Carboxylic acids esters from

AcCl, MeOH, 95-100% yield. This is a convenient method for generating anhydrous HCl in methanol. These conditions are also used to prepare methyl esters from carboxylic acids and for the formation of amine hydrochlorides. ... 

Other reactions useful for the protection of carboxylic acids are included in Section 107 (Esters from Carboxylic Acids and Acid Halides) and Section 23 (Carboxylic Acids from Esters). 

Esters from carboxylic acids and halides, sulfoxides and miscellaneous compounds... 

The main drawback to this reaction is the toxicity of diazomethane and some of its precursors. Diazomethane is also potentially explosive. Trimethylsilyldia-zomethane is an alternative reagent,42 which is safer and frequently used in preparation of methyl esters from carboxylic acids.43 Trimethylsilyldiazomethane also O-methylates alcohols.44 The latter reactions occur in the presence of fluoroboric acid in dichloromethane. 

Preparation of carboxylic esters from carboxylic acids and alcohols H+ R-C-OH + R OH R-C-OR +H20 II II 0 0... 

Example 2, in addition to oxyselenide formation, carbo- and heteroseleno cycliza-tion, A -PSP can be used to generate selenides from alcohols and selenol esters from carboxylic acids, respectively, in the presence of a stoichiometric amount of n-Bu,P. ... 

Although a carboxylate anion is only a relatively modest nucleophile (see Section 6.1.2), it is possible to exploit an Sn2 reaction to prepare esters from carboxylic acids as an alternative to the usual esterification methods (see Section 7.9). Such methods might be useful, depending upon the nature and availability of starting materials. 

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preparation of furyl phosphorodichioridate is based upon a method to prepare 2-chlorofuran (16% yield, Hormi, Nasman unpublished).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. 

Fig. 2.32 Preparation of methyl esters from carboxylic acids and diazomethane.

Hydrides from carboxylic acids Carboxylic acids from hydrides Carboxylic acids from hydrides Esters from hydrides Hydrides from aldehydes Hydrides from aldehydes Alkyls from aldehydes Ketones from methylenes Ketones from ketones Alkyls from olefins Acetylenes from halides also acetylenes from acetylenes Esters from alcohols also esters from carboxylic acids Alkyls from olefins Alkyls from olefins... 

Esters from Carboxylic Acids and Halides, Sulfoxides, and Miscellaneous compounds. 

Whereas all the alkylations in Figure 2.26 take place in basic or neutral solutions, carboxylic acids can be methylated as such with diazomethane (Figure 2.27). The actual nucleophile (the carboxylate ion) and the actual methylating agent (H3C—N+=N) Fig. 2.27. Preparation of are then produced from the reaction partners by proton transfer, methyl esters from carboxylic acids and di azomethane. 

You can t make esters from carboxylic acids and alcohols under basic conditions because the base deprotonates the carboxylic acid (see p. 288). However, you can reverse that reaction and hydrolyse an ester to a carboxylic acid (more accurately, a carboxylate salt) and an alcohol. 

In fact, acetal formation is even more difficult than ester formation while the equilibrium constant for acid-catalysed formation of ester from carboxylic acid plus alcohol is usually about 1, for... 

Diazomethane methylation is a good way of making methyl esters from carboxylic acids on a small scale because yields are excellent and the only by-product is nitrogen. However, there is a drawback diazomethane has a boiling point of-24°C, and it is a toxic and highly explosive gas. It therefore has to be used in solution, usually in ether the solution must be dilute, because concentrated solutions of diazomethane are also explosive. It is usually produced by reaction of N-methyl-N-nitrosourea or N-methyl-N-nitrosotoluenesulfonamide with base, and distilled out of that reaction mixture as an azeotrope with ether, straight into a solution of the carboxylic acid. 

Alkynes from halides also alkynes from alkynes Esters from alcohols also esters from carboxylic acids Alkyls from alkenes (Conjugate Reduction)... 

Other methods that can be used to prepare thiol esters from carboxylic acids include the use of aryl thiocyanates,12 thiopyridyl chloroformate,13 2-fIuoro- V-methylpyridinium tosylate,14 1-hydroxybenzotriazole, 5 and boron thiolate.16 Direct conversion of 0-esters to 5-esters can also be effected via aluminum and boron reagents.17 However, the applicability of these 1217 and other more recent methods18 to the selective thiol ester formation discussed above has not been clearly defined. 

Although many useful and reliable methods for esterification of carboxylic acids are usually employed, there is need to find versatile processes to replace the classical methodologies with more benign alternatives, characterized by general applicability. Two new methods for the formation of esters from carboxylic acids are shown in Scheme 1.39. 

This question may sound trivial but students starting organic chemistry often make the error of trying to form esters from carboxylic acids in basic solution. Thinking about the reasons may save you from the error. 

Esters from carboxylic acids and alcohols under acid catalysis the Aac2 and Ancl mechanism... 

Esters from Carboxylic Acids and Alcohols via Hydroxy Group Activation (HGA)... 

A new method for the transformation of —CO2H to —H has been attained by formation of the selenol ester from carboxylic acid, followed by its reduction. Owing to high chemoselectivity and mild reaction conditions, this method is often utilized for the synthesis of natural products (equation 21). ... 

Formation of the 3j8-acetoxyeti-5-enic esters has been used to obtain optically pure samples of (+)- and (—)-tran5-verbenoP and to resolve an alcohol intermediate in the synthesis of the witchweed seed germination stimulant (+)-strigol. A general synthesis of thiol esters from carboxylic acids, exemplified by the formation of the n-propylthio-, isopropylthio-, and t-butylthio-esters of cholic acid, comprises reaction with diethyl chlorophosphate-triethylamine, followed by the thallium(i) salt of the appropriate thiol. 

Yokoyama, Y., Shioiri, T., and Yamada, S., Phosphorus in organic synthesis. Part 16. Diphenyl phosphorazidate (DPPA) and diethyl phosphorocyanidate (DEPC). Two new reagents for the preparation of thiol esters from carboxylic acids and thiols, Chem. Pharm. Bull., 25, 2423, 1977. 

Diphenylammonium triflate, toluene, 80°C, 33-97% yield. This catalyst can also be used to prepare esters from carboxylic acids and alcohols, 78-96%... 

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