Friedel-Crafts reaction aliphatic

TTie true ketones, in which the >CO group is in the side chain, the most common examples being acetophenone or methyl phenyl ketone, C HjCOCH, and benzophenone or diphenyl ketone, C HjCOC(Hj. These ketones are usually prepared by a modification of the Friedel-Crafts reaction, an aromatic hydrocarbon being treated with an acyl chloride (either aliphatic or aromatic) in the presence of aluminium chloride. Thus benzene reacts with acetyl chloride... 

Alkenes can be acylated with an acyl halide and a Lewis acid catalyst in what is essentially a Friedel-Crafts reaction at an aliphatic carbon. ° The product can arise by two paths. The initial attack is by the acyl cation RCO (or by the acyl halide free or complexed see 11-14) at the double bond to give a carbocation ... 

Route (b), based on an aliphatic Friedel-Crafts reaction, gives a good yield of (31) which is duly acylated with ketene dimer. 

A solution to all these problems can be found by an alternative disconnection. Enone (1) could be made by an aliphatic Friedel-Crafts reaction from acid (7). Disconnection of the allyl group now gives synthon (8) and the regioselectivity problem disappears. 

Asides from the application of imines on conjugate addition reactions, Deng [87, 88] reported the first asymmetric chiral thiourea catalyzed Friedel-Crafts reaction of indoles with iV-tosyl imines (Scheme 35). The reaction was receptive to various aromatic, heteroaromatic, and aliphatic imines in good yield and high enantioselec-tivity (Scheme 36). 

Aminophenols from anilines, 35, 2 Anhydrides of aliphatic dibasic acids, Friedel-Crafts reaction with, 5, 5 Anion-assisted sigmatropic rearrangements, 43, 2 Anthracene homologs, synthesis of, 1, 6 Anti-Markownikoff hydration of alkenes, 13, 1... 

S. C. Eyley, The Aliphatic Friedel-Crafts Reaction, in Comprehensive Organic Synthesis (B. M. Trost, I. Fleming, Eds.), Vol. 2, 707, Pergamon Press, Oxford, 1991. 

H. Mayr, Control of electrophilicity in aliphatic Friedel-Crafts reactions, Selectivities in Lewis Acid Promoted Reactions (D. Schinzer, ed.), NATO ASI Series C, Vol. 289, 1989, pp. 21-36. 

Attempts to apply the thermal decarboxylation reaction in the liquid phase to aromatic halofor-mic acid esters have shown that their reaction is different from that ol the aliphatic haloformates. It was found that evolution of carbon dioxide occurs, but only high boiling products could be isolated.136 On heating in the presence of aromatics and Lewis acids, aryl chloroformates do not react to give chlorinated aromatics with concomitant decarboxylation, but undergo a Friedel-Crafts reaction to give phenyl benzoates.137 Under similar conditions phenyl fluoroformate undergoes only polymerization and carbonate formation.137... 

Synthesis.—This hydrocarbon is by far the most important of those in which two or more benzene rings are linked together by intervening aliphatic carbon groups. Just as methyl chloride and benzene by the Friedel-Craft reaction yield phenyl methane (methyl benzene or toluene) and methylene chloride, di-chlor methane, with benzene yields di-phenyl methane so by the same reaction tri-chlor methane, chloroform, yields with benzene a hydrocarbon which by this synthesis must be tri-phenyl methane. 

Now the aldehyde is oxidized to an add and the acid chloride does an intramolecular, Lewis-ac . -catalysed, aliphatic Friedel-Crafts reaction on the vinyl silane. Notice attack at the ipso carbon give a stable P-sUyl cation intermediate and that this vinyl silane has to react with inversion as frans-alkene is impossible in the ring. 

For some time the main emphasis of Friedel-Crafts reactions was chiefly on aromatic compounds. The development of aliphatic Friedel-Crafts chemistry was of minor importance until World War 2, when isomerization of alkanes and cycloalkanes, preparation of high-octane aviation gasoline and synthetic rubber, and polymerization of alkenes achieved considerable importance these contributed to the growth of aliphatic Friedel-Crafts chemistry. 

Despite their seemingly wide variety, Friedel-Crafts reactions can be divided into two general categories alkylations and acylations. Within these two broad areas, there is considerable diversity. Friedel-Crafts alkylations allow C—C bond formation in both aromatic and aliphatic systems, and are of substantial synthetic and industrial significance. 

In a later study. Swanson and coworkers [81] studied the cure of acetylene-terminated poly(imide)s selectively labelled at various positions with nuclei. Curing of the sample, labelled at the imide carbonyl group, confirmed the completion of the imidization reaction on heating. The product of addition onto the carboxyl group was not observed. Four new peaks were identified in the spectrum of the cured sample labelled at the Ci-acetylene group, while a similar result was obtained for the sample labelled at the C2-acetylene position. Analysis of these results rules out the participation of coupling reactions and the biradical mechanism, which would produce triple-bond structures, but confirms the presence of the product of cyclotrimerization and Friedel-Crafts reactions. The latter mechanism is confirmed from the presence of small peaks due to aliphatic carbons in the spectra of the materials labelled at the acetylene groups. 

When the aldol strategy is ideal When the aldol strategy is not ideal Symmetry as a guide Wittig-style aldol methods Strategy 4b Acylation of a Vinyl Anion Vinyl metal reagents The aliphatic Friedel- Crafts reaction Unsaturated Acyl Cations and Anions Acyl anion equivalents (d1 reagents)... 

In chapter 16 we shall discover that vinyl-copper reagents can be prepared with stereochemical control over double bond geometry and acylated directly with acid chlorides. We shall also meet vinyl silanes and see how they too can be acylated with acid chlorides. In this chapter we shall consider only the acylation of alkenes themselves with acid chlorides, that is the aliphatic Friedel-Crafts reaction.15 The normal Friedel-Crafts reaction 66 combines an aromatic compound with an acid chloride and a Lewis acid to give a cation 67 which loses a proton to give an aryl ketone 68. 

Disconnection between C=0 and C=C with the aliphatic Friedel-Crafts reaction in mind would require acylation of the unsymmetrical alkene 76 with the acid chloride 77. The alkene 76 is ideal for acylation as it is tri-substituted and therefore relatively electron-rich and will react at the required (less substituted) end. The P-chloroketone 78, formed when SnCl4 was used as the Lewis acid, was treated with base without isolation to give the enone 74 in 60% overall yield. Lithium chloride may not look very basic, but in dipolar aprotic solvents like DMF (DiMethylFormamide, Me2NCHO), that do not solvate anions, chloride is a good base. 

Strategies Based on an A Idol Reaction Using the Aliphatic Friedel-Crafts Reaction The Nazarov Reaction... 

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