Synthesis of allenes via thermal cycloreversion of .alpha.-alkylidene-.beta.-lactones
摘要:
This paper describes the application of the solution-phase [2 + 2] cycloreversion of alpha-alkylidene-beta-lactones as a practical method for the generation of substituted allenes. Upon heating in dimethylformamide solution at 110-125-degrees-C, these unsaturated beta-lactone derivatives undergo decarboxylation to provide allenes in good to excellent yield. Alpha-alkylidene-beta-lactones are conveniently prepared via the phenylselenylation of beta-lactone enolates followed by oxidative elimination of the resulting alpha-phenylseleno derivatives. The beta-lactone starting materials are synthesized by the addition of thiol ester enolates to ketones and aldehydes according to our recently reported procedure.
The boraformylation of allenes with B2(pin)2 and a formate ester as boron and formyl source, respectively, proceeds in the presence of a copper catalyst. The reaction selectively affords the corresponding β‐boryl β,γ‐unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe2Si−B(pin) as the silicon source.
Rh/Lewis Acid Catalyzed Regio-, Diastereo- and Enantioselective Addition of 2-Acyl Imidazoles with Allenes
作者:Pranjal P. Bora、Gui-Jun Sun、Wei-Feng Zheng、Qiang Kang
DOI:10.1002/cjoc.201700596
日期:2018.1
A highly regio‐, diastereo‐ and enantioselective addition of 2‐acylimidazoles or 2‐acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described. This atom economic approach leads to the formation of the branched allylic alkylated products including acyclic quaternary all‐carbon stereogenic centres in good yields with good to excellent diastereo‐ and enantioselectivities
Hydroaminomethylation Beyond Carbonylation: Allene-Imine Reductive Coupling by Ruthenium-Catalyzed Transfer Hydrogenation
作者:Susumu Oda、Brannon Sam、Michael J. Krische
DOI:10.1002/anie.201503250
日期:2015.7.13
Ruthenium(II)‐catalyzed hydrogentransfer from 2‐propanol mediates reductivecoupling of 1,1‐disubstituted allenes with formaldimines with complete branch‐regioselectivity, thus representing a new method for hydroaminomethylationbeyond classical hydroformylation/reductive amination.
Gold(I)-Catalyzed Synthesis of Indenes and Cyclopentadienes: Access to (±)-Laurokamurene B and the Skeletons of the Cycloaurenones and Dysiherbols
作者:Xiang Yin、Mauro Mato、Antonio M. Echavarren
DOI:10.1002/anie.201708947
日期:2017.11.13
between terminal allenes and aryl or styryl gold(I) carbenes generated by a retro-Buchner reaction of 7-substituted 1,3,5-cycloheptatrienes led to indenes and cyclopentadienes, respectively. These cycloaddition processes have been applied to the construction of the carbon skeleton of the cycloaurenones and the dysiherbols as well as to the total synthesis of (±)-laurokamurene B.
Rhodium-Catalyzed Hydroformylation of 1,1-Disubstituted Allenes Employing the Self-Assembling 6-DPPon System
作者:Alexander Köpfer、Bernhard Breit
DOI:10.1002/anie.201502086
日期:2015.6.1
A rhodium‐catalyzed hydroformylation of 1,1‐disubstituted allenes is reported. Using a RhI/6‐DPPon catalyst system, one can obtain β,γ‐unsaturated aldehydes in high regio‐ and chemoselectivity. The Z‐configured product is formed with up to >95 % selectivity when unsymmetrically 1,1‐disubstituted allenes are submitted to the reaction conditions. This is the first time that these interesting building
据报道,铑催化的1,1—二取代的烯丙基加氢甲酰化反应。使用Rh I / 6‐DPPon催化剂体系,可以以高区域选择性和化学选择性获得β,γ-不饱和醛。当不对称的1,1-二取代的丙二烯进入反应条件时,Z构型的产物具有高达> 95%的选择性。这是这些有趣的结构单元首次通过烯丙基的加氢甲酰化获得。通过对所获得的产物之一进行进一步的转化,证明了该方法的实用性。