24161-55-5Relevant academic research and scientific papers
Selective esterifications of alcohols and phenols through carbodiimide couplings
Shelkov, Rimma,Nahmany, Moshe,Melman, Artem
, p. 397 - 401 (2007/10/03)
Esterification of carboxylic acids capable of forming ketene intermediates upon treatment with carbodiimides permits the selective acylation of alcohols in the presence of phenols lacking strong electron-withdrawing groups. The selectivity of acylations involving highly acidic phenols could be reversed through the addition of catalytic amount of acid. Esterification of other carboxylic acids was found to proceed through the formation of symmetric anhydrides and provide the opposite chemoselectivity. In both cases the relative acylation rates of substituted phenols are consistent with a reaction mechanism involving an attack of phenolate anions on electrophilic intermediates such as ketenes and symmetric anhydrides, with the carbodiimides serving both as an activating reagent and as a basic catalyst.
Activation volumes for ester hydrolysis via elimination-addition
Isaacs, Neil S.,Najem, Tariq S.
, p. 1140 - 1144 (2007/10/02)
Esters that have an acidic proton α to the carbonyl group (or vinylogous situation) and a good leaving group may undergo hydrolysis by elimination to an intermediate ketene, which rapidly hydrates.Examples are found in p-hydroxybenzoate, malonate, and acetoacetate esters of nitrophenols.The evidence for this mechanism (E1 cb type) includes the independence of rate with pH in the region of dissociation of the acidic proton and, in particular, positive volumes of activation that contrast sharply with negative values typical of the more usual BAc2 mechanism of hydrolysis.
