5-Nitrofuranyl Derivatives Shapeshift in Polar Aprotic Solvents Which May Give Rise to Induced Ring Currents in an Applied Magnetic Field

Anisotropically induced ring currents are not confined to Hückel’s aromatics, and many non-aromatic compounds, in particular, cyclopropane exhibit ring currents in an applied magnetic field. To this end, aromatic protons of 5-nitrofurfural give rise to two signals in its 1H NMR spectrum in CDCl3 which as expected, are only ~ ±0.1 ppm apart; however, in marked contrast to 5-nitrofurfural, the analogous aforementioned protons of (E)- 5-nitrofuran-2-yl methylene hydrazine are nearly ±1.0 ppm apart in its 1H NMR spectrum in DMSO-d6. This anomaly may, though it need not of necessity, suggest that the hydrazone moiety in (E)-5-nitrofuran-2-yl methylene hydrazine force the furan ring into a puckered non-aromatic ring so as to pave the way for an induced ring current in an applied magnetic field. 5-nitro-N'-5-nitrofuran-2-carbonyl furan-2-carbohydrazide also appears to exhibit a similar perturbation; however, to a lesser extent.