Sanae Matsuura

Concise Synthesis and Crystal Structure of [12]Cycloparaphenylene

bottom-up chemical synthesis of this simple molecular entity had been recognized as a Holy Grail in synthetic chemistry, three groups including our own have recently succeeded in synthesizing some [n]CPPs. Although these studies from the three research groups established the synthetic viability of the long-awaited CPPs, important issues remain unresolved (Scheme 1). For example, any synthetic route must be more concise, cost-effective, and scalable to provide CPP in useful quantities and to ensure that this interesting molecular entity is studied further. In addition, the molecular structure of CPP must be concretely validated by X-ray crystallographic analysis. We herein report a concise nickel-based synthesis of [12]CPP and the first X-ray crystal structure of [12]CPP. Some of the key features of the previous methods of making CPPs are summarized in Scheme 2. Both the group of Bertozzi and ours utilized the palladium-catalyzed Suzuki–Miyaura coupling of terphenyl-convertible bent

A Modular and Size‐Selective Synthesis of [n]Cycloparaphenylenes: A Step toward the Selective Synthesis of [n,n] Single‐Walled Carbon Nanotubes

the groups led by Bertozzi, Itami, 7] and Yamago have finally accomplished the bottom-up organic synthesis of some [n]CPPs (n = 8, 9, 12, 18). Although several possible routes toward CPP structures have been identified in these studies, a uniform strategy allowing the flexible and size-selective synthesis of a range of [n]CPPs has yet to be developed. Devising such a strategy is important in view of the expectation that CPP could serve as a precursor or seed in the preparation of structurally uniform armchair single-walled carbon nanotubes (SWNTs) (Scheme 1). 9] As proposed and demonstrated by others, the amplification growth strategy using a relatively short hydrocarbon template such as CPP holds the promise of a long-awaited selective synthesis of SWNTs. In such a strategy, a modular and size-selective synthesis of [n]CPPs would be critically important in providing [n,n]SWNTs in a controlled and selective fashion. We now describe a modular and size-selective synthetic approach to [n]CPPs (n 14) and report the synthesis of [14]-, [15]-, and [16]CPP as a proof-of-principle of our new strategy. Our CPP synthesis is very flexible, assembling bent and linear building blocks in a controlled and programmable manner. In essence, we previously synthesized [12]CPP in a 3+3+3+3 mode using a terphenyl-equivalent L-shaped diphenylcyclohexane unit; Pd-catalyzed stepwise formation of a “box” (3+3+3 and then 9+3), followed by aromatization (Scheme 2). By strategically varying the number of bent

Size-selective synthesis of [9]–[11] and [13]cycloparaphenylenes

The first size-selective synthesis of [9]–[11] and [13]cycloparaphenylenes (CPP) has been achieved by strategically utilizing cis-1,4-diphenylcyclohexane-1,4-diyl as the key terphenyl-convertible L-shaped unit. To access the designed triangular or rectangular macrocyclic precursors, we utilized palladium-catalysed C–B/C–Br cross-coupling (Suzuki–Miyaura coupling) and/or nickel-mediated C–Br/C–Br coupling. We also established step-economical routes to [14] and [16]CPP using nickel-mediated C–Br/C–Br coupling. The final aromatization steps toward CPPs were accomplished with NaHSO4. Thus, combined with our previous size-selective synthesis of [12] and [14]–[16]CPP, we completed our size-selective synthesis of [9]–[16]CPP. The successful size-selective syntheses of [n]CPPs speak well for the flexibility and reliability of our strategy using a cyclohexane ring.

Size-selective complexation and extraction of endohedral metallofullerenes with cycloparaphenylene.

A new strategy for the non-chromatographic extraction of metallofullerenes from solutions of arc-processed raw soot is based on the size-selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for Mx @C82 (x=1, 2); for example, Gd@C82 can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes.