Furan synthesis made easy
Easy access to a versatile group of furan compounds has been provided in a one-pot procedure by scientists in Germany.
Furans are integral structural units in some pharmaceuticals, photonic chromophores and natural products. In particular, halofurans are excellent starting materials for cross-coupling or electrophilic trapping reactions. Their synthesis, however, remains a challenge.
Based on its earlier base-free approach to a so-called Sonogashira reaction, Thomas Müller's team at Ruprecht-Karls-Universität Heidelberg, coupled an acid chloride with an alkyne, catalysed by a transition metal, to generate alkynones.
Using a simple coupling-addition-cyclocondensation method, different acid chlorides and alkynes were reacted. This gave an efficient and mild route to a variety of
A challenge associated with traditional methods of this synthesis is the instability of the products, particularly iodofurans, to acid. But by introducing sodium iodide as the halide source, milder reaction conditions and shorter reaction times could be used and the target compounds were made in good yields.
To emphasise its potential, the reaction was applied to the synthesis of 2,3,5-trisubstituted furans. Significantly, the same catalytic system was consecutively applied to two different coupling reactions in one vessel and the substituted target compounds were obtained in yields higher than for the corresponding step-by-step procedure.
The group is now looking at ways to apply the reaction to other molecules.