Dehydrogenation Friedel-Crafts

The proposed iminium intermediate in the CDC-type allgmylation implies that other C-H based pronueleophiles, besides terminal allqmes, can also couple with an a-sp C-H bond of a nitrogen in amines via the same process. Thus, we examined eleetron-rieh arenes as one such nucleophile via a cross-dehydrogenative Friedel-Crafts type arylation. Indole derivatives were coupled with N-aryl-THIQs under the CuBr/TBHP system to produce the desired CDC reaction product in good-to-excellent yields (Scheme 1.9). It is worth noting that the reaction was not sensitive to moisture or air, and that the desired product was obtained in reasonable yield even when the reaction was... 

Naphthol is another electron-rich aromatic compound which can also lead to sp -sp CDC-type products. Thus, a new type of Betti base was formed via the CDC reaction of N-phenyl-THIQ with 2-naphthol derivatives under our CuBr/TBHP system with a small amount of homocoupled 2,2-binaphthol (BINOL) (Scheme 1.10). Subsequently, the scope of cross-dehydrogenative Friedel-Crafts type aiylations was significantly improved by the development of highly efficient catalyst systems, and an intramolecular Cu-catalyzed aerobic synthesis of functionalized cinnolines via a Friedel-Crafts-type CDC aiylation was reported by Zhang et al. ... 

Arylation of Aromatic Compounds. In contrast to Friedel-Crafts alkylations, arylations of aromatics are not as well known, and usually require drastic conditions. They iaclude (/) dehydrogenating condensation (SchoU reaction) (2) arylation with aryl haUdes and (J) arylation with dia2onium hahdes. 

The LAB production process (process 1) is mainly developed and licensed by UOP. The N-paraffins are partially converted to internal /z-olefins by a catalytic dehydrogenation. The resulting mixture of /z-paraffins and n-olefins is selectively hydrogenated to reduce diolefins and then fed into an alkylation reactor, together with an excess benzene and with concentrated hydrofluoric acid (HF) which acts as the catalyst in a Friedel-Crafts reaction. In successive sections of the plant the HF, benzene, and unconverted /z-paraffins are recovered and recycled to the previous reaction stages. In the final stage of distillation, the LAB is separated from the heavy alkylates. 

Another recent patent (22) and related patent application (31) cover incorporation and use of many active metals into Si-TUD-1. Some active materials were incorporated simultaneously (e.g., NiW, NiMo, and Ga/Zn/Sn). The various catalysts have been used for many organic reactions [TUD-1 variants are shown in brackets] Alkylation of naphthalene with 1-hexadecene [Al-Si] Friedel-Crafts benzylation of benzene [Fe-Si, Ga-Si, Sn-Si and Ti-Si, see apphcation 2 above] oligomerization of 1-decene [Al-Si] selective oxidation of ethylbenzene to acetophenone [Cr-Si, Mo-Si] and selective oxidation of cyclohexanol to cyclohexanone [Mo-Si], A dehydrogenation process (32) has been described using an immobilized pincer catalyst on a TUD-1 substrate. Previously these catalysts were homogeneous, which often caused problems in separation and recycle. Several other reactions were described, including acylation, hydrogenation, and ammoxidation. 

IrCl2H(cod)]2 catalyzed the synthesis of substituted quinolines, where the reachon of aniline derivahves, aromatic and alkyl aldehydes efficiently proceeds under an oxygen atmosphere (Scheme 11.34) [46]. The plausible mechanism consists of a Mannich reaction, a Friedel-Craft-type aromahc substituhon, dehydration, and dehydrogenation. This can be recognized as a formal [4+2] cycloaddition of N-aryl imine and enol (Scheme 11.35). 

Linear alkylbenzenes are made from -paraffms (Cio-Cu) by either partial dehydrogenation to olefins and addition to benzene with HF as catalyst (60%) or chlorination of the paraffins and Friedel-Crafts reaction with benzene and an aluminum chloride catalyst (40%). See Chapter 24 for more information. 

The other 60% of the alkyl groups for LAS detergents are made through linear a-olefins. n-Alkanes can be dehydrogenated to a-olefins, which then can undergo a Friedel-Crafts reaction with benzene as described above for the nonlinear olefins. Sulfonation and basification gives the LAS detergent. 

Styrene is produced by the catalytic vapor phase dehydrogenation of ethylbenzene. Ethylbenzene is made by the Friedel-Crafts condensation of ethylene and benzene. Styrene is also produced by the palladium acetate-catalyzed condensation of ethylene and benzene and by the dehydration of methylphenylcarbinol obtained by the propylation of ethylbenzene. Because of the toxicity of styrene, its concentration in the atmosphere must be severely limited. 

Aluminum chloride has extensive commercial applications. It is used primarily in the electrolytic production of aluminum. Another major use involves its catalytic applications in many organic reactions, including Friedel-Crafts alkylation, polymerization, isomerization, hydrocracking, oxidation, decarboxylation, and dehydrogenation. It is also used in the production of rare earth chlorides, electroplating of aluminum and in many metal finishing and metallurgical operations. 

Benzofuranyl)butanoic acid readily forms the acid chloride, and this undergoes intramolecular Friedel-Crafts acylation on treatment with tin(IV) chloride in carbon disulfide at room temperature, providing 1,2,3,4-tetra-hydro-l-dibenzofuranone (54%). " This intermediate has been converted to dibenzofuran by lithium aluminum hydride reduction and subsequent dehydrogenation, to 1-methyldibenzofuran by Grignard reaction and dehydrogenation, and to 1-dibenzofuranol by reaction with iV-bromosuccinimide and subsequent dehydrobromination with pyridine. 

Acrylonitrile is obtained from propylene and ammonia. 1,3-Butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking. An overview on the issues of the production of butadiene is given in the literature (5). Styrene monomer is made by the dehydrogenation of ethylbenzene, which is obtained by the Friedel-Crafts reaction of ethylene and benzene. 

Olefins are formed by dehydrogenation of the n-paraffin feed over the metallic hydrogenation-dehydrogenation function and are adsorbed on the acidic surface of the catalyst as carbonium ions by proton addition. After skeletal isomerization they are desorbed as isoolefins and subsequently hydrogenated to the corresponding isoparaffins. The net result (i.e., the formation of carbonium ions) of the action of metal and acid in dual function catalysis is, on pure Friedel-Crafts type catalysts, described by the scheme ... 

Alkylation. Ethylbenzene [100-41-4], the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either in the liquid phase in the presence of a Friedel-Crafts catalyst (A1C13, BF3, FeCl3) or in the vapor phase with a suitable catalyst. The Monsanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeolite catalyst process for liquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process using zeolite catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-3], which is obtained by dehydrogenation in the presence of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

The Friedel-Crafts cyclization of the acid chloride (19a) occurs normally at — 70°, with the formation of the azacycloheptenone (20), but the sole product at 5° is 5,6-dihydro-5-tolylsulfonylphenanthridine (21). Similarly, the related acid (19b) gives phenanthridine when heated with polyphosphoric acid at 60°.53 Presumably a 5,6-dihydro-phenanthridine is formed which undergoes dehydrogenation in the reaction medium (cf. Das Gupta et aZ.48). 

In contrast, continuous flow reactors are already being used for hydrogenation reactions industrially (Licence el al., 2003). They are simple to construct and modify, and possess excellent mass- and heat-transfer properties. In academia, flow reactors have been used in conjunction with a variety of heterogeneous catalysts to carry out many reactions, including hydrogenations, dehydrogenations, hydroformylations, Friedel-Crafts acylations and alkylations, etherifications and oxidations (Hyde et al., 2001). 

Styrene (phenylethene, 10) is an important industrial chemical that is prepared by dehydrogenation of ethylbenzene at 600 °C over zinc oxide or chromium(III) oxide on alumina (Scheme 3.7). Ethylbenzene can be produced from benzene and ethene by a Friedel-Crafts reaction. 

There are two main synthetic routes to naphthalene the Haworth synthesis and a Diels-Alder approach. In the Haworth synthesis (Scheme 12.1), benzene is reacted under Friedel-Crafts conditions with succinic anhydride (butanedioic anhydride) to produce 4-oxo-4-phenylbutanoic acid, which is reduced with either amalgamated zinc and HCl (the Clemmensen reduction) or hydrazine, ethane-1,2-diol and potassium hydroxide (the Wolff-Kischner reaction) to 4-phenylbutanoic acid. Ring closure is achieved by heating in polyphosphoric acid (PPA). The product is 1-tetraione and reduction of the carbonyl group then gives 1,2,3,4-tetrahydronaphthalene (tetralin). Aromatization is achieved by dehydrogenation over a palladium catalyst. 

Friedel-Crafts alkylations with higher dihaloalkanes generally give a mixture of products derived from processes such as isomerization, multiple addition and dehydrogenation (caused by AICI3), as seen from the examples shown in equations (73) and (74). ... 

The most useful procedure utilises a 1,4-keto-ester giving a dihydro-pyridazinone, which can be easily dehydrogenated to the fully aromatic heterocycle, often by C-bromination then dehydrobromination alternatively, simple air oxidation can often suffice. 6-Aryl-pyridazin-3-ones have been produced by this route in a number of ways using an a-amino nitrile as a masked ketone in the four-carbon component, or by reaction of an acetophenone with glyoxylic acid and then hydrazine. Friedel-Crafts acylation using succinic anhydride is an alternative route to 1,4-keto-acids, reaction with hydrazine giving 6-aryl-pyridazinones. Alkylation of an enamine with a phenacyl bromide prodnces 1-aryl-l,4-diketones, allowing synthesis of 3-aryl-pyridazines. ... 

---