Ketones as Electrophile in Nitroaldol Reaction: Synthesis of β,β-Disubstituted- 1,3-dinitroalkanes and Allylic Nitro Compounds

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.

摘要：当以碱性催化剂DBU（1,8-diazabicyclo[5.4.0]undec-7-ene）催化时，将过量硝基甲烷加入环己酮或丁酮中，通过多米诺硝基羟醛/消除/1,4-加成串联反应，可专一地得到β,β-二取代-1,3-二硝基化合物，总产率达83%。另一方面，当硝基甲烷与不同脂肪族酮以化学计量比进行反应，且体系中存在催化量的固态碳酸钾（K₂CO₃(s)）、Amberlyst®-A21或三水合四丁基氟化铵（tetra-n-butylammonium fluoride trihydrate, TBAF·3H₂O）/四氢呋喃（tetrahydrofuran, THF）时，可得到β-硝基醇，产率范围为30%~84%。此外，本研究开发了一条新颖且通用的烯丙基硝基化合物合成路线：以乙酰化硝基醇与醛类为原料，在催化量DBU或TBAF·3H₂O作用下，通过一锅法消除/硝基羟醛反应序列制得目标产物。