Ynamide Mediated Esterification Of Carboxylic Acid And Phenol/Alcohol

Esters are one class of the most important chemicals.It have been widely used in medicine,agriculture,materials,food,and other fields.Consequently,the synthesis of esters has attracted much attentions.Various esterification reactions have been developed in past decades.However,highly efficient esterification methodologies are still in great demand due to the important application of esters,especially those containing ?-chiral centers.The conventional methods of esterification include the Lewis acid or boronic acid catalyzed dehydration,transition metal catalyzed carbonylation esterification and the NHC catalyzed oxidative esterification etc.But these esterification reactions encounter shortcomings such as harsh conditions,long reaction time,poor efficiency and complicated post-processing.These shortcomings make the industrial synthesis difficult.In addition,the approach of using coupling reagents is also a popular strategy for the synthesis of esters,The coupling reagents include carbodiimides,phosphonium salts,uranium salts,immonium salts and so on.But the by-product produced by coupling reagents is difficult to separate,and their molecular weights are large.In addition,serious racemization was observed when these coupling reagents were used for carboxylic acids containing ?-chiral center.In this thesis,with the presence of base,ynamide N-ethynyl-N-methyl pmethylbenzenesulfonamide was used as the coupling reagent for ester synthesis with carboxylic acids and phenols or carboxylic acids and alcohols as the starting materials.Low level of racemization is detected when ?-amino acids were employed as the acid partners.The racemization could be suppressed by employing bulky DIEA as the base.The by-product,N-methyl-N-toylacetamide,is also a high value chemical.Ynamides show some remarkable characters and promising application in ester synthesis.