Synthesis, Structure, and Transannular π−π Interaction of Multilayered [3.3]Metacyclophanes¹

Abstract

The synthesis of a series of three- to six-layered [3.3]metacyclophanes ([3.3]MCPs) 3-6 has been successfully accomplished by the (p-tolylsulfonyl)methyl isocyanide (TosMIC) method as a critical coupling reaction. Their important synthetic intermediates are the two- and three-layered bis(bromomethyl) compounds 11, 17, 21, and tetrakis(bromomethyl) compounds 25 and 28. The structures of the three- to six-layered [3.3]MCPs (3-6) as well as three- to six-layered [3.3]MCP-di- (22-24) and tetraones (26, 27, and 29) as the synthetic intermediates have been elucidated based on the 1H NMR data and X-ray structural analysis. These multilayered cyclophanes are constructed with two different geometries, syn-[3.3]MCP and anti-[3.3]MCP-2,11-dione. In principle, their geometries are maintained in the multilayered [3.3]MCPs, but deformation of the dihedral angle of the two benzene rings of the syn-[3.3]MCP moiety is generally observed. In the four-layered MCP 4, the central [3.3]MCP moiety takes an anti geometry. These data indicate the structural flexibility of the [3.3]MCP moiety. In the electronic spectra, rather simple and structureless absorption curves are observed, and the most significant spectral change is observed for the two to three layers and becomes less effective even if it is more layered. In the charge-transfer (CT) bands of the multilayered [3.3]MCPs with tetracyanoethylene (TCNE), the lambdamax gradually shifts to the longer wavelength region, but the extent of the shift is much smaller as the number of layers increases. In the multilayered [3.3]MCP-di- and tetraones, the anti-[3.3]MCP-dione moiety works as an insulator. Therefore, the CT interaction of the four- and five-layered [3.3]MCPs with one anti-[3.3]MCP-dione moiety (23 and 24) shows the almost comparable magnitude of the interaction with the two- and three-layered [3.3]MCPs (2 and 3), respectively. The tetraones of the three and four-layered MCPs (29 and 26) do not show CT interactions except for the six-layered MCP 27.

Naphthalene-based oligothiophene-stacked polymers

“…55 We have recently reported the synthesis of aromatic-ring-layered polymers using xanthene compounds as scaffolds. [40][41][42][43][44][45][46][47] [2.2] Paracyclophane-layered polymers, which mimic multilayered cyclophanes, [56][57][58][59] exhibited fluorescence resonance energy transfer from the layered paracyclophanes to the end-capping groups. The use of xanthene as a scaffold enabled us to introduce various aromatic compounds, such as phenylenes, 44 carbazoles, 45 thiophenes 46 and anthracene, 47 into the polymers, with the distance between the layered aromatic units being B4.5 Å .…”

Synthesis and conformational studies of 9-benzyloxy-18-substituted [3.3]metacyclophanes

“…2,[11][12] A conformational study of the parent [3.3]metacyclophanes revealed that the most stable conformation has the syn geometry with a chair-chair arrangement of the trimethylene chains. [13][14][15][16][17][18] Cyclophanes have so many important applications due to flexible structure in theoretical study. Therefore, there is a continuous effort to synthesize novel cyclophanes through efficient and simple routes.…”

Four-layered [3.3]metacyclophane with ethenetetracarbonitrile

“…For the free ligand C 42 H 48 , see: Shibahara et al (2007). For multilayered [3.3]paracyclophanes, see: Shibahara et al (2008Shibahara et al ( , 2011a.…”