Isomerization of cyclic ethers having a carbonyl functional group: new entries into different heterocyclic compounds
摘要:
Oxiranes (epoxides) and oxetanes having a carbonyl functional group are chemoselectively isomerized to different heterocyclic compounds via Lewis acid-promoted 1,6- and 1,7-intramolecular nucleophilic attacks of the carbonyl oxygen on the electron-deficient carbon neighboring the oxonium oxygen: for example, cyclic imides to bicyclic acetals, esters to bicyclic orthoesters, sec-amides to 4,5-dihydrooxazole or 5,6-dihydro-4H-1,3-oxazines, and tert-amides to bicyclic acetals or azetidines. The intramolecular attack of a 1,5-positioned carbonyl oxygen predominantly results in a propagating-end isomerization polymerization. On the other hand, cyclic ethers having a 1,8- or farther positioned carbonyl group undergo conventional ring-opening polymerization. A tetrahydrofuran (oxolane) ring does not open, even with a 1,6-positioned carbonyl group. (C) 2002 Elsevier Science Ltd. All rights reserved.
Organocatalytic Enantioselective Synthesis of 1,4-Dioxanes and Other Oxa-Heterocycles by Oxetane Desymmetrization
作者:Wen Yang、Jianwei Sun
DOI:10.1002/anie.201509888
日期:2016.1.26
A new asymmetric synthesis of chiral 1,4‐dioxanes and other oxa‐heterocycles has been developed by means of organocatalytic enantioselective desymmetrization of oxetanes. This mild process proceeds with exceedingly high efficiency and enantioselectivity to establish the quaternary stereocenters. This method complements the existing, yet limited, strategies for the synthesis of these oxa‐heterocycles
Unexpected Isomerization of Oxetane-Carboxylic Acids
作者:Bohdan Chalyk、Anastasiia Grynyova、Kateryna Filimonova、Tymofii V. Rudenko、Dmitry Dibchak、Pavel K. Mykhailiuk
DOI:10.1021/acs.orglett.2c01402
日期:2022.7.8
Many oxetane-carboxylic acids were found to be unstable. They easily isomerized into new (hetero)cyclic lactones while being stored at room temperature or slightly heated. Chemists should keep in mind the high instability of these molecules, as this could dramatically affect the reaction yields and lead to negative results (especially in those reactions that require heating).