One-Pot Homolytic Aromatic Substitutions/HWE Olefinations under Microwave Conditions for the Formation of a Small Oxindole Library

Teichert, Antje; Jantos, Katja; Harms, Klaus; Studer, Armido

doi:10.1021/ol048759t

Cited by 125 publications

(47 citation statements)

References 15 publications

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“…For example, irradiation of alkoxy- A. Studer and L. Tebben Reviews 5052 www.angewandte.org amines of type 99 with microwaves for two minutes in DMF provided the products of a homolytic aromatic substitution (100), which were then subjected in a one-pot process to a Horner-Wadsworth-Emmons (HWE) olefination to finally give biologically interesting oxindoles of type 101 in moderate to good overall yield. [210] The final process was also conducted efficiently under irradiation with microwaves.…”

Section: Alkoxyamine Additions To Various Radical Acceptorsmentioning

confidence: 99%

Nitroxides: Applications in Synthesis and in Polymer Chemistry

2011

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This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.

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Section: Alkoxyamine Additions To Various Radical Acceptorsmentioning

confidence: 99%

Nitroxides: Applications in Synthesis and in Polymer Chemistry

2011

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“…[88] Microwave induced nitroxide cleavage was employed to initiate the cyclisation process, and a range of aryl aldehydes were then employed in the HWE olefination, Scheme 29. www.eurjoc.orgwhich was also accelerated using MW irradiation. Although the radical precursors 128 have to be synthesised in advance, the cyclisation process does not require an α-halogenated aniline as is often the case.…”

Section: Telescoped and Tandem Hwe Approaches To 3-alkenyl-oxindolesmentioning

confidence: 99%

3‐Alkenyl‐oxindoles: Natural Products, Pharmaceuticals, and Recent Synthetic Advances in Tandem/Telescoped Approaches

2010

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The structures and biological activities of naturally occurring 3‐alkenyl‐oxindoles are reviewed. Important man‐made3‐alkenyl‐oxindoles are covered, particularly those with pharmaceutical applications such as sunitinib (SU11248), the orally active receptor tyrosine kinase inhibitor marketed by Pfizer as Sutent®. Traditional synthetic approaches to 3‐alkenyl‐oxindoles are summarised and then recently developed tandem/telescoped synthetic routes are described.

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“…As previously reported alkoxyamine additions can be conducted efficiently under microwave irradiation. 3,5,[10][11][12] Indeed, reaction under microwave irradiation at 180°C in DMF (sealed tube) for just 10 minutes provided 4a in an improved yield (55%, Scheme 3). Even under these harsh conditions, addition occurred exclusively at the terminal double bond.…”

Section: Figure 1 Various Alkoxyamines Usedmentioning

confidence: 99%

“…4 We also presented initial results on sequential radical carboaminoxylation/ionic HornerWadsworth-Emmons reactions. 5 These alkoxyamine additions and isomerizations are controlled by the Persistent Radical Effect (PRE). 6,7 Herein we present first results on radical carboaminoxylation with subsequent Pd-catalyzed Trost-Tsuji allylation 8 for the construction of five-and six-membered carbocycles.…”

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Radical Carboaminoxylation with Subsequent Pd-Catalyzed Intramolecular Allylation for the Construction of Five- and Six-Membered Carbocycles

Schulte¹,

Studer²

2006

Synthesis

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Regioselective intermolecular radical carboaminoxylation using various alkoxyamines are presented. These environmentally benign tin-free radical additions can either be performed under microwave conditions at 180°C or by using conventional heating at 125°C. Intermolecular Trost-Tsuji allylation of the carboaminoxylation products provide five-and six-membered carbocycles in moderate to good yields. The radical addition/Pd-catalyzed intramolecular allylation can be performed as one-pot process.About five years ago, we introduced the use of TEMPOderived alkoxyamines (TEMPO = 2,2,6,6-tetramethylpiperidin-N-oxyl radical) as C-radical precursors for environmentally benign radical cyclization reactions. 1,2 Since that initial report, this chemistry has been extended to intermolecular radical alkoxyamine additions which we call radical carboaminoxylations (Scheme 1). 3 Moreover, we have shown that if TEMPO as nitroxide component in the alkoxyamine is replaced by a sterically highly demanding nitroxide, alkoxyamine additions and isomerizations occur far more efficiently. 4 We also presented initial results on sequential radical carboaminoxylation/ionic HornerWadsworth-Emmons reactions. 5 These alkoxyamine additions and isomerizations are controlled by the Persistent Radical Effect (PRE). 6,7 Herein we present first results on radical carboaminoxylation with subsequent Pd-catalyzed Trost-Tsuji allylation 8 for the construction of five-and six-membered carbocycles. 9Scheme 1 Intermolecular alkoxyamine addition using TEMPO as nitroxide component.The radical acceptors 1a-c were readily prepared in high yield from the corresponding aldehydes under Reformatsky conditions using Zn and allyl bromide with subsequent acylation (Scheme 2). The Grignard reagent prepared from bromobut-3-ene was used for the synthesis of allyl acetate 1d.Radical carboaminoxylations were studied with alkoxyamines 2 and 3a,3b (Figure 1), which were prepared according to published procedures from the corresponding nitroxides in excellent yields (81-97%, see experimental part). 4 Figure 1 Various alkoxyamines used.Reaction of TEMPO-derived alkoxyamine 2 with olefin 1a (5 equiv) in DMF (0.07 M) at 135°C for 3 days afforded adduct 4a in 30% yield as a 1:1 mixture of diastereoisomers. Importantly, radical addition occurs highly regioselectively at the terminally unsubstituted double bond. The allyl acetate moiety necessary for the planned transition metal mediated cyclization remains untouched. Moreover, products deriving from malonyl radical addition with subsequent 5-endo cyclization and TEMPOtrapping were not identified. Importantly, this radical addition reaction can be conducted without the use of any radical initiator. As previously reported alkoxyamine additions can be conducted efficiently under microwave irradiation. 3,5,10-12 Indeed, reaction under microwave irradiation at 180°C in DMF (sealed tube) for just 10 minutes provided 4a in an improved yield (55%, Scheme 3). R 2 R 1 O N R 3 ∆ R 3 R 1 R 2 O N Scheme 2 Synthesis of the radical acceptors 1a-d...

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One-Pot Homolytic Aromatic Substitutions/HWE Olefinations under Microwave Conditions for the Formation of a Small Oxindole Library

Cited by 125 publications

References 15 publications

Nitroxides: Applications in Synthesis and in Polymer Chemistry

Nitroxides: Applications in Synthesis and in Polymer Chemistry

3‐Alkenyl‐oxindoles: Natural Products, Pharmaceuticals, and Recent Synthetic Advances in Tandem/Telescoped Approaches

Radical Carboaminoxylation with Subsequent Pd-Catalyzed Intramolecular Allylation for the Construction of Five- and Six-Membered Carbocycles

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