1′-(2-Chlorophenyl)-5,6,5′,6′,7′,7a′-hexahydro-1′H,1′′H-dispiro[imidazo[2,1-b][1,3]thiazole-2,2′-pyrrolizine-3′(2′H),3′′-indole]-2′′,3(2H,3′′H)-dione