Organocatalytic asymmetric robinson annulation of alpha,beta-unsaturated aldehydes: applications to the total synthesis of (+)-palitantin.
The highly enantioselective organocatalytic Robinson annulation of alpha,beta-unsaturated aldehydes was achieved, catalyzed by l-proline and trialkylamines and providing the formal [4 + 2] cycloaddition adducts. Additionally, in some examples in the catalysis with diarylpyrrolinol silyl ethers, the reactions afforded the [4 + 2] adducts with high enantioselectivity (>99.5% ee). The structure of the adduct, obtained from the reaction of 3-methylbut-2-enal and (E)-3-(2-nitrophenyl)acrylaldehyde, was confirmed by X-ray analysis. The absolute configurations of some [4 + 2] cycloadducts were investigated, and the methodology was applied in the synthesis of (+)-palitantin.
Hong
Bor-Cherng
BC
Department of Chemistry and Biochemistry, National Chung Cheng University, Chia-Yi, 621 Taiwan, ROC. chebch@ccu.edu.tw
Wu
Ming-Fun
MF
Tseng
Hsing-Chang
HC
Huang
Guo-Fong
GF
Su
Cheng-Feng
CF
Liao
Ju-Hsiou
JH
D000447:Aldehydes / Q000138:chemical synthesis / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D003500:Cyclization; D003511:Cyclohexanols / Q000138:chemical synthesis* / Q000737:chemistry; D003512:Cyclohexanones / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism
D000447:Aldehydes; D000588:Amines; D003511:Cyclohexanols; D003512:Cyclohexanones; C108794:palitantin; D011392:Proline