Ruthenium-Catalyzed Reactions of 1-Cyclopropyl-2-propyn-1-ols with Anilines and Water via Allenylidene Intermediates: Selective Preparation of Tri- and Tetrasubstituted Conjugated Enynes

Ruthenium-catalyzed efficient preparation of the conjugated enynes can be carried out in the
reactions of 1-cyclopropyl-2-propyn-1-ols with nitrogen- and oxygen-centered nucleophiles such as anilines
and water in the presence of a catalytic amount of sulfur-bridged diruthenium complexes. The use of such
complexes as catalysts realizes the completely stereoselective preparation of tri- and tetrasubstituted
conjugated enynes, where ruthenium−allenylidene complexes work as key intermediates. The direct attack
of nucleophiles on a cyclopropane ring connected to an allenylidene ligand is a key step to obtain the
enynes stereoselectively.