Abstract Sheet - Diels-Alder Reaction

Diels-Alder Reactions:The reaction between a conjugated diene and a dienophile

IMAGE Diels-Alder01.gif

Important points:

1. Six membered rings with at least one double bond are always formed.
2. The addition reaction is stereospecific:
a. it is a syn addition - this means that the stereochemistry around the double bond in the
dienophile is always maintained in the product, i.e. if the starting dienophile has the electron withdrawing
groups trans to each other than they will be trans in the product
b. it is an endo addition - this means that the electron withdrawing group(s) will be on the
same side of the molecule when a bicyclic molecule is formed as the bridge that contains the double bond.

The easiest way to predict the products of one of these reactions is to draw a six membered ring with a
double bond, identify the 4 carbons which came from the diene and the 2 carbons which came from the
dienophile and then attach the substituents (with the correct stereochemistry).

Points 1 and 2a are illustrated in the following 2 examples:

IMAGE Diels-Alder02.gif
IMAGE Diels-Alder03.gif
IMAGE Diels-Alder04.gif
IMAGE Diels-Alder05.gif
IMAGE Diels-Alder06.gif
IMAGE Diels-Alder07.gif
IMAGE Diels-Alder07.gif
IMAGE Diels-Alder09.gif
IMAGE Diels-Alder10.gif
IMAGE Diels-Alder11.gif
IMAGE Diels-Alder12.gif

CO2CH3

H3CO2C

CO2CH3

CO2CH3

CO2CH3

CO2CH3

CO2CH3

CO2CH3

Trans stereochemistry

Trans stereochemistry

6-membered ring with double bond

6-membered ring with double bond

Cis stereochemistry

Cis stereochemistry

Point 2b is illustrated in the following example:

IMAGE Diels-Alder13.gif
IMAGE Diels-Alder14.gif
IMAGE Diels-Alder15.gif
IMAGE Diels-Alder16.gif

CO2CH3

CO2CH3

CO2CH3

H

CO2CH3

H

Same side

CO2CH3

CO2CH3

3 - Dimensional drawing

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