Synthesis of medium-sized ring compounds using enyne metathesis

A novel procedure for the synthesis of medium-sized ring compounds was developed using ruthenium-catalyzed enyne metathesis. When a CH2Cl2 solution of an enyne having a heteroatom in a tether was stirred in the presence of benzylidene ruthenium carbene complex 1 (10 mol%) at room temperature or upon heating overnight, a medium-sized ring compound was obtained in high yield. In this reaction, the reaction rate of enyne having two heteroatoms in a tether with 1 was accelerated compared with that of enyne having one heteroatom. Various eight- and nine-membered ring compounds were synthesized. Enyne having terminal alkyne gave the desired eight-membered ring compound, but under ethylene gas, the reaction rate decreased.