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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- Draw and discuss the mechanism (with arrows to show electron movements) of the Diels-Alder reaction between anthracene and maleic anhydride. Draw the orientation and phases of the reacting p-orbitals showing how they overlap in a “suprafacial” geometry to form productarrow_forwardTrue or False: Acetylene is a naturally occurring conjugated diene True or False: The Diels-Alder reaction has the stereochemistry of the dienophile is retained in the product. True or False: When looking at kinetic vs. thermodynamic products the kinetic product predominates at low temperature. True or False: the mechanism of the Diels-Alder reaction is three π bonds break; one σ bond and two π bonds form.arrow_forwardFollowing is an example of a type of reaction known as a Diels-Alder reaction 1,3-Pentadiene Ethylene 3-Methylcyclohexene (a racemic mixture) The Diels-Alder reaction between a diene and an alkene is quite remarkable in that it is one of the few ways that chemists have to form two new carbon-carbon bonds in a single reaction. Given what you know about the relative strengths of carbon-carbon sigma and pi bonds, would you predict the Diels-Alder reaction to be exothermic or endothermic? Explain your reasoning.arrow_forward
- 4.35 Formulate the reaction of cyclohexene with (i) Br2 and (ii) meta-chloro- peroxybenzoic acid followed by H30+. Show the reaction intermediates and the final products with correct cis or trans stereochemistry. 4.36 What products would you expect to obtain from reaction of cyclohexa- 1,3-diene with each of the following? (a) 1 mol Br2 in CH2C12 (c) 1 mol DCl (D = deuterium, ²H) (b) 1 mol HCl (d) 2 mol H2 over a Pd catalyst 4.37 Predict the products of the following reactions on hex-1-yne: (a) 1 equiv HBr ? (b) 1 equiv Cl2 ? (c) H2, Lindlar catalystarrow_forwardThe following Diels-Alder reaction product is an intermediate in the synthesis of cholesterol. Provide the structure of the major product. Show stereochemistry when applicable. Hint: there are two possible dienophiles, which one is the better dienophile? Provide a brief explanation of your choice. CH,O.arrow_forward(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_forward
- Styrene (vinylbenzene) undergoes electrophilic aromatic substitution much faster thanbenzene, and the products are found to be primarily ortho- and para-substituted styrenes.Use resonance forms of the intermediates to explain these results.arrow_forward4arrow_forwardCompounds X and Y are both C5H11CI products formed in the radical chlorination of pentane. Base-promoted E2 elimination of X and Y gives, in each case, a single C5H10 alkene (ignoring double bond stereochemistry). Both X and Y react in SN2 fashion with sodium iodide in acetone; Y reacts faster than X. What is the structure of Y? • 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. ChemDoodle (Previous Nextarrow_forward
- A) Write the mechanism and predict the products for the following reaction. Label each product as the thermodynamic product or the kinetic product. Write a few sentences explaining which product would predominate at low temperature and which would predominate at high temperature and explain the reason for this result. HBr ABd B) Choose reagents that would give the following product in a Diels-Alder reaction: C) Predict the major and minor product for the following Diels-Alder reaction:arrow_forwardConsider this scheme. Why does a ring form with a single ethylene glycol on A rather than two molecules of ethylene glycol to form acyclic acetals? Intramolecular reactions are A unfavorable when compared to intermolecular reactions Acyclic molecules are unfavorable compared to rings В in all cases The change in entropy is favorable for ring formation and strain is low in a five- membered ring Sterics prevents acyclic molecules from forming in this D case H HCI + HOCH2CH2OH H + H2Oarrow_forward2) Predict the major product for each Diels-Alder reaction. Include stereochemistry where appropriate. H. C=N (a) H H. CH3 CH;O, (b) Ph (c) Pharrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning