Green Method Development For Glycine Esters Synthesis

α-Amino acid esters and its derivatives have been investigated over 100 years in organic chemistry and have been widely applied in many fields.They have been used as pharmaceuticals in medicine,as additives in food industry,and as fungicides and insecticides in agriculture.As the simplest α-amino acid,glycine can be converted to structurally diverse α-amino acid esters and other highly valuable compounds.There are two traditional methods for preparing N-substituted glycine ester derivatives: First,esterification of activated carboxyl groups with hydrochloric acid,sulfuric acid or thionyl chloride.Second,nucleophilic substitution reaction using corresponding amines and α-haloacetate.However,for the first method,the acid waste in reaction system is unavoidable in principle.For the second method,the generation of halogen-containing waste is not environmentally friendly.Therefore,developing a simpler and greener method to synthesize glycine esters is still important for chemical industry and academia.The reutilization of glyoxal,a waste in bio-oil,will lead to tremendous profit in organic chemical industry.Therefore,the transformation of glyoxal fits the concept of green chemistry.In this thesis,we design a new strategy to make glycine esters from glyoxal.The amine reacts with the glyoxal to give the imine-containing aldehyde which undergo a Cannizzaro-type redox process with alcohols leading to the final glycine ester.Our experiments fulfilled this envision,a novel glycine ester synthetic method is developed based on glyoxal reutilization.We explored the effect of solvents,catalysts,additives and temperature,the optimal reaction conditions were pointed out as follow: the mixture of amine(0.2 mmol,1 eq)and glyoxal(0.6 mmol,3eq)was stirred in Et OH(2 m L)at 110 °C for 6 h.A wide variety of functional-group substituted glycine ester derivatives has been easily prepared from moderate to excellent yield.The mechanism of this reaction was also investigated by relevant control experiments.In summary,through Cannizzaro-type reactions strategy,glycine ester derivatives were prepared successfully by using simple amines,alcohols and glyoxal.This method featuring mild conditions,atomic economy and wide substrate scope meets the standard of green chemistry concept.