A preliminary study on predicting the¹³c chemical shifts for a series of disubstituted 2,3-diphenyl-l,3-thiazolidin-4-ones

A successful attempt has been made to predict¹³C chemical shifts for a series of disubstituted 2,3-diphenyl-1,3-thiazolidin-4-ones. Prior work has shown that substituents placed on either phenyl ring of the 2,3-diphenyl-1,3-thiazolidin-4-one system affect the electron density surrounding the C-2, C-4 and C-5 atoms. These changes are reflected in the different nmr chemical shifts for these carbon atoms relative to the unsubstituted compound. The¹³C chemical shifts for the C-2, C-4 and C-5 carbons of these compounds have previously been shown to correlate with Hammett a constants and Swain Lupton dual substituent parameters. Because of these correlations we decided to investigate the potential for predicting¹³C chemical shifts for C-2, C4 and C-5 in the thiazolidinone ring based on the known shifts for the two monosubstituted series of compounds. The effect of the substituents on the¹³C chemical shifts for the C-2, C-4 and C-5 carbons in the disubstituted 2,3-diphenylthiazolidinones are discussed relative to the two mono-substituted 2,3-diphenylthiazolidinone series. The data is then used to predict the¹³C chemical shift values at C-2, C-4 and C-5 in the thiazolidinone ring with all possible substituents combinations in the 2-phenyl and 3-phenyl rings.