1

Diels – Alder Reaction

1,4-CycloAddition Reaction of Dienes

Solomons and Fryhle: 13.11

2

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

3

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

4

Examples of Dienes and Dienophiles

Prefer electron withdrawing groups on dienophile

Prefer electron donating groups on diene

5

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

+

6

Diels Alder Reaction is VERY Stereospecific!!

7

CO2CH3 H

CO2CH3

H

H H

H

H

H

H H

HExo

Endo

Nomenclature

8

Diels Alder Stereochemistry

Exo Product is usually thermodynamic product but formed slowly

Endo Product is the kinetic product and frequently predominates

9

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

10

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

11

Problem provide a synthetic path for the following:

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

O

12

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

13

Now for Something New

Chapter 14

Aromatic Compounds and Chemistry

Solomons and Fryhle: 14.1,2,3,10

14

No reaction

Very Slow and requires highPressure

15Solomons and Fryhle, problem 14.16,17

R

16

orthometapara

17