Asymmetric reduction of racemic 2-isoxazolines

Gold(I)‐Catalyzed Enantioselective Synthesis of Pyrazolidines, Isoxazolidines, and Tetrahydrooxazines

“…[4] In 2007, our group reported the enantioselective hydroamination of allenes catalyzed by gold(I)/bis(p-nitrobenzoate) complexes. The heterocycles formed from these reactions, vinyl isoxazolidines [5] and pyrazolidines, [6] appear frequently in biologically important molecules. The heterocycles formed from these reactions, vinyl isoxazolidines [5] and pyrazolidines, [6] appear frequently in biologically important molecules.…”

Heterocyclization of trans-1,2,3-triphenyl-cyclopropane using nitrous acid

“…The geometry of the benzene rings in the 1,2-diphenylcyclopropanes has virtually no effect on the yield of the corresponding heterocycles [1,2]. Since not only mono-and disubstituted isoxazolines and isoxazoles but also triarylisoxazolines (and isoxazoles) are of interest for practical use [3], but synthetic methods of the latter are quite limited, we have tried to find out whether 1,2,3-triphenylcyclopropanes are converted to products of N=O fragment insertion into the three-carbon ring by the action of nitrous acid using the conditions reported in [1,2].…”

Gold(I)‐Catalyzed Enantioselective Synthesis of Pyrazolidines, Isoxazolidines, and Tetrahydrooxazines

“…[2a] We hypothesized that in addition to tosyl amines, gold(I)/bis(pnitrobenzoate) complexes would perform as efficient catalysts for the enantioselective addition of hydroxylamines and hydrazines to allenes. The heterocycles formed from these reactions, vinyl isoxazolidines [5] and pyrazolidines, [6] appear frequently in biologically important molecules. [7] In addition, these heterocycles serve as precursors to unnatural amino acid derivatives such as 5-oxaproline [7,8] as well as chiral allylic alcohols and 1,3-diamines [Eq.…”