Acid chlorides, preparation from hydrogenation

The preparation of furyl phosphorodichioridate is based upon a method to prepare 2-chlorofuran (16% yield, Hormi, Nasman unpublished). Later the preparation was extended to a general method to prepare furyl esters from carboxylic acid chlorides lacking a-hydrogens and alkyl furyl carbonates from primary (other than methyl) and secondary alkyl chloroformates. Phosphoryl chloride was the only acid chloride except carbon analogues found to give a furyl ester by the amine-catalyzed reaction. 

Nitrosyl chloride has been prepared from hydrogen chloride and nitrosylsulfuric acid,1 from sodium chloride and nitrosylsulfuric acid,2 from nitrogen dioxide and moistened potassium chloride,3 by the combination of nitric oxide and... 

The dihydroxy lactone from L-threonic acid is prepared from L-dibenzoyl tartaric anhydride by catalytic hydrogenation over palladium. The substituted anhydride is formed from tartaric acid and benzoyl chloride. 

The oxime 7, prepared from salicyl aldehyde, is converted with iV-chlorosuccinimide into the hydrox-amic acid chloride 8. From this, the nitrile oxide is obtained with KHCO3, which reacts regioselec-tively with styrene to give the 3,5-diaryl-4,5-dihydroisoxazole 9. Catalytic hydrogenation leads to the y -hydroxy ketone 10, which on acid-catalysed cyclodehydration gives the flavanone 11. 

Esters of aldonic acids are prepared from 6-lactones, slowly from 7-lac-tones, by reaction with alcohols in the presence of hydrogen chloride or of the free aldonic acid (26). The acids may be recrystallized from boiling methanol without much esterification taking place (27). At the melting point, ethyl mannonate is converted to the 7-lactone with the loss of ethyl alcohol. 

Uses. The lowest member of this class, ketene itself, is a powerful acetylating agent, reacting with compounds containing a labile hydrogen atom to give acetyl derivatives. This reaction is used only when the standard acetylation methods with acetic anhydride or acetyl chloride [75-36-5] do not work weU. Most of the ketene produced worldwide is used in the production of acetic anhydride. Acetic anhydride is prepared from the reaction of ketene and acetic acid. 

Polymeric diacyl peroxides (26) can be prepared from the reaction of dibasic acid chlorides, eg, succinoyl, fumaryl, sebacoyl, and terephthaloyl chlorides, with sodium or hydrogen peroxide (187). 

Because almost any diacid can be leaddy converted to the acid chloride, this reaction is quite versatile and several variations have been developed. In the interfacial polymerization method the reaction occurs at the boundary of two phases one contains a solution of the acid chloride in a water-immiscible solvent and the other is a solution of the diamine in water with an inorganic base and a surfactant (48). In the solution method, only one phase is present, which contains a solution of the diamine and diacid chloride. An organic base is added as an acceptor for the hydrogen chloride produced in the reaction (49). Following any of these methods of preparation, the polymer is exposed to water and the acid chloride end is converted to a carboxyhc acid end. However, it is very difficult to remove all traces of chloride from the polymer, even with repeated washings with a strong base. 

Reaction of (T)-(-)-2-acetoxysuccinyl chloride (78), prepared from (5)-mahc acid, using the magnesiobromide salt of monomethyl malonate afforded the dioxosuberate (79) which was cyclized with magnesium carbonate to a 4 1 mixture of cyclopentenone (80) and the 5-acetoxy isomer. Catalytic hydrogenation of (80) gave (81) having the thermodynamically favored aH-trans stereochemistry. Ketone reduction and hydrolysis produced the bicycHc lactone acid (82) which was converted to the Corey aldehyde equivalent (83). A number of other approaches have been described (108). 

Ethers. In the presence of anhydrous agents such as ferric chloride (88), hydrogen bromide, and acid chlorides, ethers react to form esters (see Ethers). Esters can also be prepared from ethers by an oxidative process (89). With mixed sulfonic—carboxyhc anhydrides, ethers are converted to a mixture of the corresponding carboxylate and sulfonate esters (90) ... 

The 2,4,6-trimethylbenzyl ester has been prepared from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 12 h, 60-80% yield) it is cleaved by acidic hydrolysis (CF COOH, 25°, 60 min, 60-90% yield 2 N HBr/HOAc, 25°, 60 min, 80-95% yield) and by hydrogenolysis. It is stable to methanolic hydrogen chloride used to remove A-o-nitrophenylsulfenyl groups or triphenylmethyl esters. ... 

This method with some slight modihcations is applied in the synthesis of to-bromo esters from Cs to Cn. Methyl 5-bromovalerate has been prepared by treating the silver salt of methyl hydrogen adipate with bromine. The ethyl ester has been prepared from the acid by esterification or through the acid chloride. ... 

Aconitic acid has been prepared from citric acid by the action of sulfuric acid or hydrogen chloride, or by heating. It has been prepared also from methyl acetylcitrate and from acetylcitric anhydride. The method described is essentially that of Hentschel. Phosphoric acid (85 per cent) can be used in place of sulfuric acid, but much closer regulation of the conditions seems necessary and the yield is not greatly improved. 

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