Compounds with All-Carbon Functions. 1,3-Dienes

685 Pages·2009·8.686 MB·English

by  Rawal, V. H., Kozmin, S. A.

VII
Volume 46:
1,3-Dienes
Preface ................................................................ V
TableofContents ...................................................... IX
Introduction
V.H.RawalandS.A.Kozmin ................................................ 1
46.1 SynthesisUsingtheWittigandRelatedPhosphorus-,Silicon-,or
Sulfur-BasedReactions
A.D.AbellandM.K.Edmonds .............................................. 23
46.2 SynthesisbyAlkylidenationwithMetal–CarbeneComplexesandRelated
Reagents
T.TakedaandA.Tsubouchi .................................................. 63
46.3 SynthesisbyAlkeneMetathesis
S.T.Diver ................................................................... 97
46.4 SynthesisbyAldolandRelatedCondensationReactions
K.P.C.Minbiole ............................................................. 147
46.5 SynthesisbyMetal-MediatedC-CBondFormingReactionsofAlkynes,
Diynes,andEnynes
V.Gandon,S.Thorimbert,andM.Malacria ................................... 173
46.6 SynthesisbyMetal-MediatedCouplingReactions
E.NegishiandG.Wang ..................................................... 239
46.7 SynthesisbyCycloadditionandElectrocyclicReactions
M.Shindo,T.Yoshikawa,andK.Yaji ......................................... 353
46.8 SynthesisbyExtrusion
R.S.GraingerandP.J.Jervis ................................................. 401
46.9 SynthesisbyElimination
M.P.Schramm .............................................................. 445
46.10 SynthesisbyReduction
D.J.Ram(cid:62)nandM.Yus ...................................................... 523
46.11 SynthesisbyIsomerizationofUnconjugatedDienes,Allenes,Alkynes,and
Methylenecyclopropanes
R.E.Taylor,C.R.Di(cid:23)ne,andE.M.Daly ....................................... 549
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46.12 SynthesisfromArenesandPolyenes
Y.-S.Wong .................................................................. 589
46.13 SynthesisviaMetalComplexesofDienes
I.BauerandH.-J.Knçlker .................................................... 637
KeywordIndex ............................................................. 669
AuthorIndex ............................................................... 711
Abbreviations .............................................................. 739
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IX
Table of Contents
Introduction
V.H.RawalandS.A.Kozmin
Introduction ................................................................. 1
46.1 SynthesisUsingtheWittigandRelatedPhosphorus-,Silicon-,or
Sulfur-BasedReactions
A.D.AbellandM.K.Edmonds
46.1 SynthesisUsingtheWittigandRelatedPhosphorus-,Silicon-,or
Sulfur-BasedReactions ..................................................... 23
46.1.1 TheWittigReaction ......................................................... 24
46.1.1.1 Method1: SynthesisfromPhosphorusYlidesandEnonesorEnals ....... 24
46.1.1.1.1 Variation1: FromStabilizedYlides ....................................... 25
46.1.1.1.2 Variation2: FromNonstabilizedYlides ................................... 27
46.1.1.2 Method2: SynthesisfromAllylPhosphorusYlidesandCarbonyl
Compounds ................................................. 30
46.1.1.3 Method3: SynthesisbyTandemOxidation–WittigReaction ............. 34
46.1.1.3.1 Variation1: SimultaneousDieneFormation .............................. 35
46.1.1.3.2 Variation2: SequentialDieneFormation ................................. 35
46.1.2 TheHorner–WittigReaction ................................................. 37
46.1.2.1 Method1: SynthesisfromPhosphineOxidesandEnals .................. 38
46.1.2.2 Method2: SynthesisfromAlkenylphosphineOxidesandAldehydesor
Ketones ..................................................... 38
46.1.3 TheHorner–Wadsworth–EmmonsReaction .................................. 39
46.1.3.1 Method1: SynthesisfromPhosphonatesandEnonesorEnals ........... 40
46.1.3.1.1 Variation1: TheAndoMethod ........................................... 42
46.1.3.1.2 Variation2: TheStill–GennariModification ............................... 43
46.1.3.2 Method2: SynthesisfromAlkenylphosphonatesandCarbonyl
Compounds ................................................. 44
46.1.3.2.1 Variation1: TheStill–GennariModification ............................... 46
46.1.4 ThePetersonReaction ...................................................... 46
46.1.4.1 Method1: Synthesisfroma,b-UnsaturatedCarbonylCompoundsand
Alkylsilanes ................................................. 47
46.1.4.2 Method2: SynthesisfromCarbonylCompoundsandAllylsilanes ......... 49
46.1.4.3 Method3: TheVinylogousPetersonElimination ......................... 53
46.1.5 TheJuliaReactionandItsVariations ......................................... 54
46.1.5.1 Method1: Synthesisfroma,b-UnsaturatedCarbonylCompoundsand
AlkylSulfones ............................................... 55
46.1.5.2 Method2: SynthesisfromCarbonylCompoundsandAllylSulfones ...... 57
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46.1.5.3 Method3: TheKeckVariation .......................................... 59
46.2 SynthesisbyAlkylidenationwithMetal–CarbeneComplexesandRelated
Reagents
T.TakedaandA.Tsubouchi
46.2 SynthesisbyAlkylidenationwithMetal–CarbeneComplexesandRelated
Reagents ................................................................... 63
46.2.1 Methylenation .............................................................. 63
46.2.1.1 Method1: SynthesisUsingTitanium-BasedReagents .................... 63
46.2.1.1.1 Variation1: UsingtheTebbeReagent .................................... 63
46.2.1.1.2 Variation2: UsingBis(h5-cyclopentadienyl)(dihalozinc)(m-methylene)-
titanium .................................................... 68
46.2.1.1.3 Variation3: UsingBis(h5-cyclopentadienyl)dimethyltitanium(IV)(The
PetasisReagent) ............................................ 69
46.2.1.1.4 Variation4: UsingTitanacyclobutenes ................................... 72
46.2.1.2 Method2: SynthesisUsingZinc-BasedReagents ......................... 73
46.2.1.3 Method3: SynthesisUsingMiscellaneousReagents ..................... 77
46.2.2 HalomethylenationandRelatedReactions ................................... 79
46.2.2.1 Method1: SynthesisUsingTitanium-BasedReagents .................... 80
46.2.2.2 Method2: SynthesisUsingZinc-BasedReagents ......................... 81
46.2.2.3 Method3: SynthesisUsingChromium-BasedReagents .................. 82
46.2.3 OtherAlkylidenationReactions .............................................. 87
46.2.3.1 Method1: SynthesisUsingTitanium-BasedReagents .................... 87
46.2.3.2 Method2: SynthesisUsingZinc-BasedReagents ......................... 90
46.2.3.3 Method3: SynthesisUsingChromium-BasedReagents .................. 91
46.2.3.4 Method4: SynthesisUsingMiscellaneousReagents ..................... 92
46.3 SynthesisbyAlkeneMetathesis
S.T.Diver
46.3 SynthesisbyAlkeneMetathesis .......................................... 97
46.3.1 Method1: Ring-ClosingMetathesisofEnynes .......................... 102
46.3.1.1 Variation1: UsingGrubbs’Catalysts .................................... 102
46.3.1.2 Variation2: PolycyclizationUsingGrubbs’Catalysts ..................... 107
46.3.1.3 Variation3: UsingtheHoveyda–BlechertCatalyst ....................... 112
46.3.1.4 Variation4: PolycyclizationUsingtheHoveyda–BlechertCatalyst ........ 114
46.3.1.5 Variation5: UsingtheSchrockCatalyst ................................. 115
46.3.2 Method2: Ring-ClosingMetathesisofAlkeneswithConjugatedDienes . 118
46.3.3 Method3: CrossMetathesisofAlkyneswithAlkenes ................... 121
46.3.3.1 Variation1: MetathesisofAlkyneswithEthene ......................... 121
46.3.3.2 Variation2: MetathesisofTerminalAlkyneswithOtherAcyclicAlkenes .. 125
46.3.3.3 Variation3: MetathesisofInternalAlkyneswithAcyclicAlkenes ......... 129
46.3.3.4 Variation4: Ethene-AssistedMetathesis ................................ 130
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46.3.3.5 Variation5: MetathesisofAlkyneswithCycloalkenes .................... 131
46.3.4 Method4: CrossMetathesisofAlkeneswithConjugatedDienes ........ 135
46.3.5 Method5: CrossMetathesisofAlkenesFollowedbyElimination ........ 140
46.3.6 Method6: Ring-RearrangementMetathesis ............................ 141
46.4 SynthesisbyAldolandRelatedCondensationReactions
K.P.C.Minbiole
46.4 SynthesisbyAldolandRelatedCondensationReactions .................. 147
46.4.1 Synthesisof1,3-DieneswithanElectron-WithdrawingGroupatC1 .......... 148
46.4.1.1 Method1: Formationofthea,b-Alkene ............................... 148
46.4.1.1.1 Variation1: UnderBasicConditionswithThermodynamicControl ....... 149
46.4.1.1.2 Variation2: UnderKineticConditionswithSubsequentElimination ...... 150
46.4.1.1.3 Variation3: UnderLewisAcidicConditions .............................. 151
46.4.1.1.4 Variation4: OtherApproaches ......................................... 153
46.4.1.2 Method2: Formationoftheg,d-Alkene ................................ 153
46.4.1.2.1 Variation1: DrivenbyExtendedConjugation ............................ 154
46.4.1.2.2 Variation2: LactoneFormation ......................................... 154
46.4.1.2.3 Variation3: OtherReactions ............................................ 156
46.4.2 Synthesisof1,3-DieneswithanElectron-WithdrawingGroupatC2 .......... 158
46.4.2.1 Method1: Formationofthea,b-Alkene ............................... 158
46.4.2.1.1 Variation1: Single-StepReactions ...................................... 159
46.4.2.1.2 Variation2: MultistepReactions ........................................ 159
46.4.2.1.3 Variation3: OtherStrategies ........................................... 160
46.4.3 Synthesisof1,3-DieneswithTwoElectron-WithdrawingGroupsatC1 ....... 160
46.4.3.1 Method1: Formationofthea,b-Alkene ............................... 161
46.4.3.1.1 Variation1: UnderStandardBasicConditions ........................... 161
46.4.3.1.2 Variation2: UsingAlternativePromoters ................................ 162
46.4.3.1.3 Variation3: FromNon-EsterSubstrates ................................. 162
46.4.3.2 Method2: Formationoftheg,d-Alkene ................................ 163
46.4.4 Synthesisof1,3-DieneswithElectron-WithdrawingGroupsatC1andC3 .... 164
46.4.4.1 Method1: KnoevenagelandRelatedCondensations ................... 165
46.4.5 Synthesisof1,3-DieneswithElectron-WithdrawingGroupsatC2andC3 .... 166
46.4.5.1 Method1: SingleStobbeReaction ..................................... 166
46.4.5.2 Method2: DoubleStobbeReaction ................................... 167
46.5 SynthesisbyMetal-MediatedC-CBondFormingReactionsofAlkynes,
Diynes,andEnynes
V.Gandon,S.Thorimbert,andM.Malacria
46.5 SynthesisbyMetal-MediatedC-CBondFormingReactionsofAlkynes,
Diynes,andEnynes ....................................................... 173
46.5.1 Acyclic1,3-Dienes ......................................................... 173
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46.5.1.1 Method1: Nickel-CatalyzedAldehyde–AlkyneandAldehyde–Enyne
Coupling .................................................. 173
46.5.1.1.1 Variation1: Nickel-CatalyzedAldehyde–AlkyneCoupling ................ 173
46.5.1.1.2 Variation2: Nickel-CatalyzedAldehyde–EnyneCoupling ................. 174
46.5.1.2 Method2: CouplingofAlkynes ........................................ 175
46.5.1.2.1 Variation1: Titanium-MediatedCarbometalationofInternalAlkynes .... 176
46.5.1.2.2 Variation2: Zirconium-MediatedCarbometalationofAlkynes ........... 177
46.5.1.2.3 Variation3: Ruthenium-CatalyzedDimerizationofPropargylAlcohols ... 180
46.5.1.3 Method3: 2:1Co-oligomerizationofAlkynesandAlkenes ............. 181
46.5.1.3.1 Variation1: Cobalt-MediatedC-HActivation ........................... 181
46.5.1.3.2 Variation2: Nickel-MediatedC-HActivation ........................... 182
46.5.2 Endocyclic1,3-Dienes ...................................................... 183
46.5.2.1 Method1: SynthesisviaZirconacyclopentadienes ...................... 183
46.5.2.2 Method2: Six-MemberedRingsby[2+2+2]Cycloaddition ............ 185
46.5.2.2.1 Variation1: Titanium-CatalyzedCycloaddition .......................... 186
46.5.2.2.2 Variation2: Zirconium-MediatedCycloaddition ......................... 186
46.5.2.2.3 Variation3: Ruthenium-CatalyzedCycloaddition ........................ 187
46.5.2.2.4 Variation4: Cobalt-MediatedCycloaddition ............................. 190
46.5.2.2.5 Variation5: Rhodium-CatalyzedCycloaddition .......................... 197
46.5.2.2.6 Variation6: Iridium-CatalyzedCycloaddition ............................ 201
46.5.2.2.7 Variation7: Nickel-CatalyzedCycloaddition ............................. 203
46.5.2.3 Method3: Six-MemberedRingsbyCycloisomerizationof1,5-Enynes ... 205
46.5.2.4 Method4: Seven-MemberedRingsbyCycloadditionor
CycloisomerizationofDiynes ............................... 206
46.5.2.5 Method5: CodimerizationReactionbetween1,3-DienesandAlkynes .. 207
46.5.2.6 Method6: Cobalt-MediatedSynthesesofAlkaloidsandSteroids ........ 207
46.5.3 1,3-DienesHavingTwoExocyclicDoubleBonds ............................. 210
46.5.3.1 Method1: CyclizationofDiynes ....................................... 210
46.5.3.1.1 Variation1: Titanium-PromotedCyclizationofDiynes ................... 210
46.5.3.1.2 Variation2: Zirconacene-Derivative-PromotedCyclizationofDiynes ..... 211
46.5.3.1.3 Variation3: Nickel-CatalyzedCyclizationofDiynes ...................... 212
46.5.3.2 Method2: CyclizationofEnynes ....................................... 213
46.5.3.2.1 Variation1: Palladium-CatalyzedCycloisomerizationofEnynes .......... 214
46.5.3.2.2 Variation2: Ruthenium-CatalyzedCycloisomerizationofEnynes ......... 215
46.5.3.2.3 Variation3: Iridium(I)-CatalyzedCycloisomerizationofEnynes ........... 216
46.5.3.2.4 Variation4: Cobalt(I)-MediatedCycloisomerizationof1,n-Enynes ........ 217
46.5.3.3 Method3: CyclizationofAllenynes .................................... 218
46.5.4 ConjugatedVinylicCycloalkenes ............................................ 219
46.5.4.1 Method1: Cycloisomerizationof1,6-Enynes ........................... 219
46.5.4.1.1 Variation1: Palladium-CatalyzedCycloisomerizationToGive
Vinylcyclopentenes ........................................ 219
46.5.4.1.2 Variation2: Ruthenium-CatalyzedCycloisomerizationToGive
Vinylcycloalkenes .......................................... 220
46.5.4.1.3 Variation3: Platinum-andGold-CatalyzedCycloisomerizationToGive
Vinylcycloalkenes .......................................... 221
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46.5.4.1.4 Variation4: Iridium-CatalyzedCycloisomerizationToGive
Vinylcycloalkenes .......................................... 223
46.5.4.2 Method2: CycloisomerizationofAllenynes ............................ 224
46.5.4.2.1 Variation1: Platinum-CatalyzedCycloisomerizationToGive
Vinylcycloalkenes .......................................... 224
46.5.4.2.2 Variation2: Gold-andPlatinum-CatalyzedCycloisomerizationToGive
Cross-ConjugatedTrienes .................................. 225
46.5.4.2.3 Variation3: Rhodium-CatalyzedIsomerizationToGiveCross-Conjugated
Trienes .................................................... 225
46.5.4.2.4 Variation4: Titanium(II)-MediatedCyclizationToGiveCross-Conjugated
Trienes .................................................... 226
46.5.4.2.5 Variation5: Cobalt(I)-MediatedCyclizationToGiveCross-Conjugated
Trienes .................................................... 227
46.5.5 1,3-DienesHavingEndocyclicandExocyclicDoubleBonds .................. 227
46.5.5.1 Method1: Cycloisomerizationof1,6-and1,7-Enynes .................. 228
46.5.5.1.1 Variation1: Palladium-CatalyzedCycloisomerization .................... 228
46.5.5.1.2 Variation2: Gold-CatalyzedCycloisomerization ......................... 228
46.5.5.1.3 Variation3: Rhodium-CatalyzedCycloisomerization ..................... 230
46.5.5.1.4 Variation4: Ruthenium-CatalyzedCycloisomerization ................... 231
46.5.5.2 Method2: CycloisomerizationofAllenynes ............................ 231
46.5.6 s-trans-Heteroannular1,3-Dienes ........................................... 232
46.5.6.1 Method1: CycloisomerizationofDienynes ............................. 232
46.5.6.2 Method2: CycloisomerizationofAllenynes ............................ 232
46.6 SynthesisbyMetal-MediatedCouplingReactions
E.NegishiandG.Wang
46.6 SynthesisbyMetal-MediatedCouplingReactions ........................ 239
46.6.1 Method1: StoichiometricSynthesisof1,3-DienesbyMetal-Mediated
CouplingReactionsviaMigratoryInsertion ................. 244
46.6.1.1 Variation1: 1,4-DisubstitutedE,E-1,3-Dienesby[2C+2C]Alkenyl–Alkenyl
CouplingviaOrganoboronMigratoryInsertionReactions .... 245
46.6.1.2 Variation2: 1,4-DisubstitutedE,Z-1,3-Dienesby[2C+2C]Alkynyl–Alkenyl
CouplingviaOrganoboronMigratoryInsertionReactions .... 246
46.6.1.3 Variation3: 1,4-DisubstitutedZ,Z-1,3-Dienesby[2C+2C]Alkynyl–Alkynyl
CouplingviaBoron-orZirconium-MediatedMigratory
Insertion ................................................... 247
46.6.1.4 Variation4: OtherOrganozirconiumMigratoryInsertionReactionsforthe
Synthesisof1,3-Dienes .................................... 248
46.6.2 Method2: StoichiometricSynthesisof1,3-DienesbyMetal-Mediated
[2C+2C]CouplingviaCarbometalation .................... 249
46.6.2.1 Variation1: Synthesisof1,3-DienesbyControlledAlkyneDimerizationvia
syn-Carbometalation ....................................... 251
46.6.2.2 Variation2: Chelation-Guidedanti-CarbometalationwithAlkenyl-and
Alkynylmetals .............................................. 252
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46.6.2.3 Variation3: Zirconium-PromotedEne–YneCouplingandAlkyne
Dimerization ............................................... 252
46.6.2.4 Variation4: Titanium-PromotedEne–YneCouplingandAlkyne
Dimerization ............................................... 255
46.6.3 Method3: Synthesisof1,3-DienesbyPalladium-Catalyzed
Cross-CouplingReactions .................................. 256
46.6.3.1 Variation1: 1,3-DienesContainingtheParentVinyland/or
1-MonosubstitutedVinylGroups ........................... 266
46.6.3.2 Variation2: 1,4-Disubstituted1,3-Dienes ............................... 271
46.6.3.3 Variation3: Trisubstituted1,3-DienesExcludingThoseContainingaVinyl
orVinylideneGroup ........................................ 275
46.6.3.4 Variation4: Tetrasubstituted1,3-DienesExcludingThoseContaininga
FullySubstitutedAlkenylGroup ............................ 285
46.6.3.5 Variation5: Tetra-,Penta-,andHexasubstituted1,3-DienesContaining
OneorTwoFullySubstitutedAlkenylGroupsExcluding
1,1,2,3-Tetrasubstituted1,3-Dienes ........................ 287
46.6.4 Method4: 1,3-DienesthroughModificationof4CCompounds ......... 290
46.6.4.1 Variation1: 1,3-DienesviaHeterofunctionalized1,3-Dienes ............. 290
46.6.4.2 Variation2: 1,3-Dienesvia1,3-Enynesand1,3-Diynes ................... 300
46.6.5 Method5: Synthesisof1,3-DienesbyCatalyticCarbometalationand
OxymetalationReactions ................................... 308
46.6.5.1 Variation1: 1,3-DienesviatheHeckReaction ........................... 308
46.6.5.2 Variation2: OtherCatalyticCarbopalladationRoutesto1,3-Dienes ...... 315
46.6.5.3 Variation3: 1,3-DienesviaOxymetalationReactions .................... 326
46.6.6 Method6: Synthesisof1,3-Diene-ContainingOligoenesand
OligoenynesofNaturalOriginandRelatedCompounds ..... 332
46.7 SynthesisbyCycloadditionandElectrocyclicReactions
M.Shindo,T.Yoshikawa,andK.Yaji
46.7 SynthesisbyCycloadditionandElectrocyclicReactions .................. 353
46.7.1 Method1: ThermalElectrocyclicRing-OpeningReactionsof
Cyclobutenes .............................................. 353
46.7.1.1 Variation1: Acyclic1,3-Dienesfrom3,4-UnsubstitutedCyclobutenes .... 354
46.7.1.2 Variation2: Acyclic1,3-Dienesfrom3-SubstitutedCyclobutenes ........ 356
46.7.1.3 Variation3: Acyclic1,3-DienesfromMultisubstitutedCyclobutenes ..... 359
46.7.1.4 Variation4: Cycloalka-1,3-dienesfrom3,4-FusedCyclobutenes(Ring
Expansion) ................................................. 364
46.7.1.5 Variation5: 1,3-Dienesfrom1,2-FusedCyclobutenes ................... 368
46.7.1.6 Variation6: 1,3-Dienesfrom1,4-FusedCyclobutenes ................... 369
46.7.2 Method2: PhotochemicalReactionsofCyclobutenes .................. 370
46.7.3 Method3: ThermalSix-ElectronElectrocyclizationsToGive
Cyclohexa-1,3-dienes ...................................... 371
46.7.3.1 Variation1: Cyclohexa-1,3-dienesfromAcyclic1,3,5-Trienes ............ 374
46.7.3.2 Variation2: 1,6-FusedCyclohexa-1,3-dienesfrom1,2-Fused1,3,5-Trienes 377
46.7.3.3 Variation3: 1,2-FusedCyclohexa-1,3-dienesfrom2,3-Fused1,3,5-Trienes 380
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46.7.3.4 Variation4: 2,3-Ring-FusedCyclohexa-1,3-dienesfrom3,4-Ring-Fused
1,3,5-Trienes ............................................... 382
46.7.3.5 Variation5: 5,6-FusedCyclohexa-1,3-dienesfromCycloalka-1,3,5-trienes. 383
46.7.4 Method4: PhotochemicalSix-ElectronElectrocyclizations .............. 385
46.7.5 Method5: UnsaturatedCarbocyclesviaaCombinationofThermally
InducedElectrocyclizations ................................. 386
46.7.6 Method6: [6+4]CycloadditionsbetweenButa-1,3-dienesand
Hexa-1,3,5-trienes ......................................... 389
46.7.6.1 Variation1: [6+4]CycloadditionsofTropones .......................... 389
46.7.6.2 Variation2: [6+4]CycloadditionsofFulvenes ........................... 394
46.8 SynthesisbyExtrusion
R.S.GraingerandP.J.Jervis
46.8 SynthesisbyExtrusion .................................................... 401
46.8.1 ExtrusionofAlkenes ....................................................... 401
46.8.1.1 Method1: ThermalCrackingofCyclohexene ........................... 401
46.8.1.2 Method2: ExtrusionofCyclopentadiene ............................... 402
46.8.1.2.1 Variation1: CrackingofDicyclopentadiene ............................. 402
46.8.1.2.2 Variation2: CyclopentadieneasaProtectingGroup ..................... 402
46.8.1.3 Method3: ExtrusionofMaleicAnhydride .............................. 403
46.8.2 ExtrusionofCarbonDioxide ................................................ 404
46.8.2.1 Method1: CarbonDioxideExtrusionfromSix-MemberedLactones ..... 404
46.8.2.2 Method2: CarbonDioxideExtrusionwithInSituTrappingoftheDiene . 405
46.8.2.3 Method3: CarbonDioxideExtrusionfromVinyl-Substitutedb-Lactones . 406
46.8.2.3.1 Variation1: DecarboxylativeExtrusionfromb-Lactones ................. 406
46.8.2.3.2 Variation2: TandemLactoneFormation–CarbonDioxideExtrusion ...... 407
46.8.3 ExtrusionofCarbonMonoxide ............................................. 408
46.8.3.1 Method1: CarbonMonoxideExtrusionfromMonocyclic
Cyclopent-3-en-1-ones ..................................... 408
46.8.3.2 Method2: ExtrusionofaBridgingCarbonMonoxidefromStrainedRings 409
46.8.3.3 Method3: CarbonMonoxideExtrusionwithInSituTrappingoftheDiene 410
46.8.3.4 Method4: CarbonMonoxideExtrusionToAffordCyclooctatetraenes ... 411
46.8.3.5 Method5: CarbonMonoxideExtrusionfromb-AllenylAldehydes ....... 411
46.8.4 ExtrusionofSulfurDioxide ................................................. 412
46.8.4.1 Method1: ThermalExtrusionofSulfurDioxidefrom
2,5-Dihydrothiophene1,1-Dioxides ......................... 412
46.8.4.1.1 Variation1: Preparationof1,4-Disubstituted1,3-DienesviaThermolysis . 413
46.8.4.1.2 Variation2: PreparationofTerminal1,3-DienesviaThermolysis ......... 415
46.8.4.1.3 Variation3: Preparationof2,3-Disubstituted1,3-DienesviaThermolysis . 416
46.8.4.1.4 Variation4: PreparationofOtherSubstitutionPatternsviaThermolysis .. 418
46.8.4.2 Method2: ThermolysisFollowedbyInSituTrapping ................... 418
46.8.4.2.1 Variation1: IntermolecularDiels–AlderTrappingoftheDiene ........... 419
46.8.4.2.2 Variation2: IntramolecularDiels–AlderTrappingoftheDiene ........... 420
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