Synthesis and NMR studies of 5-aryl-2-furfural O-(methyl carbamoyl) oximes

Abstract

The new 5-aryl-2-furaldehyde O-(methyl carbamoyl) oximes were synthesized for the evaluation of the pesticidal activities. The requisite 5-aryl-2-furaldehyde oximes were obtained by the coupling of the corresponding benzenediazonium chloride with 2-furaldehyde, followed by the oximation. The 5-aryl-2-furaldehyde O-(methyl carbamoy)oximes were prepared from oximes by treatment with methyl isocyanate using triethylamine as catalyst. In the NMR studies, generally, we have observed chemical shift difference between the syn and antiisomers in which the oxime proton of the anti form is more deshielded than the corresponding syn proton. One explanation for deshielding in the anti isomers appears to be due to the intramolecular hydrogen bonding. We also have measured the apparent syn and anti ratios by NMR and separated mixture of syn and anti forms by fractional crystallization.