Ethyl o-bromobenzoate

For example, the Br-Li exchange reaction of ethyl o-bromobenzoate was carried out using 5-BuLi at -48 °C, and the resulting aryllithium species was then reacted with ethanol to give a protonated product. The results are shown in Fig. 4.7. The starting material, ethyl o-bromobenzoate, is consumed almost entirely within the residence time of 0.1 s, generating the protonated product in about 90 % yield. The yield of the product is lower at a longer residence time, presumably because the aryllithium intermediate should decompose. The optimal residence time at this temperature is ca. 0.1 s. 

Fig. 4.7 Br-Li exchange of ethyl o-bromobenzoate followed by protonation with ethanol at -48 °C. Plots of the yield of the protonated product and that of the unchanged starting material against logarithm of the residence time...

Fig. 4.8 Temperature-residence time map for Br-Ii exchange of afkyl o-bromobenzoate followed by protonation, a t-butyl o-bromobenzoate, b isopopyl o-bromobenzoate, c ethyl o-bromobenzoate, and d methyl o-bromobenzoate...

Fig. 4.9 Br-Li exchange reaction of ethyl o-bromobenzoates using i-BuLi followed by the reaction with an electrophile using a flow microreactor system...

A mixture of 20 g. (0.1 mole) of o-bromobenzoic add, 63 cc. of 10% potassium hydroxide solution, 20 cc. of ethyl alcohol, 40 cc. of 50% tripotassium arsenite solution, and a little freshly reduced copper is refluxed at 90-95° for twelve hours with constant stirring. The reaction mixture is filtered hot to remove copper, made add to Congo red paper with 20 cc. of concentrated hydrochloric add, and evaporated to dryness on a steam cone. The resulting residue is extracted with absolute methanol the methanol extract is evaporated to dryness, and the residue is washed with ether to remove salicylic acid and unchanged o-bromo-... 

Nonactivated esters are reduced only slowly if at all in strongly acidic medium at a lead cathode [45], whereas alkyl benzoates are reduced to a mixture of benzyl alcohol and alkyl benzyl ether [45,46], and alkyl 4-imidazolecarboxylates similarly are reduced to a mixture of the corresponding alcohol and ether [76]. Phenyl and benzyl benzoate give predominantly esters [23,34], as do also ethyl o-chloro- and m-bromobenzoate [46]. 

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