Kilogram-Scale Production of Corannulene

An efficient entry process for the synthesis of corannulene has been demonstrated on kilogram scale. Compared to the discovery and gram-scale syntheses, the amounts of solvents and reagents per gram of product were greatly reduced. Priority was given to implement the least toxic agents possible. Improvements in the purification of products obviated the need for column chromatography, alleviating four chromatographic operations. A new reduction method for the final step of the synthesis decreased reaction time from 6 to 0.5 days, and avoided the use of 100 equiv of zinc metal. The process now comprises nine steps, each of which runs smoothly at 100-L scale with a charging of 3-12 kg of educt. A total of 1.3 kg corannulene was isolated. This kilogram-scale process reduces material costs by over 2 orders of magnitude compared to that for the published gram-scale syntheses. Key opportunities in the process are identified for further improvements that should make synthesis on 100-kg scale feasible with a target price for 1 that is suitable for commercial production and engineering application.