Diels – Alder Reaction 1,4-CycloAddition Reaction of ww2. 2003-08-283 What’s Going With Respect...

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Transcript of Diels – Alder Reaction 1,4-CycloAddition Reaction of ww2. 2003-08-283 What’s Going With Respect...

  • 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

    Whats Going With Respect to a Diels-Alder 1,4 Cycloaddition Reaction?

    XX+

    Diene

    S-cis

    Dieneophile Diels Alder Adduct

    Cyclohexene derivative

    3 bonds convert into one bond + two bonds

    Note: bond stronger >

    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 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