An enantioselective α-oxyamination of unprotected 3-substituted oxindoles with nitrosobenzene catalyzed by tertiary amine–thiourea bifunctional organocatalysts has been developed and affords the corresponding 3-amino-2-oxindole derivatives in good yields and with moderate to excellent enantioselectivities (up to > 99.9 : 0.1 er when the product is isolated by direct filtration from the reaction mixture)
Two yellow pigments, I and II were isolated from the rhizomes of Cimicifuga dahurica MAXIM. (Ranunculaceae) and were elucidated as geometric isomers, (E)-3-(3'-methyl-2'-butenylidene)-2-indolinone and (Z)-3-(3'-methyl-2'-butenylidene)-2-indolinone, by chemical and spectral studies and by X-ray diffraction analysis, respectively. On standing, and ethanolic solution of II gave a colorless substance, which was regarded as a product of dimerization.
Catalytic asymmetric α‐arylation of N‐unprotected 3‐substituted oxindoles with diaryliodoniumsalts has been realized by a chiral Lewis acid promoted electrophilic addition and aryl‐rearrangement process. Single C3‐arylated products containing a quaternary carbon center were generated in high enantioselectivity and reactivity.
Quinidine derivative (QD)2PYR was found to catalyze the asymmetric direct amination of unprotected prochiral 3-oxindole with DIAD to construct quaternary stereocenters at the C3 position with excellent enantioselectivity.
Alkylation of Oxazolones and Related Heterocycles through an SN1 Reaction
作者:Andrea-Nekane R. Alba、Teresa Calbet、Mercé Font-Bardía、Albert Moyano、Ramon Rios
DOI:10.1002/ejoc.201100046
日期:2011.4
The alkylation of oxazolonesthrough an S(N)1 reaction by using stabilized carbocations is reported. The reaction (catalyzed by Bronsted acids, such as TFA or thioureas) affords the final compounds in excellent yields. Reaction with other heterocycles has also been studied, rendering pyrazolone or oxindole derivatives in good yields.