Synthesis of unsymmetrical 1,3-diynes via alkyne cross-metathesis.

The tungsten benzylidyne complex [PhC≡W{OSi(OtBu)3}3] (1) efficiently catalyses the metathetic conversion between symmetrical and unsymmetrical 1,3-diynes, which provides the opportunity to prepare the latter species directly from terminal alkynes by a combination of copper-catalysed homocoupling and catalytic alkyne cross-metathesis (ACM).