Cycloaddition Reactions: Synthesis - II
The molecule shown below can be prepared by a simple [4+2]
cycloaddition reaction. Using the drawing pallet on the
right, draw the structures of the diene and
dienophile required for this synthesis, paying
particular attention to the stereochemistry of the
reactants.
To identify the reactants in a [4+2] cycloaddition
reaction, identify the carbons of the dienophile (they will
be the two carbons in a six-member ring which are
opposite to the double bond in the product) and
mentally split the bonds, separating the carbon
skeletons of the diene and the dienophile. In the
cyclohexene ring, the substituents which were originally on
the dienophile are trans- (1,2-diequatorial),
therefore the starting dienophile must also have
trans stereochemistry.
Using the drawing pallet on the right, draw the structure
of the major organic product for the reaction shown below:
To identify the reactants in a [4+2] cycloaddition
reaction, identify the carbons of the dienophile (they will
be the two carbons in a six-member ring which are
opposite to the double bond in the product) and
mentally split the bonds, separating the carbon
skeletons of the diene and the dienophile. In the
cyclohexene ring, the substituents which were originally on
the dienophile are cis- (1,2-axial-equatorial),
therefore the starting dienophile must also have cis
stereochemistry.
Using the drawing pallet on the right, draw the structure
of the major organic product for the reaction shown below:
In this problem, it is helpful to first convert the
chair cyclohexene into the boat form. In the cyclohexene
ring, the substituents which were originally on the
dienophile are cis- (1,2-axial-equatorial),
therefore the starting dienophile must also have cis
stereochemistry. The methyl groups on the diene are
trans (1,4-diequatorial), therefore the two double
bonds in the diene must be cis-trans.
Using the drawing pallet on the right, draw the structure
of the major organic product for the reaction shown below:
In this
problem, you must first rotate the ring so that the double
bond is towards the back of the molecule, then convert to
the boat conformation. In the chair cyclohexene ring, the
substituents which were originally on the dienophile are
cis- (1,2-axial-equatorial), therefore the starting
dienophile must also have cis stereochemistry. The
methyl group on the diene is equatorial, and therefore must
have cis stereochemistry.
Using the drawing pallet on the right, draw the structure
of the major organic product for the reaction shown below:
To identify the reactants in a [4+2] cycloaddition
reaction, identify the carbons of the dienophile (they will
be the two carbons in a six-member ring which are
opposite to the double bond in the product) and
mentally split the bonds, separating the carbon
skeletons of the diene and the dienophile. In the
cyclohexene ring, the substituents which were originally on
the dienophile are cis- (1,2-axial-equatorial),
therefore the starting dienophile must also have cis
stereochemistry.
Using the drawing pallet on the right, draw the structure
of the major organic product for the reaction shown below:
To identify the reactants in a [4+2] cycloaddition
reaction, identify the carbons of the dienophile (they will
be the two carbons in a six-member ring which are
opposite to the double bond in the product) and
mentally split the bonds, separating the carbon
skeletons of the diene and the dienophile. In the
cyclohexene ring, the substituents which were originally on
the dienophile are cis- (1,2-axial-equatorial),
therefore the starting dienophile must also have cis
stereochemistry. The methyl groups on the diene are
cis (1,4-axial-equatorial), therefore the two double
bonds in the diene must both be trans.
That is correct!
Sorry, that is not correct. You should modify your
structures and try again. Remember to use the NEW
button to draw the second structure and show cis
-trans stereochemistry when appropriate.
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Note: Use NEW to begin
drawing a second molecule.
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