2 research outputs found
Enantioselective Desymmetrization of <i>para</i>-Quinamines through an Aminocatalyzed Aza-Michael/Cyclization Cascade Reaction
An unprecedented organocatalytic
asymmetric desymmetrization of <i>para</i>-quinamines leading
to functionalized hydroindoles,
a common motif in many alkaloids, has been reported. The ability of
diarylprolinol silyl ethers to promote iminium and enamine activation
of α,β-unsaturated aldehydes in one catalytic cycle is
the centerpiece of the strategy involving a challenging aza-Michael/intramolecular
cyclization cascade reaction. A range of prochiral <i>para</i>-quinamines and α,β-unsaturated aldehydes were investigated
to afford 16 examples of hydroindoles possessing four contiguous stereocenters
including one quaternary carbon. The hydroindole structures include
multiple orthogonal functionalities, which underwent various transformations
Solvent- and Catalyst-Free Synthesis of Nitrogen-Containing Bicycles through Hemiaminal Formation/Diastereoselective Hetero-Diels–Alder Reaction with Diazenes
A solvent-
and catalyst-free synthesis of nitrogen-containing bicyclic
derivatives through a three-bond forming process is reported. Starting
from dienals and readily available diazenes, the strategy involving
the hemiaminal formation/hetero-Diels–Alder reaction affords
the bicyclic products in a highly diastereoselective manner. This
simple and green procedure has been applied to a selection of substrates,
giving rise to 12 examples of nitrogen-containing bicyclic architectures.
These products underwent various synthetic transformations. A sequence
involving the cleavage of the hydrazine allowed the preparation of
a hydantoin motif bearing an aminopropyl side chain, which is a structure
found in natural products. A mechanism has also been suggested to
explain the observed selectivities