45) |
| 12 | C(O)CF3 (1.2) | n-Bu4NClb (1.5) | MeCN | 0 °C | 15 minc | 6a (36) |
| 13 | C(O)CF3 (1.2) | n-Bu4NClb (1.5) | CH2Cl2 | 0 °C | 15 minc | 6a (85) |
aIsolated yields; bslow addition of a 0.1 M solution of the TBA salt; c5 min of addition followed by 10 min of stirring; dalong with 6% of 2a; eslow addition of a 0.1 M aqueous solution of LiBr; ffull conversion was not reached; galong with 25% of 2a; hslow addition of a 0.1 M solution of PIFA; iinitially 1.1 equiv of PIFA and 1.2 equiv of TBAI, followed by 0.2 equiv of PIFA and 0.3 equiv of TBAI to reach completion; jalong with 20% of 1a.