7214-61-1

Nitrogen oxide (NOx) conversion is an important process for balancing the global nitrogen cycle. Distinct from the biological NOx transformation, we have devised a synthetic approach to this issue by utilizing a bifunctional metal catalyst for producing value-added products from NOx. Here, we present a novel catalysis based on a Ni pincer system, effectively converting Ni-NOx to Ni-NO via deoxygenation with CO(g). This is followed by transfer of the in situ generated nitroso group to organic substrates, which favorably occurs at the flattened Ni(I)-NO site via its nucleophilic reaction. Successful catalytic production of oximes from benzyl halides using NaNO2 is presented with a turnover number of >200 under mild conditions. In a key step of the catalysis, a nickel(I)-?NO species effectively activates alkyl halides, which is carefully evaluated by both experimental and theoretical methods. Our nickel catalyst effectively fulfills a dual purpose, namely, deoxygenating NOx anions and catalyzing C-N coupling.

The use of silyl nitronates is reported for the isothiourea-catalyzed synthesis of ?3-nitro-substituted silyl esters containing up to two contiguous stereocenters in good yields with excellent enantioselectivities (up to 93% yield and 99:1 er). The serendipitously discovered formation of silyl ester products in this reaction demonstrates a novel platform for catalyst turnover in α,β-unsaturated acyl ammonium catalysis.

A novel access to isoxazolines was developed using the [4+1]-annulation of α-keto-stabilized sulfur ylides with N,N-bis(siloxy)enamines derived from aliphatic nitro compounds. The resulting 5-keto-substituted isoxazolines were shown to be convenient precursors of polysubstituted 3-hydroxypyrrolidines via the one-pot catalytic N?O hydrogenolysis/intramolecular reductive amination sequence. Application of this approach to the formal synthesis of Merck's potent NK1 receptor antagonist was demonstrated. (Figure presented.).

The synthetic utility of the aza-Henry reaction can be diminished on scale by potential hazards associated with the use of peracid to prepare nitroalkane substrates and the nitroalkanes themselves. In response, a continuous and scalable chemistry platform to prepare aliphatic nitroalkanes on-demand using the oxidation of oximes with peracetic acid and direct reaction of the nitroalkane intermediate in an aza-Henry reaction is reported. A uniquely designed pipes-in-series plug-flow tube reactor addresses a range of process challenges, including stability and safe handling of peroxides and nitroalkanes. The subsequent continuous extraction generates a solution of purified nitroalkane, which can be directly used in the following enantioselective aza-Henry chemistry to furnish valuable chiral diamine precursors with high selectivity, thus completely avoiding isolation of the potentially unsafe low-molecular-weight nitroalkane intermediate. A continuous campaign (16 h) established that these conditions were effective in processing 100 g of the oxime and furnishing 1.4 L of nitroalkane solution.

The efficacy of custom surfactant FI-750-M, designed to mimic polar solvents such as DMF and 1, 4-dioxane, has been demonstrated with the palladium-catalyzed sp2-sp3 coupling of nitroalkanes to aryl bromides using a heteroleptic palladium catalyst under unprecedentedly mild conditions. Optimized reaction conditions mostly provided good yields up to gram scale, with high selectivity and functional group tolerance for a wide scope of aryl bromides. Use of surfactant FI-750-M makes water the gross reaction medium and enables in-flask recycling. The behavior of the surfactant has been elucidated with DLS and cryo-TEM measurements, and mechanistic investigations have revealed the importance of the π-allyl ligand in the catalytic cycle.

The invention belongs to the field of organic chemical industries, and provides a green synthesis method for preparing nitroalkanes by oxime oxidation. At the temperature of 55 to 120 DEG C and under the pressure of 0 to 1.0 MPa, oxime, a solvent and hydrogen peroxide are reacted for 20 to 200min in the presence of certain amounts of nanoporous skeleton metal hybrid catalysts and cocatalysts, a reaction liquid is subjected to membrane separation, the catalysts can be repeatedly used for more than 7 times, and distilled to obtain nitroalkane products, the purity of the products is not less than 99%, and the yield of the products is not less than 95%. Furthermore, the green synthesis method for preparing nitroalkanes by the oxime oxidation disclosed by the invention is a green synthesis method of nitroalkanes, and suitable for large-scale industrialized production.

Novel catalytic systems consisting of cationic gold complexes, N-hydroxyphthalimide (NHPI), and transition-metal-based Lewis acids have been developed for the one-pot synthesis of functionalized oxazoles from N-propargylamides with excellent functional group tolerance. These transformations demonstrated the excellent compatibility of homogeneous gold catalysis with organocatalytic oxidative carbon-nitrogen bond formations using tert-butyl nitrite as the terminal oxidant. Moreover, oxazolecarbonitriles or carboxamides can be easily synthesized in a one-pot protocol according to the different synthetic requirements.

Provided is a process for the formation of nitrated compounds by the nitration of hydrocarbon compounds with dilute nitric acid. Also provided are processes for preparing industrially useful downstream derivatives of the nitrated compounds, as well as novel nitrated compounds and derivatives, and methods of using the derivatives in various applications.

The reaction of various secondary nitro compounds with 1.1 equivalents of potassium hydride in 1,4-dioxane and then with 0.10 equivalent of chlorotrimethylsilane gave the corresponding ketones in 62-90% yields. By a similar strategy, poly(1,3-diketones) were synthesized directly from nitroalkenes with sodium ethoxide, potassium hydride, and chlorotrimethylsilane in 1,4-dioxane. The use of chlorotrimethylsilane in a catalytic amount was the key to the success of this transformation; the use of an excess of chlorotrimethylsilane led to poor yields for the same reactions. Georg Thieme Verlag Stuttgart.

Nitration of light alkanes and the alkyl side-chain of aromatic compounds with NO2 and HNO3 was successfully achieved by the use of N-hydroxyphthalimide (NHPI) as a catalyst under relatively mild conditions. For example, the nitration of propane with NO2 catalyzed by NHPI at 100 °C for 14 h gave 2-nitropropane in good yield without formation of 1-nitropropane and cleaved products such as nitroethane and nitromethane. Various aliphatic nitroalkanes, which are difficult to prepare by conventional methods, could be selectively obtained by means of the present methodology by using NHPI as the key catalyst. In addition, the side-chain nitration of alkylbenzenes such as toluene was selectively carried out to lead to α-nitrotoluene without the ring nitration. The present reaction provides an efficient selective method for the nitration of light alkanes and alkylbenzenes, which has been very difficult to carry out so far.

A general protocol for the Pd-catalyzed-arylation of nitroalkanes is described. Substituted aryl bromides as well as aryl chlorides can be coupled efficiently with a variety of nitroalkanes under mild conditions to selectively yield the monoarylated products. This method tolerates a number of functional groups including ketones, esters, and olefins. Notably, the arylation of nitroalkanes can be effected chemoselectively over ketone and ester arylation.

The coupling reaction beween a chiral C2-symmetric nitroxide, trans-2,5-dimethyl-2,5-diphenylpyrrolidin-1-oxyl (DPPO; 1), and a series of stabilized secondary prochiral radicals was studied to determine the factors that affect stereoselectivity. Both steric and electronic perturbations on the selectivity by the substituents of the prochiral radical were observed. The effects of temperature, solvent polarity, and solvent viscosity were examined. High selectivity for reactions carried out in solvents of low viscosity provides evidence for the formation of an encounter complex on the reaction path. Ab initio calculations on simplified model systems predict the C-O-N angle of attack to be greater than 110°at a carbon-oxygen bond-forming distance of approximately 2.2 A, although no transition state was found.

A simple and highly efficient one-pot synthesis of aliphatic nitro compounds from the corresponding alcohols with NaNO2-AcOH-HCl system is described.

The method provides nitro compounds at a high conversion and selectivity by nitrating substrates under comparatively mild conditions in the absence of catalysts. Organic substrates are nitrated using no catalysts or ozone, but using (1) at least one nitrogen compound selected from N2 O or NO and oxygen. It is advantageous for the nitration reaction to employ a nitrogen compound obtained by a reaction of the nitrogen compound with oxygen, particularly a nitrogen oxide comprising N2 O3 as a main component. Additionally, organic substrates are nitrated using (2) NO2. The substrates include a compound having a methine-carbon atom, and a compound having a methyl group or methylene group in an adjacent position to an aromatic ring.

A convenient oxidation of oximes to nitroalkanes has been developed using oxone in acetonitrile.

Primary aliphatic amines are oxidized with tert-butyl hydroperoxide to the corresponding nitro compounds in 50-98% yield using Zr(Ot-Bu)4 as the catalyst. The CH-acidic nitro compounds are not epimerized under these reaction conditions.

1-Methyl-2-chloromethyl-5-nitroimidazole reacts by an S(RN)1 mechanism with various aliphatic, cyclic or heterocyclic nitronate anions to afford, in high yields, new 5-nitroimidazoles bearing a trisubstituted ethylenic double bond at the 2 position. Some of these compounds are as active as metronidazole in vitro and in vivo against protozoa and anaerobic bacteria. Structure-activity relationships are discussed.

The study of S(RN)1 reaction between 2-chloromethyl-3-nitroimidazo[1,2-a] pyridine and 2-nitropropane salts has been extended to various aliphatic, cyclic and heterocyclic nitronate anions. From C-alkylation products, base-promoted nitrous acid elimination afforded new potential pharmacological derivatives with a trisubstituted double bond at the 2 position.

Synthetic routes to various quaternary α-nitro α-methyl carboxylic acid esters from simpler nitroalkanes and nitroalkane derivatives are described.These quaternary α-amino acid precursors can be kinetically resolved by using α-chymotrypsin.It was found that partial hydrolysis of these α-nitro α-methyl esters and recovery of the unhydrolyzed ester proceeds preferentially by hydrolysis of the D enantiomer.Reduction of the α-nitro group thus then affords highly enantiomerically enriched L-α-methyl α-amino acids.

2-Nitropropane reacts with phenyllead triacetate in dimethyl sulfoxide to give 2-nitro-2-phenylpropane in good yield.This arylation of nitroalkanes has been examined with a variety of substrates and a number of aryllead triacetates, and in those cases where there was no steric hindrance the reaction was found to be quite general.Reactions of nitroethane and methyl nitroacetate, compounds with two α-hydrogens, were readily controlled to give either the mono- or di-arylated products.The corresponding nitronate salts were also examined and found to undergo the arylation reaction in similar yield but at a very much faster rate.

Additional mechanistic and synthetic details concerning the formation of nitroalkylated aromatic products from the reaction of nitroalkans with manganese(III) acetate and an aromatic compound are presented.A large isotope effect (kH/kD = 4.02-4.20) was found for both manganese(III)- and cerium(IV)-promoted nitromethylations with nitromethane-d3 while no isotope effect (kH/kD = 1.05) was observed with benzene-d6.This indicated that deprotonation (most likely from an aci radical cation) to the nitromethyl radical is the slow step while subsequent rearomatization of a ?-radical complex occurs rapidly.Somewhat more convenient methods of activating the manganese(III) acetate promoter were found.However, attempts to find cooxidants or other additives which could improve this process met with only limited success.The reaction of either toluene or benzene with nitroethane or the nitropropanes and manganese(III) acetate in refluxing acetic acid gave much poorer yields (3-8percent) of the corresponding nitroalkylated products.Incorporation of sodium acetate into these systems completely eliminated the aromatic substitution products and formed α-nitroalkyl acetates instead.Implications of this finding on the mechanism for the generation of nitroalkyl radicals are discussed.

Nitroalkanes and their nitronate salts undergo α-arylation in good yield when treated with an aryllead triacetate in dimethyl sulfoxide.