Abstract
β,β-Disubstituted-1,3-dinitro compounds were obtained exclusively with an overall yield of 83% through a domino nitroaldol/elimination/1,4-addition process, when excess nitromethane was added to cyclohexanone or butanone using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), as a basic catalyst. On the other hand, β-nitroalcohols could be obtained in 30-84% yield, when nitromethane reacts with different aliphatic ketones in stoichiometric amounts, in the presence of catalytic amounts of K2CO3(s), Amberlyst®-A21 or TBAF.3H2O (tetra-n-butylammonium fluoride trihydrate)/THF (tetrahydrofuran). In addition, a new and versatile route to obtainment of allylic nitro compounds, by treatment of acetylated nitroalcohols and aldehydes in catalytic amounts of DBU or TBAF.3H2O, via a one-pot elimination/nitroaldol reaction sequence, was developed.
Highlights
The nitroaldol reaction (Henry’s reaction) is one of the most important reactions used to form C-C bonds
The use of ketones as electrophiles in nitroaldol reactions is more limited than aldehydes, because of the lower electrophilicity generated by the electronic and steric effects of α,α’-carbonyl substituents, and
1,3-Dinitro alkanes have gained importance in synthesis organic for preparation of different targets such as 1,3-diketones, 1,3-diamines, polyfunctionalized carbacycles, highly substituted arenes, phenols, among others.32-36. They are usually prepared in two ways: the first one occurs by adding nitronate anions to conjugated nitroalkenes produced from aldehydes
Summary
The nitroaldol reaction (Henry’s reaction) is one of the most important reactions used to form C-C bonds. We hypothesized that allylic nitro compounds could be obtained from reaction between the aldehydes 18, 19 and the acetylated β-nitroalcohols 16, 17, via a base catalyzed one pot elimination/nitroaldol sequence.
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