Concept explainers
(a)
Interpretation: The compounds are formed by the tandem reaction with given substrates are to be predicted.
Concept introduction: The ring-closing metathesis (RCM) by Grubbs catalyst occurs, when the starting material is diene. This reaction is facilitated under high-dilution condition as it favors intramolecular metathesis instead of intermolecular metathesis.
(b)
Interpretation: The synthesis of the substrate in part (b) that uses a Diels–Alder reaction with diethylmaleate as the dienophile is to be devised.
Concept introduction: Diels-alder reaction is a cycloaddition reaction in which two molecules combine to form a new ring. In this type of reaction, syn addition takes place. It is a reaction between diene with a dienophile to yield a cyclohexene. The dienophile adds to one side of the diene, and diene adds to the one side of the dienophile. Thus, they have syn stereochemistry.
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Organic Chemistry
- (a) Complete the following sequence of reactions (i.e., give the structure for compounds A and B), giving structural details of all key intermediates. heat & A COOCH3 H₁₂ Ni (b) Provide the bond line structures for the pair of compounds used for the Diels-Alder synthesis of the compound shown below. O B COOCH3 (c) Draw the two major products obtained when (3E,5Z)-2,2,3,6,7-pentamethylocta-3,5-diene reacts with HBr at low and high temperatures. Label the products as the kinetic or thermodynamic product AND, if applicable, use dashes and wedges to show the correct stereochemistry in the obtained products.arrow_forwardWhen heated, allyl aryl ethers and allyl vinyl ethers undergo a reaction called a Claisen rearrangement, a concerted reorganization of bonding electrons similar to the Diels-Alder reaction. The reaction proceeds through a six-membered, cyclic transition state. Draw the structure of the expected product when this compound undergoes a Claisen rearrangement. You do not have to consider stereochemistry. For the purposes of this problem, assume that double bonds in an aromatic ring are localized at the positions indicated in the figure. Include isomerization to a phenol IF appropriate.arrow_forwardWhen heated, allyl aryl ethers and allyl vinyl ethers undergo a reaction called a Claisen rearrangement, a concerted reorganization of bonding electrons similar to the Diels-Alder reaction. The reaction proceeds through a six-membered, cyclic transition state. Draw the structure of the expected product when this compound undergoes a Claisen rearrangement. You do not have to consider stereochemistry. For the purposes of this problem, assume that double bonds in an aromatic ring are localized at the positions indicated in the figure. Include isomerization to a phenol IF appropriate.arrow_forward
- (c) Diels-Alder reactions are a highly effective way to synthesise stereospecifically fused cyclic structures. (1) Using suitable diagrams, curly arrows and/or reaction schemes, explain why the reaction between cyclopentadiene and maleic anhydride favours formation of the endo product. (ii) If the reaction in part (i) were conducted using furan instead of cyclopentadiene, what difference would you observe in the product/s, with respect to their stereochemistry? (No need to draw reaction mechanisms) (iii) Draw the stereospecific 3D structure of the product formed during the Diels-Alder reaction below. (No need to show the reaction mechanism) Нeat Br Br (Figure Q11ciii)arrow_forwardThe highly reactive triple bond of benzyne is a powerful dienophile. Predict the productof the Diels–Alder reaction of benzyne (from chlorobenzene and NaOH, heated) withcyclopentadiene.arrow_forwardThe Wittig reaction can be used for the synthesis of conjugated dienes, as, for example, 1-phenyl-1,3-pentadiene. -CH=CHCH CHCH, 1-Phenyl-1,3-pentadiene Propose two sets of reagents that might be combined in a Wittig reaction to give this conjugated diene.arrow_forward
- The Diels–Alder Reaction – A [4+2] Cycloaddition Experiment. (a) Explain why the endo-rule is not obeyed when furan is used as the diene. Use chemical structures and models to support your answer.arrow_forwardOf the three 1,4-diphenyl-1,3-butadiene isomers (E,E or E,Z or Z,Z) indicate the most suitable diene that can be used as a reactant in a Diels-Alder reaction. Explain your choice.arrow_forward21. (a) Predict the product of the following Diels-Alder reaction( Show the correct stereochemistry for the product). cyclopentadiene + cis 1,2-dicyanoethylene (NC-CH=CH-CN) -------> (b) Show the mechanism for the reaction in(a) above.arrow_forward
- Compounds X and Y are both C7H15Cl products formed in the radical chlorination of 2,4-dimethylpentane. Base-promoted E2 elimination of X and Y gives, in each case, a single C7H₁4 alkene. Both X and Y undergo an SN2 reaction with sodium iodide in acetone solution to give C7H15l products; in this reaction Y reacts faster than X. What is the structure of X? • Do not use stereobonds in your answer. • In cases where there is more than one possible structure for each molecule, just give one for each. . Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner. Separate structures with + signs from the drop-down menu. наarrow_forwardElectrophilic addition to an alkene proceeds via Markovnikov regiochemistry due to the formation of the more stable carbocation intermediate. In the case of conjugated dienes, that is dienes that are separated by one sigma bond, the carbocation that is formed is stabilized additionally by resonance. Addition of the nucleophile to the carbocation intermediate can therefore give two types of products: direct addition to the double bond, also called 1,2-addition, and conjugate addition to the resonance stabilized carbocation, also called 1,4-addition.Allylic carbocation stability is affected by both the nature of the carbocation (primary allylic, secondary allylic, or tertiary allylic) and by the degree of substitution of the double bond. The latter is typically the dominant effect and so a primary allylic carbocation with a trisubstituted double bond is more stable than a tertiary allylic carbocation with a monosubstituted double bond.Electrophilic addition to a conjugated diene is…arrow_forwardA certain class of natural products is formed in nature first by action of ADH-like enzymes on a starting material, followed by spontaneous (non-enzyme-catalyzed) steps that generate the final structure. One such product, Compound P, was formed when the ADH-like enzyme was provided with NAD²H₂ as cofactor. (As a reminder, NAD²H₂ is NADH wherein both transferable hydrogens have been replaced by deuterium.) 1. ADH-like enzyme, NAD²H₂ ° 2. spontaneous steps Starting Material I I OH Compound P Using NAD²H₂ as cofactor, provide a complete curved-arrow mechanism for this transformation. Make sure your mechanism accounts for the location of the deuterium in the product. For the spontaneous steps, you may use general acids and bases, but no other cofactors. (Hint: numbering your carbons will be helpful.)arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning