Auto Tandem Catalysis: Asymmetric Vinylogous Cycloaddition/Kinetic Resolution Sequence for the Enantioselective Synthesis of Spiro‐Dihydropyranone from Benzylidene Meldrum's Acid
has been achieved from ketone-derived benzylidene Meldrum's acid and α-ketolactones to provide spirolactone dihydropyranones with more than 99% ee. An Auto Tandem Catalysis (ATC) process resulting from dual and complementary role of (DHQ)2PHAL organocatalyst resulted in a sequence involving an asymmetric vinylogous formal (4+2) cycloaddition of benzylidene and the subsequent kinetic resolution operating
Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Conjugate Addition to Alkylidene and Indenylidene Meldrum’s Acids
作者:Ashraf Wilsily、Eric Fillion
DOI:10.1021/jo901559d
日期:2009.11.20
aryl group consistently leading to high enantioselectivities. The nature of the organozinc reagent on the efficiency and selectivity of the conjugateaddition was also investigated. The solid-state conformation was determined for a number of alkylidene Meldrum’s acids and correlated with the observed enantioselectivity in relation to the arene pattern of substitution.
Probing Persistent Intramolecular C−H···X (X = O, S, Br, Cl, and F) Bonding in Solution Using Benzyl Meldrum’s Acid Derivatives
作者:Eric Fillion、Ashraf Wilsily、Dan Fishlock
DOI:10.1021/jo802311w
日期:2009.2.6
Persistent intramolecular interactions between acidic C−H hydrogens and a variety of acceptors (X) (X = O, S, Br, Cl, and F) in solution were probed by 1H NMR experiments, using 5-benzyl Meldrum’s acid derivatives. To bring about formation of intramolecular C−H···X bonding, ortho-substituted benzyl Meldrum’s acids were designed, for which hydrogenbonding occurred through a six-membered ring. Introduction
酸性CHH氢与溶液中各种受体(X)(X = O,S,Br,Cl和F)之间的持久分子内相互作用通过1 H NMR实验使用5-苄基Meldrum的酸衍生物进行探测。为了形成分子内CH键·X键,设计了邻位取代的苄基麦德鲁姆酸,通过六元环进行氢键键合。在芳族部分上和在系链中引入取代基允许电子和空间因素的变化。麦德鲁姆酸的优越酸度影响了CH氢参与非经典CH-··X键的能力,并结合了空间位阻因子A 1,3,推动了苄基麦德鲁姆酸的构象性质。-烯丙基菌株。通过表征固态的苄基麦德鲁姆酸,通过X射线分析以及与溶液中观察到的相关构象,可以进一步了解分子内C-H···X键。
Expedient Synthesis of Complex γ-Butyrolactones from 5-(1-Arylalkylidene) Meldrum’s Acids via Sequential Conjugate Alkynylation/Ag(I)-Catalyzed Lactonization
作者:Siawash Ahmar、Eric Fillion
DOI:10.1021/ol502811j
日期:2014.11.7
The conjugate alkynylation of alkylidene Meldrums acids with alkynylalanes and alkynyl Grignards allows for the formation of propargylic all-carbon quaternary stereocenters in high yields. Ag2CO3-catalyzed intramolecular cyclization of propargylic Meldrums acid derivatives offers a two-step entry into complex gamma-alkylidene butyrolactones containing an all-carbon quaternary center at the C-4 position.
Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Cu-Catalyzed Conjugate Addition of Dialkylzinc Reagents to 5-(1-Arylalkylidene) Meldrum's Acids
作者:Eric Fillion、Ashraf Wilsily
DOI:10.1021/ja056692e
日期:2006.3.1
The asymmetric synthesis of all-carbon benzylic quaternary stereocenters has been successfully achieved through copper-catalyzed addition of dialkylzinc reagents to 5-(1-arylalkylidene) and 5-(dihydroindenylidene) Meldrum's acids in the presence of phosphoramidite ligand. The resulting benzyl-substituted Meldrum's acids and 1,1-disubstituted indanes were obtained in good yields and up to 99% ee. The significance of substituting the position para, meta, and ortho to the electrophilic benzylic center was highlighted. A benzyl Meldrum's acid product was further transformed to a 3,3-disubstituted 1-indanone and a beta,beta-disubstituted pentanoic acid.