Enantioselective N-heterocyclic carbene catalyzed formal [3+2] cycloaddition using α-aroyloxyaldehydes and oxaziridines
摘要:
An enantioselective N-heterocyclic carbene catalysed formal [3+2] cycloaddition has been developed for the synthesis of oxazolindin-4-one products. The reaction of oxaziridines and alpha-aroyloxyaldehydes under N-heterocyclic carbene catalysis provides the formal cycloaddition products with excellent control of the diastereo- and enantioselectivity (12 examples, up to >95:5 dr, >99:1 er). A matched-mismatched effect between the enantiomer of the catalyst and oxaziridine was identified, and preliminary mechanistic studies have allowed the proposal of a model to explain these observations. (C) 2016 Published by Elsevier Ltd.
A visible-light-induced photosensitizer-free decarbonylative Minisci-type reaction
作者:Ming Qi、An-Wu Xu
DOI:10.1039/d4ob00021h
日期:——
A photoinduced photosensitizer-free Minisci-type reaction using aldehydes as radical precursors was reported, which showed excellent yields and functional groups tolerance. This effective method could achieve alkylation of natural products smoothly.
Synthesis of <sup>18</sup>
F-Difluoromethylarenes from Aryl (Pseudo) Halides
作者:Hang Shi、Augustin Braun、Lu Wang、Steven H. Liang、Neil Vasdev、Tobias Ritter
DOI:10.1002/anie.201604106
日期:2016.8.26
readily prepared from aryl chlorides, bromides, iodides, and triflates. Seven 18F‐difluoromethylarene drug analogues and radiopharmaceuticals including Claritin, fluoxetine (Prozac), and [18F]DAA1106 were synthesized to show the potential of the method for applications in PET radiopharmaceutical design.
Scaled-up procedures and preparation of glyceollin I in multigram quantities are described. The synthesis features construction of a cis-fused ring system in high enantiomeric excess after Sharpless asymmetricdihydroxylation of a key intermediate that is initially produced by an intramolecular Wittig reaction to afford the requisite alkene while simultaneously forming the first ring. The overall yield