Base‐free Enantioselective C(1)‐Ammonium Enolate Catalysis Exploiting Aryloxides: A Synthetic and Mechanistic Study
作者:Calum McLaughlin、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1002/anie.201908627
日期:2019.10.14
An isothiourea-catalyzed enantioselective Michael addition of aryl ester pronucleophiles to vinyl bis-sulfones via C(1)-ammonium enolate intermediates has been developed. This operationally simple method allows the base-free functionalization of aryl esters to form α-functionalized products containing two contiguous tertiary stereogenic centres in excellent yield and stereoselectivity (all ≥99:1 er)
Catalytic enantioselective synthesis of 1,4-dihydropyridines <i>via</i> the addition of C(1)-ammonium enolates to pyridinium salts
作者:Calum McLaughlin、Jacqueline Bitai、Lydia J. Barber、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1039/d1sc03860e
日期:——
addition of C(1)-ammonium enolates – generated in situ from aryl esters and the isothiourea catalyst (R)-BTM – to pyridinium salts bearing an electron withdrawing substituent in the 3-position allows the synthesis of a range of enantioenriched 1,4-dihydropyridines. This represents the first organocatalytic approach to pyridine dearomatisation using pronucleophiles at the carboxylic acid oxidation level. Optimisation
Isothiourea-Catalyzed Enantioselective Addition of 4-Nitrophenyl Esters to Iminium Ions
作者:Jude N. Arokianathar、Aileen B. Frost、Alexandra M. Z. Slawin、Darren Stead、Andrew D. Smith
DOI:10.1021/acscatal.7b02697
日期:2018.2.2
alternative aryl esters, with the observed enantioselectivity markedly dependent on the nature of the iminium counterion. Highest yields and enantioselectivity were obtained using iminium bromide ions generated in situ via photoredox catalysis using BrCCl3 and Ru(bpy)3Cl2 (0.5 mol %) and commercially available tetramisole (5 mol %) as the Lewis base catalyst. The scope and limitations of this procedure
Enantioselective isothiourea-catalysed reversible Michael addition of aryl esters to 2-benzylidene malononitriles
作者:Alastair J. Nimmo、Jacqueline Bitai、Claire M. Young、Calum McLaughlin、Alexandra M. Z. Slawin、David B. Cordes、Andrew D. Smith
DOI:10.1039/d3sc02101g
日期:——
translating to stereoisomeric product ratios. Herein, stereoselectivity resulting from an unusual reversible Michael addition of an aryl ester to 2-benzylidene malononitrile electrophiles using an isothiourea as a Lewis base catalyst is demonstrated. Notably, the basicity of the aryloxide component and reactivity of the isothiourea Lewis base both affect the observed product selectivity, with control studies
An asymmetric protocol for the synthesis of novel benzofused ϵ-lactones starting from quinone methides and activated acetic acid esters using chiral isothiourea Lewis base catalysts has been developed.
已经开发了一种不对称方案,用于使用手性异硫脲 Lewis 碱催化剂从醌甲化物和活性乙酸酯合成新型苯并化 ε-内酯。