Syntheses, crystal structures and Hirshfeld surface analyses of -aryl-sulfonyl derivatives of cytisine.

By aryl-sulfonyl-ation of cytisine in the presence of tri-ethyl-amine, three new compounds have been obtained in good yields: (7,9)--[(4-ethyl-phen-yl)sulfon-yl]cytisine, CHNOS () {systematic name: (1,5)-3-[(4-ethyl-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8-1,5-methano-pyrido[1,2-][1,5]diazo-cin-8-one}, (7,9)--[(4-chloro-phen-yl)sulfon-yl]cytisine, CHClNOS () {systematic name: (1,5)-3-[(4-chloro-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8-1,5-methano-pyrido[1,2-][1,5]diazo-cin-8-one} and (7,9)--[(3-nitro-phen-yl)sulfon-yl]cytisine, CHNOS () {systematic name: (1,5)-3-[(3-nitro-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8-1,5-methano-pyrido[1,2-][1,5]diazo-cin-8-one}. The crystal structures of the compounds were determined on the basis of single-crystal X-ray diffraction data. The crystal structures of ()-() are distinguished by the arrangement of two fragments of the mol-ecule around the sulfonyl site. For all structures, weak C-H⋯O hydrogen bonds are developed. Hirshfeld surface analysis shows that H⋯H (for and ) and H⋯O/O⋯H (for ) inter-actions make the most important contribution to the crystal packing.