Diels – Alder Reaction 1,4-CycloAddition Reaction of...

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1 Diels – Alder Reaction 1,4-CycloAddition Reaction of Dienes Solomons and Fryhle: 13.11

Transcript of Diels – Alder Reaction 1,4-CycloAddition Reaction of...

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Diels – Alder Reaction

1,4-CycloAddition Reaction of Dienes

Solomons and Fryhle: 13.11

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What is a Diels-Alder 1,4 Cycloaddition Reaction?

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What’s Going With Respect to a Diels-Alder 1,4 Cycloaddition Reaction?

XX+

Diene

S-cis

Dieneophile Diels Alder Adduct

Cyclohexene derivative

3 π bonds convert into one π bond + two σ bonds

Note: σ bond stronger > π

Note: No formal charge formed, hence solvents polarity is not that important

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Examples of Dienes and Dienophiles

Prefer electron withdrawing groups on dienophile

Prefer electron donating groups on diene

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Examples of Dienes and Dienophiles

OR>> Employ electron withdrawing groups on dienes and electron donating groups on dienophile

+

100% yield

30o C

OO

HH

200o C

20% yield

+

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Diels Alder Reaction is VERY Stereospecific!!

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CO2CH3 H

CO2CH3

H

H H

H

H

H

H H

HExo

Endo

Nomenclature

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Diels Alder Stereochemistry

Exo Product is usually thermodynamic product but formed slowly

Endo Product is the kinetic product and frequently predominates

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Diels Alder Stereochemistry

Endo and exo addition require different approach and transition state geometries

Endo Exo

Better secondary overlap of π orbitals for endo>> Kinetic Product

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Problem from Solomons and Fryhle 13.24 b and f: What diene and dienophile wouldyou employ in a synthesis of the following?

Me

Me

O

O

O

OMe

Me

H

O

OCH3

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Problem provide a synthetic path for the following:

Starting Material >>>>>>>>>>>>>>> Product

O

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For “fun/practice” look atS&F 13,16, 18, 19, 24, 25, 28, 40

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Now for Something New

Chapter 14

Aromatic Compounds and Chemistry

Solomons and Fryhle: 14.1,2,3,10

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No reaction

Very Slow and requires highPressure

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R

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orthometapara

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