Search results for "Pyrazolone"
showing 4 items of 14 documents
Enantioselective synthesis of pyrazolone α-aminonitrile derivatives via an organocatalytic Strecker reaction
2017
A new organocatalytic enantioselective Strecker reaction of pyrazolone-derived ketimine electrophiles has been developed. Using pseudo-enantiomeric squaramide catalysts the nucleophilic 1,2-addition of trimethylsilyl cyanide to the ketimines efficiently provides a direct entry to both enantiomers of pyrazolone α- aminonitrile derivatives at will in good yields and high enantioselectivities for a wide variety of substrates. peerReviewed
ChemInform Abstract: Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter.
2016
An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2 O/Et3 N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.
Asymmetric Synthesis of Five-Membered Spiropyrazolones via N-Heterocyclic Carbene (NHC)-Catalyzed [3+2] Annulations
2016
A new synthetic strategy for the asymmetric synthesis of five-membered spiropyrazolones via N-heterocyclic carbene-catalyzed [3+2] annulations employing enals and unsaturated pyrazolones as substrates has been developed. The new protocol allows the flexible variation of all four substituents of the pharmaceutically important spiropyrazolones in moderate to very good yields and in most cases with excellent diastereoselectivities and good to excellent enantioselectivities.
Zur Reaktion von ?Pyrazolonblau? mit Diazomethan
1989
About the Reaction of „Pyrazolone Blue” with Diazomethane The reaction of “pyrazolone blue” with diazomethane was investigated. A pyridazinone derivative 3, a heterocyclic spiro-cyclopropyl product 4 and a compound 7, which contains three pyrazolone and two diazomethane entities, are formed. 3 reacts with an excess of diazomethane to the methoxy derivative 6. The spiro-cyclopropyl compound 4 is not stable and isomerizes to the corresponding 4,4′-methylidene-bispyrazolone 5. The structures of the products were established by spectroscopic methods and X-ray analysis.