Nitroalkanes. Roberto BalliniЧитать онлайн книгу.
PMHS, polymethylhydrosiloxane.
1.6.1 Nitroalkylation of Aryl Halides
Aryl halides can be converted into “aryl nitromethanes” via a cross-coupling reaction with nitromethane, catalyzed by Pd2(dba)3, tris(dibenzylideneacetone)dipalladium, as reported in Scheme 1.18 [40].
A more general protocol provides the arylation of primary nitroalkanes (different from nitromethane), via Pd-catalyzed reaction with aryl bromide or chlorides (Scheme 1.19) [41].
More detailed applications are reported in Chapter 6.
Scheme 1.17 Reductive nitromethylation of aldehydes.
Table 1.5 Nitration of alkanes (selected examples).
| Substrate | Nitrating agent | Nitroalkane | Yield (%) |
|---|---|---|---|
|
|
NHPI (NO2) |
|
63 |
|
|
NAPI (HNO3) |
|
69 |
|
|
NAPI (NO2) |
|
69 |
|
|
NHPI (HNO3) |
|
70 |
|
|
NHPI (NO2) |
|
54 |
|
|
NHPI (NO2) |
|
65 |
1.6.2 Nitroalkylation of Allylic Esters
Pd catalyzes even the asymmetric allylic alkylation of cyclic allyl esters [42] in the presence of O,N-bis-trimethylsilylacetamide (BSA) as base and a chiral biphosphine ligand (Table 1.6). The method allows a practical way to primary chiral nitroalkanes with an extra carbon atom.
1.6.3 Nitroalkylation of Allylic Alcohols
Unactivated nitroalkenes (mainly nitromethane) can be added to vinyl epoxides, under Pd(0) catalysis, affording nitroalkenols (Scheme 1.20).
Scheme 1.18 Nitromethylation of aryl halides.
Scheme 1.19 Nitroalkylation of aryl halides.
Table 1.6 Asymmetric nitromethylation of cyclic allyl esters (selected examples).
| Substrate | Reaction conditions | Nitroalkane | Yield (%), (ee) |
|---|---|---|---|
|
|
CH3NO2/CH2Cl2, Pd2(dba)3, ligand, BSA |
|
82 (99%) |
|
|
CH3NO2/CH2Cl2, Pd2(dba)3, ligand, Bu4NCl/BSA |
|
99 (99%) |