Table 4.
Mn-Mediated Radical Additions to N-Acylhydrazones.
| |||||
|---|---|---|---|---|---|
| entry | aldehyde (or acetal) | yield, hydrazonea | halide R2X | yield, radical additionb | dr |
| 1 | CH3CH2CHO | 81% | CH3CH2I | 85% | - |
| 2 | CH3I | 48%c,d (S) | 95:5e | ||
| 3 | n-PrI | 66% (R) | 94:6e | ||
| 4 | n-BuI | 78% (R) | 95:5e | ||
| 5 | n-C5H11I | 79% (R) | 96:4e | ||
| 6 | i-BuI | 54%c (R) | 95:5f | ||
| 7 | i-PrI | 75% (R) | 95:5f | ||
| 8 | ClCH2I | 63% (R) | 93:7e | ||
| 9 | Cl(CH2)3I | 52% (R) | 96:4f | ||
| 10 | Cl(CH2)4I | 55% (R) | 96:4e | ||
| 11 | Cl2CHBr | 38%c,d (R) | 98:2f | ||
| 12 | CH3CHO | 66% | CH3CH2I | 66% (R) | 95:5e |
| 13 | n-PrCHO | 87% | 63% (S) | 95:5e | |
| 14 | n-BuCHO | 89% | 72% (S) | 97:3e | |
| 15 | n-C5H11CHO | 88% | 77% (S) | 97:3e | |
| 16 | i-BuCHO | 85% | 65% (S) | 95:5f | |
| 17 | ClCH2CH(OMe)2 | 85% | 57% (S) | 93:7e | |
| 18 | Cl(CH2)3CHO | 95% | 60% (S) | 93:7f | |
| 19 | Cl(CH2)4CHO | 89% | 62% (S) | 97:3e | |
| 20 | Cl2CHCH(OEt)2 | 54% | 34%c (S) | 89:11f | |
Reaction conditions: (1) Aldehyde or acetal (5–10 equiv), 9a, p-toluenesulfonic acid, CH2Cl2, rt. (2) Hydrazone in deoxygenated CH2Cl2 (0.1 M), InCl3 (2.2 equiv), Mn2(CO)10 (1–2 equiv), R2X (10 equiv), hν (300 nm, pyrex), 1–2 d, ca. 35 °C.
a
Isolated yield.
b
Isolated yields of purified diastereomer mixtures. R or S denotes the configuration of the new stereogenic center. Addition of methyl iodide gives opposite configurations due to the lower priority of the methyl ligand.
c
20 equiv of R2X was used.
d
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was used in removal of Mn byproducts.
e
Ratio by HPLC (Chiralcel OD, 2-PrOH/hexane).
f
Ratio by 1H NMR.