Synthesis and structure of 1,2-dimethylene[2.10]metacyclophane and its conversion to chiral [10]benzenometacyclophanes

International audienceBromination of 5,21-di-tert-butyl-8,24-dimethoxy-1,2-dimethyl[2.10]metacyclophan-1-ene (MCP-1-ene) 1 with benzyltrimethylammonium tribromide exclusively afforded 1,2-bis(bromomethyl)-5,21-di-tert-butyl-8,24-dimethoxy[2.10]MCP-1-ene 2. Debromination of 2 with Zn and AcOH in CH2Cl2 solution at room temperature for 24 h produced the identical dimethylene[2.10]MCP 7 in 92% yield, which is a stable solid compound. Subsequently, compound 7 was reacted with dimethyl acetylenedicarboxylate (DMAD) to provide 1,2-(3',6'-dihydrobenzo)-5,21-di-tert-butyl-8,24-dimethoxy[2.10]MCP-4',5'-dimethylcarboxylate 8 in good yield. Diels-Alder adduct 8 was converted to a novel and inherently chiral areno-bridged dimethoxy[2.10]MCP-4',5'-dimethylcarboxylate 9 by aromatization with dichlorodicyano-p-benzoquinone (DDQ), possessing C1 symmetry. Also a new type of N-phenyl-maleimide substituted 1,2-(3',6'-dihydrobenzo)-5,21-di-tert-butyl-8,24-dimethoxy [2.10]MCP-4',5'-N-phenylmaleimide 10 was synthesised from 7 via treatment with N-phenylmaleimide in toluene at 110°C followed by aromatization with DDQ. Single crystal X-ray analysis of 9 revealed the adoption of a syn-isomer