AbstractCyclization were occurred via the coupling reactions of some mercuric chloride derivatives of sydnone with LiPdCl3‐CuCl2.A unique six‐membered ring, 3,3′‐ethylene‐4,4′‐bissydnone, was obtained by the cyclization reation of 1,2‐di[3‐(4‐chloromercuric)sydnonyl]ethane. However, the seven‐membered 3,3′‐trimethylene‐4,4′‐bissydnone and 1,3‐di[3‐(4‐chloro)sydnonyl]‐propane were obtained from the corresponding mercuric chlroide of sydnone. Onyl substitution reaction took place when 4,4′‐di[3‐(4‐chloromercuric)sydnonyl]biphenyl, 4,4′‐di[3‐(4‐chloromercuric)sydnonyl]benzene, di(p‐[3‐(4‐chloromercuric)sydnonyl]‐phenyl}methane and, di(p‐[3‐(4‐chl