Other Acylated Compounds

2-Hydroxybenzoic acid, 2-chloro-4-(2-hydroxybenzoyl)phenyl ester [123861-93-8] QoHjjCIO, mol.wt. 368.77 

Also obtained by Fries rearrangement of phenyl salicylate (salol) with aluminium chloride [1475], without solvent at 180-182° for 3 h (10%) [155], 

Also obtained (by-product) by Fries rearrangement of phenyl 2-(nicotinoyloxy) benzoate with aluminium chloride without solvent at 140-145° for 2 h (16%) [346], 

Martin, Aromatic Hydroxyketones Preparation and Physical Properties, 

Also obtained by Friedel-Crafts reaction between p-anisoyl chloride and anisole, followed by demethylation of the obtained product [1505]. 

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Acid halides, also called acyl halides, are activated derivatives used for the synthesis of other acyl compounds such as esters, amides, and acylbenzenes (in the Friedel-Crafts acylation). The most common acyl halides are the acid chlorides (acyl chlorides), and we will generally use acid chlorides as examples. 

These reactions are used to make anhydrides, carboxylic acids, esters, and amides, but not acid chlorides, from other acyl compounds. Acid chlorides are the most reactive acyl compounds (they have the best leaving group), so they are not easily formed as a product of nucleophilic substitution reactions. They can only be prepared from carboxylic acids using special reagents, as discussed in Section 22.10A. 

A thioester (RCOSR ) has a good leaving group ( SR ), so, like other acyl compounds, it undergoes substitution reactions with other nucleophiles. 

The carbonyl carbon of an amide is sp hybridized and has trigonal planar geometry. A second resonance structure can be drawn that delocalizes the nonbonded electron pair on the N atom. Amides are more resonance stabilized than other acyl compounds, so the resonance structure having the C=N makes a significant contribution to the hybrid. 

FIGURE 18.42 By analogy to what we know of other acyl compounds, we might well expect the treatment of an amide with a metal hydride to result in the formation of an alcohol. In fact, this reaction does not take place. An amine is formed instead. 

Most other acylating agents act on salts of either primary or secondary nitroparaffins by O-acylation, giving first the nitronic anhydrides which rearrange to give, eg, nitrosoacyloxy compounds (28). 

Like other aromatic compounds, aromatic ethers can undergo substitution in the aromatic ring with electrophilic reagents, eg, nitration, halogenation, and sulfonation. They also undergo Eriedel-Crafts (qv) alkylation and acylation. 

The predominance of structure 65 (R = H) in the equilibrium 65 66 has been reported on the basis of the ultraviolet spectral similarity of the potentially tautomeric compound and of 67. However, when R = COCH3, this hydroxy pyridine 1-imide reacts with diazomethane to yield 68, which has been interpreted to indicate that 66 is the predominant tautomer this conclusion is supported by the resultant changes in the pif values when the acetyl group is replaced by other acyl groups. 

There has been recent interest in naphtho-fused dithiepines as chiral acyl anion equivalents, particularly since the starting dithiol 128 can be obtained in enan-tiomerically pure form (89TL2575). This is transformed using standard methods into the dithiepine 129, but showed only moderate diastereoselectivity in its addition to carbonyl compounds. On the other hand, as we have seen previously for other systems, formation of the 2-acyl compound 130 and reduction or addition of a Grignard reagent gave the products 131 with much better stereoselectivity (91JOC4467). 

The enolates of ketones can be acylated by esters and other acylating agents. The products of these reactions are [Tdicarbonyl compounds, which are rather acidic and can be alkylated by the procedures described in Section 1.2. Reaction of ketone enolates with formate esters gives a P-ketoaldehyde. As these compounds exist in the enol form, they are referred to as hydroxymethylene derivatives. Entries 1 and 2 in Scheme 2.16 are examples. Product formation is under thermodynamic control so the structure of the product can be predicted on the basis of the stability of the various possible product anions. 

Organopalladium intermediates are also involved in the synthesis of ketones and other carbonyl compounds. These reactions involve acylpalladium intermediates, which can be made from acyl halides or by reaction of an organopalladium species with carbon monoxide. A second organic group, usually arising from any organometallic reagent, can then form a ketone. Alternatively, the acylpalladium intermediate may react with nucleophilic solvents such as alcohols to form esters. 

See related acyl azides See other silver compounds... 

Appel, R. et al., Angew. Chem. (Intern. Ed.), 1983, 22, 785 Reaction with water is violent, forming triazinetricarboxylic acid. See Other ACYL HALIDES, CYANO COMPOUNDS... 

See other acyl azides, high-nitrogen compounds... 

See related ACYL HALIDES See other ENDOTHERMIC COMPOUNDS... 

See Other ACYL AZIDES, CYANO COMPOUNDS, HIGH-NITROGEN COMPOUNDS... 

Oxopropanedinitrile (Carbonyl dicyanide) [1115-12-4] 0 C(CN)2 Water Martin, E. L., Org. Synth., 1971, 51, 70 The nitrile reacts explosively with water. See related ACYL HALIDES See other CYANO COMPOUNDS c3n2o... 

See 2,4-Hexadiynylene chloroformate also Dimethylformamide See other acetylenic compounds, acyl halides... 

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