Silyl Nitronate Cycloadditions Catalyzed by Cu(II)-Bisoxazoline
摘要:
Cu(OTf)(2) and chiral BOX ligand-catalyzed 1,3-dipolar cydoadditions Of triisopropylsilyl nitronates with alpha,beta-unsaturated carboximides produced chiral isoxazolines in high yields, high enantioselectivities, and complete diastereoselectivities. These chiral isoxazoline products were further converted into structurally diversified derivatives, which demonstrated the utility of the new method of constructing isoxazolines. The transition-state structure of cydoaddition was proposed in the light of the relative and absolute configurations of the products.
Asymmetric silyl nitronate cycloadditions with bornane-10,2-sultam derivatives
摘要:
Asymmetric silyl nitronate cycloadditions with N-acryloyl (2R)-bornane-10,2-sultam, N-acryloyl (2S)-bornane-10,2-sultam, and N-methacryloyl (2R)-bornane-10,2-sultam have been studied. The asymmetric silyl nitronate cycloaddition/elimination methodology provides a general route for the asymmetric synthesis of 2-isoxazolines.
The preparation of optically active δ2- isoxazolines. A model for asymmetric induction in the non lewis acid catalyzed reactions of oppolzer's chiral sultam
作者:Dennis P Curran、Byeang Hyean Kim、James Daugherty、Timothy A Heffner
DOI:10.1016/0040-4039(88)85291-2
日期:1988.1
Good diastereoselectivity (ca. ) is reported in the cycloaddition reactions of Oppolzer'schiralsultam with nitrile oxides. A model is proposed which may apply to other nonLewisacid promoted reactions of this sultam.
Highly concise syntheses of (+)-macrosphelides A and B were accomplished in this study. The key feature of our synthetic route involved the direct three-carbon homologation of the readily available Weinreb amide 6 by the addition of a trans-vinylogous ester anion equivalent and facile construction of the 16-membered macrolide skeleton of macrosphelides via an intramolecular nitrile oxide−olefin cycloaddition