Medium-Sized Cyclophanes. 43.1 First Evidence for anti−syn-Ring Inversion under the Nitration of 5,13-Di-tert-butyl-8,16-dimethoxy[2.2]metacyclophane
摘要:
Nitration of 5,13-di-tert-butyl-8,16-dimethoxy[2.2]MC (metacyclophane = MCP) (1) with various nitrating reagents led to ipso-nitration at the tert-butyl group to give 5-tert-butyl-8,16-dimethoxy-13-nitro[2.2]MCP (2), as well as the corresponding 8,16-epoxy[2.2]MCP (4) arising from intramolecular condensation reaction via anti-syn-ring inversion of the nitration intermediate. This novel intramolecular condensation reaction to afford 8,16-epoxy[2.2]MCP (4) was also observed in the presence of Nafion-H under chlorobenzene reflux. The mechanism of the ipso-nitration as well as the present novel intramolecular condensation reaction is also discussed.