Name: facile preparation of (2z,4e)-dienamides by the olefination of electron-deficient alkenes with allyl acetate
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Dikkat: Kullanmadan önce lütfen ilgili tüm malzeme güvenlik bilgi formlarına (MSDS) başvurun. Tüm çapraz bağlanma reaksiyonları, kapalı bir argon atmosferi altında (1 atm) şişelerde yapılmalıdır. 1. Allyl Asetat ile Akrilamidlerin Olefinasyonu ile Butadienlerin Hazırlanması <ol><li> Uyumlu bir manyetik karıştırma çubuğuna sahip vidalı kapaklı bir şişeyi (8 mL) 120 ° C&#39;de fırında 2 saatten fazla kurutun. Kullanmadan önce ateşli flakonu üfleyerek oda sıcaklığına soğutun. </li><li> Analitik bir balans kullanın ve 3.7 mg (~ 3 mol%, 0.005 mmol) [Ru ( p- simen) Cl2] 2 (kahverengi toz) ve 13.7 mg (% 20 mol, 0.04 mmol) AgSbF6 Katı) yukarıdaki reaksiyon şişesine ilave edin. NOT: Bu yeni bir metodolojidir, çapraz kuplaj reaksiyonları atık oluşumunu azaltmak için konsept ispatı için küçük bir ölçekte yapılmıştır. AgSbF 6 , bir klorürü oluşturmak üzere klorürü soyabilen bir katkı maddesi olarak kullanılır.Elektrofilik CH bağ aktivasyonu için katyonik rutenyum kompleksi 13 . Ag2C03 gibi diğer gümüş tuzları da test edilmiştir, ancak ürün saptanmamıştır. Katalizörün ağırlığı ([Ru ( p- simen) Cl2] 2 ) çok doğru değildir ve 3.4-3.9 mg aralığındadır. </li><li> Reaksiyon şişesine 1 mL kuru 1,2-dikloroetan ilave edin. NOT: Çözücü miktarı esnektir-1 mL 1,2-dikloroetan, çapraz bağlanma reaksiyonu için minimum hacim hacmini karşılamak için yeterlidir. Bununla birlikte, bu ölçeğin reaksiyonu için biraz daha (~ 0.1 mL) çözücü de izin verilir. 1,2-dikloroetan, kullanımdan önce 3-A&#39;lik bir moleküler elek üzerinde kurutulmuştur. </li><li> Analitik bir balans kullanın ve yukarıdaki reaksiyon şişesine akrilamit (0,2 mmol, 1.0 eşdeğer katı veya yağ) ekleyin. </li><li> 43 μL (0.4 mmol, 2.0 eşdeğer) allil asetat (renksiz bir sıvı) eklemek için bir mikro-şırınga kullanın. <br/&gt; NOT: Burada, akrilamidin homo-eşlenmesini engellemek ve akrilamidin tamamen dönüştürülmesini sağlamak için aşırı miktarda allil asetata ihtiyaç duyulmaktadır. Daha az alil asetat (1.5 eşdeğer) eklendiğinde, ürün verimi düşer. Daha fazla alil asetat (3.0 eşdeğer) ilavesi, verimi daha da iyileştiremez. Uygulamada, allil asetatın homo-birleşimi gözlemlenmemiştir ve kalan alil asetat geri kazanılabilir. </li><li> Reaksiyon şişesini argon gazı ile hafifçe üfleyin ve şişeyi mümkün olan en kısa sürede uyumlu bir vidalı kapakla örtün. NOT: Flakon mümkün olduğunca çabuk bir vidalı kapakla örtülmelidir çünkü çapraz bağlanma reaksiyonu için atıl bir atmosfer önemlidir. Yukarıdaki protokolü bir eldiven kutusunda yapmak daha iyidir. </li><li> Reaksiyon karışımını ilave bir 5 dakika boyunca oda sıcaklığında karıştırın. </li><li> Reaksiyon şişesini bir yağ banyosu içinde 16-18 saat karıştırarak 110 ° C&#39;ye ısıtın. NOT: Genellikle, koyu kırmızıya renk değişikliği indBu reaksiyonun gerçekleştiği anlamına gelir. </li><li> Şişeyi soğuttuktan sonra, çözeltinin etil asetat: petrol eteri (2: 1 veya 1: 3) karışımlarını kullanarak karışımın bir akrilamit standardıyla karşılaştırılarak reaksiyonun ilerlemesini izlemek için ince tabakalı kromatografi (TLC) plakaları geliştirin . NOT: Başlangıç ​​materyalinin niteliğine bağlı olarak, reaksiyon tamamlanmayabilir. Ürünlerin ve başlangıç ​​malzemelerinin tipik Rf değerleri 0,3-0,7 aralığındadır. Akrilamid başlangıç ​​malzemesi bütadien ürününden daha düşük bir çalışma noktası olarak gözlemlenmiştir. </li><li> Ham ürünü en az DCM&#39;de eritin ve onu petrol eteri ile ıslak bir silika sütunun üzerine koyun. Çapraz bağlayıcı ürün , eluent olarak bir etil asetat: petrol eteri (1: 100 ila 1: 4) karışımı kullanılarak kolon kromatografisiyle ayrılır. <ol><li> Ayrıştırıcıyı ayrı bir şişe içerisinde toplayın, çözücüyü bir döner buharlaştırıcıda buharlaştırın veD 2 saat boyunca yüksek vakum altına yerleştirin. </li><li> NMR spektroskopisi ile karakterizasyon için yaklaşık 20-50 mg ürün elde edin. NOT: Tepkime karışımı doğrudan reaksiyon tamamlandıktan sonra saflaştırma için sütun kromatografisine uygulanmalıdır. </li></ol></li></ol> 2. Dienamidlerin Karakterizasyonu <ol><li> 1 H ve 13 C NMR spektroskopisini kullanarak nihai ürünün saflığını karakterize edin ve değerlendirin 14 . Tipik olarak, karbonil karbonun kimyasal kayması 13 C NMR spektrumunda 170 ppm civarında gözükmektedir. Butadien fonksiyonel grubunun üç sp 2 protonu 6.0 ve 5.6 ppm civarında karakteristik pikler ile temsil edilmektedir. </li><li> Dien ürününün karakteristik karbonil ve CC çift bağ pikini tanımlamak için kızılötesi spektroskopiyi 14 kullanın. </li><li> Ürünün moleküler kütlesini belirleyin ve yüksek tayf kullanılarak kimliğini doğrulayın.Çözünürlüklü Kütle Spektrometresi (HRMS) 14 . </li><li> Katı ürünlerin erime noktalarını belirleyin 14 . </li></ol>

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Zhejiang Eyaleti Doğal Bilimler Vakfı (ZJNSF) (No. LY15B020008), PCSIRT (No. IRT 1231) ve Hangzhou (Çin) Ulusal Doğal Bilim Vakfı (NSFC) (No 21502037, 21373073 ve 21672048) Mali destek Normal Üniversitesi. GZ, Çin&#39;in Zhejiang Eyaletinden bir Qianjiang Edebiyat ödülünü onayladı.

[Ru ( p- simen) Cl2] 2 , CH / CH eşleşme bütadien ürünlerini vermek için hafif reaksiyon koşullarında etkili bir şekilde çalışan mükemmel işlevsel grup toleranslı, ucuz, kolay erişilebilir, hava-kararlı ve yüksek aktif Ru bazlı bir katalizördür. Gümüş tuz AgSbF 6 , aşağıdaki CH bağ aktivasyonu için katyonik bir rutenyum kompleksi üretmek üzere [Ru ( p- simen) Cl2] 2&#39;nin kloridini soyutlayan bir katkı maddesi olarak kullanıldı. Bunun...

Butadienes yaygın olarak görülür ve çoğu doğal ürünler, ilaçlar ve biyoaktif moleküller 1&#39;de bulunur . Kimyagerler, 1,3-butadien 2 , 3 sentezi için etkili, seçici ve pratik bir sentetik metodoloji geliştirmek için yoğun çaba sarfettiler . Son zamanlarda, çift vinilik CH bağ aktivasyonu yoluyla iki alken arasındaki direkt çapraz bağlar geliştirildi, bu da bütadien sentezi için yüksek bir atomik ve basamaklı ekonomi ile etkili bir strateji olduğunu gösteriyor. Bunların arasında, iki alkenin paladyum katalizli çapraz bağlanması dikkat çekti ve alkenil-Pd türü 4 , 5 yoluyla ( E, E ) konfigüre bütadiyenler sağladı. Örneğin, Liu&#39;nun grubu, alkenlerin ve alil asetatın doğrudan çapraz bağlanmasıyla bir Pd-katalizli bütadien sentezi geliştirdi ( Şekil 1 </Strong&gt; ve Denklem 3 ) 4 . Bu arada, alkenler arasındaki fonksiyonel grup yönlendirmeli çapraz bağlama, tamamlayıcı bir yöntem olan 6 olefinik CH siklometalasyon olayından dolayı mükemmel ( Z, E ) -stereoselektifliğe sahip butadienleri sağladı. Bugüne kadar, enolatlar, amidler, esterler ve fosfatlar gibi bazı yönlendirme grupları, bir dizi değerli ve fonksiyonel 1,3-bütadien temin eden alkenler arasındaki çapraz bağlamaya başarıyla dahil edildi. Bununla birlikte, direkt pratik kullanımda sınırlı yönlendirme grupları olduğundan, yönetilen çapraz bağlanma reaksiyonu geliştirilmemiştir. Özellikle, büyük oranda organik ve inorganik atıklar üreten katalitik döngüyü korumak için stoikiometrik bir oksidan miktarı genellikle gereklidir. Elektron zengin alkenleri kuplaj ortak olarak kullanan çok sınırlı örnekler var. Alil asetat ve türevleri derinden iKatalizör çapraz bağlama, elektron zengin arenlerin Friedel-Crafts allilasyonu ve elektron yetersiz arenlerin katalitik CH harekete geçirilmesi ( Şekil 1 ve Denklem 1 ) de dahil olmak üzere güçlü alilasyon ve olefinleştirme reaktifleri olarak organik dönüşümler üzerinde incelenmiştir. Daha yakın bir zamanda, Loh grubu, allyl asetatlar ile elektron yetersiz alkenlerin rodyum (III) katalizli bir CH alilasyonunu geliştirdi ve 1,4-dienler oluşturdu ( Şekil 1 ve Denklem 2 ). Bu arada, Kanai grubu, bir Co (III) katalizörü 9 kullanarak allil alkoller ile dehidratif bir doğrudan CH allilasyonunu bildirdi. İlginçtir ki, Snaddon ve arkadaşları, asiklik esterlerin doğrudan asimetrik α- alalanımı için yeni bir kooperatif kataliz bazlı yöntem açıkladı 10 . Çok yakın bir tarihte, Ackermann grubu birkaç yeni alilasyon örneğini bildirmişti.G ucuz Fe, Co ve Mn katalizörleri 11 içerir . Bu raporlar, alilasyon ve olefinasyon reaksiyonlarında atılımlar yapmış, ancak çift bağ göçü ve zayıf rejim seçiciliği genellikle kaçınılmaz ve kolayca kontrol edilemiyor. Bu nedenle, değerli molekülleri oluşturmak için allil asetatların daha etkin ve seçici reaksiyon modelleri geliştirilmesi halen çok arzu edilmektedir. CH olefinasyon yoluyla yeni 1,3-butadien sentezine olan ilgimiz ile, allil asetatın önce 1,4-dien veren elektron yetersiz alkenlerin yönlendirilmiş allyrasyonuna katılabileceğini varsaydık. Daha sonra, CC çift bağı 7&#39;nin göç izomerleşmesinden sonra, termodinamik açıdan daha kararlı 1,3-butadien oluşabilir; bu, propen gibi elektronca zengin alkenlerin, kuplaj ortağı olarak çapraz bağlanmasıyla elde edilemeyen dien ürününün oluşturulmasıyla oluşabilir 6 . Burada ucuz bir Ru (III) katalizli olefinik CH bağ olefinatiN, ( Z, E ) -butadienlerin ( Şekil 1 ve Denklem 4 ) oluşturulması için yeni bir sentetik yol açan herhangi bir oksidan yokluğunda allil asetatlarla akrilamid&#39;lerin birleşmesidir 13 .

<table><tbody><tr><td>Allyl Acetate</td><td>TCI</td><td>A0020</td><td>&gt;98.0%(GC), 25 mL package</td></tr><tr><td>Dichloro(p-cymene)ruthenium(II) dimer</td><td>TCI</td><td>D2751</td><td>&gt;95.0%(T), 5 g package</td></tr><tr><td>Silver hexafluoroantimonate</td><td>TCI</td><td>S0463</td><td>&gt;97.0%(T),&amp;nbsp; 5 g package</td></tr><tr><td>1,2-Dichloroethane</td><td>TCI</td><td>D0364</td><td>&gt;99.5%(GC), 500 g package</td></tr><tr><td>Rotavapor</td><td>EYELA</td><td>N-1200A</td><td>Use to dry solvent</td></tr><tr><td>Silica gel</td><td>Merck</td><td>107734</td><td>Silica gel 60 (0.063-0.2 mm), for column chromatoraphy</td></tr></tbody></table>

facile preparation of (2z,4e)-dienamides by the olefination of electron-deficient alkenes with allyl acetate

Vinil CH bağ aktivasyonu yoluyla iki alken arasındaki doğrudan çapraz bağlanma, yüksek atomik ve adım ekonomisine sahip butadienlerin sentezi için etkili bir strateji oluşturmaktadır. Bununla birlikte, işlevselliğe yönelik bu çapraz bağlanma reaksiyonu geliştirilmemiştir çünkü pratik kullanımda halen sınırlı yönlendirme grupları bulunmaktadır. Özellikle, büyük miktarlarda atık üreten, genellikle stoikiometrik bir oksidan miktarı gereklidir. Yeni 1,3-bütadien sentezine olan ilgimizden ötürü, elektron yetersiz alkenlerin allil asetat ve dış oksidan içermeyen rutenyumla katalize edilmiş olefinasyonunu tarif ederiz. 2-fenil akrilamid ve allil asetat reaksiyonu bir model reaksiyon olarak seçildi ve istenen dien ürünü optimal koşullar altında iyi stereoseçebilirlik ( Z, E / Z, Z = 88:12) ile% 80 izole verimle elde edildi: 110 ºC&#39;de DCE içinde Ru ( p- simen) Cl2] 2 (% 3 mol) ve AgSbF6 (% 20 mol)Veya 16 saat. Elde edilen optimum katalitik koşullarla, temsil eden α - ve / veya β - ikameli akrilamitler araştırıldı ve alifatik veya aromatik gruplara bakılmaksızın sorunsuz bir şekilde reaksiyona girdi. Ayrıca, farklı N -ikameli akrilamidlerin iyi substratlar olduğu kanıtlanmıştır. Üstelik, farklı alil türevlerinin reaktivitesini inceledik ve asetat oksijenin metale kenetlenmesinin katalitik süreç için çok önemli olduğunu düşündürdü. Reaksiyon mekanizmasını araştırmak için döteryum etiketli deneyler de yapıldı. Akrilamid üzerinde sadece Z- seçmeli H / D değişimleri gözlemlenerek, tersinir bir siklometalizasyon olayı belirlenmiştir. Ek olarak, molekül içi izotop çalışmasında 3.2&#39;lik bir kinetik izotop etkisi (KIE) gözlendi ve olefinik CH metalasyon adımının muhtemelen hız belirleme adımında yer aldığını düşündürdü.

Çalışmalarımız akrilamid ve allil asetattan 1,3-bütadien&#39;in hazırlanması üzerine yoğunlaştı. Tablo 1 , katalizör olarak [Ru ( p- simen) Cl2] 2 kullanılarak çeşitli katkı maddelerinin ve çözücülerin taranması da dahil olmak üzere, koşulların optimizasyonunu göstermektedir. Bir dizi temsilci çözücüyü taradıktan sonra, ürün veriminin% 80&#39;e iyi bir seç...

Watch this Scientific Journal Video about Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate at JoVE.com

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Elektron yetersiz alkenlerin allil asetat ile rutenyum katalizli olefinasyonu burada tarif edilmiştir. Bir yönlendirici grup olarak aminokarbonil kullanılarak, bu dış oksidan içermeyen protokol, ( Z , E ) -butadien iskeletlerine yeni bir sentetik yol açan yüksek verimlilik ve iyi stereo- ve bölgesel seçiciliğe sahiptir.

Kolay Hazırlık (2<em&gt; Z</em&gt; 4<em&gt; E</em&gt;) - Alil Asetat ile Elektronuz Alkenlerin Olefinasyonu ile Dienamidler

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high ...

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Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

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Alkene Structure and Reactivity

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7.3K Görüntüleme.  Hangzhou Normal University.  Elektron yetersiz alkenlerin allil asetat ile rutenyum katalizli olefinasyonu burada tarif edilmiştir. Bir yönlendirici grup olarak aminokarbonil kullanılarak, bu dış oksidan içermeyen protokol, ( Z , E ) -butadien iskeletlerine yeni bir sentetik yol açan yüksek verimlilik ve iyi stereo- ve bölgesel seçiciliğe sahiptir. 

Video: Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile N-(2-alkoxyvinyl)sulfonamides, which react under a variety of conditions to afford useful N- and O-containing compounds. Acid-catalyzed addition of alcohols or thiols to N-(2-alkoxyvinyl)sulfonamide-containing phthalans provides access to ketals and thioketals, respectively. Selective reduction of the vinyl group in N-(2-alkoxyvinyl)sulfonamide-containing phthalans via hydrogenation yields the corresponding phthalan in good yield, whereas reduction with sodium bis(2-methoxyethoxy)aluminumhydride generates a ring-opened phenethylamine analogue. Because the N-(2-alkoxyvinyl)sulfonamide functional group is synthetically versatile, but often hydrolytically unstable, this protocol emphasizes key techniques in preparing, handling, and reacting these pivotal substrates in several useful transformations.

Preparation of N-2-alkoxyvinylsulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Representative experimental procedures for the synthesis of N-(2-alkoxyvinyl)sulfonamides and subsequent conversion to phthalan and phenethylamine derivatives are presented in detail.

Nhazırlanması-(2-alkoxyvinyl) N- tosyl-1,2,3-triazoles ve yerine Phthalans ve fenitilaminler sonraki dönüşüm sülfonamidler

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile ...

Kimya

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

Ketonlar ile Enolonium türler Umpolung Functionalization için bir iki adım iletişim kuralı

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ketones. The reactions were carried out achieving indoles without any catalyst and with excellent regioselectivity. No traces of 2-aroylindole products were detected. Working with 4-nitronitrosobenzene as starting material, the 3-aroyl-N-hydroxy-5-nitroindole products precipitated from the reaction mixtures and were isolated by filtration without any further purification technique. Differently from the corresponding N-hydroxy-3-aryl indoles that, spontaneously in solution, give dehydrodimerization products, the N-hydroxy-3-aroyl indoles are stable and no dimerization compounds were observed.

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

3-Aroyl-N-hydroxy-5-nitroindoles were synthesized by cycloaddition of 4-nitronitrosobenzene with a conjugated terminal alkynone in a one-step thermal procedure. Preparation of the nitrosoarene and of the alkynones were adequately reported and respectively through oxidation procedures on the corresponding aniline and on the alkynol.

Alkiyonları ile 4-Nitronitrosobenzene Sikloaddition tarafından 3-Aroyl- N-hidroksi-5-nitroinollerin Direkt, Regiosel ve Atom-Ekonomik Sentezi

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ...

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine

Nitrogen-containing heterocycle aziridines are synthetically very valuable for the preparation of azacyclic and acyclic molecules. However, it is very difficult and laborious to make aziridines in optically pure forms on a large scale to apply asymmetric synthesis of aza compounds. Fortunately, we successfully achieved both enantiomers (2R)- and (2S)-aziridine-2-carboxylates with the electron-donating &#945;-methylbenzyl group at the ring nitrogen as non-activated aziridines. These starting aziridines have two distinct functional groups-highly reactive three-membered ring and versatile carboxylate. They are applicable in ring-opening or ring-transformation with aziridine and in functional group transformation to others from carboxylate. Both of these enantiomers were utilized in the preparation of biologically important amino acyclic and/or aza-heterocyclic compounds in an asymmetric manner. Specifically, this report describes the first expedient asymmetric synthesis of both enantiomers of 5, 6-dihydrouracil-type marine natural products biemamide B and D as potential TGF-&#946; inhibitors. This synthesis consisted of regio- and the stereoselective ring-opening reaction of aziridine-2-carboxylate and subsequent formation of 4-aminoteterahydropyrimidine-2,4-dione. One more example in this protocol dealt a highly stereoselective Mukaiyama reaction of aziridine-2-carboxylate and silyl enol ether, following intramolecular aziridine ring-opening to provide easy and facile access to (-)-epiallo-isomuscarine.

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine

In this study, we prepare both enantiomers of aziridine-2-carboxylate, which are used in the asymmetric synthesis of alkaloids, including biemamide B and D, and (-)-epiallo-isomuscarine.

Enantioprepure Non-Aktive Aziridinlerin Hazırlanması ve Biemamid-B, D ve Epiallo-İzomuskarin Sentezi

Nitrogen-containing heterocycle aziridines are synthetically very valuable for the preparation of azacyclic and acyclic molecules. However, it is very ...

Preparation of Alkynes: Alkylation Reaction

<h4>Introduction</h4>
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
<img alt="Alkyne alkylation reaction using NaNH2 and ethyl bromide, chemical equation diagram." src="/files/ftp_upload/11834/11834_PT_Figure_1.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure1">
The reaction takes place in two steps:
1. The first step is the deprotonation of the terminal alkyne by the strong base forming an acetylide ion.
<img alt="Alkyne ionization reaction equation NaNH2, diagram shows acetylene converting to acetylide ion." src="/files/ftp_upload/11834/11834_PT_Figure_2.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure2">
2. The second step is a nucleophilic substitution reaction in which the acetylide ion reacts with the alkyl halide to form a new C–C bond.
<img alt="Organic reaction mechanism, Na+ and Br- ion exchange, illustrates chemical synthesis process." src="/files/ftp_upload/11834/11834_PT_Figure_3.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure3">
<h4>Reaction Mechanism —SN2 pathway </h4>
Acetylide ions are strong bases and can also function as good nucleophiles. The substitution reaction follows an SN2 pathway where the nucleophilic acetylide ion attacks the electrophilic carbon of the primary alkyl halide from the backside.
<img alt="Nucleophilic substitution reaction mechanism diagram with alkynes, NaBr formation, chemical process." src="/files/ftp_upload/11834/11834_PT_Figure_4.svg" style="text-align: center; height: 250px;" data-altupdatedat="1747908711000" data-alt="Figure4">
Since this is a concerted process, the nucleophilic attack and the departure of the leaving group takes place simultaneously to form the product with an inverted stereochemistry at the reaction center.
The reaction works best with unhindered alkyl halides like methyl halide and other primary halides. With secondary and tertiary alkyl halides, acetylide ions act as strong bases, in which case E2 elimination is the preferred pathway.
<h4>Application in organic synthesis </h4>
Alkylation of simple terminal alkynes is a useful method to extend the length of the carbon chain. Acetylene, a terminal alkyne, can be converted to a higher internal alkyne by repeated alkylation as shown below:
<img alt="Alkyne chain elongation via NaNH₂, CH₃Br; reaction equation diagram for organic synthesis." src="/files/ftp_upload/11834/11834_PT_Figure_5.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure5">

Alkinlerin Hazırlanması: Alkilasyon Reaksiyonu

Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for ...

Organik Kimya

Alkinler

KEY TERMS AND CONCEPTS

Preparation of Alkynes: Dehydrohalogenation

<h4>Introduction</h4>
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
<img alt="Chemical reaction diagram, alkyne synthesis, 2NaNH2/NH3, hydrogen elimination, organic chemistry." src="/files/ftp_upload/11835/11835_PT_Figure_1.svg" style="text-align: center; height: 200px;" data-altupdatedat="1747908711000" data-alt="Figure1">
<h4>Reaction Mechanism – E2 pathway</h4>
Vicinal dihalides
In the first elimination step, the strong base abstracts the proton from the dihalide that is oriented anti to the leaving group. Since E2 reactions follow a concerted pathway, the abstraction of a proton and departure of the halide leaving group occur simultaneously to form a haloalkene.
<img alt="Birch reduction mechanism diagram, showing electron flow in organic compound reaction." src="/files/ftp_upload/11835/11835_PT_Figure_2.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure2">
In the second elimination reaction, another equivalent of the strong base reacts with the haloalkene in a similar fashion to give the desired alkyne.
<img alt="Elimination reaction mechanism diagram, E2 mechanism, showing alkene formation from alkyl halide." src="/files/ftp_upload/11835/11835_PT_Figure_3.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure3">
Geminal dihalides
Likewise, geminal dihalides, when treated with two equivalents of a sodium amide, undergo double dehydrohalogenation to give alkynes.
<img alt="Alkyne formation reaction; sodium amide abstracting proton; chemical equation diagram; synthesis method." src="/files/ftp_upload/11835/11835_PT_Figure_4.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure4">
<img alt="Chemical reaction mechanism, arrow-pushing diagram, alkyne formation using sodium amide." src="/files/ftp_upload/11835/11835_PT_Figure_5.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure5">
Terminal dihalides 
Dehydrohalogenation of terminal dihalides yields terminal alkynes as the final product. In the presence of a strong base like sodium amide, terminal alkynes get converted to acetylide ions. In such cases, a third equivalent of the base is required to complete the dehydrohalogenation of the remaining haloalkene.
<img alt="Hofmann elimination reaction; chemical equations diagram; synthesis process using NaNH2; alkyne formation." src="/files/ftp_upload/11835/11835_PT_Figure_6.svg" style="text-align: center; height: 70px;" data-altupdatedat="1747908711000" data-alt="Figure6">
Protonation of the acetylide ions with water or an aqueous acid completes the reaction.
<img alt="Organic reaction mechanism with sodium acetylide, water; diagram illustrating nucleophilic attack." src="/files/ftp_upload/11835/11835_PT_Figure_7.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure7">
<h4>Application in Organic Synthesis</h4>
Dehydrohalogenation of vicinal dihalides is a useful intermediate step in the conversion of alkenes to alkynes. For example, chlorination of 1-propene gives 1,2-dichloropropane – a vicinal dihalide, which upon double dehydrohalogenation yields 1-propyne.
<img alt="Alkene to alkyne conversion diagram; chemical reaction mechanism, dichlorination, dehydrohalogenation." src="/files/ftp_upload/11835/11835_PT_Figure_8.svg" style="text-align: center; height: 60px;" data-altupdatedat="1747908711000" data-alt="Figure8">
Similarly, alkynes can also be synthesized from ketones via dehydrohalogenation of geminal dihalides. For example, treatment of acetone with phosphorous pentachloride yields 2,2-dichloropropane – a geminal dihalide, which undergoes double dehydrohalogenation to give 1-propyne.
<img alt="Organic synthesis mechanism; ketone to alkyne via substitution and elimination; chemical reaction diagram." src="/files/ftp_upload/11835/11835_PT_Figure_9.svg" style="text-align: center; height: 80px;" data-altupdatedat="1747908711000" data-alt="Figure9">

Alkinlerin Hazırlanması: Dehidrohalojenasyon

Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ...

Preparation of Epoxides

<h4>Overview</h4>
Epoxides result from&#160;alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
<h4>Epoxidation with Peroxy Acids</h4>
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon&#8211;carbon double bond to an epoxide using the oxidizing agent&#160;meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O&#8211;O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to alkenes occurs with ease, thereby following syn addition. Hence, the epoxides are produced with the retention of the alkene configuration.
<h4>Epoxidation via Air Oxidation</h4>
Although peroxy-mediated epoxidation is the most common method for alkene oxidation, ethylene oxide is synthesized at the industrial scale via air oxidation by treating a mixture of ethylene and air in the presence of a silver catalyst.
<h4>Cyclization of Halohydrins</h4>
Cyclization of halohydrins of alkenes in the presence of a base also yields epoxides, and the reaction follows the SN2 substitution mechanism. Hence, the nucleophile&#8212;the oxygen anion&#8212;and the leaving group&#8212;the chloride ion&#8212;must orient anti to each other in the transition state to make the halohydrins cyclization feasible.
<img alt="Figure1" src="/files/ftp_upload/12094/12094Figure 1.svg" style="text-align: center; height: 260x;" />
In noncyclic halohydrins, this anti-relationship is achieved by an internal rotation. For instance, in 1-chloro-2-methyl-2-propanol, shown in Figure 1, the hydroxyl and the chloro group are not oriented anti to each other. To achieve the anti-relationship, the carbon-bearing chloro group undergoes an internal rotation, thereby making the nucleophile attack&#8212;from the backside of the C&#8211;X bond&#8212;and the ejection of the leaving group feasible. Thus, the epoxides formed via halohydrin cyclization also retain the alkene configuration.
Similarly, the cyclic halohydrins must undergo conformational changes to achieve the anti-relationship. For example, the halohydrin of cyclohexane, shown in Figure 2, undergoes a conformational change from diequatorial to diaxial to successfully form&#160;an epoxide.
<img alt="Figure2" src="/files/ftp_upload/12094/12094Figure 2.svg" style="text-align: center; height: 120px;" />

Preparation of Epoxides via Alkene Oxidation

Epoksitlerin Hazırlanması

Overview
Epoxides result from&#160;alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin ...

Eterler, Epoksitler, Sülfitler

Carboxylic Acids to Methylesters: Alkylation using Diazomethane

Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.
<img alt="Esterification reaction: carboxylic acid with diazomethane formula, chemical process diagram." src="/files/ftp_upload/12349/12349_PT_Figure_1.svg" style="text-align: center; height: 60px;" data-altupdatedat="1747908711000" data-alt="Figure1">
Diazomethane is a yellow gas having a boiling point of −23 °C. It is conveniently prepared by the action of a base on N-methyl-N-nitrosourea or N-methyl-N-nitrosotoluenesulphonamide.
The esterification mechanism involves the protonation of diazomethane by the carboxylic acid to yield a carboxylate salt and methyldiazonium cation. The methyldiazonium cation is highly unstable due to the presence of N≡N, which functions as an excellent leaving group.
<img alt="Chemical reaction, Curtius rearrangement equations, molecular transformation diagram." src="/files/ftp_upload/12349/12349_PT_Figure_2.svg" style="text-align: center; height: 72px;" data-altupdatedat="1747908711000" data-alt="Figure2">
In the final alkylation step, an SN2 attack on the methyldiazonium ion by the carboxylate anion produces a methyl ester, along with the elimination of N2 gas.
<img alt="SN2 reaction mechanism diagram; nucleophile attack on carbonyl, forming new bond, expelling N2." src="/files/ftp_upload/12349/12349_PT_Figure_3.svg" style="text-align: center; height: 70px;" data-altupdatedat="1747908711000" data-alt="Figure3">
However, diazomethane is a potentially explosive gas and requires precautions during its handling and storage. It undergoes spontaneous detonation upon contact with rough or scratched surfaces. Therefore, flame-polished glassware and a blast shield are often recommended in reactions involving diazomethane. Moreover, diazomethane is highly toxic as well as carcinogenic.
Diazomethane decomposes in the presence of heat or light to generate carbenes and eliminate nitrogen.
<img alt="Chemical reaction diagram; azide decomposition to form methylene and nitrogen under heat or light." src="/files/ftp_upload/12349/12349_PT_Figure_4.svg" style="text-align: center; height: 52px;" data-altupdatedat="1747908711000" data-alt="Figure4">

Karboksilik Asitlerden Metilesterlere: Diazometan kullanarak alkilasyon

Carboxylic acids react with diazomethane in an ether solvent&#160;via alkylation at the carboxylate oxygen atom&#160;to give&#160;methyl esters of the ...

Karboksilik Asitler

Amines to Alkenes: Hofmann Elimination

Alkenes can be obtained from amines via an E2 elimination. The amine is first converted into a good leaving group, such as a quaternary ammonium salt. This is accomplished by treating the amine with an excess of alkyl halide, which results in a halide salt. Next, the halide salt is transformed into a hydroxide salt that functions as a base to enable elimination.
Under thermal conditions, the hydroxide can abstract a proton from the &#946; carbon; this generates an alkene with the simultaneous release of a neutral amine molecule. This elimination process is called the Hofmann elimination. For the elimination to occur, the &#946; proton and tertiary amine group must be positioned opposite or anti-periplanar to each other. This reaction yields the less substituted alkene as the major product, also known as the Hofmann product.

Aminlerden Alkenlere: Hofmann Eliminasyonu

Alkenes can be obtained from amines via an E2 elimination. The amine is first converted into a good leaving group, such as a quaternary ammonium salt. ...

Aminler

&alpha;-Alkylation of Ketones via Enolate Ions

Ketones with &#945; protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the &#945; carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the &#945;&nbsp;carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction of the positive counterpart of the base with the anionic oxygen, which restricts the approaching electrophile, making the reaction less favorable. Also, the product obtained through C-attack is more stable than that obtained through O-attack, as the stronger C=O &#960; bond is retained in the former, whereas a weaker C=C &#960; bond is preserved in the latter.
A subsequent reaction of the enolate with electrophiles such as alkyl halides produces an &#945;-alkylated ketone via the SN2 pathway. The &#945;-alkylation of ketones is achieved with the halides of primary alkyl, benzyl, and allylic groups. With secondary and tertiary alkyl halides, elimination predominates over substitution.

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