ABSTRACT
A Ni-catalyzed reductive carboxylation of N-substituted aziridines with CO2 at atmospheric pressure is disclosed. The protocol is characterized by its mild conditions, experimental ease, and exquisite chemo- and regioselectivity pattern, thus unlocking a new catalytic blueprint to access ß-amino acids, important building blocks with considerable potential as peptidomimetics.
ABSTRACT
We report on gold(I)-catalyzed oxidative annulation involving ynamides, nitriles, and 2,3-dichloropyridine N-oxide. The application of 2,3-dichloropyridine N-oxide as an oxygen atom transfer reagent reverses the regioselectivity to give 5-amino-1,3-oxazoles, in comparison with the previously reported syntheses of aminooxazoles based on gold-catalyzed nitrene transfers to ynamides to furnish 4-amino-1,3-oxazoles. The developed oxygen atom transfer approach allows the generation of 1,3-oxazoles containing a variety of sulfonyl-protected alkylamino groups in the fifth position of the oxazole ring (29 examples; up to 88% yields). In addition, the use of N-substituted nitriles, namely cyanamides, leads to the facile generation of difficult-to-obtain 2,5-diaminooxazoles. The process is feasible for wide ranges of ynamides or nitriles, and it can be conducted in gram scale.
ABSTRACT
Facile gold-catalyzed hydrohydrazidation of alkynes with various hydrazides R2CONHNH2 (R = Alk or Ar; including those with an additional nucleophilic moiety) in the presence of Ph3PAuNTf2 (6 mol %) leading to a wide range of substituted keto- N-acylhydrazones (18 examples) in excellent to good yields (99-66%) is reported. This novel metal-catalyzed coupling proceeds under mild conditions (chlorobenzene, 60 °C), exhibits high functional group tolerance, and is insensitive to the electronic and steric effects of the substituents in the reactants.
