ИСТИНА

The present invention pertains to a cost-​efficient method for prepn. of di-​substituted fluorenes in high yield. For example, diphenylmethane was reacted with tert-​Bu chloride for 4,​4'-​di-​tert-​butyldiphenylmethane, which was further treated with bromine for 2,​2'-​dibromo-​4,​4'-​di-​tert-​butyldiphenylmethane. 2,​2'-​Dibromo-​4,​4'-​di-​tert-​butyldiphenylmethane prepd. above was treated with zinc dust in presence of tetraethylammonium iodide and a catalyst of NiBr2(DME) with a ligand of s-​trans-​N,​N'-​di-​tert-​butylethanediimine (prepn. given) in THF under dry nitrogen atm. with refluxing to give 3,​6-​di-​tert-​butylfluorene as a final product. Advantageously, the title process avoided using expensive and hazardous materials in prepn. of substituted fluorenes, and hence, is safe and cost efficient.