Abstract The versatile synthon (E)-2-((dimethyl amino) methylene) cyclooctanone (2) was used as a key intermediate for the synthesis of cyclooctanones and cyclooctane-based heterocycles with pyrazole, isoxazole, pyrimidine, pyrazolopyrimidine, triazolopyrimidine and imidazopyrimidine derivatives via its reactions with several nitrogen nucleophiles. The newly synthesized compounds were screened in vitro for their antimicrobial activity ...