Syntheses, crystal structures and Hirshfeld surface analyses of N -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 R ,9 R )- N -[(4-ethyl-phen-yl)sulfon-yl]cytisine, C 19 H 22 N 2 O 3 S ( I ) {systematic name: (1 R ,5 R )-3-[(4-ethyl-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8 H -1,5-methano-pyrido[1,2- a ][1,5]diazo-cin-8-one}, (7 R ,9 R )- N -[(4-chloro-phen-yl)sulfon-yl]cytisine, C 17 H 17 ClN 2 O 3 S ( II ) {systematic name: (1 R ,5 R )-3-[(4-chloro-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8 H -1,5-methano-pyrido[1,2- a ][1,5]diazo-cin-8-one} and (7 R ,9 R )- N -[(3-nitro-phen-yl)sulfon-yl]cytisine, C 17 H 17 N 3 O 5 S ( III ) {systematic name: (1 R ,5 R )-3-[(3-nitro-phen-yl)sulfon-yl]-1,2,3,4,5,6-hexa-hydro-8 H -1,5-methano-pyrido[1,2- a ][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 ( I )-( III ) 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 I and II ) and H⋯O/O⋯H (for III ) inter-actions make the most important contribution to the crystal packing.