Name: preparation and use of carbonyl-decorated carbenes in the activation of white phosphorus
Uploaded: 2014-10-03T15:00:00.000+00:00
Duration: 14 min 7 s
Description: Watch this Scientific Journal Video about Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus at JoVE.com

We are grateful to the Research Corporation for Science Advancement (20092), the National Science Foundation (CHE-1362140), and Texas State University for their generous support.

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Commun. 46, 4288-4290 (2010).</li><li>Lugan, N., Lavigne, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reprogramming+of+a+Malonic+N-Heterocyclic+Carbene:+A+Simple+Backbone+Modification+with+Dramatic+Consequences+on+the+Ligand's+Donor+Properties.">Reprogramming of a Malonic N-Heterocyclic Carbene: A Simple Backbone Modification with Dramatic Consequences on the Ligand's Donor Properties.</a> Eur. J. Inorg. Chem. 3, 361-365 (2010).</li><li>Blake, G. A., Moerdyk, J. P., Bielawski, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+the+Electronic+Properties+of+Carbenes:+A+Systematic+Comparison+of+Neighboring+Amino+versus+Amido+Groups.">Tuning the Electronic Properties of Carbenes: A Systematic Comparison of Neighboring Amino versus Amido Groups.</a> Organometallics. 31, 3373-3378 (2012).</li><li>Martin, C. D., Weinstein, C. M., Moore, C. E., Rheingold, A. L., Bertrand, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploring+the+reactivity+of+white+phosphorus+with+electrophilic+carbenes:+synthesis+of+a+P4+cage+and+P8+clusters.">Exploring the reactivity of white phosphorus with electrophilic carbenes: synthesis of a P4 cage and P8 clusters.</a> Chem. Commun. 49, 4486-4488 (2013).</li></ol>

The authors have nothing to disclose.

ويرد إجراءات واضحة لتوليد carbenes زينت الكربونيل وتطبيقها في تفعيل الفسفور الأبيض هنا. الخطوات الحاسمة في البروتوكول لتوليف وcarbenes هي: (أ) التأكد من جميع المذيبات المجففة بشكل صحيح قبل استخدامها، (ب) التأكد من يتم إضافة حمض الكلوريد إلى formamidine ببطء شديد، (ج) إذا كان هو Celite ...

ظهرت carbenes مستقر كما الكواشف في كل مكان في الحفز المتجانس 1، 2 organocatalysis، وعلوم المواد 3،4، ومؤخرا الكيمياء مجموعة الرئيسي 5-9. في سياق هذا الأخير، وقد تم مؤخرا استخدام carbenes مستقر في تفعيل وfunctionalization الفوسفور الأبيض (P 4) 5-9. أصبحت القدرة على تحويل مباشرة P 4 إلى مركبات الفوسفور العضوية هدف البحث موضعي في محاولة لتطوير أساليب &quot;خضراء&quot; أن الالتفاف على استخدام السلائف الفوسفور المكلورة أو oxychlorinated. على الرغم من استخدامها على نطاق واسع، وإعداد ومناولة carbenes والمركبات المتفاعلة مثل P 4 يمكن أن يكون مهمة شاقة. لهذا السبب، فإننا قد كتبت هذه المخطوطة لتوفير بروتوكول واضح ودقيق من شأنها أن تسمح الكيميائيين الاصطناعية من جميع مستويات المهارة لتجميع والتلاعب اثنين ج مستقرة فريدة جداarbenes. بالإضافة إلى ذلك، وتفعيل P 4 باستخدام carbenes وصف مفصل. نحن هنا بالتفصيل بروتوكول لتركيب اثنين الإلكترون نقص الكربونيل carbenes زينت. لقد اخترنا هذه carbenes لأنها تختلف فقط في ممتلكاتهم بالإلكترونات، وليس المعلمات الخاصة بهم الفراغية، مما يجعلها مثالية لدراسة آثار الالكترونيات carbene على التفاعل. ويتمثل أهمية الالكترونيات carbene فيما يتعلق التفاعل من قبل اثنين من مركبات مماثلة للصيغة العامة carbene P-2 -carbene التي تم الإبلاغ عنها من قبل برتراند وروبنسون 5،8. ويدعم برتراند P 2 مشتق من قبل اثنين من دوري carbene ألكيل الأمينية (CAAC) بروابط، و هو هيكليا، photophysically، ومختلفة electrochemically من مجمع روبنسون وهو جزء P 2 تساندها طائرتان carbenes N-الحلقية غير المتجانسة (NHCs) 5،8. في الواقع، P برتراند 2 </يتميز الفرعية&gt; مجمع كمادة صلبة الأصفر الذي يتميز carbene إلى الفوسفور روابط مزدوجة في الحالة الصلبة، في حين أن مشتقات ذكرت روبنسون هو الأحمر الداكن الصلبة التي تحتوي NHC → P السندات صيغة المجرور. هذا الاختلاف الهيكلي كما يتجلى هذا electrochemically أن مجمع روبنسون يحتوي على المزيد من مراكز الفوسفور الإلكترون الغنية التي يمكن أن تخضع للعكس الأكسدة 1- أو 2 الإلكترون على النقيض من مجمع برتراند التي يمكن أن تخضع إلا الأكسدة عكسها واحدة 10. بناء على الدراسات المذكورة أعلاه، أصبحنا مهتمين في دراسة تفعيل P 4 باستخدام ثنائي الأميد وmonoamidoamino carbenes بالإلكترونات للغاية لتحديد ما إذا كان يمكن إعداد المتآصلة استقرت carbene جديدة من الفوسفور. ركزنا على diamidocarbene (DAC) 1، وcarbene monoamidoamino (MAAC) 2 التي تختلف فقط في electrophilicities كل منهم في interrogأكل ما هو الدور الذي تلعبه في الالكترونيات carbene P 4 التنشيط. ومن المثير للاهتمام عند استخدام DAC أكثر بالإلكترونات، وتريس (phosphaalkenyl) phosphane (3) يمكن أن تكون معزولة كمنتج حصري، بينما عند استخدام MAAC، واستقرت carbene P 8 متآصل (4) ويمكن الحصول على 11. نحن التحقيق أيضا آلية لتشكيل (4)، ووجدت أن يتم تشكيلها عن طريق [2 + 2] cylcoaddition dimerization رد فعل diphosphene عابرة. تم تأكيد وجود هذا diphosphene من خلال محاصرة مع 2،3-ثنائي ميثيل-1،3-بوتادين لتأثيث [4 + 2] الاضافه الحلقيه 5 معقد إضافي. يوصف بروتوكول لتوليف هذه carbenes زينت الكربونيل وعلى المقابلة P 4 مركبات تنشيط هنا.

<table><tbody><tr><td>2,4,6-Trimethylaniline</td><td>Alfa Aesar</td><td>AAA13049-0E</td><td>98%</td></tr><tr><td>Triethylorthoformate</td><td>Alfa Aesar</td><td>AAA13587</td><td>98%</td></tr><tr><td>Dimethylmalonyl dichloride</td><td>TCI</td><td>D2723</td><td>&gt;98%</td></tr><tr><td>3-Chloro-pivaloyl chloride</td><td>Aldrich</td><td>225703-25G</td><td>98%</td></tr><tr><td>Triethylamine</td><td>Alfa Aesar</td><td>AAA12646</td><td>Stored over dried, activated 3 &amp;Aring; molecular sieves</td></tr><tr><td>Celite&amp;trade; 545</td><td>EMD</td><td>CX0574-3D</td><td>Oven-dried at 180 &amp;deg;C for a minimum of 12 hr</td></tr><tr><td>Sodium hexamethyldisilazide</td><td>Across</td><td>200014-462</td><td>95+%</td></tr><tr><td>2,3-Dimethyl-1,3-butadiene</td><td>Alfa Aesar</td><td>AAAL04207-09</td><td>98%</td></tr><tr><td>Dichloromethane</td><td>EMD</td><td>DX0835-5</td><td>Purified through solvent purification system, or standard methods</td></tr><tr><td>Tetrahydrofuran</td><td>Mallinckrodt</td><td>8498-09</td><td>Purified through solvent purification system, or standard methods</td></tr><tr><td>Hexanes</td><td>EMD</td><td>HX0299-3</td><td>Purified through solvent purification system, or standard methods</td></tr><tr><td>Benzene</td><td>EMD</td><td>BX0220-5</td><td>Purified through solvent purification system, or standard methods</td></tr><tr><td>Toluene</td><td>BDH</td><td>1151-19L</td><td>Purified through solvent purification system, or standard methods</td></tr><tr><td>White phosphorus</td><td>Generously donated from the Texas A&amp;amp;M chemistry store room.</td><td></td><td>Purified through sublimation and transferred directly into a glovebox while under vacuum in the sublimator</td></tr></tbody></table>

preparation and use of carbonyl-decorated carbenes in the activation of white phosphorus

هنا نقدم بروتوكول لتركيب اثنين متميزة carbenes زينت الكربونيل. كلا carbenes يمكن إعدادها باستخدام إجراءات متطابقة تقريبا بكميات نطاق متعددة غرام. الهدف من هذا المخطوط هو بوضوح بالتفصيل كيفية التعامل مع وإعداد هذه carbenes فريد بحيث الكيميائي الاصطناعية في أي مستوى المهارات يمكن أن تعمل معهم. وcarbenes المذكورين هم diamidocarbene (DAC، carbene 1) وmonoamidoaminocarbene (MAAC 2). هذه carbenes ودرجة عالية من نقص الإلكترون وعلى هذا النحو ملامح العرض التفاعلية التي هي شاذة من أكثر carbenes N-الحلقية غير المتجانسة التقليدية. بالإضافة إلى ذلك، هذه carbenes اثنين فقط تختلف في طابعها بالإلكترونات وليس المعلمات الخاصة بهم الفراغية، مما يجعلها مثالية لدراسة كيفية تأثير carbene الالكترونيات التفاعل. لإثبات هذه الظاهرة، نحن تصف أيضا تفعيل الفوسفور الأبيض (P 4) استخدام هذه carbenes. اعتمادا على carbenالبريد المستخدمة، واثنين من المركبات المحتوية على الفوسفور مختلفة جدا يمكن أن تكون معزولة. عند استخدام DAC 1، وتريس (phosphaalkenyl) phosphane يمكن عزل كمنتج حصري. لكن اللافت للنظر، عندما MAAC 2 يضاف إلى P 4 تحت ظروف التفاعل متطابقة، يتم عزل والمدعومة carbene غير متوقع P 8 متآصل من الفوسفور حصرا. وتظهر الدراسات أن هذه الآلية المدعومة carbene P 8 أشكال متآصل عبر [2 + 2] الاضافه الحلقيه dimerization من diphosphene عابرة الذي حوصر من قبل العلاج مع 2،3-ثنائي ميثيل-1،3-بوتادين.

القدرة على عزل تريس (phosphaalkenyl) phosphane مثل 3 أو -allotrope P 8 (4) من الفسفور الأبيض تعتمد على استخدام وسيلة carbene بالإلكترونات لتفعيل P 4 رباعي الوجوه 11،16. لذا، فمن الأهمية بمكان لإعداد carbenes مع تعزيز π حموضة المعدة، وبالتالي electrophilicity الشكل 2...

Watch this Scientific Journal Video about Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus at JoVE.com

Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

إعداد واستخدام Carbenes الكربونيل زينت في تفعيل الفسفور الأبيض

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures ...

preparation-use-carbonyl-decorated-carbenes-activation-white

Universidad San Sebastian

Research

JoVE Journal

Chemistry

13.6K Views.  Texas State University. Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

Video: Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Mizoroki-هيك ردود الفعل عبر اقتران يحفزه ديكلورو {مكرر [1،1 &#39;،&#39;&#39; 1 - (phosphinetriyl) tripiperidine]} البلاديوم تحت ظروف التفاعل معتدل

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

عكس التجميعي بوساطة Microemulsion من الواحد من المعدن ومتعلق بنظام المعدنين في وقت مبكر الانتقال المعادن كربيد ونتريد النانوية

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Preparation of Carbon Nanosheets at Room Temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into defined aggregates in aqueous media and at the air-water interface. In the aggregated state, the oligoynes can then be carbonized under mild conditions while preserving the morphology and the embedded chemical functionalization. This novel approach provides direct access to functionalized carbon nanomaterials. In this article, we present a synthetic approach that allows us to prepare hexayne carboxylate amphiphiles as carbon-rich siblings of typical fatty acid esters through a series of repeated bromination and Negishi-type cross-coupling reactions. The obtained compounds are designed to self-assemble into monolayers at the air-water interface, and we show how this can be achieved in a Langmuir trough. Thus, compression of the molecules at the air-water interface triggers the film formation and leads to a densely packed layer of the molecules. The complete carbonization of the films at the air-water interface is then accomplished by cross-linking of the hexayne layer at room temperature, using UV irradiation as a mild external stimulus. The changes in the layer during this process can be monitored with the help of infrared reflection-absorption spectroscopy and Brewster angle microscopy. Moreover, a transfer of the carbonized films onto solid substrates by the Langmuir-Blodgett technique has enabled us to prove that they were carbon nanosheets with lateral dimensions on the order of centimeters.

We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

إعداد Nanosheets الكربون في درجة حرارة الغرفة

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

البلاديوم<em&gt; N</em&gt; مجمعات كربينية هيتروكليكليك: توليف من أملاح بنزيميدازوليوم والنشاط الحفاز في التفاعلات تشكيل السندات الكربون الكربون

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable low-valent-phosphorus-containing compound acts as a useful P+ transfer agent. Unlike traditional methods employed to access low-coordinate phosphorus species which usually require pyrophoric phosphorus-containing precursors (white phosphorus, Tris(trimethylsilyl)phosphine, etc.), or harsh reducing agents (alkali metals, potassium graphite, etc.), the current approach does not involve pyrophoric or explosive reagents and can be done on large scales (&#62;20 g) in excellent yields by undergraduates with basic air-free synthetic training. The bromide counter ion is readily exchanged with other anions such as tetraphenyl borate (described herein) using typical salt metathesis reagents to obtain materials with desired properties and reactivities. The versatility of this P+ transfer approach is exemplified by the reactions of these triphosphenium precursors with an N-heterocyclic carbene and an anionic bisphosphine, each of which readily displace the neutral bisphosphine to give an NHC-stabilized phosphorus(I) cation and a phosphorus(I) containing zwitterion, respectively.

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

The synthesis of a triphosphenium bromide salt is described and its use as a P+ transfer agent is outlined by reactions with an N-heterocyclic carbene and an anionic bisphosphine, yielding an NHC-stabilized P(I) cation and a P(I) containing zwitterion, respectively.

إعداد والتفاعلية من Triphosphenium بروميد الملح: والمصدر مريحة ومستقرة من الفوسفور (I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

تحقيق ضغوط معتدلة في سفن مختومة باستخدام الثلج الجاف كمصدر2 CO الصلبة

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals

Protocols for the isolation of the commonly employed cyclic (alkyl)(amino) carbene (CAAC) and N-heterocyclic carbene (NHC) are reported. Furthermore, the synthesis of their mixed CAAC&#8211;NHC &#8220;Wanzlick&#8221; dimer and the synthesis of the related stable organic &#8220;olefin&#8221; radical are presented. The main goal of this manuscript is to give a detailed and general protocol for the synthetic chemist of any skill level on how to prepare free heterocyclic carbenes by deprotonation using filter cannulas. Due to the air-sensitivity of the synthesized compounds, all experiments are performed under inert atmosphere using either Schlenk technique or a dinitrogen filled glovebox. Controlling Wanzlick&#8217;s equilibrium (i.e., the dimerization of free carbenes), is a crucial requirement for the application of free carbenes in coordination chemistry or organic synthesis. Thus, we elaborate on the specific electronic and steric requirements favoring the formation of dimers, heterodimers, or monomers. We will show how proton catalysis allows for the formation of dimers, and how the electronic structure of carbenes and their dimers affects the reactivity with either moisture or air. The structural identity of the reported compounds is discussed based on their NMR spectra.

We present protocols for the isolation of stable heterocyclic carbenes. The synthesis of a cyclic (alkyl)(amino) carbene (CAAC) and an N-heterocyclic carbene (NHC) is demonstrated using filter cannulas and Schlenk technique. We furthermore present the synthesis of the related oxygen-sensitive, electron-rich mixed &#8220;Wanzlick dimer&#8221; and the reduced stable organic radical.

عزل كاربينيس الحرة، Dimers مختلطة والجذور العضوية

Protocols for the isolation of the commonly employed cyclic (alkyl)(amino) carbene (CAAC) and N-heterocyclic carbene (NHC) are reported. Furthermore, the ...

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

[(DPEPhos) (bcp) Cu] PF6: A العامة والمطبقة علي نطاق واسع محفز فوتوريدوكس المستندة إلى النحاس

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the ...

Introduction to Catalysis

Source: Laboratory of Dr. Ryan Richards &#8212; Colorado School of Mines
Catalysis is among the most important fields of modern technology and presently accounts for approximately 35% of the gross domestic product (GDP) and sustenance of approximately 33% of the global population through fertilizers produced via the Haber process.1 Catalysts are systems that facilitate chemical reactions by lowering the activation energy and influencing the selectivity. Catalysis will be a central technology in addressing the energy and environmental challenges of modern times.

Catalysis: Homogeneous and Heterogeneous Catalysts

مقدمة في التحفيز

Source: Laboratory of Dr. Ryan Richards &#8212; Colorado School of Mines
Catalysis is among the most important fields of modern technology and presently ...

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Organic Chemistry

Aldehydes and Ketones to Alkenes: Wittig Reaction Overview

The Wittig reaction is the conversion of carbonyl compounds-aldehydes and ketones-to alkenes using phosphorus ylides, or the Wittig reagent. The reaction was pioneered by Prof. Georg Wittig, for which he was awarded the Nobel Prize in Chemistry.
<img alt="Wittig reaction mechanism; equation diagram illustrating carbonyl to alkene conversion process." src="/files/ftp_upload/12335/12335_PT_Figure_1.svg" style="text-align: center; height: 75px;" data-altupdatedat="1747908711000" data-alt="Figure1">
Phosphorus ylide is a neutral molecule containing a negatively charged carbon directly bonded to a positively charged phosphorus atom. The molecule is stabilized by resonance.
<img alt="Wittig reaction mechanism diagram with phosphonium ylide resonance forms." src="/files/ftp_upload/12335/12335_PT_Figure_2.svg" style="text-align: center; height: 75px;" data-altupdatedat="1747908711000" data-alt="Figure2"> 
The Wittig reagents are synthesized from unhindered alkyl halides in two steps. At first, the alkyl halide undergoes an SN2 attack by a triphenylphosphine molecule generating a phosphonium salt. Next, in the presence of a strong base such as butyllithium, sodium hydride, or sodium amide, the salt undergoes deprotonation of the weakly acidic α hydrogen, producing the carbanionic ylide nucleophile.
<img alt="Wittig reaction mechanism; SN2 nucleophilic substitution; chemical reaction diagram; organic synthesis." src="/files/ftp_upload/12335/12335_PT_Figure_3.svg" style="text-align: center; height: 75px;" data-altupdatedat="1747908711000" data-alt="Figure3">
Wittig reactions are regioselective, as the new C＝C bond is formed explicitly at the carbonyl position. The stereoselectivity depends on the nature of the phosphorus ylide. Ylides with electron-withdrawing groups, such as carbonyl or aromatic rings that are stabilized by additional resonance structure, predominantly generate E alkenes. Alternatively, Wittig reagents with simple alkyl groups primarily form Z alkenes.
<img alt="Wittig reaction equation; diagram shows reactants and formation of E/Z alkenes via phosphonium ylides." src="/files/ftp_upload/12335/12335_PT_Figure_4.svg" style="text-align: center; height: 200px;" data-altupdatedat="1747908711000" data-alt="Figure4">
The yield of Wittig reactions is influenced by steric crowding around the carbonyl group. Ketones that are sterically more hindered give poor yields compared to aldehydes. A variation of the Wittig reaction is the Horner–Wadsworth–Emmons reaction that involves a phosphonate ester reagent producing the E alkene as the major product.
<img alt="Wittig reaction mechanism, chemical equation, illustrating phosphorus ylide for alkene synthesis." src="/files/ftp_upload/12335/12335_PT_Figure_5.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure5">

الألدهيدات والكيتونات إلى الألكينات: نظرة عامة على رد فعل Wittig

The Wittig reaction is the conversion of carbonyl compounds-aldehydes and ketones-to alkenes using phosphorus ylides, or the Wittig reagent. The reaction ...

إعداد واستخدام Carbenes الكربونيل زينت في تفعيل الفسفور الأبيض

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Mizoroki-هيك ردود الفعل عبر اقتران يحفزه ديكلورو {مكرر [1،1 '،'' 1 - (phosphinetriyl) tripiperidine]} البلاديوم تحت ظروف التفاعل معتدل

عكس التجميعي بوساطة Microemulsion من الواحد من المعدن ومتعلق بنظام المعدنين في وقت مبكر الانتقال المعادن كربيد ونتريد النانوية

إعداد Nanosheets الكربون في درجة حرارة الغرفة

البلاديوم

إعداد والتفاعلية من Triphosphenium بروميد الملح: والمصدر مريحة ومستقرة من الفوسفور (I)

تحقيق ضغوط معتدلة في سفن مختومة باستخدام الثلج الجاف كمصدر₂ CO الصلبة

عزل كاربينيس الحرة، Dimers مختلطة والجذور العضوية

[(DPEPhos) (bcp) Cu] PF₆: A العامة والمطبقة علي نطاق واسع محفز فوتوريدوكس المستندة إلى النحاس

مقدمة في التحفيز

الألدهيدات والكيتونات إلى الألكينات: نظرة عامة على رد فعل Wittig