Palladium(II)-catalyzed coupling of allenoic acids and α,β-unsaturated carbonyl compounds through tandem intramolecular oxypalladation and conjugate addition reactions
作者:Guosheng Liu、Xiyan Lu
DOI:10.1016/s0040-4039(02)02507-8
日期:2003.1
A regioselective divalent palladium-catalyzed tandem coupling reaction of allenoic acids with α,β-unsaturated carbonylcompounds was developed. The reaction involves intramolecular oxypalladation of an allene, followed by insertion of the α,β-unsaturated carbonylcompound and protonolysis of the CPd bond to regenerate the Pd(II) species in the presence of excess halide ions. Functionalized lactones
Intramolecular Palladium(II)-Catalyzed 1,2-Addition to Allenes
作者:Catrin Jonasson、Attila Horváth、Jan-E. Bäckvall
DOI:10.1021/ja001748k
日期:2000.10.1
were performed in the presence of LiBr with Pd(OAc)2 as the catalyst. Two different reoxidants, p-benzoquinone or Cu(OAc)2, were used, the choice of oxidant being dependent on the substrate. The reaction proceeds through an external nucleophilic attack (Br-) on a (π-allene)palladium complex to produce a (π-allyl)palladium intermediate. Subsequent intramolecular attack by the second internal nucleophile
钯 (II) 催化分子内 1,2-加成到被内部亲核试剂取代的丙二烯。羧酸、醇、N-取代酰胺和氨基甲酸酯用作钯催化反应中的内部亲核试剂,以良好的分离产率提供内酯、四氢吡喃、四氢呋喃、吡咯烷和恶唑烷酮。该反应在 LiBr 存在下以 Pd(OAc)2 作为催化剂进行。使用了两种不同的再氧化剂,对苯醌或 Cu(OAc)2,氧化剂的选择取决于底物。该反应通过对(π-丙二烯)钯络合物的外部亲核攻击(Br-)进行,以产生(π-烯丙基)钯中间体。随后第二个内部亲核试剂的分子内攻击产生产物。中间体(π-烯丙基)钯配合物被分离和表征。研究了反应的范围和局限性及其机理和选择性,在不同的反应...
Allene Trifunctionalization <i>via</i> Amidyl Radical Cyclization and TEMPO Trapping
作者:Robert M. Ward、Jennifer M. Schomaker
DOI:10.1021/acs.joc.1c00675
日期:2021.7.2
well-studied radical difunctionalizations of alkenes and alkynes. In this article, we describe a light-promoted reaction that transforms all three allene carbons to new carbon–heteroatom bonds in one pot with no expensive transition-metal catalyst. Formation of an electron donor-acceptor complex between an electron-deficient aryl and K2CO3, followed by photochemical generation of an amidylradical and cyclization
与经过充分研究的烯烃和炔烃的自由基双官能化相比,丙二烯的自由基介导的三官能化实际上是未知的。在这篇文章中,我们描述了一种光促进反应,该反应在一个锅中将所有三个丙二烯碳转化为新的碳 - 杂原子键,无需昂贵的过渡金属催化剂。在缺电子芳基和 K 2 CO 3之间形成电子供体-受体复合物,然后光化学生成酰胺基自由基并环化,产生乙烯基自由基,该自由基可以被 TEMPO 捕获以最终提供产品。介绍了对丙二烯取代模式、自由基来源和供体的影响的见解,以及解开这种不寻常转变机制的研究。
Highly Regio- and Stereoselective Cyclic Iodoetherification of 4,5-Alkadienols. An Efficient Preparation of 2-(1′(<i>Z</i>)-Iodoalkenyl)tetrahydrofurans
作者:Bo Lü、Xinpeng Jiang、Chunling Fu、Shengming Ma
DOI:10.1021/jo802079b
日期:2009.1.2
In this paper, an efficient way to synthesize 2-(1'(Z)-iodoalkenyl)tetrahydrofurans from 4,5-alkadienols and 12 was developed. The reaction of the 4,5-allenols with a substituent in the 3-position afforded the trans-2,3-disubstituted tetrahydrofurans with very high diastereoselectivity. However, when the axially optically active 4,5-allenol was treated with 12 in n-hexane, the efficiency for chirality transfer was low. This problem was circumvented by conducting the reaction in CH2Cl2 at room temperature and applying N-iodosuccinimide as the electrophilic reagent; however, the Z/E ratio for the products is much lower. Highly optically active Z-products may be prepared via the kinetic resolution via a Sonogashira coupling reaction with propargyl alcohol.
Highly Stereoselective Iodolactonization of 4,5-Allenoic Acids-An Efficient Synthesis of 5-(1′-Iodo-1′(<i>Z</i>)-alkenyl)-4,5-dihydro-2(3<i>H</i>)-furanones
作者:Xinpeng Jiang、Chunling Fu、Shengming Ma
DOI:10.1002/chem.200801363
日期:2008.10.29
In this paper, it is reported that the efficientiodolactonization of 4,5-allenoic acid with I2 in cyclohexane in the presence or absence of K2CO3 afforded 5-(1'-iodo-1'(Z)-alkenyl)-4,5-dihydro-2(3H)-furanoneshighlystereoselectively. However, the reaction of axially optically active 4,5-allenoic acids (R)-(-)-5 a and (R)-(-)-5 b with I2 afforded the corresponding products with a serious loss of chirality