Synthèses de dioxolannes α-iodés

Daubié, Christophe; Bacquet-Einhorn, Cathy; Lelandais, D.

doi:10.1139/v84-264

Cited by 4 publications

(8 citation statements)

References 5 publications

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“…This proved true: after five hours in the presence of two equivalents of ICl, signals at 2.85–2.93 ppm, 3.96 ppm, and 4.36 ppm, in addition to the phenyl protons, were observed, without any evidence of 10 being present. Based on literature reports for α-iodo ketones [21–22], it was clear that the signal at 3.96 ppm corresponded to H-1 in 9 . This was substantiated by a 1 H, 13 C-HSQC experiment, which showed the signal corresponding to C-1 at 6.92 ppm in the 13 C NMR spectrum, upfield from those for C-3 and C-4 (Fig.…”

Section: Resultsmentioning

confidence: 94%

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

Lee

Jones

Nkengbeza

et al. 2019

Beilstein J. Org. Chem.

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An iodine-mediated hydration reaction of alkynes serves as a green alternative to metal-catalyzed procedures. Previous work has shown that this method works well with terminal alkynes on keto-functionalized scaffolds, including 1,3-dicarbonyls and their heteroatom analogues. It was hypothesized that the reaction proceeds through a 5-exo-dig neighboring group participation (NGP) cyclization and an α-iodo intermediate. The work described herein probes the existence of the intermediate through NMR investigations and explores the scope of the hydration process with internal alkynes. The NMR experiments confirm the existence of the α-iodo intermediate, and methodology studies demonstrate that alkyl-capped, asymmetric, internal alkynes undergo a regiospecific hydration, also via the 5-exo-dig NGP pathway.

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Section: Resultsmentioning

confidence: 94%

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

Lee

Jones

Nkengbeza

et al. 2019

Beilstein J. Org. Chem.

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“…Likewise, vinylic ester 5 v and aliphatic ester 5 z underwent CAC mono‐ or bischloro homologation in 60 % yield in the presence of excess reagent. Notably, the aliphatic homologation product 1 m shows regioselectivity opposite to that of analogous halogenation reactions . Furthermore, the cyclopropane trans ‐diester 5 ab furnished the stereoisomerically pure cyclopropanoate 2 q in 61 % yield.…”

Section: Methodsmentioning

confidence: 96%

“…More electron-rich benzoic esters 5rt required the use of more than 1.1 equiv of dianion 4 to furnish the desired products 1i and 2k-m in satisfying yields of 60-76 %( entries 18-21). [17] Furthermore,the cyclopropane trans-diester [18] 5ab furnished the stereoisomerically pure cyclopropanoate 2q in 61 %y ield. Finally,b romopyridine 5u and quinoline 5v furnished the heterocyclic chloroketones 2n-o in 66-80 %yield.…”

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confidence: 99%

“…Besides symmetrical diesters (5c, e and 5o), sterically biased (5p-q)d iesters also underwent as ingle homologation to the expected monochloroketones 2h-j in 82-89 %yield and excellent selectivity even in presence of intentionally added excess reagent (entries [15][16][17]. Besides symmetrical diesters (5c, e and 5o), sterically biased (5p-q)d iesters also underwent as ingle homologation to the expected monochloroketones 2h-j in 82-89 %yield and excellent selectivity even in presence of intentionally added excess reagent (entries [15][16][17].…”

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confidence: 99%

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Mild Homologation of Esters through Continuous Flow Chloroacetate Claisen Reactions

et al. 2018

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The selective chloromethylenation of functionalized esters using chloroacetic acid (CA) and LiHMDS (HMDS = hexamethyldisilazide) in ac ontinuous-flows etup is reported. This Claisen homologation is for the first time extended to bischloromethylenation using dichloroacetic acid (DCA), thus giving access to under-explored a,a'-bis-chloroketones.T he use of flow conditions enables efficient generation and reaction of the unstable chloroacetate dianion intermediates,leading to unprecedented mild and scalable reaction conditions at an economical reagent stoichiometry (À10 8 8C, < 1min, 1.0-2.4 equiv dianion). The clean reaction profiles allows ubsequent use of the unpurified crude products,w hichi sd emonstrated in the synthesis of various heterocycles of broad interest. Furthermore,wereport anovel, catalyst-free substitution of the obtained monochloro ketone products with (hetero)aryl zinc enolates to give valuable 1,4-diketones.Mono-andbis-a-chloroketonesareusefulbis-electrophiles (C À Cl and C = O; compare 1,X= Cl and 2,X= H, Scheme 1), which accounts for their widespread use,p articularly in cyclocondensations to give heterocycles. [1] Such cyclizations of functionalized precursors are cost-economic,a void challenging cross-coupling steps and transition-metal purging, [2,3] thus making novel approaches to pre-functionalized a-chloro [*] M. A. Ganiek,D r. M. V. Ivanova, Prof.

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“…Bemerkenswerterweise weist das CAC‐Produkt 1 m eine zur Chlorierung komplementäre Regioselektivität auf (Nr. 5) . Weiterhin lieferte der trans ‐Cyclopropandiester 5 ab das Cyclopropanoat 2 q stereoisomerenrein in 61 % Ausbeute.…”

Section: Methodsunclassified

Milde Chlorhomologisierung von Estern durch Chloracetat‐Claisen‐Reaktion unter kontinuierlichen Durchflussbedingungen

et al. 2018

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Die selektive Chlormethylierung funktionalisierter Ester mit Chloressigsäure (CE) und LiHMDS (HMDS = Hexamethyldisilazid) in einem kontinuierlich betriebenen Mikroreaktorsystem wird beschrieben. Diese Homologisierungsmethode nachC laisen wird zum ersten Mal auf die bis-Chloromethylierung mit Dichloressigsäure (DCE) angewendet, was einen Zugang zu den weniger untersuchten a,a'-bis-Chlorketonen ermçglicht. Durch das Mikroreaktorsystem kçnnen die unstabilen dianionischen Enolate der Essigsäuren besser erzeugt werden, was zu bisher unerreicht milden und skalierbaren Reaktionsbedingugen und ausgeglichener Reagenzstçchiometrie führt (À10 8 8C, < 1min, 1.0-2.4 ¾quiv.D ianion). Der selektive Reaktionsverlauf machtdie Verwendung der Reaktionsprodukte ohne weitere Aufreinigung mçglich, was anhand der Synthese verschiedener Heterozyklen von allgemeinem Interesse demonstriert wird. Zudem wird eine neuartige,k atalysatorfreie Substitution der Monochlorketone mit (Hetero)arylzinkenolaten beschrieben, die zu wertvollen 1,4-Diketonen führt.Monound bis-a-Chlorketone sind vielseitige bis-Elektrophile (CÀCl und C=O; vergleiche 1,X= Cl und 2,X= H, Schema 1), was deren breite Verwendung, insbesondere zum Aufbau von Heterozyklen durch Cylcokondensationen begründet. [1] Solche Cyclokondensationen sind kosteneffizient und vermeiden zudem potenziell schwierige Kreuzkupplun-Schema 1. Verschiedene Synthesewege zu a-Chlorketonen (1, X = H) und bis-a,a'-Chlorketonen (1, X = Cl). LG = Abgangsgruppe.

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Synthèses de dioxolannes α-iodés

Abstract: Three methods of iodination of cyclic ketals are described. Direct iodination by monoiodine chloride in ether leads to very good yields in monoiodo compounds. A high selectivity is obtained when one of the α-carbon atoms is tertiary.

Cited by 4 publications

References 5 publications

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

Mild Homologation of Esters through Continuous Flow Chloroacetate Claisen Reactions

Milde Chlorhomologisierung von Estern durch Chloracetat‐Claisen‐Reaktion unter kontinuierlichen Durchflussbedingungen

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