Nitromethane (MeNO2)

Abstract

(A) The catalytic enantioselective Henry reaction of α-keto esters with NM affords β-nitro-α-hydroxy esters.9 The reaction proceeds via a 1,2-addition reaction and the product can be converted into β-amino acids. (Chemical Equation Presented) (B) The efficacy of NM has been extended to the base-catalyzed solid-phase condensation of steroidal, alicyclic or aromatic β-formyl enamides under microwave irradiation. 10 Boruah and co-workers found a new application of the Henry reaction and provided a route for facile, one-pot combinatorial synthesis of annelated pyridines. (Chemical Equation Presented) (C) NM reacts with N-sulfinylimines in the presence of NaOH to produce nitroamines in a highly diastereoselective manner.11 In the presence of TBAF, the reaction rates are strongly increased and the stereoselectivity is inverted. This approach offers enantiomerically pure β-nitroamines, which have been hardly accessible by azaHenry reactions so far. (Chemical Equation Presented) (D) α,α-Dipeptides are valuable synthetic intermediates and biologically active compounds. Recently, Petrini and Seri12 have utilized NM in a two-step synthesis of α,α-dipeptide from α-amido sulfone. The procedure involves the nitromethylation of 1 followed by Nef conversion of the nitro group to furnish product 2. (Chemical Equation Presented) (E) NM undergoes an enantioselective Michael addition with 1-(2-alkenoyl)-3,5-dimethyl pyrazoles by a catalytic double activation method using chiral Lewis acid and achiral amine catalyst to give 1-(3-substituted 4-nitrobutanoyl)-3,5-dimethyl pyrazole in high yields.13 This method has been successfully employed for the total synthesis of the antidepressant (R)-rolipram (1). (Chemical Equation Presented) (F) A three-component Michael addition reaction of NM with two unsymmetrical α,β-unsaturated carbonyl compounds in the presence of base provides a convenient one-pot synthesis of 1,7-dicarbonyl compounds. 14 1,7-Dicarbonyl compounds are initial starting materials for the synthesis of enantiomerically pure alcohols, which are useful building blocks for natural product synthesis. (Chemical Equation Presented) (G) Under solvent-free conditions, γ-nitroacetamido ester can be obtained via Michael addition from the commercial acetamido acrylate and NM.15 The product is a versatile precursor for the preparation of α-amino acids. © Georg Thieme Verlag Stuttgart.