Phosphine-Catalyzed Synthesis of 1,3-Dioxan-4-ylidenes

Zhu, Xue‐Feng; Henry, Christopher E.; Wang, Jay; Dudding, Travis; Kwon, Ohyun

doi:10.1021/ol050203y

Cited by 145 publications

(63 citation statements)

References 14 publications

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“…[138] Interestingly, Kwon and co-workers showed that the phosphane-catalyzed reaction of allenoates and aldehydes does not give the expected formal [3+2] cycloaddition products, 2,5-dihydrofurans. Depending on the catalyst struc-ture and reaction conditions, 1,3-dioxan-4-ylidenes 91 [139] or 2-pyrones 92 [140] can be prepared with high selectivity (Scheme 32). This change in the reaction pathway is traced to the fate of the intermediate zwitterion XL.…”

Section: Phosphane-catalyzed Cycloadditionsmentioning

confidence: 99%

Lewis Base Catalysis in Organic Synthesis

2008

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The legacy of Gilbert Newton Lewis (1875-1946) pervades the lexicon of chemical bonding and reactivity. The power of his concept of donor-acceptor bonding is evident in the eponymous foundations of electron-pair acceptors (Lewis acids) and donors (Lewis bases). Lewis recognized that acids are not restricted to those substances that contain hydrogen (Brønsted acids), and helped overthrow the "modern cult of the proton". His discovery ushered in the use of Lewis acids as reagents and catalysts for organic reactions. However, in recent years, the recognition that Lewis bases can also serve in this capacity has grown enormously. Most importantly, it has become increasingly apparent that the behavior of Lewis bases as agents for promoting chemical reactions is not merely as an electronic complement of the cognate Lewis acids: in fact Lewis bases are capable of enhancing both the electrophilic and nucleophilic character of molecules to which they are bound. This diversity of behavior leads to a remarkable versatility for the catalysis of reactions by Lewis bases.

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Section: Phosphane-catalyzed Cycloadditionsmentioning

confidence: 99%

Lewis Base Catalysis in Organic Synthesis

2008

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“…[136] Das Verfahren wurde erfolgreich in den Totalsynthesen von Hirsuten [137] und Hinesol genutzt. [138] Interessanterweise erhielten Kwon und Mitarbeiter bei der phosphankatalysierten Reaktion von Allenoaten mit Aldehyden nicht die erwarteten 2,5-Dihydrofurane als die formalen [3+2]-Cycloadditionsprodukte, sondern es entstanden -je nach Katalysatorstruktur und Reaktionsbedingungenhoch selektiv die 1,3-Dioxan-4-ylidene 91 [139] oder die 2-Pyrone 92 [140] (Schema 32). Diese Abweichung wird auf das intermediäre Zwitterion XL zurückgeführt.…”

Section: Phosphankatalysierte Cycloadditionenunclassified

Lewis‐Base‐Katalyse in der organischen Synthese

2008

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Das Erbe von Gilbert Newton Lewis (1875–1946) ist im Wörterbuch der chemischen Bindung und Reaktivität allgegenwärtig. Die Bedeutung seines Konzepts der Donor‐Akzeptor‐Bindung kommt in den eponymen Grundbegriffen für Elektronenpaarakzeptoren (Lewis‐Säuren) und ‐donoren (Lewis‐Basen) zum Ausdruck. Lewis erkannte, dass Säuren nicht automatisch Wasserstoff enthalten müssen (Brønsted‐Säuren) und trug so zum Sturz des “modernen Protonenkults” bei. Seine Entdeckung läutete zunächst die Entwicklung von Lewis‐Säuren als Reagentien und Katalysatoren für organische Reaktionen ein, in den letzten Jahren wurde aber offensichtlich, dass für diese Zwecke auch Lewis‐Basen eingesetzt werden können. Bezüglich der Beschleunigung chemischer Reaktionen ergänzen Lewis‐Basen die entsprechenden Lewis‐Säuren nicht nur elektronisch: Tatsächlich können Lewis‐Basen die Elektrophilie wie auch die Nucleophilie der Verbindungen verstärken, an die sie gebunden werden. Diese unterschiedliche Reaktivität resultiert in einer bemerkenswerten Vielfalt Lewis‐Base‐katalysierter Reaktionen.

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“…Accordingly, a nitrogen-containing Lewis base such as triethylamine (Et 3 N) was also tried, but no reaction occurred under the same conditions (entry 6). Using PBu 3 (50 mol%) as the optimized catalyst, the solvent effects were then explored (entries 1,2,[7][8][9][10][11], all the reactions were carried out below the reflux temperature of the solvent. Compared with THF, toluene, CH 3 CN, DMF, DCM, and CCl 4 , CHCl 3 was the best reaction solvent in which the product 3a was obtained in 66% yield (entry 2).…”

Section: Resultsmentioning

confidence: 99%

“…[5] This motif is also an important structural skeleton found in many natural products and bioactive molecules. [6] Alternatively, allenes could also react with aldehydes to produce dioxanes, pyrones, dihydropyrone, 1,3-dienes, or vinylcyclopropanes, and with ketones to construct dihydrofurans, [7] but there is only one example of galkyl allenates with aryl aldehydes giving tetrahydrofurans, in which the g-methyl or methylene was directly involved in the carbon-carbon bond-forming steps, [7g] rather than the normal [3+2] cycloaddition.…”

Section: Introductionmentioning

confidence: 99%

A Phosphine‐Catalyzed Regioselective [3+2] Cycloaddition of Ethyl 5,5‐Diarylpenta‐2,3,4‐trienoate with Aromatic Aldehydes and α,β‐Unsaturated Carbonyl Compounds

et al. 2014

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Tributylphosphine-catalyzed regioselective [3+2] cycloadditions between ethyl 5,5-diarylpenta-2,3,4-trienoate 1 and various aromatic aldehydes 2 to produce a wide variety of polysubstituted 2,5-dihydrofurans 3, and between 1 and b-unsubstituted a,bunsaturated carbonyl compounds 5 to give polysubstituted cyclopentenes 6 with a quaternary carbon center, are reported. In both cases the reaction partners approach each other via the sterically less hindered orientation to afford the target products in excellent regioselectivity. The reaction mechanism involved first the generation of a zwitterionic intermediate between the butatriene 1 and PBu 3 . For the formation of 2,5-dihydrofurans 3, the preferred cyclization mode encompassed the nucleophilic attack of the a-position of butatriene to the aldehydic carbon of 2, followed by the ring closure between the aldehydic oxygen of 2 and the g-position of butatriene, which is the first report of a normal [3+2] cycloaddition between cumulenes and aldehydes. For the formation of cyclopentenes 6, the reaction involved attack of the g-position of the butatriene to the electron-deficient b-position of the a,b-unsaturated carbonyl compounds 5, followed by the ring closure between the a-position of 5 and the a-position of butatriene, which shows a different regioselectivity to the previously reported [3+2] cycloadditions between butatriene and olefins.

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Phosphine-Catalyzed Synthesis of 1,3-Dioxan-4-ylidenes

Cited by 145 publications

References 14 publications

Lewis Base Catalysis in Organic Synthesis

Lewis Base Catalysis in Organic Synthesis

Lewis‐Base‐Katalyse in der organischen Synthese

A Phosphine‐Catalyzed Regioselective [3+2] Cycloaddition of Ethyl 5,5‐Diarylpenta‐2,3,4‐trienoate with Aromatic Aldehydes and α,β‐Unsaturated Carbonyl Compounds

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