Hydrolysis acyl halide

Olefinic acyl halides, hydrolysis, 418 preparation, 547, 549 preparations listed in table 61, 551 Olefinic alcohols, alkylation by alkyl sulfates, 229 dehydration, 33, 42 isomerization, to aldehydes, 296 to ketones, 349... 

Azoles containing a free NH group react comparatively readily with acyl halides. N-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (66) -> (67) or type (70)->(71) or (72). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. When two isomeric products could result, only the thermodynamically stable one is usually obtained because the acylation reactions are reversible and the products interconvert readily. Thus benzotriazole forms 1-acyl derivatives (99) which preserve the Kekule resonance of the benzene ring and are therefore more stable than the isomeric 2-acyl derivatives. Acylation of pyrazoles also usually gives the more stable isomer as the sole product (66AHCi6)347). The imidazole-catalyzed hydrolysis of esters can be classified as an electrophilic attack on the multiply bonded imidazole nitrogen. 

Lehn s approach is slightly more complex than that illustrated above in that the diol is chloromethylated and then treated with cyanide. Hydrolysis then affords the diacid which may be carried through as shown. It should also be noted that once the bis-acyl halide is in hand, it may be treated directly with an open-chained amine to yield a lipophilic diazacrown, after reduction ... 

The Cunius degradation of acyl azides prepared either by treatment of acyl halides with sodium azide or trimethylsilyl azide [47] or by treatment of acyl hydrazides with nitrous acid [f J yields pnmarily alkyl isocyanates, which can be isolated when the reaction is earned out in aptotic solvents If alcohols are used as solvents, urethanes are formed Hydrolysis of the isocyanates and the urethanes yields primary amines. 

In the alkyl chain hydroxy groups or side chains may be present. The reaction is somewhat different when acyl halides are used. Hydroxymethanediphosphonic acid is prepared by reacting phosgene with an alkali metal, dialkyl phosphite. The reaction is rapid and exothermic. The temperature is controlled between 10 and 20°C. After hydrolysis with HC1, hydroxymethanediphosphonic acid is recovered [91,92]. 

Acyl halides are so reactive that hydrolysis is easily carried out. In fact, most simple acyl halides must be stored under anhydrous conditions lest they react with water in the air. Consequently, water is usually a strong enough nucleophile for the reaction, though in difficult cases hydroxide ion may be required. The reaction is... 

Hydrolysis of acyl halides is not usually catalyzed by acids, except for acyl fluorides, where hydrogen bonding can assist in the removal of There are several methods available for the hydrolysis of acyl fluorides. ... 

Other carbanionic groups, such as acetylide ions, and ions derived from a-methylpyridines have also been used as nucleophiles. A particularly useful nucleophile is the methylsulfinyl carbanion (CH3SOCHJ), the conjugate base of DMSO, since the P-keto sulfoxide produced can easily be reduced to a methyl ketone (p. 549). The methylsulfonyl carbanion (CH3SO2CH2 ), the conjugate base of dimethyl sulfone, behaves similarly, and the product can be similarly reduced. Certain carboxylic esters, acyl halides, and DMF acylate 1,3-dithianes (see 10-10. )2008 Qxj(jatjye hydrolysis with NBS or NCS, a-keto aldehydes or a-... 

In an indirect amination process, acyl halides are converted to amino acids. Reaction of the acyl halide with a chiral oxazolidinone leads to a chiral amide, which reacts with the N=N unit of a dialkyl azodicarboxylate [R"02C—N=N—CO2R ]. Hydrolysis and catalytic hydrogenation leads to an amino acid with good enantioselectivity. ... 

Scheme 7 comprises the following patterns First, a metallacycle gives rise to ketones by CO insertion and reductive elimination. Next, a nickel hydride inserts an unsaturated substrate L, followed by CO. The acyl intermediate can give rise to reductive elimination with formation of acyl halides or acids and esters by hydrolysis, or it can insert a new ligand with subsequent reductive elimination as before. Alternatively, there may be a new insertion of carbon monoxide with final hydrolysis. Third, an intermediate R—Ni—X is formed by oxidative addition. It can react in several ways It can insert a new ligand L, followed by CO to give an... 

All carboxylic acid derivatives are hydrolysed to carboxylic acids by the action of water as nucleophile. Acyl halides and anhydrides of low molecular weight are hydrolysed quite vigorously. Esters and amides react much more slowly, and hydrolysis normally requires acid or base catalysis. This is nicely... 

Both acyl halides and anhydrides react with water (hydrolysis). Acyl halides react to form one mole of the carboxylic acid and one mole of the hydrohalic acid, HX. Anhydrides react to form two moles of carboxylic acid. 

The most frequently used method for the preparation of isoquinoline Reissert compounds is treatment of an isoquinoline with acyl chloride and potassium cyanide in water or in a dichloromethane-water solvent system. Though this method could be successfully applied in a great number of syntheses, it has also some disadvantages. First, the starting isoquinoline and the Reissert compound formed in the reaction are usually insoluble in water. Second, in the case of reactive acyl halides the hydrolysis of this reaction partner may became dominant. Third, the hydroxide ion present could compete with the cyanide ion as a nucleophile to produce a pseudobase instead of Reissert compound. To decrease the pseudobase formation phase-transfer catalysts have been used successfully in the case of the dichloromethane-water solvent system, resulting in considerably increased yields of the Reissert compound. To avoid the hydrolysis of reactive acid halides in some cases nonaqueous media have been applied, e.g., acetonitrile, acetone, dioxane, benzene, while utilizing hydrogen cyanide or trimethylsilyl cyanide as reactants instead of potassium cyanide. 

Acid-catalyzed hydrolysis of Reissert compounds results in an aldehyde, a formal reduction product of the acyl halide utilized in the Reissert compound formation (11). The mechanism of the reaction according to McEwen and Cobb (3), is shown in Scheme 2. 

Alkyl and acyl halides react directly with quinoline to give A-alkyl-or A-acylquinolinium salts (Scheme 3.4). Whereas the A-alkyl salts are stable and can often be isolated as crystalline solids, the A -acyl analogues are unstable and undergo rapid hydrolysis in moist air or in aqueous solution. 

Probably the nickel carbonyl-catalyzed synthesis of acrylates from CO, acetylene, and hydroxylic solvent (78) involves an acetylene-hydride insertion reaction, followed by a CO insertion, and hydrolysis or acyl halide elimination. The actual catalyst in the acrylate synthesis is probably a hydride formed by the reversible addition of an acid to nickel carbonyl. 

Anhydrides are somewhat more difficult to hydrolyze than acyl halides, but here too water is usually a strong enough nucleophile. The mechanism is usually tetrahedral. Only under acid catalysis does the SnI mechanism occur and seldom even then.s06 Anhydride hydrolysis can also be catalyzed by bases. Of course, OH- attacks more readily than water, but other bases can also catalyze the reaction. This phenomenon, called nucleophilic catalysis (p. 334). is actually the result of two successive tetrahedral mechanisms. For example, pyridine catalyzes the hydrolysis of acetic anhydride in this manner.507... 

Hydrolysis of enol esters 0-83 Reduction of acyl halides 0-84 Reduction of carboxylic acids, esters, or anhydrides 0-85 Reduction of amides 0-95 Alkylation and hydrolysis of imines, alkylation of aldehydes 0-97 Alkylation and hydrolysis of dithi-anes... 

Alcoholysis of trihalides 0-6 Hydrolysis of ortho esters 0-20 Alcoholysis of acyl halides 0-21 Alcoholysis of anhydrides 0-22 Esterification of carboxylic acids 0-23 Transesterification 0-24 Alkylation of carboxylic acid salts 0-25 Cleavage of ethers with anhydrides 0-26 Alkylation of carboxylic acids with diazo compounds... 

Oxygen abstraction reactions from alcohols, ketones, acyl halides and other oxygen-containing compounds by MCI or related derivatives also afforded a route to relatively simple complexes of the oxo halides (Table 24). Thus Nb2Cli0 was found to abstract oxygen from higher ketones to yield, after hydrolysis, alkanes, chloroalkanes or arylalkanes.414... 

Acyl halides may be identified by —hydrolysis to the corresponding acids (the latter may be further characterised as in Section IV,175) conversion into amides (Section IV,191), anilides or p-toluidides (Section IV,100) and conversion into solid esters (Section IV,183). 

The existence of acylium ions in the reactions of acyl halides with Lewis acids has been amply demonstrated88,89, but they have not so far been directly observed in hydrolysis reactions. To achieve direct observation of an acylium ion, it must, at best, be generated into a non-reactive environment if its rate of formation is slow, or be detectable in small concentrations if it is destroyed rapidly. The limiting factors are, therefore, the rate and mechanism of heterolysis and the stability and concentration of the acylium ion formed. In this... 

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