Allenes are a useful class of compounds, acting as versatile intermediates in organic synthesis and existing in many natural products and pharmaceuticals. So far, several one-step syntheses of terminal allenes from 1-alkynes with paraformaldehyde in the presence of amines and CuI salts have been developed.

Hongwen Luo, East China Normal University, and Shengming Ma, Chinese Academy of Sciences, both in Shanghai, China, report a facile and efficient CuI-catalyzed gram-scale synthesis of functionalized terminal allenes from 1-alkynes, paraformaldehyde, and diisopropylamine. This method accommodates different functional groups such as hydroxyl or carbonyl, and it also performed well in the synthesis of allenylamides and 2,3-butadien-1-ol.

The researchers say that owing to the easy availability of all the reagents, the high potential of the functionalized allenes, and the simple operation as well as the reaction’s catalytic nature, this method will be of interest to organic and medicinal chemists although it is still somewhat lower-yielding relative to the reaction using CuI (0.5 equiv.) and Cy₂NH (1.8 equiv.). Further studies in this area are being actively pursued in their laboratory.

• CuI-Catalyzed Synthesis of Functionalized Terminal Allenes from 1-Alkynes,
  Hongwen Luo, Shengming Ma,
  Eur. J. Org. Chem. 2013.
  DOI: 10.1002/ejoc.201201696