Enantioselective Ring Opening of meso-Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N-Oxides Fused with the Bicyclo[3.3.1]nonane Framework

The synthesis of new chiral Lewis basic organocatalysts that contain pyridine N‐oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N‐oxides were employed as catalysts in the enantioselective ring opening of meso‐epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4‐diaryl‐substituted pyridine N‐oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner–Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4‐aryl substituents, exhibited moderate to high levels of asymmetric induction (47–88 % ee) with alicyclic epoxide substrates. Chiral Lewis basic catalysts with pyridine N‐oxide moieties fused with a bicyclo[3.3.1]nonane framework were used in the enantioselective ring opening of meso‐epoxides. 2,4‐Diaryl‐substituted N‐oxide exhibited excellent asymmetric induction with norbornene oxide (96 % ee), whereas less‐substituted congener was most effective with alicyclic epoxide substrates (47–88 % ee).