A practical synthesis of valuable strained 8-membered ring derivatives for click chemistry

Abstract : A convenient and cost-effective synthetic access to cyclooctyne and trans-cyclooctene derivatives is described. A cyclopropanation step using copper powder in lieu of Rh₂(OAc)₄ as catalyst and a symmetric diazomalonate enabled to drastically reduce the overall cost of the synthesis. Further derivatizations allowed to characterize, for the first time, the structure of a BCN analogue by X-ray crystallography and obtain a library of derivatives potentially useful for applications in metal free click chemistry.