More On Corannulene Synthesis

Stu Borman’s article on the scale-up of corannulene nicely points out the increasing utility of this molecule as various workers have devised means of scaling it up (C&EN, March 5, page 49). However, Borman should have mentioned the original synthesis paper, “The Synthesis of Corannulene” by Wayne E. Barth and Richard G. Lawton (J. Am. Chem. Soc.,DOI: 10.1021/ja00736a028). This remarkable publication resulted from the outstanding work of one student (Barth) and the creative genius of Lawton, professor emeritus in the University of Michigan chemistry department.

In particular, the highly strained hydrocarbon corannulene, C₂₀H₁₀, was understood by Lawton to not only push the idea of nonplanar aromaticity to the limit with its bowl-like array of five fused benzene rings, but also to show that the structure represented fully one-third of the carbon framework of buckyball, C₆₀, discovered by Harold Kroto, Robert Curl, and Richard Smalley in 1985. Indeed, only the cautious tenor of the times prevented Lawton from mentioning this relationship that he had quickly recognized. More than 40 years later, the expectations and implications of the original work are still coming to fruition.

By Paul G. Rasmussen
Ann Arbor, Mich.

I was pleased to read the article on the new route to the synthesis of corannulene. In addition to the notable syntheses by Jay Siegel, Lawrence Scott, Andrzej Sygula, and Peter Rabideau, the article also touted the notable electronic properties of corannulene relative to its more famous cousin, C₆₀. However, I was surprised that the first synthesis by Barth and Lawton was not mentioned. They not only predicted the correct electronic structure for corannulene but used that electronic disposition to derive the common name of corannulene. It is also valuable to put that first synthesis in historical context, as it was completed more than 40 years ago and highlights the determination and ingenuity of Barth and Lawton.

By Brad Savall
San Diego