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

Abstract

Bromination 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 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‐butyl‐8,24‐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 C1 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′‐N‐phenylmaleimide 10 was also synthesized from 7 through treatment with N‐phenylmaleimide in toluene at 110 °C followed by aromatization with DDQ. Single‐crystal X‐ray analysis of 9 revealed the formation of a syn‐isomer.