Toluene as substrate

Figure 1.31 Electrophilic and radical paths in direct-fluorination chemistry leading to substitutions, additions and polymerizations with the example of toluene as substrate.

The pH dependence of the system was investigated using toluene as substrate in a phosphate-citrate buffer. In the pH range 2.6-5.2 the yield and cresol isomer ratios remain unchanged above this value the yield decreases (Table IV). 

Kim and co-workers have reported that the Friedel-Crafts reaction of aza-MBH adducts of A-tosylimine derivatives 93 with arenes catalyzed by sufuric acid provides a stereoselective methodology for the preparation of stereo-chemically defined trisubstituted olefins (Scheme 3.31). They have also investigated the Friedel-Crafts reaction by using chlorobenzene and toluene as substrates however, mixtures of ortho and para isomers were obtained. 

With toluene as substrate formylation proceeded in a high yield (99%) with respect to aldehyde formation and with good para-selectivity (90%) in a reaction time of only 1 hour. The reaction was carried out on phenol under the same reaction conditions. Surprisingly, the reactivity of phenol proved to be much lower than that of toluene and a reaction time of more than 4 hours was required to obtain acceptable yields, albeit with reduced para-selectivity. When the reaction was extended to anisole, only small differences compared to phenol were observed within the first hour of the reaction, but at extended reaction times phenol proved to give better conversions. The results indicate that the reaction is sustained for a longer time with phenol than with anisole. 

The superacidity of chloro-aluminate melts, cf paragraph 4.4) allows them to be ideal candidates for CO formylations. In order to compare the formylation of phenolics to that of aromatic hydrocarbons in ionic liquids, a study of formylation using CO in an ionic liquid was started with toluene as substrate and acidic chloro-aluminate melts (Table 2.15). A 1 1 mol ratio of toluene to ionic liquid with mol fraction AlCb = 0.67 gave moderate yields of the aldehyde derivative at mild temperature (Runs 1 and 2). When the ethyl-derivative of the melt was used, a slight increase in the conversion was observed which may be attributed to the higher solubility of CO in this specific melt. 

Hopkins GD, PL McCarty (1995) Field evaluation of in situ aerobic cometabolism of trichloroethylene and three dichloroethylene isomers using phenol and toluene as primary substrates. Environ Sci Technol 29 1628-1637. 

Fries MR, GD Hopkins, PL McCarty, LJ Forney, JM Tiedje (1998a) Microbial succession during a field evaluation of phenol and toluene as the primary substrates for trichloroethene cometabolism. Appl Environ Microbiol 63 1515-1522. 

Synthetic Method 1 6-(dimethylamino)-3-(N-acetyl-N-methylamino)-10-acetylphenothiazine 8a (procedure from US. Patent 4,652,643).5 A mixture of 9.0g of 6-(dimethylamino)-3-(methylamino)phenothiazin-5-ium chloride (Azure B), 150.0ml of acetic anhydride, and lO.Og of zinc dust was maintained at reflux temperature for approximately 4 hs. After the reaction mixture was cooled to ambient temperature, it was poured into ice water with stirring and 300ml of toluene was added. After stirring for approximately 30 min the toluene layer was separated and washed twice, once with tap water and once with saturated aqueous sodium chloride solution. The toluene was then distilled off at reduced pressure. The residue which remained was dissolved in ethyl acetate and separated into various components by subjecting the solution to column chromatography using silica gel as substrate. Elution with ethyl acetate yielded a white-colored solid. 

Pt/Al2C>3-cinchona alkaloid catalyst system is widely used for enantioselective hydrogenation of different prochiral substrates, such as a-ketoesters [1-2], a,p-diketones, etc. [3-5], It has been shown that in the enantioselective hydrogenation of ethyl pyruvate (Etpy) under certain reaction conditions (low cinchonidine concentration, using toluene as a solvent) achiral tertiary amines (ATAs triethylamine, quinuclidine (Q) and DABCO) as additives increase not only the reaction rate, but the enantioselectivity [6], This observation has been explained by a virtual increase of chiral modifier concentration as a result of the shift in cinchonidine monomer - dimer equilibrium by ATAs [7],... 

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

The competihve hydrogenation of alkyl-substituted arenes was also performed with lr(0) nanoparhcles [49]. Using toluene as a standard substrate, several toluene/ benzene and toluene/monoalkylbenzene hydrogenation experiments were conducted in order to determine the selectivity constants of the transition-metal nanoparticles. These selechvity constants can be used to predict the relative reactivity of any other couple of monoalkylbenzenes. A series of initial reaction... 

To demonstrate the catalytic efficiency of thiourea 9 and urea 16 (each 10mol% loading), Friedel-Crafts alkylation of various aromatic and heteroaromatic substrates was performed at room temperature in toluene as well as under solvent-free conditions. The results for the products 1-7 shown in Scheme 6.6 revealed that in all cases the 9-catalyzed reactions gave higher yields. In toluene N-methylpyrroIe reacted smoothly to give the 2-substituted Friedel-Crafts adduct 1, while the adducts 3-5 and 7 formed slowly and required longer reaction times (72 h). The... 

In the presence of 42 (2mol% loading), aliphahc and aromafic N-allyl as well as N-benzyl aldimines were efficiently converted after 20 h at -70 °C in toluene to the respective Strecker adducts and subsequently trifluoroacetylated to obtain the products 1-10 in good to excellent yields (65-99%) and ee values J7-97%) (Scheme 6.41). It turned out that N-benzyl imines could be used as substrates without significant difference in comparison to analogous N-allyl imines (e.g., N-benzyl adduct 8 85% yield, 87% ee N-allyl adduct 9 88% yield, 86% ee Scheme 6.41). 

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