Organolanthanide-Catalyzed Cyclization/Silylation of Nitrogen-Containing Enynes

Cyclization/silylation reactions of nitrogen-containing enynes catalyzed by the complexes Cp* 2 LnMe·THF (Ln = Y, Lu) were investigated. Utilizing standard conditions previously developed for carbocyclic systems, the Cp* 2 YMe·THF complex suffered from poor reactivity at room temperature with nitrogen α to the alkyne. This was overcome in the current studies either by slow catalyst addition or by using the smaller lutetium catalyst Cp* 2 LuMe·THF. The use of Cp* 2 LuMe·THF allowed the preparation of various nitrogen-containing ring systems in excellent yields with good to excellent diastereoselectivities at room temperature. The results of this study highlight the ability to tune the reactivity of an organolanthanide complex by changing the metal center.