Direct catalytic synthesis

Kumar, R., Sithambaram, S. and Suib,S.L. (2009) Cyclohexane oxidation catalyzed by manganese oxide octahedral molecular sieves - effect of acidity of the catalyst. Journal of Catalysis, 262,304—313. Sithambaram, S., Kumar, R., Son, Y. and Suib, S.L. (2008) Tandem catalysis direct catalytic synthesis of imines from alcohols using manganese octahedral molecular sieves. Journal of Catalysis, 253, 269-277. 

In the direct catalytic synthesis of H202 the main findings of the earlier patents can be summarized as follows ... 

Table 8.3 Comparison of selected recent patents on the direct catalytic synthesis of H2O2. 

The main objective of this work consists in the direct catalytic synthesis of R2NCH3 or RN(CH3)2 dissymetricai tertiary amines, which find many applications in the industry of tensio-active products. To this end acids, esters, alcohols, nitriles obtained from triglycerides of natural origin can be used as raw materials. Starting from nitriles the following are the reactions to be performed... 

Also in ruthenium chemistry some reactions between alkynes and carbon dioxide have been published, however, no C-C linkage reactions were found. Dixneuf and Sasaki [93] reported the direct catalytic synthesis of vinyl carbamates from terminal alkynes, carbon dioxide and diethyl amine in the presence of trirutheniumdodecacarbonyl (Equation 17). 

The direct catalytic synthesis of azo or azoxy compounds from nitro compounds is not a common reaction. Apart from Fe(CO)5, Ru3(CO)i2 has been reported to catalyse reaction 17 [113], but mononitro compounds failed to give appreciable amounts of azo compounds with this catalyst. Very recently, however, it has been reported that good selectivities (up to 72.5 %) in azoxybenzene can be obtained by using Pd(Phen)(OTf)2 as catalyst in the presence of an excess (best 12.5 1 with respect to palladium) of sodium benzoate [114]. Conditions were 60 bar and 135 °C in methanol as solvent (note that no water was added). The principal by-product was methyl phenylurethane, with minor amounts of aniline and diphenylurea being also formed. The study was principally aimed at evidencing the effect of benzoate anion on the synthesis of carbamates, so no attempt has apparently been made to optimise the experimental conditions for the synthesis of azoxybenzene and better yields can be probably obtained under different conditions. 

When specifically labelled compounds are required, direct chemical synthesis may be necessary. The standard techniques of preparative chemistry are used, suitably modified for small-scale work with radioactive materials. The starting material is tritium gas which can be obtained at greater than 98% isotopic abundance. Tritiated water can be made either by catalytic oxidation over palladium or by reduction of a metal oxide ... 

A direct catalytic conversion of esters, lactones, and carboxylic acids to oxazolines was efficiently achieved by treatment with amino alcohols in the presence of the tetranuclear zinc cluster Zn4(0C0CF3)60 as catalyst, essential for condensation and cyclodehydration reactions. For example, the use of (5)-valinol allowed the easy synthesis of oxazolines 125 and 126 in satisfactory yields <06CC2711>. A one-pot direct preparation of various 2-substituted oxazolines (as well as benzoxazoles and oxadiazoles) was also performed from carboxylic acids and amino alcohols (or aminophenols or benzhydrazide) using Deoxo-Fluor reagent <06TL6497>. 

Non-directed C-H functionalizations of arenes can be mediated by Cp Ir complexes as in the catalytic synthesis of... 

In conclusion, there is interest for bioethanol upgrading to fuel additives and some research is active in this direction, but much more effort is needed to demonstrate the validity and the viability of the concept of preparing oxygenated diesel fuel additives from bioethanol and glycerol. The key to success is to develop selective multifunctional solid catalysts, in which interest is more general, because similar multifunctionality is necessary in the catalytic synthesis of fine chemicals [67]. There is, thus, the possibility of cross-fertilization between the two research areas. 

Re species are in a dimeric form with a direct Re-Re bond. Re Lj-edge XANES in part (ii) of Figure 10.9a did not show the pre-edge peak attributed to tetrahedral conformation of Re and the edge posihon shifted to lower energy. These results indicate that the NH3 treatment reduced the Re monomers accompanied with dimerization. Negligible catalytic achvity at this stage demonstrates that small Re clusters such as dimers do not act as achve species for direct phenol synthesis from benzene and O2. 

Bpgevig, A., Sund, H. and Cordova, A. Direct Catalytic Enantioselective a-Aminoxylation of Ketones A Stereoselective Synthesis of a-Hydroxy and a,a -Dihydroxy Ketones. Angew. Chem. Int. Ed. 2004, 43, 1109-1111. 

Tanaka and co-workers have reported two routes for the catalytic synthesis of cyclic silyl enol ethers from silacylobutanes. The strained silacarbo-cycle174 can react directly with an acid chloride175,176 or in a three-component reaction with an organic halide and carbon monoxide177 to yield cyclic products that contain an Si-O bond [Eqs. (68) and (69)]. 

Catalytic synthesis of hydroxylamine from nitrogen oxide and hydrogen is widely used in industry as a constituent part of caprolactam production. The reaction is conducted in aqueous sulfuric acid solution saturated with NO and H2 at 40°C and a pressure of approximately 1 atm. Platinum supported on porous graphite, in the form of fine particles suspended in the intensely stirred solution, is used as a catalyst. The main direction of the reaction is... 

The ester enolate-imine condensation, also called Gilman-Speeter reaction, is another well-accepted method for (3-lactam synthesis (Scheme 4) [67-69]. In 1997, Tomioka reported the first example of a direct catalytic enantioselective synthesis of (3-lactam by using this method [70]. The active reagent is a ternary complex (comprising LDA, the ester enolate, and tridentate amino diether), which finally affords the (3-lactam compounds in high yields and good ee values. 

Table 2.5 Catalytic performance of pulse reactions on the CVD-Re/ HZSM-5 (Si02/AI203 = 19) catalyst (Re 0.58 wt%) for direct phenol synthesis from benzene and 02 at 553 K in the absence of NH3a .

The dynamic XAFS study of the catalytically active structures under the reaction conditions should enable us to further develop novel catalysts for direct phenol synthesis from benzene and the efficient activation of molecular oxygen. 

The Stacker reaction has been employed on an industrial scale for the synthesis of racemic a-amino acids, and asymmetric variants are known. However, most of the reported catalytic asymmetric Stacker-type reactions are indirect and utilize preformed imines, usually prepared from aromatic aldehydes [24]. A review highlights the most important developments in this area [25]. Kobayashi and coworkers [26] discovered an efficient and highly enantioselective direct catalytic asymmetric Stacker reaction of aldehydes, amines, and hydrogen cyanide using a chiral zirconium catalyst prepared from 2 equivalents of Zr(Ot-Bu)4, 2 equivalents of (R)-6,6 -dibromo-1, l -bi-2-naphthol, (R)-6-Br-BINOL], 1 equivalent of (R)-3,3 -dibromo-l,l -bi-2-naphthol, [(R)-3-Br-BINOL, and 3 equivalents of N-methylimida-zole (Scheme 9.17). This protocol is effective for aromatic aldehydes as well as branched and unbranched aliphatic aldehydes. 

A highly diastereo- and enantioselective synthesis of trans-l,2-disubstituted cyclohexanes by means of the first direct catalytic asymmetric 6-enolexo aldoliza-tion has been developed very recently by the List group [120] (previously only 6-enolendo aldolizations had been reported). Dialdehydes were usually used as starting materials and proline was a very effident catalyst for this reaction also. A selected example of this 6-enolexo-aldolization is given in Scheme 6.50 in this... 

Shibasaki and coworkers have conducted extensive research on the use of hetero-bimetallic complexes as catalysts for asymmetric synthesis [11]. The reactions are catalyzed by heterobimetallic complexes that function as both a Lewis acid and a Bronsted base. Among these, LaLi3tris(binaphthoxide) catalyst 1 (LLB) was proven to be an effective catalyst in direct asymmetric aldol reactions (Fig. 1) [12]. On the basis of this research, Shibasaki et al. reported the first report of a direct catalytic asymmetric Mannich reaction [13],... 

The reaction can be regarded as a regiospecific asymmetric synthesis of 3-amino-l-ols. Proline also catalyzes the first one-pot three-component direct catalytic enantioseledive Mannich readions with two unmodified aldehydes and anilines (Eq. 11) [39, 40],... 

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