Studies On The Synthesis Of 1-Amino-Cyclopropanecarboxylic Acid, Imine And Aldol Condensation Reaction Under Microwave Irradiation

A piece of memoir written by R. N. Gedye and his fellows in 1986 uncovered the prelude of the application of Microwave irradiation (MWI) technology in organic reaction. During the recent fourteen years, the microwave-assisted organic reaction has become one of the most attractive branches in the domain of chemistry ?MORE chemistry (Microwave ?Induced Organic Reaction Enhancement Chemistry).We carried on the studies on the sjnthesis of 1-amino-cyclopropanecarboxylic acid (ACC) , imine and aldol condensation reaction of benzaldehyde using MWI technology combining phase transfer catalysis (PTC) technology under solvent free condition.Owing to the unique biological activity, ACC processes important application value and wide perspective in plant chemistry, medicine chemistry and agriculture science etc. Among the various approaches to the preparation of ACC, the alkylation of Schiff base derived from glycine is a direct, high-efficient one. We prepared ethyl N-benzylidene-glycinate and ethyl N-diphenylmethylene-glycinate respectively and achieved their fast alkylation with 1,2-dibromoethane under the following conditions: mixed base KOH/K2CO3as base, TBAB as phase transfer catalyst, Al:03 as external bath, irradiation power 240W, irradiation time Imin.Because of the different activities aroused from conformational constrains, N-benzylidene-glycinate carried out sequential dialkylation and formed cyclopropane frame which transformed ACC followed by hydrolysis ,but N-diphenylmethylene-glycinate only obtained monoalkylated product.The compounds of imine are important intermediates in organic synthesis. We prepared three imines using the reactions of aniline with benzaldehyde, cinnamic aldehyde and benzophenone under microwave irradiation .In the studies of benzaldehyde's aldol condensation reaction, we discussed the different factors which affect the reaction of benzyldehyde with n-heptanal. By gas chromatography analysis, we determined the yields of different experiment conditions. The optimum conditions were obtained as follows: PhCHO/C7HMO, 2.5/1 (mol ratio), KOH as base, A1203 as solid mineral support, 25%TEBAC as PTC, irradiation power 560W, irradiation time lmin.The yield of jasminaldehyde is 90.4%.Under the same condition, a -hexyl cinnamic aldehyde and chalcone were obtained in 82.8% and 78.8% yield respectively.All the products were characterized by IR and 'HNMR.The experimental result indicated that the application of MWI technology in organic reaction has significant advantages when compared with the conventional method: the shortened reaction time ,the mild condition, the simple operation, the good yield , the absence of solvent and the innocuity to environment. So the MWI technology is in keeping with the development tendency of chemical industry. It can be expected that the application of the MWI technology will bring out outstanding economic, social and environmental benefits. We believe that MORE chemistry will become one of the most promising fields in the 21st century.