Synthesis, UV-Vis spectra, and Hammett correlation of some novel bis(dihydropyrrolo[3,4-c]pyrazoles)

Twenty-nine novel bis(dihydropyrrolo[3,4-c]pyrazole) derivatives were obtained by reacting C,N-phenyl-substituted nitrilimines generated in situ from corresponding hydrazonyl chlorides with bismaleimides. The structures were elucidated by physical and spectroscopic methods [m.p., R (f), infrared (IR), H-1 nuclear magnetic resonance (NMR), C-13 NMR, correlation spectroscopy (COSY), heteronuclear correlation (HETCOR), nuclear Overhauser effect (NOE), and high-resolution mass spectrometry (HRMS)]. Also, Hammett correlation graphs were obtained between Hammett constants sigma (p) and lambda (max) values of bis(pyrrolopyrazoles) carrying p-substituted phenyl-ring-bearing electron-withdrawing and electron-donating groups and discussed in terms of substituent effects.