5469-65-8Relevant academic research and scientific papers
Synthesis of the (Z) and (E) Isomers of 1,2-Diaryl-3-methyl-4,5-dioxo-3-pyrrolidinecarboxylic Acid Esters. Structural Assignment by NMR and Mass Spectroscopy
Titus, Richard L.,Emerson, David W.,Gonzales, Rowena M.
, p. 1857 - 1860 (2007/10/02)
Reaction of N-benzylideneaniline, 1a, with 3-methyl-2-oxobutanedioic acid diethyl ester, 2a, produced isomeric 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid ethyl esters, 3a and 3b.The higher melting isomer, 3a, was shown to have (Z) configuration by nmr spectroscopy.The (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid methyl esters, 3c and 3d, were prepared from 1a and 3-methyl-2-oxobutanedioic acid dimethyl ester, 2b.The higher melting isomer, 3c, was shown to have the (Z) configuration.Similarly, N-benzylidene-p-toluidine, 1b, reacted with 2a to form (Z) and (E) isomers of 3-methyl-4,5-dioxo-1-(4-methylphenyl)-2-phenyl-3-pyrrolidinecarboxylic acid ethyl esters, 3e and 3f.Assignment o the 13C carbonyl carbon nmr chemical shift was made by preparing 2-methyl-3-oxobutanedioic-1-13C acid diethyl ester, 4, and from it the corresponding (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic 13C acid ester, 5a and 5b.The mass spectra of the (Z) isomers exhibit prominent ions corresponding to the masses of the Schiff bases used to make them, and ions corresponding to the loss of Ar-NCOCO from the parent ion.The (E) isomers 3b, 3d and 5b exhibit a prominent ion of mass 264; 3f gives mass 278, corresponding to the loss of the carboalkoxy group.
