Search results for "Compostos heterocíclics"
showing 5 items of 5 documents
Recent Advances in Photocatalytic Functionalization of Quinoxalin‐2‐ones
2020
Quinoxalin‐2(1H)‐one is an important class of nitrogen heterocycle in medicinal and pharmaceutical industry, which became a synthetic target in organic chemistry in recent years. This review covers the recent advances in the functionalization of this particular nitrogen heterocycle through photocatalysis.
Photocatalytic Functionalization of Dihydroquinoxalin‐2‐Ones with Pyrazolones
2022
A visible-light photoredox functionalization of 3,4-dihydro-quinoxalin-2-ones with pyrazolones using an inexpensive organophotoredox catalyst is described. The reaction uses 9,10-phenanthrenedione as photocatalyst, a very simple and cheap photocatalyst, a HP single Blue LED (455 nm) as visible-light source and oxygen from air as terminal oxidant, obtaining the corresponding acetylated pyrazoles with good yields. The reaction can be extended to other nitrogen heterocycles such as 5-aminopyrazoles with good results.
Organocatalytic enantioselective Mannich reaction of isoxazol-5(4H)-ones to isatin-derived ketimines
2022
An efficient organocatalytic asymmetric Mannich reaction between isoxazol-5(4H)-ones and isatin-derived ketimines has been developed. A bifunctional squaramide/Brønsted base organocatalyst catalyzed the enantioselective Mannich addition to afford chiral 3-aminooxindoles bearing a tetrasubstituted stereocenter at C3 decorated with an isoxazole moiety in good yields and with excellent enantioselectivities. Additionally, several synthetic transformations were described showing the versatility of the prepared compounds.
Organocatalytic enantioselective 1,6-aza-Michael addition of isoxazolin-5-ones to p-quinone methides
2020
A thiourea-Brønsted base bifunctional catalyst allowed the enantioselective 1,6-aza-Michael addition of isoxazolin-5-ones to p-quinone methides to give isoxazolin-5-ones having a chiral diarylmethyl moiety attached to the N atom with fair to good yields and enantiomeric excesses. To the best of our knowledge this reaction represents the first example of enantioselective N-alkylation of isoxazolin-5-ones as well as the first example of enantioselective 1,6-aza-Michael reaction involving p-quinone methides.
Recent Advances in Catalytic Enantioselective Synthesis of Pyrazolones with a Tetrasubstituted Stereogenic Center at the 4-Position
2020
AbstractPyrazolone [2,4-dihydro-3H-pyrazol-4-one] represents one of the most important five-membered nitrogen heterocycles which is present in numerous pharmaceutical drugs and molecules with biological activity. Recently, many catalytic methodologies for the asymmetric synthesis of chiral pyrazolones have been established with great success, specially, for the synthesis of pyrazolones bearing a tetrasubstituted stereocenter at C-4. This review summarizes these excellent research studies since 2018, including representative examples and some mechanistic pathways explaining the observed stereochemistry.1 Introduction2 Catalytic Enantioselective Synthesis of Chiral Pyrazolones with a Full Car…