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Alkenes Friedel-Crafts alkylation

An elegant and efficient synthesis of 6,11-dihydro-ll-ethyl-57/-dibenz[6,c]azepine derivatives 53 has been described which involves a BFs-catalysed aromatic amino-Claisen rearrangement of 51a-d to 52a-d followed by an intramolecular alkene Friedel-Crafts alkylation (acid catalysed) to access the 7-membered ring in 53 in high yield. With the amino-Claisen rearrangement of 51e, an inseparable mixture of 54e and 54e was obtained, since in this case both ortho positions in 56 are free for the rearrangement <04SL2721>. [Pg.395]

We will show here the classification procedure with a specific dataset [28]. A reaction center, the addition of a C-H bond to a C=C double bond, was chosen that comprised a variety of different reaction types such as Michael additions, Friedel-Crafts alkylation of aromatic compounds by alkenes, or photochemical reactions. We wanted to see whether these different reaction types can be discerned by this... [Pg.193]

Friedel-Crafts alkylation using alkenes has important industrial appHcations. The ethylation of benzene with ethylene to ethylbenzene used in the manufacture of styrene, is one of the largest scale industrial processes. The reaction is done under the catalysis of AlCl in the presence of a proton source, ie, H2O, HCl, etc, although other catalysts have also gained significance. [Pg.551]

All lation of Phenols. The approach used to synthesize commercially available alkylphenols is Friedel-Crafts alkylation. The specific procedure typically uses an alkene as the alkylating agent and an acid catalyst, generally a sulfonic acid. Alkene and catalyst interact to form a carbocation and counter ion (5) which interacts with phenol to form a 7T complex (6). This complex is held together by the overlap of the filled TT-orbital of the aromatic... [Pg.58]

Alkylation of furan and thiophene has been effected with alkenes and catalysts such as phosphoric acid and boron trifluoride. In general, Friedel-Crafts alkylation of furans or thiophenes is not preparatively useful, partly because of polymerization by the catalyst and partly because of polyalkylation. [Pg.53]

FRIEDEL - CRAFTS Alkylation-Acylation Alkylation or acylation ol aromatic compounds by means of alryl halides, alcohols.alkenes, acyl halides in the presence of Lewis acids... [Pg.131]

The synthesis of an alkylated aromatic compound 3 by reaction of an aromatic substrate 1 with an alkyl halide 2, catalyzed by a Lewis acid, is called the Friedel-Crafts alkylation This method is closely related to the Friedel-Crafts acylation. Instead of the alkyl halide, an alcohol or alkene can be used as reactant for the aromatic substrate under Friedel-Crafts conditions. The general principle is the intermediate formation of a carbenium ion species, which is capable of reacting as the electrophile in an electrophilic aromatic substitution reaction. [Pg.120]

As catalysts Lewis acids such as AICI3, TiCU, SbFs, BF3, ZnCh or FeCl3 are used. Protic acids such as FI2SO4 or FIF are also used, especially for reaction with alkenes or alcohols. Recent developments include the use of acidic polymer resins, e.g. Nafion-Fl, as catalysts for Friedel-Crafts alkylations and the use of asymmetric catalysts. ... [Pg.123]

An important use of the Friedel-Crafts alkylation reaction is to effect ring closure. The most common method is to heat with aluminum chloride an aromatic compound having a halogen, hydroxy, or alkene group in the proper position, as, for example, in the preparation of tetralin ... [Pg.710]

For a monograph, see Roberts, R.M. Khalaf, A.A. Friedel-Crafts Alkylation Chemistry Marcel Dekker NY, 1984. For a treatise on Friedel-Crafts reactions in general, see Olah, G.A. Friedel-Crafts and Related Reactions Wiley NY, 1963-1965. Volume 1 covers general aspects, such as catalyst activity, intermediate complexes, and so on. Volume 2 covers alkylation and related reactions. In this volume the various reagents are treated by the indicated authors as follows alkenes and alkanes, Patinkin, S.H. Friedman, B.S. p. 1 ... [Pg.747]

Intermodular Alkylation by Carbocations. The formation of carbon-carbon bonds by electrophilic attack on the ir system is a very important reaction in aromatic chemistry, with both Friedel-Crafts alkylation and acylation following this pattern. These reactions are discussed in Chapter 11. There also are useful reactions in which carbon-carbon bond formation results from electrophilic attack by a carbocation on an alkene. The reaction of a carbocation with an alkene to form a new carbon-carbon bond is both kinetically accessible and thermodynamically favorable. [Pg.862]

Highly reactive mixed anhydrides can also promote acylation. Phenylacetic acid reacts with alkenes to give 2-tetralones in TFAA-H3P04.55 This reaction involves an intramolecular Friedel-Crafts alkylation subsequent to the acylation. [Pg.882]

Friedel-Crafts alkylation can occur intramolecularly to form a fused ring. Intramolecular Friedel-Crafts reactions provide an important method for constructing polycyclic hydrocarbon frameworks. It is somewhat easier to form six-membered than five-membered rings in such reactions. Thus, whereas 4-phenyl-1-butanol gives a 50% yield of a cyclized product in phosphoric acid, 3-phenyl-1-propanol is mainly dehydrated to alkenes.43... [Pg.1016]

However, one of the most common mechanisms is undoubtedly proton transfer but whereas in alkene polymerizations this reaction leaves a terminal double bond, in arylene polymerizations these are generally not found. Instead the terminal group is usually a substituted indane formed by an internal Friedel-Crafts alkylation [8, 21, 23], e.g., for a-methyl styrene ... [Pg.251]

Note This reaction involves a polar acidic mechanism, not a free-radical mechanism It is a Friedel-Crafts alkylation, with the slight variation that the requisite carbocation is made by protonation of an alkene instead of ionization of an alkyl halide. Protonation of C4 gives a C3 carbocation. Addition to Cl and fragmentation gives the product. [Pg.125]

In 2007, two groups independently described asymmetric phosphoric acid-catalyzed Friedel-Crafts alkylations of indoles. While You et al. chose the conventional approach and employed imines as substrates (Scheme 11), Terada and coworkers came up with a different concept and used electron-rich alkenes as precursors (Scheme 49) [73]. Enecarbamates 125 reacted with indoles 29 in the presence of BINOL phosphate (R)-io (5 mol%, R = bearing 2,4,6-triisopropyl-... [Pg.434]

Shortly after the discovery of the first asymmetric phosphoric acid-catalyzed transformation of enecarbamates, Zhou et al. expanded the scope of the Friedel-Crafts alkylation of indoles 29 with electron-rich alkenes to enamides 127 (Scheme 51) [74],... [Pg.435]

Dibenzofuran undergoes Friedel-Crafts alkylation with alkyl ha-lides " " or alkenes in the presence of Lewis acids. The products... [Pg.67]

The Friedel-Crafts alkylation reaction usually involves the interaction of an alkylation agent such as an alkyl halide, alcohol, or alkene with an aromatic compound, to form an alkylated aromatic compound (Scheme 5.1-44). [Pg.196]

Besides aluminum chloride, the most often used and studied Friedel-Crafts catalyst, many other acid catalysts are effective in alkylation. Although Friedel-Crafts alkylation was discovered and explored mainly with alkyl halides, from a practical point of view, alkenes are the most important alkylating agents. Others include alcohols, ethers, and esters. [Pg.230]

A binuclear Ir3+ complex used in the reaction of benzene with alkenes induces the formation of straight-chain alkylbenzenes with higher selectivity than in the branched isomers 407 The selectivity, unusual in conventional acid-catalyzed Friedel-Crafts alkylations, is suggested to result from the complex activating the C—H bond of benzene instead of the alkene. [Pg.265]

Alkylation. Friedel-Crafts alkylation (qv) of benzene with ethylene or propylene to produce ethylbenzene [100-41 -4], CgH10, or isopropylbenzene [98-82-8], C9H12 (cumene) is readily accomplished in the liquid or vapor phase with various catalysts such as BF3 (22), aluminum chloride, or supported polyphosphoric acid. The oldest method of alkylation employs the liquid-phase reaction of benzene with anhydrous aluminum chloride and ethylene (23). Ethylbenzene is produced commercially almost entirely for styrene manufacture. Cumene [98-82-8] is catalytically oxidized to cumene hydroperoxide, which is used to manufacture phenol and acetone. Benzene is also alkylated with C1Q—C20 linear alkenes to produce linear alkyl aromatics. Sulfonation of these compounds produces linear alkane sulfonates (LAS) which are used as biodegradable deteigents. [Pg.40]

Supercritical hydrogenation is just one example of continuous reactions which can be carried out in SCCO2 solution. Other reactions which have been carried out successfully include Friedel-Crafts alkylation of aromatics by alcohols [64], the dehydration of alcohols to form ethers [65] (using acid catalysts), and the hydroformylation of alkenes [52] (using rhodium catalysts immobilized on Si02). In each of these reactions, it is possible to obtain a selectivity which is at least as good, and often better, than with conventional solvents. However, the precise role of the scCC>2 in these reactions is not as obvious as in supercritical hydrogenation. [Pg.481]

C-Alkylations have been performed with both support-bound carbon nucleophiles and support-bound carbon electrophiles. Benzyl, allyl, and aryl halides or triflates have generally been used as the carbon electrophiles. Suitable carbon nucleophiles are boranes, organozinc and organomagnesium compounds. C-Alkylations have also been accomplished by the addition of radicals to alkenes. Polystyrene can also be alkylated under harsh conditions, e.g. by Friedel-Crafts alkylation [11-16] in the presence of strong acids. This type of reaction is incompatible with most linkers and is generally only suitable for the preparation of functionalized supports. Few examples have been reported of the preparation of alkanes by C-C bond formation on solid phase, and general methodologies for such preparations are still scarce. [Pg.171]


See other pages where Alkenes Friedel-Crafts alkylation is mentioned: [Pg.551]    [Pg.565]    [Pg.158]    [Pg.145]    [Pg.1014]    [Pg.1017]    [Pg.535]    [Pg.230]   
See also in sourсe #XX -- [ Pg.313 , Pg.314 , Pg.315 , Pg.316 , Pg.317 , Pg.318 , Pg.319 ]




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Alkylation alkene

Friedel Crafts alkylation

Friedel-Crafts alkylations

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