Direct Asymmetric Catalytic Thienylaluminum Addition to Ketones: A Concise Approach to the Synthesis of (S)-Tiemonium Iodide

A direct asymmetric addition of a (2-thienyl)aluminum reagent to ketones catalyzed by a titanium catalyst of (S)-BINOL to afford chiral tertiary 2-thienyl alcohols is reported. The catalytic system works excellently for aromatic ketones and for 1-acetylcyclohexene, furnishing products in excellent enantioselectivities of up to 97% ee. However, the additions to dialkyl ketones afford products in low enantioselectivities of 8−17% ee. Importantly, a concise 3-step synthesis of (S)-tiemonium iodide with an 84% yield is demonstrated.