A novel ring tansfer reaction of furans to fused furans by tandem intramolecular Diels-Alder reaction and base-catalyzed ring-opening of the adducts has been developed.
Trialkylaluminium reagents have been found to undergo a copper-catalyzedasymmetricconjugateaddition (ACA) reaction with oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylates with the simultaneous creation of two stereocenters. Different types of ligands were tested, and chiral phosphoramidite ligands allowed the reaction to proceed with good yields and good to excellent enantioselectivity. The syn
已发现三烷基铝试剂与氧杂双环 [2.2.1] 庚-2,5-二烯-2,3-二羧酸酯发生铜催化的不对称共轭加成 (ACA) 反应,同时产生两个立体中心。测试了不同类型的配体,手性亚磷酰胺配体使反应能够以良好的产率和良好的对映选择性进行。通过 X 射线分析观察到的顺式取代产物表明亲核试剂的外切攻击。在此,我们报告了在这种铜催化 ACA 方法的开发中获得的结果,该方法提供了具有未取代和取代的氧杂环迈克尔受体的全碳四元中心。该研究是通过为阐明原始反应途径而进行的机理研究完成的。
A facile access to masked isobenzofurans ; High exo-stereoselectivity in the Diels-Alder reactions of 4,7-dihydro-4,7-ethanoisobenzofuran.
作者:Dominique Stephan、Alain Gorgues、André Le Coq
DOI:10.1016/s0040-4039(00)94257-6
日期:——
The isobenzofuran derivatives precursors a-c are readily prepared from ; their Diels-Alder adducts with cis-dienophiles present a stereochemistry endoexo from b,c and, interestingly, only exo (towards the furan moiety) from a.
Novel Isobenzofuran Generation from Silylated Lactol Leading to Desilylated or Silylated Adducts Depending on the Choice of Metal Fluorides
作者:Koichi Mikami、Hirofumi Ohmura
DOI:10.1055/s-2002-34871
日期:——
A new method of isobenzofuran generation was developed by treating silylated lactol with metal fluorides. The reactions with hard early transition metal fluorides gave de-silylated dimethyl acetylenedicarboxylate (DMAD) adduct mainly. By contrast, the silyl-retained DMAD adduct, which could be used for further transformation, was also obtained depending on the choice of metal fluorides such as lanthanoides or low valent transition metal fluorides.
Palladium-Catalyzed Isobenzofuran Generation under Neutral Conditions via Oxidative Addition to Lactol Methyl Ether
作者:Koichi Mikami、Hirofumi Ohmura
DOI:10.1021/ol0265416
日期:2002.10.1
[GRAPHICS]A novel method for generation of isobenzofuran is developed from lactol methyl ether using palladium catalysts. This reaction can be carried out under neutral conditions and hence improves on the precedent methods under acidic or basic conditions and at high temperatures. Furthermore, this Pd-catalyzed isobenzofuran generation suggests the involvement of oxidative addition of Pd catalyst into benzylic or allylic methyl ethers.