Base dependence in copper-catalyzed Huisgen reactions: Efficient formation of bistriazoles

(Chemical Equation Presented) Click, click: Using a carbonate base as an additive in the copper-accelerated click reaction of alkynes and azides led to an oxidative coupling to form predominately 5,5′-bistriazoles (see scheme). The reaction proved more facile for propargylic ethers and less hindered substrates. Use of an optically active azide gave separable atropisomeric products and provides a convenient access to optically pure derivatives. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.