A new method of forming biphenylenes substituted on one ring is described using gas-phase pyrolysis of mixtures of precursors of appropriate benzynes. The reaction of two benzynes coming from two different sources leads to the formation of the biphenylenes. The mixture of compounds is sublimed into a current of nitrogen and led into an unpacked quartz column heated externally by a furnace.The simultaneous pyrolysis of ninhydrin and tetrachlorophthalic anhydride (molar ratio, 2:1) at 800 °C gives 1,2,3,4-tetrachlorobiphenylene in a 31% yield. The pyrolysis of a mixture of phthalic anhydride and 4-methylphthalic anhydride at 850 °C leads to the formation of 2-methylbiphenylene (molar ratio, 9:1) (16%).