Synthesis and Structure of 1,2-Dimethylene[2.10]metacyclophane and Its Conversion into Chiral [10]Benzenometacyclophanes

Bromination of 5,21-di-tert-butyl-8,24-dimethoxy-1,2dimethyl[ 2.10] metacyclophan-1-ene (MCP-1-ene; 1) with benzyltrimethylammonium tribromide exclusively afforded 1,2bis( bromomethyl)-5,21-di-tert-butyl-8,24-dimethoxy[ 2.10] MCP1- ene (2). Debromination of 2 with Zn and AcOH in CH2Cl2 solution at room temperature for 24 h produced dimethylene[ 2.10] MCP 7 in 92 % yield, which is a stable solid compound. Compound 7 was treated with dimethyl acetylenedicarboxylate (DMAD) to provide 1,2-(3', 6'-dihydrobenzo)-5,21-di-tert-butyl8,24- dimethoxy[ 2.10] MCP-4', 5'-dimethylcarboxylate (8) in good yield. Diels-Alder adduct 8 was converted into a novel and inherently chiral areno-bridged dimethoxy[2.10] MCP-4', 5'-dimethylcarboxylate 9, possessing C-1 symmetry, by aromatization with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). 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'-Nphenylmaleimide 10 was also synthesized from 7 through treatment with N-phenylmaleimide in toluene at 110 degrees C followed by aromatization with DDQ. Single-crystal X-ray analysis of 9 revealed the formation of a syn-isomer.