Syntheses, crystal structures and Hirshfeld surface analyses of N-arylsulfonyl derivatives of cytisine

By arylsulfonylation of cytisine in the presence of triethylamine, three new compounds have been obtained in good yields: (7R,9R)-N-[(4-ethylphenyl)sulfonyl]cytisine, C19H22N2O3S (I) {systematic name: (1R,5R)-3-[(4-ethylphenyl)sulfonyl]-1,2,3,4,5,6- hexahydro-8H-1,5-methanopyrido[1,2- a][ 1,5]diazocin-8-one}, (7R,9R)-N-[(4-chlorophenyl)sulfonyl]cytisine, C17H17ClN2O3S (II) {systematic name: (1R,5R)-3-[(4-chlorophenyl)sulfonyl]-1,2,3,4,5,6-hexahydro-8H-1,5-methanopyrido[1,2-a][1,5]diazocin-8-one} and (7R,9R)-N-[(3nitrophenyl)sulfonyl]cytisine, C17H17N3O5S (III) {systematic name: (1R,5R)-3[(3-nitrophenyl)sulfonyl]-1,2,3,4,5,6-hexahydro-8H-1,5-methanopyrido[ 1,2-a][1,5]diazocin-8-one}. The crystal structures of the compounds were determined on the basis of single-crystal X-ray diffraction data. The crystal structures of (I)(III) are distinguished by the arrangement of two fragments of the molecule around the sulfonyl site. For all structures, weak C-H...O hydrogen bonds are developed. Hirshfeld surface analysis shows that H...H (for I and II) and H...O/O...H (for III) interactions make the most important contribution to the crystal packing.