Conversion of aromatics

25-P-06 - Isopropylation of naphthalene over large pore zeolites 

Department of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-1193 (JAPAN). Email sugi apchem.gifu-u.ac.jp Fax. 81-58-293-2597 

25-P-07 - Shape-selective tert-butylation of biphenyl over HM, HY and H 3 zeolites in the liquid phase 

Mravec(a), J. Homiakovd(a), M. Kralik(a), M. Hronec(a), J. Joffre(b) and P. Moreau (b) a Slovak University of Technology, Bratislava, mravec chtf.stuba.sk, Slovak Republic h,Ecole Nationale Superieure de Chimie, Montpellier, France 

The alkylation of biphenyl with /ert-butanol has been carried out over different zeolites under liquid phase conditions. HM (17.5) and HY (15) zeolites have been found to be the most active, with a maximum biphenyl conversion near 60 %. Dealuminated mordenite HM (17.5) leads to very high selectivities to 4-(ter/-butyl)biphenyl (99%) and 4,4 -di(/er/-butyl)biphenyl (96%). Selectivity to linear 4-TBB and 4,4 -DTBB depends on diffusional possibilities of relatively voluminous mono tert-butyl- and di (rert-butyl)biphenyl isomers from the zeolite pores. The most suitable temperature has been found to be 160 C. An increase of the temperature leads to a significant decrease of selectivities to the desired products, as a result of secondary reactions. 

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CoF is used for the replacement of hydrogen with fluorine in halocarbons (5) for fluorination of xylylalkanes, used in vapor-phase soldering fluxes (6) formation of dibutyl decalins (7) fluorination of alkynes (8) synthesis of unsaturated or partially fluorinated compounds (9—11) and conversion of aromatic compounds to perfluorocycHc compounds (see Fluorine compounds, organic). CoF rarely causes polymerization of hydrocarbons. CoF is also used for the conversion of metal oxides to higher valency metal fluorides, eg, in the assay of uranium ore (12). It is also used in the manufacture of nitrogen fluoride, NF, from ammonia (13). 

The conversion of aromatic monomers relative to C-5—C-6 linear diolefins and olefins in cationic polymerizations may not be proportional to the feedblend composition, resulting in higher resin aromaticity as determined by nmr and ir measurements (43). This can be attributed to the differing reactivity ratios of aromatic and aHphatic monomers under specific Lewis acid catalysis. Intentional blocking of hydrocarbon resins into aromatic and aHphatic regions may be accomplished by sequential cationic polymerization employing multiple reactors and standard polymerization conditions (45). 

Conversion of Aromatic Rings to Nonaromatic Cyclic Structures. On treatment with oxidants such as chlorine, hypochlorite anion, chlorine dioxide, oxygen, hydrogen peroxide, and peroxy acids, the aromatic nuclei in lignin typically ate converted to o- and -quinoid stmctures and oxinane derivatives of quinols. Because of thein relatively high reactivity, these stmctures often appear as transient intermediates rather than as end products. Further reactions of the intermediates lead to the formation of catechol, hydroquinone, and mono- and dicarboxyhc acids. 

Recently (82CC450) the conversion of aromatic hydrazides into indazolones in good yield when treated with three equivalents of n-butyllithium has been described. For example, benzoylhydrazine afforded indazolone in an 80% yield (Scheme 51). 

Analogous to DPNH (144-146), 1,4-dihydropyridines (147) act as reducing agents. For instance, the conversion of aromatic nitro compounds to amines (148) and reduction of enones to ketones (749) has been achieved. 

In the moving bed processes, the preheated feed meets the hot catalyst, which is in the form of beads that descend by gravity to the regeneration zone. As in fluidized bed cracking, conversion of aromatics is low, and a mixture of saturated and unsaturated light hydrocarbon gases is produced. The gasoline product is also rich in aromatics and branched paraffins. 

Metabolic pathways containing dioxygenases in wild-type strains are usually related to detoxification processes upon conversion of aromatic xenobiotics to phenols and catechols, which are more readily excreted. Within such pathways, the intermediate chiral cis-diol is rearomatized by a dihydrodiol-dehydrogenase. While this mild route to catechols is also exploited synthetically [221], the chirality is lost. In the context of asymmetric synthesis, such further biotransformations have to be prevented, which was initially realized by using mutant strains deficient in enzymes responsible for the rearomatization. Today, several dioxygenases with complementary substrate profiles are available, as outlined in Table 9.6. Considering the delicate architecture of these enzyme complexes, recombinant whole-cell-mediated biotransformations are the only option for such conversions. E. coli is preferably used as host and fermentation protocols have been optimized [222,223]. 

We observed that the reduction side-reaction can be suppressed substantially by applying CO2 as the carrier gas (ref. 31). Perhaps the adduct of CO2 and NH3 acts as a Cu(I) ligand and protects the Cu(I) for reduction towards Cu(0). Recently a similar CO2 promoting effect was reported (ref. 32) for the liquid phase conversion of aromatic bromides towards methoxyarenes. 

Specifically, it has recently been found 149) that diarylthallium tri-fluoroacetates may be converted into aromatic iodides by refluxing a solution in benzene with an excess of molecular iodine. Yields are excellent (74-94%) and the overall conversion represents, in effect, a procedure for the conversion of aromatic chlorides or bromides into aromatic iodides via intermediate Grignard reagents. The overall stoichiometry for this conversion is represented in Eq. (10), and it would appear that the initial reaction is probably formation of 1 mole of aromatic iodide and 1 mole of arylthallium trifluoroacetate iodide [Eq. (8)] which subsequently spontaneously decomposes to give a second mole of aromatic iodide and thallium(I) trifluoroacetate [Eq. (9)]. Support for this interpretation comes from the... 

This section contains dehydrogenations to form alkenes and unsaturated ketones, esters and amides. It also includes the conversion of aromatic rings to alkenes. Reduction of aryls to dienes is found in Section 377 (Alkene-Alkene). Hydrogenation of aryls to alkanes and dehydrogenations to form aryls are included in Section 74 (Alkyls from Alkenes). 

Saponification of Esters or Lactones and Reaction of Persilylated Amides and Lactams with Aikaii Trimethylsilanolates. Conversion of Aromatic Esters into Nitriies by Use of Sodium-HMDS... 

The reaction is useful in the conversion of aromatic carboxylic acids to aromatic amines. 

Hydrogenation of a C=0 double bond followed by catalytic hydrogenolysis of the resulting OH group is an alternative method for the conversion of aromatic aldehydes and ketones to alkanes. Pd/C and Pt02 are the most often used catalysts.49-51 In this way, dimethyltetralone was hydrogenated-hydrogenolyzed under 60 psi H2 for 5 hours in MeOH-HCl with 10% Pd/C (Scheme 4.22).52... 

Conversion of aromatic amines to azides was studied by Scechter et al. <2002TL8421> and these studies lead to the recognition of a new approach to tetrazolo[l,5- ]pyridine. Thus, reaction of 2-aminopyridine 142 with butyl-lithium followed by treatment with azidotris(diethylamino)phosphonium bromide gave rise to tetrazolo[l,5- ]pyr-idine 1 in 80% yield. The first intermediate is obviously the azide 7. 

Nonaqueous solvents, 14 32 Nonaqueous systems ion exchange in, 14 397 in nitrogen fixation, 17 311-315 Nonaromatic cyclic structures, conversion of aromatic rings to, 15 5 Nonaromatics, 23 329, 330 Non-azeotropes, methyl isobutyl ketone, 16 33 It... 

Horseradish peroxidase (HRP) an enzyme routinely used in immunohisto-chemistry for labeling antibodies. Histochemichal detection of peroxidase is based on the conversion of aromatic phenols or amines, such as diamino-benzidine (DAB), into water-insoluble pigments in the presence of hydrogen peroxide (H202). 

One-pot conversion of aromatic acids into benzyl chlorides... 

Anodic conversion of aromatics proceeds in most cases by le-transfer to the anode to form a radical cation (34) (Scheme 9). Oxidation is facilitated by extension of the 7T-system ( 1/2 vs. Ag/Ag+ benzene 2.08 V, pyrene 0.86 V) and by electron donating substituents ( 1/2 vs. Ag/Ag+p-phenylenediamine —0.15 V). Oxidation potentials of polycyclic aromatics and substituted benzenes are collected in Ref [140-142]. 

The conversion of aromatic compounds comprises coupling, nuclear and ben-zylic substitution, and in some cases, addition. Homo- and in a more limited scope, heterocoupling is achieved for unsubstituted and substituted aromatic compounds in direct or indirect anodic processes. Chemically, there is a limited variety of expensive oxidation reagents available, but a large scope of transition... 

The first use of dinitrogen pentoxide as an A-nitrating agent appears to have been for the conversion of aromatic amines to arylnitramines. Difficulties in preparing pure dinitrogen pentoxide meant that reactions with aliphatic amines were not properly examined for another 60 years. 

Once a favorite reducing agent for the conversion of aromatic nitro compounds to amines, tin is used nowadays only exceptionally. The reason is partly unavailability, the necessity for the use of strongly acidic media, and... 

The most popular reducing agent for conversion of aromatic nitro compounds to amines is iron [166]. It is cheap and gives good to excellent yields [165, 582]. The reductions are usually carried out in aqueous or aqueous alcoholic media and require only catalytic amounts of acids (acetic, hydrochloric) or salts such as sodium chloride, ferrous sulfate or, better still, ferric chloride [165]. Thus the reductions are run essentially in neutral media. The rates of the reductions and sometimes even the yields can be increased by using iron in the form of small particles [165]. Iron is also suitable for reduction of complex nitro derivatives since it does not attack many functional groups [555]. 

Reduction of aromatic aldehydes to pinacols using sodium amalgam is quite rare. Equally rare is conversion of aromatic aldehydes to alkenes formed by deoxygenation and coupling and accomplished by treatment of the aldehyde with a reagent obtained by reduction of titanium trichloride with lithium in dimethoxyethane. Benzaldehyde thus afforded /ra/is-stilbene in 97% yield [206, 209]. 

The reduction of a dinitro ketone to an azo ketone is best achieved with glucose. 2,2 -Dinitrobenzophenone treated with glucose in methanolic sodium hydroxide at 60° afforded 82% of dibenzo[c,f [i 2]diazepin-l 1-one whereas lithium aluminum hydride yielded 24% of bis(o-nitrophenyl)methanol [575], Conversion of aromatic nitro ketones with a nitro group in the ring into amino ketones has been achieved by means of stannous chloride, which reduced 4-chloro-3-nitroacetophenone to 3-amino-4-chloroacetophenone in 91% yield [178]. A more dependable reagent for this purpose proved to be iron which, in acidic medium, reduced m-nitroacetophenone to m-aminoacetophenone in 80% yield and o-nitrobenzophenone to o-aminobenzophenone in 89% yield (stannous chloride was unsuccessful in the latter case) [903]. Iron has also been used for the reduction of o-nitrochalcone, 3-(o-nitrophenyl)-l-phenyl-2-propen-l-one, to 3-(o-aminophenyl)-l-phenyl-2-propen-l-one in 80% yield [555]. 

An alternative method for the conversion of aromatic nitriles to aldehydes is their heating with Raney nickel and sodium hypophosphite in water-acetic acid-pyridine (1 1 2) at 40-45° for 1-1.5 hours (yields 40-90%) [1154], or heating with Raney nickel and formic acid at 75-80° for 30 minutes (yields 35-83%) [7/55], or even their refluxing for 30 minutes with Raney nickel alloy in 75% aqueous formic acid (yields 44-100%) [1156]. 

Arabidopsis cytochrome P450 (CYP83A1, CYP83B1) Conversion of aromatic and aUphatic oximes to glucosinolates 101... 

Conversion data listed in Table 2 indicate that in the hydrogenation of 4-amino-ethyl benzoate using cyclohexane as a solvent the AI2O3 supported Ru and Rh catalysts are more active than the carbon supported ones. In addition, the conversion of aromatic ester is smaller on Pd/C catalyst than on the carbon supported Ru and Rh. In ethyl acetate the hydrogenation proceeded slower than in cyclohexane, and Rh being more active than Ru. The trans/cis isomer ratio estimated from TLC results varied between 1/3 and 1/1. The UV active by-products were formed in coupling reactions. 

Aldehydes lacking an OH group at C2 are also transformed by transketolase, leading to a 3S configuration of the hydroxyl group in the deoxyketose product [7a, 9] albeit with a significantly lower rate than with the hydroxylated acceptors [6b, 10. In contrast to the transketolases from spinach and yeast [9, no conversion of aromatic aldehydes, e.g., benzaldehyde or hydroxybenzaldehydes, could be detected with purified E. coli transketolase [6b]. 

The Baudisch reaction permits conversion of aromatic hydrocarbons to nitrosophenols. 

Mass spectrometer analyses of the fractions taken at regular intervals indicate the optimum conversions of aromatic hydrocarbons directly to aldehydes and alcohols by oxidation, as shown in Table III. Semiquanti-tative yields derived from low voltage mass spectral intensities and values found by gas chromatography were generally in good agreement—for example, oxidations of toluene and p-xylene, worked up after 2 hours, gave the results shown in Table IV. 

Both aliphatic and aromatic amines have been investigated in this reaction with similar results. This confirms that the reaction is a general reaction with amines in aqueous medium. The conversions of aromatic amines to secondary amides are lower than that of the aliphatic amines. This is because aromatic amines are generally weaker bases and poorer nucleophiles. 

Nicolaou et al. <2002AGE3866, 2004CEJ5581> introduced the Burgess-type reagent for the conversion of aromatic aminoalcohols 47 into cyclic sufamides 48 (Equation 8). 

The preparation of toluamide (Expt 6.167) illustrates a useful procedure for the conversion of aromatic nitriles into acid amides with the aid of alkaline hydrogen peroxides (see discussion, Section 5.12.4, p. 708). 

The reagent is generally useful for conversion of aromatic, heteroaromatic, and aliphatic aldehydes into the homologous carboxylic acid in satisfactory yield.1... 

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