Anhydrides halides

The simplest procedures for 2-acylation involve reaction of an jV-protected 2-lithioindole with an acyl halide, anhydride or ester. Such reactions typically give good yields of 2-acylindoles. Table 10.3 presents some examples. Aryl... 

Most of the known acylations have been described for 2-aminothiazoles, the activity of the acylating agent being in the order, acid halides > anhydrides > esters > acids — amides. 

Imides can be prepared by the attack of amides or their salts on acyl halides, anhydrides, and carboxylic acids or esters. The best synthetic method for the preparation of acyclic imides is the reaction between an amide and an anhydride at 100°C catalyzed by H2S04. When acyl chlorides are treated with amides in a2 l molar ratio at low temperatures in the presence of pyridine, the products are N,N-diacylamides, (RCO)3N. ... 

Tertiary alkyl azides can be prepared by stirring tertiary alkyl chlorides with NaN3 and ZnCl2 in 82 ° or by treating tertiary alcohols with NaN3 and CF3-COOH or with HN3 andTiCl4 or BF3. Acyl azides, which can be used in the Curtius reaction (18-14), can be similarly prepared from acyl halides, anhydrides, " esters, or other acyl derivatives. ° Acyl azides can also be prepared... 

An important use of the Friedel-Crafts acylation is to effect ring closure. This can be done if an acyl halide, anhydride, or acid group is in the proper position. An example is... 

Scheme 2.15. Acylation of Ester Enolates with Acyl Halides, Anhydrides, and Imidazolides... 

In a similar approach (Equation 53), the use of a resin-bound nitrile allowed access to the corresponding resin-bound amidoximes 274, which could be converted into 1,2,4-oxadiazoles 275 via acylation with either an appropriate acid halide/ anhydride in the presence of a base or a carboxylic acid in the presence of a coupling reagent followed by cyclization, where the latter step was performed by heating in pyridine or diglyme and could be accelerated by the use of a microwave oven. Cleavage from the resin was easily achieved by the use of TFA in dichloromethane <2000BML1431>. 

Organic acid halides/anhydrides Acetic anhydride, acetyl chloride... 

The toxicity of the P-halidc anhydrides, like that of phosphoroxychloride (POCl3) and of other organophosphorus compounds discussed earlier in this section, is due to their high efficiency as irreversible inactivators of acetylcholinesterase [157]. The main target organs for the lethal effects of these chemical weapons are the brain and diaphragm. As for the detoxification of the P-halide anhydrides, it can occur by a number of biochemical mechanisms, namely chemical hydrolysis, enzymatic hydrolysis, and binding to hydrolases such as carboxylesterases, cholinesterases, and albumin [68][158][159]. 

Acyl halides, anhydrides, esters and acids all react with LAH to give a primary alcohol. Amides (see later) behave differently. 

Alkyl halides, acyl halides, anhydrides, and related substances. It was discovered as early as 1861 by Rcboul and Luurenool<4t> that epicblorohydrin may be caused to react with ethyl bromide on heating in a sealed tube to an elevated temperature. The product isolated from this condensation was ]-broJHo-3-chloro-2-ethoxyprt>pane. Some year later Paalli6 extended this reaction to include also methyl iodide, ethyl iodide, n-propyl iodide, and isopropyl iodide do2-propunol was formed. 

Alkyl halides, acyl halides, anhydrides, and related substance. ... 

The amides are sharp-melting crystalline compounds and make good derivatives for any of the acyl classes of compounds, i.e.. esters, acids, acid halides, anhydrides, and lactones. 

Esters are formed from the alcohol and acyl halide, anhydride, or acid (Section 15-4D). The alcohol can be regenerated easily by either acid or base hydrolysis of the ester ... 

Methods of Preparation of Acyl Halides, Anhydrides, Amides, and Related Compounds... 

Acylations are most often carried out with BF3 or A1C13 and an acyl halide, anhydride, ester, or a carboxylic acid (Equation 7.67). 

Carboxylic acid derivatives are compounds in which the carboxyl -OH group is replaced by other groups. Examples include esters, acyl halides, anhydrides, and amides. 

R. Sustmann, Synthesis of Acid Halides, Anhydrides and Related Compounds, in Comprehensive Organic Synthesis (B. M. Trost, I. Fleming, Eds.), Vol. 6, 301, Pergamon Press, Oxford, 1991. 

Like acid halides, anhydrides are activated derivatives of carboxylic acids, although anhydrides are not as reactive as acid halides. In an acid chloride, the chlorine atom activates the carbonyl group and serves as a leaving group. In an anhydride, the car-boxylate group serves these functions. 

REACTIONS WITH ACYL HALIDES, ANHYDRIDES, ESTERS AND... 

Peracids can also be prepared from reaction of hydrogen peroxide with acyl halides, anhydrides, amides, dialkyl phosphates, N-acylimidazoles, aromatic aldehydes, lipase catalysis and esters (Figure 2.38).100-107... 

The 1,4-dinucleophilic building blocks used most are 1,2-disubstituted ethanes of the type HXCHiCHjYH, semicarbazides, thiosemicarbazides, hydroxamic acid amides, amidrazones, and 1,2-disubstituted aromatic and heteroaromatic compounds. 1,1-Dielectrophilic building blocks preferentially used are perfluorinated carboxylic acids and their derivatives, such as acid halides, anhydrides, imidoesters, nitriles, perfluoroalkyl chlorosul-... 

A different approach toward preparation of phosphinous and phosphonous iodides uses the reaction of iodoalkanes with either PI3 or PI5. This reaction is specific for iodoalkanes and phosphorus iodides and is not applicable to other halides. From the resultant highly reactive phosphinous and phosphonous iodides, the full range of the parent acid derivatives may be prepared (esters, other acid halides, anhydrides, amides). We will not be concerned here with these preparations of derivatives of the parent acids, topics that are considered in other reports. ... 

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