Esterifications acid functional groups, diazomethane

Esterification of Carboxyfic Acids and Other Acidic Functional Groups. A variety of functional groups will tolerate the esterification of acids with diazomethane. Thus a. -unsaturated carboxylic acids and alcohols survive the reaction (eq 1), as do ketones (eq 2), isolated alkenes (eq 3), and amines (eq4).i2... 

Diazomethane is used in the synthesis of methyl esters from carboxylic acids. However, it is exceedingly toxic and highly explosive in the gaseous state (b.p. -24°C) and in concentrated solutions. It is therefore usually generated in dilute ether solution and immediately allowed to react with the acid. This method is very mild and permits esterification of molecules possessing acid- and base-sensitive functional groups, as shown in the following example. 

The reaction of trialkyloxonium salts with carboxylic acids is a mild, general esterification procedure that does not require the use of more hazardous reagents such as Hexamethylphospho-lie Triamide-Thionyl Chloride, lodomethane. Dimethyl Sulfate, 3-Methyl-l-p-tolyltriazene, or Diazomethane. The reaction proceeds smoothly with sterically hindered acids, as well as with acids containing various functional groups such as amides or nitriles (eq 10). ... 

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