TABLE 1.
Evaluation of additives on the regioselectivity of Rh-alkyl nitrene.
|
| Entry | Additive (x equiv) | Conversion (%) a | 12a:13a b |
|---|---|---|---|
| 1 | — | >95 | 21:79 |
| 2 | TFA (3) | >95 | 29:71 |
| 3 | TFA (10) | >95 | 31:69 |
| 4 c | TfOH (3) | 12 (21) | 4:>96 (4: > 96) |
| 5 | PPTS (3) | 27 | 4:>96 |
| 6 | 2,6-Lutidine (3) | >95 | 24:76 |
| 7 | Et3N (3) | >95 | 26:74 |
| 8 | Cs2CO3 (3) | >95 | 19:81 |
| 9 | Barton’s base (3) | Complex mixture |
a
Conversion was determined using 1H NMR, analysis of unpurified reaction mixture.
b
The regioselectivity was determined using 1H NMR, and reverse-phase HPLC, analysis of unpurified reaction mixture.
c
The values in parentheses were obtained after 48 h. TFA, trifluoroacetic acid; TfOH, trifluoromethanesulfonic acid; PPTS, pyridinium p-toluenesulfonate.