Highly efficient one- or two-step sequences for the synthesis of fine chemicals from versatile nitroalkanes

Ni(II)-Aroylhydrazone Complexes as Catalyst Precursors Towards Efficient Solvent-Free Nitroaldol Condensation Reaction

The aroylhydrazone Schiff bases 2-hydroxy-(2-hydroxybenzylidene)benzohydrazide and (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide have been used to synthesize the bi- and tri-nuclear Ni(II) complexes [Ni2(L1)2(MeOH)4] (1) and [Ni3(HL2)2(CH3OH)8]· (NO3)2 (2). Both complexes have been characterized by elemental analysis, spectroscopic techniques [IR spectroscopy and electrospray ionization-mass spectrometry (ESI-MS)], and single-crystal X-ray crystallography. The coordination behavior of the two ligands is different in the complexes: The ligand exhibits the keto form in 2, while coordination through enol form was found in 1. Herein, the catalytic activity of 1 and 2 has been compared with the nitroaldol condensation reaction under various conditions. Complex 2 exhibits the highest activity towards solvent-free conditions.

Reaction of Meldrum's Acid with an Aminomethylating Agent and Nitroalkanes

5-(2-Nitroalkyl)isopropylidene malonate and 5,5′-(2-nitro-1,3-propylidene)bis(isopropylidene malonate) were easily synthesised by one-pot tandem reaction of substituted Meldrum's acids with the aminomethylating agent (Me2NCH2OAc) and nitroalkanes in the presence of a weak acid, such as acetic acid.

Iron-catalyzed unprecedented formation of benzo[d]imidazo[2,1-b]thiazoles under solvent-free conditions

The unprecedented formation of benzo[d]imidazo[2,1-b]thiazole during iron-catalyzed coupling of 2-aminobenzothiazole, aldehydes with nitroalkane in air has been observed.

Palladium-Catalyzed α-Arylation of Aryl Nitromethanes

Catalytic conditions for the α-arylation of aryl nitromethanes have been discovered using parallel microscale experimentation, despite two prior reports of the lack of reactivity of these aryl nitromethane precursors. The method efficiently provides a variety of substituted, isolable diaryl nitromethanes. In addition, it is possible to sequentially append two different aryl groups to nitromethane. Mild oxidation conditions were identified to afford the corresponding benzophenones via the Nef reaction, and reduction conditions were optimized to afford several diaryl methylamines.

Crystal structure of (2S,4R)-ethyl 4-nitromethyl-1-[(S)-1-phenylethyl]-6-sulfanylidenepiperidine-2-carboxylate

In the title compound, C₁₇H₂₂N₂O₄S, a thio­piperidine derivative, the piperidine ring has an envelope conformation with the methyl­ene C atom opposite to the C=S bond as the flap. The nitro­methyl substituent is equatorial while the eth­oxy­carbonyl group is axial. The mean planes of the nitro­methyl group, the carb­oxy group and phenyl ring are inclined to the mean plane through the five planar atoms of the piperidine ring [maximum deviation = 0.070 (4) Å] by 56.8 (2), 83.8 (5) and 87.1 (2)°, respectively. There is an intra­molecular C—H⋯O hydrogen bond involving an H atom of the eth­oxy­carbonyl group and a nitro O atom. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by further C—H⋯O hydrogen bonds, forming corrugated layers lying parallel to (001).

Selective amination reactions of α-nitro aryl and heteroaryl enoates

Highly functionalized tetrasubstituted alkenes were obtained by an unexpected amination reaction promoted by ethyl nosyloxycarbamate on various α-nitro aryl and heteroaryl enoates. A nitrene is likely the aminating species responsible for the observed insertion reaction leading to (E)-β-amino α-nitro enoates as the major products, regardless of the substrate configuration. The compounds, bearing two nitrogenous functional groups in different oxidation states, can be regarded as interesting synthons. In contrast, aziridination was observed for α-nitro alkyl enoates or β-nitro allylic alcohols.

Minimizing the amount of nitromethane in palladium-catalyzed cross-coupling with aryl halides

A method for the formation of arylnitromethanes is described that employs readily available aryl halides or triflates and small amounts of nitromethane in a dioxane solvent, thereby reducing the hazards associated with this reagent. Specifically, 2-10 equiv (1-5% v/v) of nitromethane can be employed in comparison to prior work that used nitromethane as solvent (185 equiv). The present transformation provides high yields at relatively low temperatures and tolerates an array of functionality, including heterocycles and substantial steric encumbrance.

Easy and direct conversion of tosylates and mesylates into nitroalkanes

Tosylates and mesylates were directly converted into the corresponding nitroalkanes, by their treatment with tetrabutylammonium nitrite (TBAN) under mild conditions.

One-pot Synthesis of 1,3-dinitroalkanes Catalysed by Nickel Species

The reaction of aromatic aldehydes with nitromethane afforded a one-pot preparation of 1,3-dinitroalkanes in the presence of a nickel catalytic system. This efficient and simple method proceeded with moderate to high yields (56–99%) under mild conditions.

Toxicity and metabolism of nitroalkanes and substituted nitroalkanes

A series of low molecular weight nitro-containing compounds has recently been discovered to have a variety of biological activities including the reduction of anaerobic methane production in ruminant animals and activity against economically important human pathogens, including Salmonella sp. and shigella-toxin producing Escherichia coli . Although some of these nitrocompounds, nitroethane and 2-nitropropane, for example, have been industrial chemicals and synthetic intermediates for years, others such as carboxymethyl nitro-amino acid analogues are new to science and have not been previously described. The purpose of this paper is to review the toxicological profiles, especially as related to events occurring during metabolism and biotransformation, which contribute to toxicological end points of established nitroaliphatic compounds. It is hoped that by summarizing existing knowledge, an understanding of the activities and toxicological profiles of newly established nitrocompounds might be anticipated or adverse events associated with their use might be avoided.

Palladium-catalyzed nitromethylation of aryl halides: an orthogonal formylation equivalent

An efficient cross-coupling reaction of aryl halides and nitromethane was developed with the use of parallel microscale experimentation. The arylnitromethane products are precursors for numerous useful synthetic products. An efficient method for their direct conversion to the corresponding oximes and aldehydes in a one-pot operation has been discovered. The process exploits inexpensive nitromethane as a carbonyl equivalent, providing a mild and convenient formylation method that is compatible with many functional groups.

Facile and efficient conjugate additions of β-dicarbonyl compounds and nitroalkanes to 4-aryl-4-oxobut-2-enoates

Facile and efficient conjugate additions of carbon nucleophiles, such as ?-dicarbonyl compounds and nitroalkanes, to 4-aryl-4-oxobut-2-enoates have been achieved under simple base catalysis. A variety of multi-functional ?-keto esters could be conveniently obtained in good to excellent yields with complete regioselectivity.