One‐Pot Catalytic Enantioselective Synthesis of 2‐Pyrazolines

A scalable, one‐pot, enantioselective catalytic synthesis of 2‐pyrazolines from beta‐substituted enones and hydrazines is described. Pivoting on a two‐stage catalytic Michael addition/condensation strategy, the use of an aldehyde to generate a suitable hydrazone derivative of the hydrazine was found to be key for curtailing background reactivity and tuning the catalyst‐controlled enantioselectivity. The new synthetic method is easy to perform, uses a new and readily prepared cinchona‐derived bifunctional catalyst, is broad in scope, and tolerates a range of functionalities with high enantioselectivity (up to >99:1 e.r.). The significant scalability of this methodology was demonstrated with the synthesis of more than 80 grams of a pyrazoline product with 89 % catalyst recovery.     

Enantioselective Iridium‐Catalyzed Allylic Substitution with 2‐Methylpyridines

An enantioselective iridium‐catalyzed allylic substitution with a set of highly unstabilized nucleophiles generated in situ from 2‐methylpyridines is described. Enantioenriched 2‐substituted pyridines, which are frequently encountered in natural products and pharmaceuticals, could be easily constructed by this simple method in good yields and excellent enantioselectivity. The synthetic utility of the pyridine products is demonstrated through the synthesis of a key intermediate of a reported Na⁺/H⁺ exchanger inhibitor and the total synthesis of (−)‐lycopladine A.