Gold‐Catalyzed Oxidative Cycloadditions to Activate a Quinoline Framework

Huple, Deepak B.; Ghorpade, Satish; Liu, Ru‐Shi

doi:10.1002/chem.201302533

Cited by 43 publications

(27 citation statements)

References 52 publications

(35 reference statements)

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“…[12] Such transformations provide a safe alternative to the use of diazo compounds as carbene precursors. Despite significant achievements in the functionalization of alkynes by this novel strategy, [13] there was no catalytic enantioselective version of the reaction [14] until Liu and co-workers [15] disclosed a single example of the asymmetric intramolecular cyclopropanation of a 1,5-enyne, although unfortunately to afford the cyclopropane as a by-product with only 17 % ee (Scheme 1 a). Herein, we describe a highly diastereo-and enantioselective intramolecular cyclopropanation of 1,6-enynes through gold(I)-catalyzed alkyne oxidation with a chiral phophoramidite ligand.…”

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confidence: 99%

Gold(I)‐Catalyzed Highly Diastereo‐ and Enantioselective Alkyne Oxidation/Cyclopropanation of 1,6‐Enynes

et al. 2014

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A highly enantioselective oxidative cyclopropanation of 1,6-enynes catalyzed by cationic Au(I)/chiral phophoramidite complexes is presented. The new method provides convenient access to densely functionalized bicyclo[3.1.0]hexanes bearing three contiguous quaternary and tertiary stereogenic centers with high enantioselectivity (up to e.r. 98:2). Control experiments suggest that the quinoline moiety of the β-gold vinyloxyquinolinium intermediate in the reaction plays an important role in promoting good enantioselectivity through a transitional auxiliary effect in the transition state.

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confidence: 99%

Gold(I)‐Catalyzed Highly Diastereo‐ and Enantioselective Alkyne Oxidation/Cyclopropanation of 1,6‐Enynes

et al. 2014

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“…In 2013, Liu and co‐workers developed a cascade oxidative cycloaddition of 3, n ‐dien‐1‐ynes ( n =5 or 6) and 8‐alkylquinoline (Scheme ) . This process was viewed as a concerted [3+2] dipolar cycloaddition of the tethered electron‐deficient alkenes with intramolecular α‐carbonyl pyridinium ylide 38 , which was produced by carbon cation capture of the α‐oxo gold carbene 37 by nucleophilic attack of the N atom of 8‐alkylquinoline.…”

Section: Cycloaddition Reactionsmentioning

confidence: 99%

Gold‐Catalyzed Enantioselective Annulations

Zhang

2016

Chemistry A European J

215

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Non-oxidative,regioselective,and convergent access to densely functionalized oxazoles is realized in af unctional-group tolerant manner using alkynyl thioethers.S ulfur-terminated alkynes provideaccess to reactivity previously requiring strong donor-substituted alkynes such as ynamides.Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides. Compared to other heteroatom-substituted alkynes,alkynyl thioethers are remarkably little explored in intermolecular late-transition-metal catalysis,d espite being readily accessed and robust. [1, 2] Ynamides,i nc ontrast, are privileged sub-strates:i np-acid catalysis their donor nature aids metal-alkyne coordination and affords highly polarized electro-philes,t hus providing the high chemo-and regioselectivity required for the discovery of efficient intermolecular reactions (Scheme 1a). [3,4] As the resulting inclusion of ad onor-nitrogen atom limits the utility of the products,r etaining the reactivity profile of these transformations whilst accessing more flexible and readily elaborated substitution patterns would be desirable.T he value of sulfur-substituted compounds [5] coupled with progress in C À Ca nd C-heteroatom bond formation from CÀSbonds, [6] renders alkynyl thioethers appealing alternatives to ynamides.I ndeed the ketenethio-nium pathway (Scheme 1a)f rom alkynyl thioethers has recently been invoked in proton-catalyzed reactions with nitriles [2g,h] and gold-catalyzed reactions with sulfides. [2i] Ynamides enabled the discovery of formal [3+ +2] dipolar cycloadditions with nucleophilic nitrenoids, [7] thus allowing intermolecular access to a-imino gold carbene-type reactivity for heterocycle synthesis (Scheme 1b). [8, 9] Such reactions, which do not depend on ynamides,a re scarce. [8b,h] As trong donor alkyne substituent proved critical in the formation of oxazoles using N-acyl pyridinium N-aminides,aselectron-rich alkynes such as anisole derivatives did not react (Scheme 1b, inset). [8a,b] Oxazoles are valuable synthetic intermediates [10,11] and structural components in bioactive natural products, [12] agrochemicals, [13] ligands, [14] and functional materials. [15] Despite recent advances,asingle modular and convergent route to trisubstituted oxazoles,which provides the structural and functional-group diversity needed across the 2-, 4-, and 5-positions,r emains unrealized. [16] Following our interest in the use of gold catalysis with sulfides [17] we report here on the reactivity of alkynyl thioethers with nucleophilic nitrenoids to prepare oxazoles. Importantly,t he regioselectivity is not consistent with ac on-trolling ketenethionium species.T he sulfur group plays an alternative role in enabling reactivity,t hus proving complementary to donor-enabled approaches. Ther eaction of the alkynyl thioether 1a and aminide 2a (Table 1) showed that conversion into the oxazole 3 was possible at 125 8 8Ci n1 ,2-dichlorobenzene (1,2-DCB;s ...

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“…2-Bromopyridine N-oxide 2e [11c] was similarly effective but degrades on standinga tr oom temperature, leaving 2a as am ore practical choice. Other N-oxides used in alkyne oxidation, such as 8-ethylquinoline N-oxide 2b, [19] were inferiorhere.…”

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confidence: 99%

A Gold Carbene Manifold to Prepare Fused γ‐Lactams by Oxidative Cyclisation of Ynamides

Sánchez-Cantalejo

Priest

Davies

2018

Chemistry A European J

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Gold‐catalysed oxidative cyclisation reactions of ynamides offer great promise in γ‐lactam synthesis but are limited by preferential over‐oxidation to form α‐keto imides. Evaluating the factors that might limit N‐cyclisation pathways led to effective gold‐catalysed conditions that allow access to different fused γ‐lactams on changing the ynamide N‐substituent and accommodate previously incompatible substitution patterns. New and efficient methods for the synthesis of functionalised 3‐aryl indoles and cyclohepta[c]pyrrol‐1‐one derivatives are presented. These conditions illustrate the complementarity of gold catalysis to other metals.

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Gold‐Catalyzed Oxidative Cycloadditions to Activate a Quinoline Framework

Cited by 43 publications

References 52 publications

Gold(I)‐Catalyzed Highly Diastereo‐ and Enantioselective Alkyne Oxidation/Cyclopropanation of 1,6‐Enynes

Gold(I)‐Catalyzed Highly Diastereo‐ and Enantioselective Alkyne Oxidation/Cyclopropanation of 1,6‐Enynes

Gold‐Catalyzed Enantioselective Annulations

A Gold Carbene Manifold to Prepare Fused γ‐Lactams by Oxidative Cyclisation of Ynamides

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