Publications by authors named "Urbano Osorio-Nieto"

By using cheap and innocuous reagents, such as NaClO, NaOCl, and catalytic amounts of TEMPO, a new environmentally friendly protocol for the selective and catalytic TEMPO C(sp)-H oxidation of piperazines and morpholines to 2,3-diketopiperazines (2,3-DKP) and 3-morpholinones (3-MPs), respectively, has been developed. This novel direct access to 2,3-DKP from piperazines provides significant advantages over the traditional N-monoacylation/intramolecular C-N cyclization procedure. Additionally, by modulating the amounts of TEMPO, 2-alkoxyamino-3-morpholinone can be prepared from morpholine derivatives, which would enable further functionalization at the C2 position of the morpholine skeleton.

View Article and Find Full Text PDF

The substrate-controlled asymmetric total synthesis and absolute configurational assignment of biologically active 3α,4α-epoxy-5β-pipermethystine, a minor component in the aerial parts of kava, has been achieved by featuring, as a key step, the environmentally friendly and direct synthesis of 2,3-epoxyamides from allyl amines. By using the chiron approach, first a carbohydrate-derived dehydropiperidine was prepared and subjected to a stereoselective tandem C-H/C[double bond, length as m-dash]C oxidation reaction. In this attempt, the required α,α-trans-epoxy-2-piperidone skeleton of the kava metabolite precursor was not achieved, although the tandem oxidation was highly stereoselective.

View Article and Find Full Text PDF

The first chemical method for selective dual sp(3) C-H functionalization at the alpha-and beta positions of cyclic amines to their corresponding 3-alkoxyamine lactams is reported. Unlike traditional Cα-H oxidation of amines to amides mediated by transition metals, the present protocol, which involves the use of NaClO2/TEMPO/NaClO in either aqueous or organic solvent, not only allows the Cα-H oxidation but also the subsequent functionalization of the unreactive β-methylene group in an unprecedented tandem fashion and using environmentally friendly reactants.

View Article and Find Full Text PDF