Indium(<scp>iii</scp>) triflate-catalysed [4 + 2] benzannulation reactions of o-alkynylbenzaldehydes with enolisable carbonyl compounds: selective synthesis of naphthyl ketones
作者:Karuppusamy Sakthivel、Kannupal Srinivasan
DOI:10.1039/c3ob41439f
日期:——
Indium(III) triflate is found to be an effective catalyst for the benzannulation reactions of o-alkynylbenzaldehydes with enolisable aldehydes, ketones, 1,3-diketones and β-keto esters. The reactions produce naphthyl ketones through ring opening of adducts arising from the inverse electron demand Diels–Alder reactions between in situ generated isochromenylium cations and enols. The main feature of the method is selective formation of naphthyl ketones in a highly regioselective manner without any decarbonylation.
The first transition-metal-free synthesis of 2,3-diarylindenones with tunable selectivity via tandem annulation of 2-alkynylbenzaldehydes with phenols has been developed.
Asymmetric Cascade Annulation Based on Enantioselective Oxa-Diels–Alder Cycloaddition of in Situ Generated Isochromenyliums by Cooperative Binary Catalysis of Pd(OAc)<sub>2</sub> and (<i>S</i>)-Trip
作者:Shu-Yan Yu、Hao Zhang、Yang Gao、Lei Mo、Shaozhong Wang、Zhu-Jun Yao
DOI:10.1021/ja405764p
日期:2013.7.31
An asymmetric cascade annulation between 2-hydroxystyrenes and 2-alkynylbenaldehyes or 1-(2-alkynylphenyl)ketones has been established with good to excellent enantioselectivities (up to >99.5% ee), on the basis of an enantioselective oxa-Diels-Alder cycloaddition of in situ generated metallo-isochromenylium intermediates, by cooperative binary catalysis of Pd(OAc)(2) and (S)-Trip. The developed methodology is workable for a broad spectrum of substrates and shows great efficiency in establishing dense multiple chiral centers including quaternary carbons of variable bridged ring systems. The mechanism study suggests that (S)-Trip plays multiple roles in assembling the reactants and controlling the stereoselectivity.
Visible-Light-Promoted Generation of α-Ketoradicals from Vinyl-bromides and Molecular Oxygen: Synthesis of Indenones and Dihydroindeno[1,2-c]chromenes
作者:Santosh K. Pagire、Peter Kreitmeier、Oliver Reiser
DOI:10.1002/anie.201702953
日期:2017.8.28
can be converted by a visible‐light‐mediated photocascade reaction with molecularoxygen into either indenones or dihydroindeno[1,2‐c]chromenes. The one‐step process features key photochemical steps, that is, the initial activation of vinyl bromides through energy transfer to give α‐ketoradicals in a reaction with molecularoxygen, followed by α‐oxidation of an arene moiety by 6‐π electrocyclization
Neighbouring Formyl Group Assisted Oxidation of o-Alkynylarenecarbaldehydes by an Iodine/Water System
作者:Karuppusamy Sakthivel、Kannupal Srinivasan
DOI:10.1002/ejoc.201001746
日期:2011.5
The oxidation of o-alkynylarenecarbaldehydes into tricarbonyl compounds by an iodine/watersystem is described. The reaction takes place via isochromenol intermediates formed by intramolecular assistance of the formylgroup. The procedure was applied to various o-alkynylarenecarbaldehydes to afford the corresponding products in good to excellent yields.