The pericyclic reactions involved in the reaction shown are to be identified and how the rearrangement occurs also is to be indicated. Concept introduction: An electrocyclic reaction involves the cyclization of a conjugated acyclic system. These reactions are reversible and are highly stereospecific. In elecrocyclic reactions involving even number of electron pairs, a thermal reaction occurs in conrotatory manner and a photochemical reaction occurs in disrotatory manner. In elecrocyclic reactions involving odd number of electron pairs, a thermal reaction occurs in disrotatory manner and a photochemical reaction occurs in conrotatory manner.

Question

The endiandric acids comprise a group of unsaturated carboxylic acids isolated from a tree that grows in the rainforests of eastern Australia. The methyl esters of endiandric acids D and E have been prepared from polyene Y by a series of two successive electrocyclic reactions: thermal ring closure of the conjugated tetraene followed by ring closure of the resulting conjugated triene. (a) Draw the structures (including stereochemistry) 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 a possible structure for endiandric acid A.

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Question

Chapter 30.SE, Problem 19AP

Interpretation Introduction

Interpretation:

The pericyclic reactions involved in the reaction shown are to be identified and how the rearrangement occurs also is to be indicated.

Concept introduction:

An electrocyclic reaction involves the cyclization of a conjugated acyclic system. These reactions are reversible and are highly stereospecific.

In elecrocyclic reactions involving even number of electron pairs, a thermal reaction occurs in conrotatory manner and a photochemical reaction occurs in disrotatory manner.

In elecrocyclic reactions involving odd number of electron pairs, a thermal reaction occurs in disrotatory manner and a photochemical reaction occurs in conrotatory manner.

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The endiandric acids comprise a group of unsaturated carboxylic acids isolated from a tree that grows in the rainforests of eastern Australia. The methyl esters of endiandric acids D and E have been prepared from polyene Y by a series of two successive electrocyclic reactions: thermal ring closure of the conjugated tetraene followed by ring closure of the resulting conjugated triene. (a) Draw the structures (including stereochemistry) 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 a possible structure for endiandric acid A.

Show how the following starting material is converted to the given product by a series of two pericyclic reactions. Account for the observed stereochemistry.

The endiandric acids comprise a group of unsaturated carboxylic acids isolated from a tree that grows in the rain forests of eastern Australia. The methyl esters of endiandric acids D and E have been prepared from polyene Y by a series of two successive electrocyclic reactions: thermal ring closure of the conjugated tetraene followed by ring closure of the resultingconjugated triene. (a) Draw the structures (including stereochemistry) 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 a possible structure for endiandric acid A.