Ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with thiols: a general synthetic route to propargylic sulfides.

A novel cationic methanethiolate-bridged diruthenium complex [CpRuCl(mu2-SMe)2RuCp(OH2)]OTf (1e) has been disclosed to promote the catalytic propargylic substitution reaction of propargylic alcohols bearing not only terminal alkyne group but also internal alkyne group with thiols. It is noteworthy that neutral thiolate-bridged diruthenium complexes (1a-1c), which were known to promote the propargylic substitution reactions of propargylic alcohols bearing a terminal alkyne group with various heteroatom- and carbon-centered nucleophiles, did not work at all. The catalytic reaction described here provides a general and environmentally friendly preparative method for propargylic sulfides, which are quite useful intermediates in organic synthesis, directly from the corresponding propargylic alcohols and thiols.