Streocontrolled construction of six vicinal stereogenic centers on spiropyrazolones via organocascade Michael/Michael/1,2-addition reactions.
A highly stereoselective one-pot procedure for the synthesis of spiropyrazolone derivatives bearing six contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential catalysis by two organocatalysts, a cinchona-derived aminosquaramide and DBU, a series of diversely functionalized spiropyrazolones are obtained in good yields (47-62%) and excellent stereoselectivities (up to >25:1 dr and 98-99% ee). The opposite enantiomers of the spiropyrazolones are also accessible by employing a pseudoenantiomeric aminosquaramide catalyst.
Institute of Organic Chemistry, RWTH Aachen University Landoltweg 1 , 52074 Aachen, Germany.
Pankaj
P
Chauhan
Suruchi
S
Mahajan
Charles C J
CC
Loh
Gerhard
G
Raabe
Dieter
D
Enders
D002384:Catalysis; D002929:Cinchona / Q000737:chemistry*; D018360:Crystallography, X-Ray; D015394:Molecular Structure; D047069:Pyrazolones / Q000138:chemical synthesis* / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D047069:Pyrazolones; D013141:Spiro Compounds