Regio- and stereoselective synthesis of spiro-heterocycles bearing the pyrazole scaffold via [3+2] cycloaddition reaction

Abstract

Herein we reported the utility of one-pot multicomponent based [3+2] cycloaddition reaction transformation to prepare a new two hybrids of spirooxindoles engrafted with pyrazole skeleton. Upon treatment of the electron-deficient olefins based pyrazole motif with in situ the generated azomethine ylides (AY) of sarcosine with the 6-chloro-isatin afforded spiroadducts. To enlighten the regio- and diastereo-selectivity of these spiroheterocycles, single crystal X-ray diffraction analysis was presented. Using Hirshfeld calculations, many short distance contacts such as O…H, Cl…H, N…H, H…C, C…C and Cl…S have a great impact on the molecular packing and the crystal stability of 8a and 8b. The latter showed some Cl…Cl inter halogen interactions (Cl1…Cl3; 3.358 Å). In addition, DFT calculations were used to compute the electronic properties as well as the 1H- and 13C-NMR spectra of the studied systems. Both compounds are polar where 8b (3.995 Debye) has higher dipole moment than 8a (3.414 Debye). The NMR chemical shifts were calculated and found in excellent correlations between the calculated and experimental data were obtained (R2 = 0.94–0.98).