lecture 24.2

lecture 24.2 - 24-24-11Organic Organic...

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Unformatted text preview: 24-24-11Organic Organic ChemistryChemistryWilliam H. BrownWilliam H. BrownChristopher S. FooteChristopher S. FooteBrent L. IversonBrent L. Iverson24-24-22Carbon-Carbon Bond Carbon-Carbon Bond Formation and Formation and SynthesisSynthesisChapter 24Chapter 2424-24-33Diels-Alder ReactionDiels-Alder Reaction(2Z,4Z)-2,4-hexadiene is unreactive in Diels-Alder reactions because nonbonded interactions prevent it from assuming the planar s-cis conformation(2Z,4Z)-2,4-Hexadienes-trans conformation(lower energy)s-cis conformation(higher energy)methyl groupsforced closer thanallowed by vander Waals radii24-24-44Diels-Alder ReactionDiels-Alder Reactionreaction is facilitated by a combination of electron-withdrawing substituents on one reactant and electron-releasing substituents on the otherCyclohexeneEthylene1,3-Butadiene200Cpressure3-Buten-2-one140C+1,3-ButadieneOO+2,3-Dimethyl-1,3-butadiene+30C3-Buten-2-oneOO24-24-55Diels-Alder ReactionDiels-Alder ReactionElectron-WithdrawingGroupsElectron-ReleasingGroups-CN (cyano)-OR (ether)-OOCR (ester)-CHO (aldehyde, ketone)-COOH (carboxyl)-COOR (ester)-NO2(nitro)-CH3, alkyl groups24-24-66Diels-Alder ReactionDiels-Alder Reactionthe Diels-Alder reaction can be used to form bicyclic systems+roomtemperature170CDiene DienophileDicyclopentadiene(endo form)HH24-24-77Diels-Alder ReactionDiels-Alder Reactionexo and endo are relative to the double bond derived from the dienethe double bondderived fromthe dieneendo (inside)exo (outside)relative tothe doublebond24-24-88Diels-Alder ReactionDiels-Alder Reactionfor a Diels-Alder reaction under kinetic control, endo orientation of the dienophile is favoredMethyl bicyclo[2.2.1]hept-5-en-endo-2-carboxylateMethylpropenoateCyclopentadiene+OCH3OHCOOCH3COOCH3redraw24-24-99Diels-Alder ReactionDiels-Alder Reactionthe configuration of the dienophile is retainedCOOCH3COOCH3COOCH3COOCH...
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lecture 24.2 - 24-24-11Organic Organic...

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