Search results for "Oxygen heterocycles"
showing 6 items of 6 documents
Stereoselective synthesis of the naturally occurring 2-pyranone dodoneine
2008
The first total synthesis of the naturally occurring dihydropyranone dodoneine is reported. Asymmetric allylation reactions were used for the stereoselective generation of the two stereogenic centers. The pyranone ring was created by ring-closing metathesis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
A joint experimental and ab initio study on the reactivity of several hydroxy selenides. Stereoselective synthesis of cis-disubstituted tetrahydrofur…
2001
Abstract The reactivity of several hydroxy selenides bearing an ethereal chain with catalytic amounts of perchloric acid in dichloromethane was investigated. Results showed that the position of the oxygen atom with respect to the seleniranium ring was crucial in order to get a good yield of the cyclized product. The factors on which yields of the 5- endo cyclization of the seleniranium ions depend were analysed by ab initio (HF/3-21G ∗ ) studies. An explanation of the different coordinating ability, towards the positively charged selenium atom, of the allylic OMe and homoallylic OH-2 groups was given.
Electrochemical Synthesis of Fluorinated Orthoesters from 1,3‐Benzodioxoles
2019
Abstract Invited for this month's cover picture is the group of Professor Siegfried Waldvogel. The cover picture displays the robustness achieved by the installation of fluorinated alcohols on 1,3‐benzodioxoles, protecting the obtained orthoesters against acids and bases, like the shield of a knight. The simple protocol allows access to interesting compounds, whose lipophilicity is tremendously increased by the incorporation of fluorinated groups. This makes it possible to adjust the physicochemical properties of the biologically active 1,3‐benzodioxole motif. The surprisingly high stability against acids and bases gives rise to subsequent functionalizations or direct application in medicin…
Dehydrogenative Anodic C−C Coupling of Phenols Bearing Electron‐Withdrawing Groups
2019
Abstract We herein present a metal‐free, electrosynthetic method that enables the direct dehydrogenative coupling reactions of phenols carrying electron‐withdrawing groups for the first time. The reactions are easy to conduct and scalable, as they are carried out in undivided cells and obviate the necessity for additional supporting electrolyte. As such, this conversion is efficient, practical, and thereby environmentally friendly, as production of waste is minimized. The method features a broad substrate scope, and a variety of functional groups are tolerated, providing easy access to precursors for novel polydentate ligands and even heterocycles such as dibenzofurans.
Recent Advances in Enantioselective Desymmetrizations of Prochiral Oxetanes
2021
Abstract Strain relief of oxetanes offers a plethora of opportunities for the synthesis of chiral alcohols and ethers. In this context, enantioselective desymmetrization has been identified as a powerful tool to construct molecular complexity and this has led to the development of elegant strategies on the basis of transition metal, Lewis acid, and Brønsted acid catalysis. This review highlights recent examples that harness the inherent reactivity of prochiral oxetanes and offers an outlook on the immense possibilities for synthetic application.
Enantioselective Synthesis of 4-Substituted Dihydrocoumarins through a Zinc Bis(hydroxyamide)-Catalyzed Conjugate Addition of Terminal Alkynes
2013
A new enantioselective catalyst for the conjugate addition of terminal alkynes has been developed. Terminal alkynes react with 3-alkoxycarbonylcoumarins in the presence of diethylzinc and bis(hydroxyamide) ligands to give chiral non-racemic dihydrocoumarins substituted with an alkynyl group on the C-4 position with good yields and enantiomeric excesses up to 95%.