Microwave-promoted Synthesis Of N-(Diphenylmeth Ylene)Glycine Alkyl Esters And The Alkylation With Asymmetric Catalysis

N-(diphenylmethylene) glycine alkyl esters are one type of important imines, and they have received considerable attention due to their wide use for preparation of natural and unnatural a-amino acids and corresponding esters in enantiomerically pure.Several methods have been reported to prepare N-(diphenylmethylene) glycine alkyl esters[1]. However, up to now, limited by long reaction time, low yields, toxic solvents and harsh conditions, efficient synthesis of N-(diphenylmethylene) glycine alkyl esters with high yields is still a challenge. So a green method is urgent and necessary. Recently the use of microwave irradiation has become an increasingly popular and useful technique to accomplish variety reaction types in an efficient way with higher chemical yield and less reaction time. We predict that N-(diphenylmethylene) glycine alkyl esters can be prepared in efficient way using microwave irradiation. Our researches are included as follows:1. N-(diphenylmethylene) glycine t-butyl ester was synthesized from benzophenone imine and t-butyl chloroacetate using microwave irradiation, and under the optimum conditions chemical yield gets 98%. 2. The reaction parameters such as microwave power, reaction temperature, reaction time were optimized . It was found that 700W, 120℃and irradiating for 20 min were the optimal conditions. It was also found that K2CO3 and PEG-400 were respectively the opportune base and phase-transfer catalyst.3. With the optimized conditions in hand, we synthesized 8 N-(diphenylmethylene) glycine alkyl esters, with chemical yields ranging from 69~98%.4. To investigate the electrical influence on enatioselectivities of asymmetric phase transfer reaction,we have designed and synthesized 8 new chiral quaternary salts from cinchona alkaloids and 2-chloromethyl benzimidazole or 1-chloromethyl benzotriazole.5. The chiral phase transfer catalysts were tested in enantioselective alkylation of N-(diphenylmethylene) glycine t-butyl ester. Under optimal conditions, good chemical yields (up to 85%) and excellent enatioselectivities (up to 99%ee) were observed.6. N-(diphenylmethylene) glycine alkyl esters were synthesized in water using microwave heating, with the highest chemical yield getting 85%.