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, C(19)H(22)N(2)O(3)S (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, C(17)H(17)ClN(2)O(3)S (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-[(3-nitro­phen­yl)sulfon­yl]cytisine, C(17)H(17)N(3)O(5)S (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.