Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane

Thamina Akhter (1) , Md. Monarul Islam (2, 1) , Taisuke Matsumoto (3) , Junji Tanaka (3) , Pierre Thuéry (4) , Carl Redshaw (5) , Takehiko Yamato (1)

1 Saga University [Japon]
2 Chemical Research Division (Bengladesh)
3 Institute of Materials Chemistry and Engineering (Japan)
4 LCMCE - Laboratoire de Chimie Moléculaire et de Catalyse pour l'Energie (ex LCCEF)
5 University of Hull [United Kingdom]

The reductive coupling reaction of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane 3 was carried out using TiCl4-Zn in pyridine followed by a McMurry coupling reaction to afford the compounds anti and syn 1,2-dimethyl[2.4]MCP-1-ene 4. Bromination of 4 with BTMA-Br$_3$ in dry CH$_2$Cl$_2$ afforded the interesting compound 1,2-bis-(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene 6 and consecutive debromination with Zn and AcOH in CH2$_C$l$_2$ solution afforded the stable solid 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 89% yield. Compound 7 was conveniently employed in a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3′,6′-dihydrobenzo)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-4′,5′-dimethylcarboxylate 8 in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP 9 by aromatization. The chirality of the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other.

Mots clés: Metacyclophane; McMurry reaction; Bromination; Diels–Alder reaction; chirality

Domaines: Matériaux; Chimie inorganique

Thamina Akhter, Md. Monarul Islam, Taisuke Matsumoto, Junji Tanaka, Pierre Thuéry, et al.. Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane. Tetrahedron, 2018, 74, pp.329-335. ⟨10.1016/j.tet.2017.11.075⟩. ⟨cea-01656007⟩