Sequential synthesis of furans from alkynes: successive ruthenium(II)- and copper(II)-catalyzed processes.

Step in time: 2,5-Disubstituted furans can be prepared from terminal alkynes in one pot using two successive catalytic reactions (see scheme; p-TSA = para-toluenesulfonic acid). First, a 1,3-dienyl alkyl ether is produced by the dimerization of a terminal alkyne and addition of an alcohol catalyzed by [RuCp*(NCMe)(3)][PF(6)]. Then, consecutive hydrolysis and cyclization catalyzed by CuCl(2) provides the 2,5-disubstituted furan.