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.
Want to see the full answer?
Check out a sample textbook solutionChapter 26 Solutions
ORG.CHEMISTRY W/ACCESS+MODEL KIT PKG
- One step in the synthesis of dodecahedrane involves reaction of the tetraene C with dimethylacetylene dicarboxylate (D) to afford two compounds having molecular formula C16H16O4. This reaction has been called a domino Diels–Alder reaction. Identify the two products formed.arrow_forwardThe endiandric acids comprise a group of unsaturated carboxylic acidsisolated from a tree that grows in the rainforests of eastern Australia.The methyl esters of endiandric acids D and E have been prepared frompolyene Y by a series of two successive electrocyclic reactions: thermalring closure of the conjugated tetraene followed by ring closure of theresulting conjugated triene. (a) Draw the structures (includingstereochemistry) of the methyl esters of endiandric acids D and E. (b)The methyl ester of endiandric acid E undergoes an intramolecular [4 +2] cycloaddition to form the methyl ester of endiandric acid A. Propose apossible structure for endiandric acid A.arrow_forwardExplain, with reference to the mechanism, why addition of one equivalent of HCl to diene A forms only two products of electrophilic addition, even though four constitutional isomers are possible.arrow_forward
- For the Diels–Alder reaction, the product's skeletal structure and configuration at the bridgehead carbons are given (and the given wedge bond and dash bond should not be changed). Complete the structure of the major product. Indicate the stereochemistry, by adding two wedges and two dash bonds, at only the fused‑ring stereocenters.arrow_forwardOne synthetic advantage of olefin metathesis is that the catalyst tolerates a variety of functional groups in the reactant. In a synthesis of the antiinfluenza drug Tamiflu (oseltamivir), ring-closing metathesis was used to prepare the highly functionalized cyclohexene derivative shown. What was the reactant?arrow_forwardDehydrohalogenation of 1-chloro-1-methylcyclopropane affords two alkenes (A and B) as products. Explain why A is the major product despite the fact that it contains the less substituted double bond.arrow_forward
- The Diels–Alder reaction between butadiene and dimethyl maleate yields a ring structure, as shown in the product. Complete the structure by drawing any missing bonds and indicating the stereochemistry of the new stereocenters.arrow_forward-Ocimene is a pleasant-smelling hydrocarbon found in the leaves of certain herbs. It has the molecular formula C10H16 and a UV absorption maximum at 232 nm. On hydrogenation with a palladium catalyst, 2,6-dimethyloctane is obtained. Ozonolysis of -ocimene, followed by treatment with zinc and acetic acid, produces the following four fragments: (a) How many double bonds does -ocimene have? (b) Is -ocimene conjugated or nonconjugated? (c) Propose a structure for -ocimene. (d) Write the reactions, showing starting material and products.arrow_forwardMany variations of ring-closing metathesis have now been reported. Tandem ring-opening-ring-closing metathesis can occur with cyclic alkenes that contain two additional carbon-carbon double bonds. In this reaction, the cycloalkene is cleaved, and two new rings are formed. [1] What compounds are formed in this tandem reaction with the following substrates? [2] Devise a synthesis of the substrate in part (b) that uses a Diels–Alder reaction with diethyl maleate as the dienophile.arrow_forward
- Many variations of ring-closing metathesis have now been reported. Tandem ring–opening–ring-closing metathesis can occur with cyclic alkenes that contain two additional carbon–carbon double bonds. In this reaction, the cycloalkene is cleaved, and two new rings are formed. [1] What compounds are formed in this tandem reaction with the following substrates? [2] Devise a synthesis of the substrate in part (b) that uses a Diels–Alder reaction with diethyl maleate as the dienophile.arrow_forwardDraw 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_forwardTwo isomers, A and B, of molecular formula C5H8 undergo catalytic hydrogenation with hydrogen gas and palladium on carbon to form the same C5H10 product. On ozonolysis followed by treatment with hydrogen peroxide (H2O2), isomer A gave a product of molecular formula C5H8O4 that has two carboxylic acid groups in it whereas isomer B gave a product of molecular formula C5H8O3 that contains a carboxylic acid group and a ketone group. Which of the following isomeric pairs best match this data?arrow_forward