Haruka Omachi, Yasutomo Segawa, and Kenichiro Itami

Acc. Chem. Res. 2012, ASAP. DOI: 10.1021/ar300055x

This Account highlights our efforts toward the bottom-up synthesis of structurally uniform carbon nanotubes (CNTs). We envisioned a bottom-up synthesis of structurally uniform CNTs through a controlled growth process from a short carbon nanoring (template) that corresponds to the target structure of CNTs. Our simple retrosynthetic analysis led to the identification of cycloparaphenylenes (CPPs), acene-inserted CPPs, and cyclacenes as the shortest sidewall segments of armchair, chiral, and zigzag CNTs, respectively. With this overall picture in mind, we initiated our synthetic studies of aromatic rings/belts as an initial step toward structurally uniform CNTs in 2005. This research has led to (i) a general strategy for the synthesis of CPPs and related carbon nanorings using cyclohexane derivatives as a benzene-convertible L-shaped unit, (ii) a modular, size-selective, and scalable synthesis of [n]CPPs (a shortest segment of armchair CNTs), (iii) the X-ray crystal structure analysis of CPPs, (iv) the design and synthesis of acene-inserted CPPs as the shortest segment of chiral CNTs, and (v) the first synthesis of cyclo-1,4-naphthylene, a π-extended CPP. We believe this work will serve as important initial steps toward a controlled synthesis of CNTs.