Structural studies of racemic and diastereomeric 2-amino-3-carbonitrile-based chromene derivatives

Abstract

In this study, we present a comprehensive exploration of sixteen novel 2-amino-4-aryl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles synthesized through a streamlined multicomponent microwave method. These chromene derivatives, obtained in remarkable yields (92–94 %), exhibit a fascinating array of stereochemical complexities. The influence of electron-withdrawing groups was subtly evident in chemical shifts, underscoring the nuanced interplay between structure and substituent effects. Infrared spectroscopy confirmed characteristic NH₂ functionalities across the series, with notable deviations in compounds featuring electron-withdrawing groups. Compounds studied by single crystal X-Ray diffraction, were all in the monoclinic crystal system, with interesting molecular disorder in select diastereomers. Intermolecular hydrogen bonding networks formed between the amino functional group and the chromenone O atom or a solvent O atom, lead to motifs similar to the previously reported motifs by our group including an extra N—H_b…O_3-interaction involving the amino and the methoxy substituent in compound 3c. Hirshfeld surface analysis further showed the contributions of key intermolecular contacts, while energy calculations highlighted the dominant role of electrostatics in motif stabilization. This work not only enriches the structural landscape of chromene derivatives but also opens avenues for future investigations into their potential applications in material science and beyond.