The reaction between carboxylic acids (RCOOH) and dialkyl dicarbonates [(R 1 OCO) 2 O], in the presence of a weak Lewis acid such as magnesium chloride and the corresponding alcohol (R 1 OH) as the solvent, leads to the esters RCOOR 1 in excellent yields. The mechanism involves a double addition of the acid to the dicarbonate, affording a carboxylic anhydride [(RCO) 2 O], R 1 OH and carbon dioxide
Catalytic Enantioselective Synthesis of 2,5-Dihydrooxepines
作者:Su Yong Shim、Soo Min Cho、Anipireddy Venkateswarlu、Do Hyun Ryu
DOI:10.1002/anie.201700890
日期:2017.7.17
addition initiated cyclopropanation/retro-Claisen rearrangement tandem reaction was developed for the enantioselectivesynthesis of highly functionalized 2,5-dihydrooxepines. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeds to give good yields and high enantioselectivity.