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.
Synthesis of Cyclopentadienes for Cyclopentadienyl Ligands via Cp*Rh<sup>III</sup>-Catalyzed Formal sp<sup>3</sup> C–H Activation/Spiroannulations
作者:Yongzhuang Wang、Xiaoli Huang、Qin Wang、Yuhai Tang、Silong Xu、Yang Li
DOI:10.1021/acs.orglett.0c03982
日期:2021.2.5
An efficient Cp*RhIII-catalyzed formal C(sp3)–H activation/spiroannulation of alkylidene Meldrum’s acids with alkynes has been developed using catalytical Cu(OAc)2 and air as the oxidant. This reaction demonstrates a new and straightforward approach to spirocyclopentadienes with Meldrum’s acid moieties in good to excellent yields under mild reaction conditions with a broad substrate scope. Notably
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.