Acyl chlorides, electrophilic

Finally, chiral nitroxyl radicals can be synthesized by the intramolecular coupling of enones with nitro compounds under reductive conditions [109]. Thus reaction of appropriately substituted nitro enones with Sml2, followed by a quench with reactive acyl chloride electrophiles, provides a-asymmetric nitroxide radicals in excellent yields (Eq. 97). 

Friedel-Crafts acylation of aromatic compounds (Section 12 7) Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of alumi num chloride The reaction is electrophil ic aromatic substitution in which acylium ions are generated and attack the ring... 

Friedel-Crafts acylation (Section 12 7) An electrophilic aro matic substitution in which an aromatic compound reacts with an acyl chloride or a carboxylic acid anhydride in the presence of aluminum chlonde An acyl group becomes bonded to the nng... 

There are large differences in reactivity among the various carboxylic acid derivatives, such as amides, esters, and acyl chlorides. One important factor is the resonance stabilization provided by the heteroatom. This decreases in the order N > O > Cl. Electron donation reduces the electrophilicity of the carbonyl group, and the corresponding stabilization is lost in the tetrahedral intermediate. 

The reaction is initiated by formation of a donor-acceptor complex 4 from acyl chloride 2, which is thereby activated, and the Lewis acid, e.g. aluminum trichloride. Complex 4 can dissociate into the acylium ion 5 and the aluminum tetrachloride anion 4 as well as 5 can act as an electrophile in a reaction with the aromatic substrate ... 

Oxidation to adds by KMnO 100 °C subsequent acces to acyl chlorides nitriles, amides J deprotcnation by tBuOK followed by alkylation or functionalization fay electrophiles... 

Subsequently rates of benzoylation of a range of aromatics were determined under the same conditions (Table 105)407. The high negative entropy of activation is consistent with the high degree of ordering required for the polarised acyl chloride-aluminium chloride complex to be the electrophile. 

Organomercury reagents do not react with ketones or aldehydes but Lewis acids cause reaction with acyl chlorides.187 With alkenyl mercury compounds, the reaction probably proceeds by electrophilic attack on the double bond with the regiochemistry being directed by the stabilization of the (3-carbocation by the mercury.188... 

The intermediate adduct can be substituted at the a-position by a variety of electrophiles, including acyl chlorides, epoxides, aldehydes, and ketones.79... 

Symmetrically substituted BODIPY dyes are relatively easy to be synthesized via the condensation of pyrroles with carbonyl electrophiles, such as acyl chlorides,... 

Friedel-Crafts acylation of a pyrazolo[l,5- ][l,3,5]triazine derivative 137 was published by Raboisson et al. <2002TL9501> and the transformation is shown in Scheme 20. The electrophilic attack of various acyl chlorides took place in position 3 to yield the new ketones 138 in moderate to excellent yields. 

N-Acylation. Acyl chlorides or carboxylic anhydrides, which generally have a hard electrophilic character, can selectively convert OZTs into IV-acylated derivatives.59... 

The 1,3,2-dioxastannolanes are important in organic synthesis because they can readily be derived from dialkyltin oxide and 1,2-diols, as in carbohydrates the reaction can be carried out in toluene in a few minutes under microwave irradiation.387 The dioxastannolanes can then be subjected to regioselective reaction with an electrophile such as an acyl chloride (Equation (140)) or sulfonyl chloride, or an isocyanate. The acylation or sulfonation can be carried out with catalytic amounts of the dialkyltin oxide, including the recoverable (C6F13CH2CH2)2Sn0.388... 

Acyl chlorides themselves may be synthesized by a similar type of reaction, in which we invoke nucleophilic attack of an acid onto thionyl chloride as shown. As we shall see later (see Section 7.13.1), the S=0 group behaves as an electrophile in the same way as a C=0 group. 

Also in the case of intennediate 374, a lithium-copper transmetallation with a copper(I) halide (bromide or chloride) allowed one to carry out the conjugate addition [to electrophilic olefins R CH = CH2Z (Z = COR, CO2R) giving compounds 381 in 31-76% yield], the acylation (with acyl chlorides yielding ketones 382 in 35-65% yield) and dimerization [using copper(II) chloride as the additive, to give compound 383 in 59% yield] processes ... 

Most reactions of alkenylsilanes require strong carbon electrophiles, and Lewis acid catalysts are often involved. Reaction with acyl chlorides is catalyzed by aluminum chloride or stannic chloride.57... 

As in the alkylation reaction, the reactive intermediate can be a dissociated acylium ion or a complex of the acyl chloride and Lewis acid.43 Recent mechanistic studies have indicated that with benzene and slightly deactivated derivatives, it is the protonated acylium ion that is the kinetically dominant electrophile.44... 

This mechanism explains much of the experimental evidence obtainedhfrom studies of the solvolysis of acyl chlorides, but it may not be in agreement (as was pointed out to Minato by a referee) with the linear relationship between electrophilic catalysis observed in the solvolysis of certain acid chlorides would possibly be explained by a simpler mechanism such as the SN1 or hydration-ionisation mechanism. However, it is of interest to see how the mechanism applies to acetyl, benzoyl and mesitoyl chlorides. For acetyl chloride, kY and k-Y would be very large and the rate would approximate to... 

When an aminoacyl-tRNA synthetase catalyzes the esterification of tRNA with an amino acid, the amino acid is activated by formation of an enzyme-bound mixed anhydride with AMP (equation 2.67) in the same way that an organic chemist activates a carboxylic acid by forming an acyl chloride or a mixed anhydride. (Note that in equation 2.67 the substrate is the magnesium complex of ATP, with the metal ion acting as an electrophilic catalyst. The Mg2+ binds primarily to the /3,y-phosphates.50 51)... 

The electrophilic cyclization of /3-(arylchalcogeno)propenoic acids 62 and acyl chlorides 63 may occur in two different ways. Whereas ortho acylation involving formation of the intermediate 64 gives rise to the six-membered heterocycles, chalcogenachromones (flavones) 65, ipso acylation is accompanied by formation of the typical c-complex 66, which transforms to the five-membered heterocycle, 1,2-oxachalcogenolium chloride 67. 

Acyliron complexes have found many applications in organic synthesis [40]. Usually they are prepared by acylation of [CpFe(CO)2] with acyl chlorides or mixed anhydrides (Scheme 1.13). This procedure affords alkyl, aryl and a,P-unsaturated acyliron complexes. Alternatively, acyliron complexes can be obtained by treatment of [Fe(C5Me5)(CO)4]+ with organolithium reagents, a,P-Unsaturated acyliron complexes can be obtained by reaction of the same reagent with 2-alkyn-l-ols. Deprotonation of acyliron complexes with butyllithium generates the corresponding enolates, which can be functionalized by reaction with various electrophiles [40]. 

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