Catalysts 2,4-dinitrophenol

Titanium ions can also he used as redox catalysts for the indirect cathodic reduction of nitro compounds (417). The electroreduction is carried out in an H20-H2S04/Ti(S04)2-(Pb/Cu) system at 45 80°C under 5 20Am . Nitrobenzene, dinitrobenzene, nitrotoluene, 2,4-dinitrotoluene, 2-nitro-m-xylene, nitro-phenol, 2,4-dinitrophenol, nitrophenetole, o-nitroanisole, 4-nitrochlorotoluene, ni-trobenzenesulfonic acid, and 4,4 -dinitro-stilbene-2,2 -disulfonic acid can all be reduced by this procedure to the corresponding amino compounds (418) in good yields (Scheme 146) [513-516]. Tin... 

CASRN 3209-22-1 molecular formula C6H3CI2NO2 FW 192.00 Photolytic. An aqueous solution containing 2,3-dichloronitrobenzene and a titanium dioxide (catalyst) suspension was irradiated with UV light (X >290 nm). 2,3-Dichloro-l,5-dinitrophenol formed as the intermediate product. Continued irradiation caused further degradation yielding carbon dioxide, water, hydrochloric and nitric acids (Hustert et al, 1987). 

Lu and coworkers have synthesized a related bifunctional cobalt(lll) salen catalyst similar to that seen in Fig. 11 that contains an attached quaternary ammonium salt (Fig. 13) [36]. This catalyst was found to be very effective at copolymerizing propylene oxide and CO2. For example, in a reaction carried out at 90°C and 2.5 MPa pressure, a high molecular weight poly(propylene carbonate) = 59,000 and PDI = 1.22) was obtained with only 6% propylene carbonate byproduct. For a polymerization process performed under these reaction conditions for 0.5 h, a TOF (turnover frequency) of 5,160 h was reported. For comparative purposes, the best TOF observed for a binary catalyst system of (salen)CoX (where X is 2,4-dinitrophenolate) onium salt or base for the copolymerization of propylene oxide and CO2 at 25°C was 400-500 h for a process performed at 1.5 MPa pressure [21, 37]. On the other hand, employing catalysts of the type shown in Fig. 12, TOFs as high as 13,000 h with >99% selectivity for copolymers withMn 170,000 were obtained at 75°C and 2.0 MPa pressure [35]. The cobalt catalyst in Fig. 13 has also been shown to be effective for selective copolymer formation from styrene oxide and carbon dioxide [38]. 

The imine-azomethine ylide tautomerization [Eq. (7)] is catalyzed by either protonic or Lewis acids (82CC384). For example, the cycloaddition of methyl Af-benzylidenephenylglycinate with A/-phenylmaleimide in toluene is catalyzed by 2,4-dinitrophenol and proceeds 40 times faster than the same reaction in the absence of the catalyst. The rate-determining step of N-protonation of the imine forming the iminium intermediate 64 is facilitated... 

The effect of the concentration of interfacial transfer catalysts in aprotic solvents in contact with solid salts (sodium 2,4-dinitrophenolate) has been investigated with regard to their effectiveness for reaching the solid-liquid equilibrium in benzene, chlorobenzene, dichloromethane and acetonitrile at 25 °C [185], Polyethylene glycols with 300, 600 and 2000 mol. wt., trianthrylmethylammonium chloride, dodecyldi-methylammonium chloride, tetrabutylammonium chloride and a crown ether, have... 

The hydrolysis of 2,4-dinitrophenylphosphate (DNPP) to orthophosphate and 2,4-dinitrophenolate is accelerated in the presence of excess [Co(pn)2(OH2)2] or [Co(trpn)(OH2)2] at rates which vary with pH in a manner suggesting that the hydroxoaquatetraamine cobalt(III) complex is the active catalyst (pn = trimethylenediamine trpn = 3,3, 3"-triaminotripropylamine). " Detailed mechanistic schemes are proposed. For the trpn complex at pH 6.0 and a 25 1 cobalt-to-DNPP ratio (5 x 10" M DNPP) the observed rate enhancement is - 3 x 10 -fold. The calculated specific rate constant for hydrolysis in the reactive 1 1 complex (k 0.2 s" ) represents a rate acceleration of some 3 x lO -fold. 

Figure 17 (a) Footprint catalyst containing a Lewis acidic aluminum site with a tetrahedral phosphonic acid diamide template (b) acyl transfer reaction between benzoic acid anhydride and 2,4-dinitrophenole, catalyzed by imprinted silica/alumina gel. 

A soln. of the startg. m. and 4 equivalents ketal heated ca. 8 hrs. at 100° in toluene containing 2,4-dinitrophenol as catalyst, and the intermediate ketone treated at 0° with NaBH4 in methanol > product. Y up to 81% purity 98%. -This olefinic ketal Claisen reaction is useful for preparing trans-disubst as well as trans-trisubst. olefinic bonds. The above producure is the last of a succession of 3 similar steps. F. e. and catalysts s. W. S. Johnson et al., Am. Soc. 92, 4463 (1970) Proc. Natl. Acad. Sci. U.S. 67, 1462, 1465, 1810, 1824 (1970) geospecific synthesis of ethylene derivs., review, s. J. Reucroft and P. G. Sammes, Quart. Rev. 25,135 (1971). 

Simple A/-proline-based dipeptides catalyse direct aldols of aldehydes with a wide range of ketones, giving yield/de/ee up to 99/>98 (syn)/97%, at room temperature in 0 brine, with 2,4-dinitrophenol as co-catalyst. A simple organocatalyst, the methyl 0 ester of (S)-proline-(S)-phenylalanine, promotes high-yielding aldols with up to 95% ee and 82% de (anti-) under solvent-free conditions at —20 °C. Lack of solvent should 0 maximize substrate-catalyst noncovalent interactions. 0... 

Chiral diamines derived from natural primary amino acids give up to 99% ee in i yn-selective aldols of linear ketones with aromatic aldehydes, using TFA and 2,4-dinitrophenol as co-catalysts. ... 

While primary amine organocatalysts derived from amino acids have shown very low enantioselectivities and activities in the typical aldol reactions of acetone with aldehydes. Da et al. demonstrated that the introduction of the optimal co-catalyst DNP (2,4-dinitrophenol) dramatically elevated both the activities and the enantioselectivities of these catalysts. As shown in Scheme 2.39, the combination of a primary amino acid with DNP allowed the aldol products to be obtained in moderate to high yields and excellent enantioselectivities of up to 99% ee. In addition, the scope of this methodology could... 

Amino acid-derived primary-tertiary diamine catalysts have been used extensively in aldol reactions. Lu and Jiang [34] documented a direct asymmetric aldol reaction between acetone and a-ketoesters catalyzed by an L-serine-derived diamine 17. Sels et al. [35] found that several primary amino acid-based diamines (18) were efficient catalysts for the syn-aldol reaction of linear aliphatic ketones with aromatic aldehydes. Luo and Cheng utilized L-phenylalanine-derived diamine catalyst 15a for the enantioselective syn-aldol reaction of hydroxyl ketones with aromatic aldehydes [36]. Moreover, a highly enantioselective direct cross aldol reaction of alkyl aldehydes and aromatic aldehydes was realized in the presence of 15a (Scheme 3.8) [37]. Very recently, the same group also achieved a highly enantioselective cross-aldol reaction of acetaldehyde [38]. Da and coworkers [39] discovered that catalyst 22, in combination with 2,4-dinitrophenol, provided good activation for the direct asymmetric aldol reaction (Scheme 3.9). 

Feng and Hu reported a successful nitroaldol reaction of a-ketophosphonates by using a combination of bis-chiral secondary amide 22 and 2,4-dinitrophenol (23) (Scheme 29.9) [23]. In the proposed transihon state, one of the piperidine moieties is protonated by the acidic additive, which achvates the a-ketophosphonate via hydrogen bonding, and the other piperidine deprotonates nitromethane. With this catalyst system, numerous different nitroaldol compounds may be obtained with high optical purities. A Bu OMe/PhOMe (2 1) solvent mixture seems critical... 

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