Nitromethane catalyst

Aluminum chloride-nitromethane catalyst is believed to have exploded at a temperature below lO t (Ref 52)... 

In order to improve the yield of nitromethane, the first step hydrolysis damage of dimethyl sulfate should be avoided, and decreasing reaction temperature is favorable to the reaction because the hydrolysis of dimethyl sulfate is related to the pH value, strict controlling on the pH can avoid the damage on dimethyl sulfate, sodium sulfide, nitromethane catalyst can further accelerate the reaction, reduce the side reaction hydrolysis and significantly improve the yield and quality of product. The reaction is ... 

Unlike the effect of sulphuric acid upon nitration in nitric acid ( 2.2.3 where zeroth-order reactions are unknown), the form of the catalysis of zeroth-order nitration in nitromethane by added sulphuric acid does not deviate from a first-order dependence with low concentrations of catalyst. ... 

Most nitroparaffins do not react with ketones, but ia the presence of alkoxide catalysts, nitromethane and lower aUphatic ketones give nitro alcohols ia the presence of amine catalysts dinitro compounds are obtained. 

Proazaphosphao-ane, PrRNCH-,CH-j,N, is an efficient catalyst for the Henty reacdon, and arious ketones give nitro-aldols by the reacdon with nitromethane and other nitroalkanes fEq. 

Allylic nitro compounds are obtained by the reacdon of cyclic ketones with nitromethane in the presence of 1,2-diaminoethane fl mol% as catalyst. Because exa-cyclic nitroalkenes are rearranged to the fi)iifo-cyclic fi,Y-nitroalkenes, allylic nitro compounds are selecdvely produced fEq. 3.21. ... 

A kinetic isotope effect, kH/kD = 1.4, has been observed in the bromination of 3-bromo-l,2,4,5-tetramethylbenzene and its 6-deuterated isomer by bromine in nitromethane at 30 °C, and this has been attributed to steric hindrance to the electrophile causing kLx to become significant relative to k 2 (see p. 8)268. A more extensive subsequent investigation304 of the isotope effects obtained for reaction in acetic acid and in nitromethane (in parentheses) revealed the following values mesitylene, 1.1 pentamethylbenzene 1.2 3-methoxy-1,2,4,5-tetramethyl-benzene 1.5 5-t-butyl-1,2,3-trimethylbenzene 1.6 (2.7) 3-bromo-1,2,4,5-tetra-methylbenzene 1.4 and for 1,3,5-tri-f-butylbenzene in acetic acid-dioxan, with silver ion catalyst, kH/kD = 3.6. All of these isotope effects are obtained with hindered compounds, and the larger the steric hindrance, the greater the isotope... 

Since there is inherent in reactions which give low selectivities, the possibility that non-competitive conditions are responsible, Olah and Overchuck359 have measured directly the rates of benzylation, isopropylation, and fer/.-butylation of benzene and toluene with aluminium and stannic chlorides in nitromethane at 25 °C. Apparent second-order rate coefficients were obtained (assuming that the concentration of catalyst remains constant), but it must be admitted that the kinetic plots showed considerable departure from second-order behaviour. The observed rate coefficients and kreh values determined by the competition method are given in Table 88, which seems to clearly indicate that the competitive ex-... 

Transition-metal-based Lewis acids such as molybdenum and tungsten nitro-syl complexes have been found to be active catalysts [49]. The ruthenium-based catalyst 50 (Figure 3.6) is very effective for cycloadditions with aldehyde- and ketone-bearing dienophiles but is ineffective for a,)S-unsaturated esters [50]. It can be handled without special precautions since it is stable in air, does not require dry solvents and does not cause polymerization of the substrates. Nitromethane was the most convenient organic solvent the reaction can also be carried out in water. 

Recently, enantioselective organo-catalytic procedures for the aza-Henry reaction have been disclosed. The presence of either an acidic or a basic function appears to be a requisite of the catalyst. In fact, the condensation of ni-tromethane with M-phosphinoyl arylimines 72 is catalyzed by the chiral urea 85 derived from (R,R)-l,2-diaminocyclohexane and gives the product (R)-74 with good yield and moderate enantioselectivity (Scheme 15) [50]. The N-phosphinoyl substituent is determinant, as the addition of nitromethane to the N-phenyl benzaldimine failed and the reaction of the N-tosyl ben-zaldimine gave the expected adduct with quantitative yield but almost no... 

The effect of chloromethane on ethylene when aluminium chloride, a catalyst made of nickel, and nitromethane under 30-60 bar are present, gives rise to a highly violent detonation. The fact that there are so many compounds present makes it difficult to come up with a simple explanation. Ethylene (polymerisation) and nitromethane may have caused this accident (as can be seen in the paragraph about nitrated derivatives). 

All acids but especially Lewis acids (particularly aluminium chloride), give rise to dangerous interactions with nitrated derivatives and nitrates (there is not much information about nitrates). Aluminium chloride causes a large number of accidents due to nitrobenzene and sometimes nitromethane when used as a solvent in Friedel-Crafts reactions for which aluminium chloride is the common catalyst. 

Jenner investigated the kinetic pressure effect on some specific Michael and Henry reactions and found that the observed activation volumes of the Michael reaction between nitromethane and methyl vinyl ketone are largely dependent on the magnitude of the electrostriction effect, which is highest in the lanthanide-catalyzed reaction and lowest in the base-catalyzed version. In the latter case, the reverse reaction is insensitive to pressure.52 Recently, Kobayashi and co-workers reported a highly efficient Lewis-acid-catalyzed asymmetric Michael addition in water.53 A variety of unsaturated carbonyl derivatives gave selective Michael additions with a-nitrocycloalkanones in water, at room temperature without any added catalyst or in a very dilute aqueous solution of potassium carbonate (Eq. 10.24).54... 

Other authors also determined by FTIR that organic nitrocompounds are formed as primary products of the NO CH4-SCR reaction on ZSM-5-based catalysts [121-124], They preadsorbed nitromethane on the sample placed in the IR cell and followed by IR its transformation into other intermediates under 02 and NO versus time at different temperatures. For Cu- and Co-ZSM-5, it was shown that around 300°C adsorbed nitromethane is easily converted into isocyanates and then melamine via polymerization of the former species. Both species easily interact with molecular oxygen, while no reaction with NO is observed and the reactivity depends on the temperature and the nature of the transition metal cation. 

The heterobimetallic asymmetric catalyst, Sm-Li-(/ )-BINOL, catalyzes the nitro-aldol reaction of ot,ot-difluoroaldehydes with nitromethane in a good enantioselective manner, as shown in Eq. 3.78. In general, catalytic asymmetric syntheses of fluorine containing compounds have been rather difficult. The S configuration of the nitro-aldol adduct of Eq. 3.78 shows that the nitronate reacts preferentially on the Si face of aldehydes in the presence of (R)-LLB. In general, (R)-LLB causes attack on the Re face. Thus, enantiotopic face selection for a,a-difluoroaldehydes is opposite to that for nonfluorinated aldehydes. The stereoselectivity for a,a-difluoroaldehydes is identical to that of (3-alkoxyaldehydes, as shown in Scheme 3.19, suggesting that the fluorine atoms at the a-position have a great influence on enantioface selection. 

Heterobimetallic asymmetric complexes contain both Bronsted basic and Lewis acidic functionalities. These complexes have been developed by Shibasaki and coworkers and have proved to be highly efficient catalysts for many types of asymmetric reactions, including catalytic asymmetric nitro-aldol reaction (see Section 3.3) and Michael reaction. They have reported that the multifunctional catalyst (f )-LPB [LaK3tris(f )-binaphthoxide] controls the Michael addition of nitromethane to chalcones with >95% ee (Eq. 4.140).205... 

Asymmetric synthesis of tricyclic nitro ergoline synthon (up to 70% ee) is accomplished by intramolecular cyclization of nitro compound Pd(0)-catalyzed complexes with classical C2 symmetry diphosphanes.94 Palladium complexes of 4,5-dihydrooxazoles are better chiral ligands to promote asymmetric allylic alkylation than classical catalysts. For example, allylic substitution with nitromethane gives enantioselectivity exceeding 99% ee (Eq. 5.62).95 Phosphi-noxazolines can induce very high enatioselectivity in other transition metal-catalyzed reactions.96 Diastereo- and enantioselective allylation of substituted nitroalkanes has also been reported.9513... 

A novd example of a catalytic enantioselective domino process1201 is the inter-intramolecular nitro-aldol reaction described by Shibasaki et al which generates substituted indanones. As catalyst a praseodym-heterobimetallic complex with binaph-thol as chiral ligand is employed. Treatment of keto-aldehyde 41 with nitromethane in the presence of the catalyst 46 at -40 °C and successive warming to room temperature affords diredly the produd 42 in an overall yield of 41 % and 96 % ee after several recrystallizations (scheme 9). As intermediates the nitromethane adduct 43 and the hemiacetal 44 can be proposed. In a second aldol reaction 44 leads to 45 which isomerizes to the thermodynamically more stable epimer 42. 

In 1964, Kochetkov, Khorlin and Bochkov reported that the reaction of 1,2-alky-lorthoacetates with alcohols in the presence of catalytic amounts of HgBr2 and pTsOH furnished acetylated 1,2-trans glycosides or isomeric orthoesters depending on the reaction conditions [4]. Polar solvents (nitromethane, acetonitrile) and large amounts of catalyst promoted glycosylation (a, Scheme 5.5), whereas solvents of low polarity (dichloroethane) and the use of small amounts of catalyst favored transorthoesterification (b, Scheme 5.5) [16]. 

Co-catalysts other than water. Trichloro- and monochloro-acetic acids, when used as cocatalysts, induced instantaneous polymerisation at -140°. With the following co-catalysts the rate of polymerisation at -78° decreased in the order acetic acid > nitroethane > nitromethane > phenol > water [75a]. Since this is also the sequence of the acid dissociation constants of these substances in water, it appears that the catalytic activity , as shown by the rate of polymerisation, is correlated with the acidity of the cocatalyst in aqueous solution. Flowever, there are two reasons for questioning the validity of this correlation. 

The addition of nitromethane to chalcones has been studied using N-benzylquininium chloride as the chiral phase-transfer catalyst and fluoride ion as the base (46). The enantiomeric excess was moderate (up to 26%). No conclusions were drawn from this study. 

The Beckmann rearrangement of oximes to produce amides is promoted by perrhenate ions under phase-transfer catalytic conditions, in the presence of trifluoro-methanesulphonic acid in nitromethane [6]. Under these conditions, the rearrangement reaction is frequently accompanied by the solvolysis of the oxime to the ketone. This can be obviated by the addition of hydroxylamine hydrochloride. No reaction occurs in the absence of the ammonium catalyst or with the O-acetyl oximes. 

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