Conjugate Addition of Hydroxylamines to 4-Substituted Butenolides
摘要:
4-Substituted-butenolides treated with free hydroxylamine at pH=5 undergo conjugate addition - rearrangement to afford isoxazolidin-5-ones. This is in contrast to N-substituted hydroxylamines which under the same conditions produce Michael adducts only. In the presence of base, butenolides undergo racemization via flat tautomeric forms.
Direct Catalytic Asymmetric Vinylogous Additions of α,β‐ and β,γ‐Butenolides to Polyfluorinated Alkynyl Ketimines
作者:Barry M. Trost、Chao‐I. (Joey) Hung、Manuel J. Scharf
DOI:10.1002/anie.201806249
日期:2018.8.27
We report a Zn‐ProPhenol catalyzed asymmetric Mannich reaction between butenolides and polyfluorinated alkynyl ketimines to obtain vinylogous products featuring two contiguous tetrasubstituted stereogenic centers. Notably, this is the first successful use of ketimines in the ProPhenol Mannich process, and the reaction offers a new approach for the preparation of pharmaceutically relevant products possessing
Dimethylaluminum methide complex Tf2CHAlMe2: an effective catalyst for Diels–Alder reaction of α,β-unsaturated lactone derivatives with cyclopentadiene
作者:Hikaru Yanai、Arata Takahashi、Takeo Taguchi
DOI:10.1016/j.tet.2007.09.061
日期:2007.12
catalyst system for the catalytic DA reaction of less reactive α,β-unsaturated lactone derivative with cyclopentadiene (CP). In this catalyst system, Tf2CHAlMe2 is an active species and an excess amount of Me3Al plays an important role to lower the catalyst loading. Substituent effect of the lactone framework on π-facial selectivity was also examined. In the reactions of both γ-substituted 5-membered lactone