Design and synthesis of novel pyrrolo[2,3-a]carbazoles: 7-Chloro-2-oxo-3a-(2′-oxo-2′,3′-dihydro-1′H-indol-3′-yl)-2,3,3a,4,5,10-hexahydro-pyrrolo[3,2-a]carbazole-1-carbonitrile as an efficient anticancer agent