Diels alder reaction of furan

In organic chemistrythe Diels—Alder reaction is a chemical reaction between a conjugated diene and a substituted alkenecommonly termed the dienophile also spelled dieneophile [1]to form a substituted cyclohexene derivative.

It is the prototypical example of a pericyclic reaction with a concerted mechanism. It was first described by Otto Diels and Kurt Alder in For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in Through the simultaneous construction of two new carbon—carbon bonds, the Diels—Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes.

The reaction has also been generalized to other ring sizes, although none of these generalizations have matched the formation of six-membered rings in terms of scope or versatility.

The reaction is an example of a concerted pericyclic reaction. A consideration of the reactants' frontier molecular orbitals FMO makes plain why this is so. The same conclusion can be drawn from an orbital correlation diagram or a Dewar-Zimmerman analysis. However, the HOMO—LUMO energy gap is close enough that the roles can be reversed by switching electronic effects of the substituents on the two components. Regardless of which situation pertains, the HOMO and LUMO of the components are in phase and a bonding interaction results as can be seen in the diagram below.

Since the reactants are in their ground state, the reaction is initiated thermally and does not require activation by light. The "prevailing opinion" [10] [11] [12] [13] is that most Diels—Alder reactions proceed through a concerted mechanism; the issue, however, has been thoroughly contested.

Despite the fact that the vast majority of Diels—Alder reactions exhibit stereospecific, syn addition of the two components, a diradical intermediate has been postulated [8] and supported with computational evidence on the grounds that the observed stereospecificity does not rule out a two-step addition involving an intermediate that collapses to product faster than it can rotate to allow for inversion of stereochemistry.

There is a notable rate enhancement when certain Diels—Alder reactions are carried out in polar organic solvents such as dimethylformamide and ethylene glycol. The geometry of the diene and dienophile components each propagate into stereochemical details of the product.

For intermolecular reactions especially, the preferred positional and stereochemical relationship of subtituents of the two components compared to each other are controlled by electronic effects. However, for intramolecular Diels—Alder cycloaddition reactions, the conformational stability of the structure the transition state can be an overwhelming influence.

Frontier molecular orbital theory has also been used to explain the regioselectivity patterns observed in Diels—Alder reactions of substituted systems. Calculation of the energy and orbital coefficients of the components' frontier orbitals [18] provides a picture that is in good accord with the more straightforward analysis of the substituents' resonance effects, as illustrated below.

In general, the regioselectivity found for both normal and inverse electron-demand Diels—Alder reaction follows the ortho-para ruleso named, because the cyclohexene product bears substituents in positions that are analogous to the ortho and para positions of disubstituted arenes.

Pairing these two coefficients gives the "ortho" product as seen in case 1 in the figure below. A diene substituted at C2 as in case 2 below has the largest HOMO coefficient at C1, giving rise to the "para" product.

Similar analyses for the corresponding inverse-demand scenarios gives rise to the analogous products as seen in cases 3 and 4. Examining the canonical mesomeric forms above, it is easy to verify that these results are in accord with expectations based on consideration of electron density and polarization.

In general, with respect to the energetically most well-matched HOMO-LUMO pair, maximizing the interaction energy by forming bonds between centers with the largest frontier orbital coefficients allows the prediction of the main regioisomer that will result from a given diene-dienophile combination. The maximization of orbital interaction correctly predicts the product in all cases for which experimental data is available.

For instance, in uncommon combinations involving X groups on both diene and dienophile, a 1,3-substitution pattern may be favored, an outcome not accounted for by a simplistic resonance structure argument. Diels—Alder reactions, as concerted cycloadditions, are stereospecific.Please be aware that pubs.

Furan to Furfural- HCN-HCL to -CHO ! How to convert? MECHANISM-Gatterman Koch synthesis-ALLWIN

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diels alder reaction of furan

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Why does furan undergo Diels Alder reaction?

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diels alder reaction of furan

Please enable JavaScript to access the full features of the site or access our non-JavaScript page. Issue 7, Previous Article Next Article. From the journal: Green Chemistry.First, refer to this document for substantiation of what occurs at the melting point.

Now, let's examine the Diels-Alder mechanism for this particular reaction. I have a more general overview here if you want to review what the Diels-Alder reaction is. It is a concerted cyclization reaction which generates an adduct of the starting diene furan and dienophile maleic anhydride that contains two new "C"-"C" bonds.

Diels–Alder reaction

That's why the reference I showed you said to get the melting point before recrystallization. If you have done the lab before where you reacted cyclopentadiene with maleic anhydride, you might wonder, "wait It was.

But for THIS reaction, of furan with maleic anhydride, as it turns outthe thermodynamic favorability experimentally trumps the kinetic favorability.

The exo product is more thermodynamically stable by about "1. However, given that the reaction is reversible, the thermodynamic product eventually remains.

Diels-Alder Reaction

So, the exo product is still the major product. Its thermodynamic stability is actually a smaller difference than the energy barrier to ethane "C"-"C" bond rotation, yet still significant! When an adduct is formed from Diels Alder reaction of maleic anhydride and furan, what does the adduct decompose to at its melting point? Truong-Son N. Apr 28, What are alkenes and alkynes used for? Why are alkenes and alkynes called unsaturated compounds?

Are all alkenes and alkynes unsaturated hydrocarbons? Why are alkenes and alkynes more reactive? Why are electrophilic addition reactions the characteristic reactions of alkenes? How are synthetic alkynes used for birth control?

Why are alkynes less reactive than alkenes in electrophilic addition reactions? See all questions in Introduction to Reactions and Mechanisms. Impact of this question views around the world. You can reuse this answer Creative Commons License.In the case of an alkynyl dienophile, the initial adduct can still react as a dienophile if not too sterically hindered. In addition, either the diene or the dienophile can be substituted with cumulated double bonds, such as substituted allenes.

With its broad scope and simplicity of operation, the Diels-Alder is the most powerful synthetic method for unsaturated six-membered rings. A variant is the hetero-Diels-Alder, in which either the diene or the dienophile contains a heteroatom, most often nitrogen or oxygen. This alternative constitutes a powerful synthesis of six-membered ring heterocycles. The reaction is facilitated by electron-withdrawing groups on the dienophile, since this will lower the energy of the LUMO.

The diene component should be as electron-rich as possible. This alternative scenario for the reaction is favored by electron-donating groups on the dienophile and an electron-poor diene. Cyclic dienes give stereoisomeric products. The endo product is usually favored by kinetic control due to secondary orbital interactions. Liu, E. Canales, E. Corey, J. Payette, H. Yamamoto, J.

diels alder reaction of furan

Gotoh, Y. Hayashi, Org. Hayashi, S. Samanta, H. Gotoh, H. Ishikawa, Angew. Loh, Org. Nakashima, H. Fan, L. Lin, J. Liu, Y. Huang, X. Feng, Eur. Berkessel, N. Vogl, Eur. The cycloadducts can be converted directly to the corresponding dihydropyrones and dihydropyridones. Huang, V. Rawal, Org. Dai, D. Sarlah, M. Yu, S. Danishefsky, G. Jones, K. Houk, J. Fringuelli, R.Furan is a heterocyclic organic compoundconsisting of a five-membered aromatic ring with four carbon atoms and one oxygen.

Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammablehighly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcoholetherand acetoneand is slightly soluble in water. Furan is used as a starting point to other speciality chemicals. The name "furan" comes from the Latin furfurwhich means bran.

The first furan derivative to be described was 2-furoic acidby Carl Wilhelm Scheele in Furan itself was first prepared by Heinrich Limpricht inalthough he called it "tetraphenol" as if it were a four-carbon analog to phenolC 6 H 6 O.

Industrially, furan is manufactured by the palladium -catalyzed decarbonylation of furfuralor by the copper -catalyzed oxidation of 1,3-butadiene : [4]. In the laboratory, furan can be obtained from furfural by oxidation to 2-furoic acid, followed by decarboxylation. The Feist—Benary synthesis is a classic way to synthesize furans, although many syntheses have been developed. The thiophene formation reaction of 1,4-diketones with Lawesson's reagent also forms furans as side products.

Many routes exist for the synthesis of substituted furans. Because of the aromaticity, the molecule is flat and lacks discrete double bonds. The other lone pair of electrons of the oxygen atom extends in the plane of the flat ring system.

Due to its aromaticity, furan's behavior is quite dissimilar to that of the more typical heterocyclic ethers such as tetrahydrofuran.

diels alder reaction of furan

Furan is found in heat-treated commercial foods and is produced through thermal degradation of natural food constituents. Exposure to furan at doses about times the projected level of human exposure from foods increases the risk of hepatocellular tumors in rats and mice and bile duct tumors in rats. From Wikipedia, the free encyclopedia.

This article is about the industrial chemical compound. For other uses, see Furan disambiguation. Furan [1]. Oxole Oxa[5]annulene 1,4-Epoxy-1,3-butadiene 5-Oxacyclopenta-1,3-diene 5-Oxacyclo-1,3-pentadiene Furfuran Divinylene oxide. CAS Number. Interactive image. PubChem CID. Chemical formula. Autoignition temperature. LD 50 median dose. Related heterocycles. Point group. Cambridge: The Royal Society of Chemistry. Concise Encyclopedia of Chemistry. Walter de Gruyter. Ullmann's Encyclopedia of Industrial Chemistry.

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