A valuable organocatalytic
vinylogous Mannich reaction between
alkylidenepyrazolones and isatin-derived ketimines has been successfully
established. Squaramide organocatalyst, prepared from quinine, catalyzed
the diastereo- and enantioselective vinylogous Mannich addition, affording
a range of aminooxindole-pyrazolone adducts (24 examples) with excellent
outcomes: up to 98% yield with complete diastereoselectivity and excellent
enantioselectivity (up to 99% ee). Additionally, different synthetic
transformations were performed with the chiral pyrazolone-oxindole
adducts.
Herein, an efficient asymmetric aminoalkylation of pyrazolones with α-amido sulfones catalyzed by a quinine-derived squaramide in dichloromethane/aqueous media has been established.
A diastereo‐ and enantioselective synthesis of spirocyclopropylpyrazolones has been described through a Michael/alkylation cascade reaction of 4‐arylidenepyrazol‐5‐ones with diethyl 2‐bromomalonate catalyzed by (DHQ)2AQN. The reaction afforded selectively the corresponding spirocyclic compounds with 30–83% yield, diastereoselectivities ranging from 60:40 to >95:5 and 26–93% enantiomeric excess under mild reaction conditions. Moreover, we performed two selective transformations with the corresponding chiral compounds.magnified image
In this communication, an efficient asymmetric aminoalkylation of 5‐aminopyrazole derivatives with cyclic benzoxathiazine 2,2‐dioxides catalyzed by a quinine‐derived squaramide in dichloromethane has been established. This is the first example of 5‐aminopyrazole derivatives in asymmetric catalysis. A variety of chiral sulfamidates bearing an aminopyrazole moiety were obtained in good yields (up to 98 %) and moderate to excellent enantioselectivities (up to 99 %ee).
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