Silver mediated functionalization of (3.2.1) bicyclic systems obtained from tetrahalocyclopenes PDF
Preview Silver mediated functionalization of (3.2.1) bicyclic systems obtained from tetrahalocyclopenes
SILVERMEDIATEDFUNCTIONALIZATIONOF[3.2.1]BICYCLICSYSTEMS OBTAINEDFROMTETRAHALOCYCLOPROPENES By RAVISHANKARORUGUNTY ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 2003 “Intryingtounderstandthemysteryoflife,manhasfollowedmanydifferentapproaches. Amongthemtherearethewaysofthescientistandmystic,buttherearemanymore;the waysofthepoets,children,clowns,shamans,tonameafew. Thesewayshaveresulted indifferentdescriptionsoftheworld,bothverbalandnon-verbal,whichemphasize differentaspects. Allarevalidandusefulinthecontexttheyarose. Allofthem, however,areonlydescriptions,orrepresentations,ofrealityandarethereforelimited. Nonecangiveacompletepictureoftheworld.” TheTaoofPhysics,FritjofCapra Thisworkisdedicatedtoallmyteacherswhohaveeducatedme ACKNOWLEDGMENTS Iwouldliketothankmyparents,brothersandsisterfortheirenduringfaithinme throughoutthecourseofmygraduatestudies. Theirpatience,love,support,and encouragementwerevitaltomysuccess. SpecialacknowledgmentsareduetoDr. DennisWright,whoshowedgreatenthusiasmandencouragedmetopursuethisproject andotherprojectswithindependence. Hisabilitytoteachtheartofviewingmolecules, disconnection,andinsightintoanysyntheticproblemhashadadeepimpactonmy thinking. Hisdiscussionsthroughoutthecourseofthisworkwereveryhelpfuland encouraging. Ithasbeenapleasuretoworkwithhim. IwouldalsoliketothankMs. LoriClarkforhelpingmeattheoffice,registeringmeeverysemesterandhelpingmefill outalltherequiredpaperwork. Herhelphasmademystayatthisdepartmentvery uneventfulandpleasant. Withouther,Iwouldhavebeensurelylostinadministrative procedures. IwouldalsoliketoacknowledgeDr.MerleBattiste,whotookgreatinterest inmyresearch,hementored,andeducatedmeintheartandscienceoforganicchemistry especiallythevalueofelementalanalysisasaninvestigativetool. Hisabilitytomentor graduateandundergraduatestudentshasleftadeepimpactonme. Specialthanksare duetoDrIonGhiviriga,whosehelpwithNMRstudieswerevitalforthiswork. Thanks areduetoDr.TomasHudlicky,whowaseverpresentwithhishelpfuldiscussionsand encouragement. IwasveryfortunateinhavinghadmanydiscussionswithDr.Hudlicky, whogivesauniqueandrefreshingperspectiveontheartoforganicchemistryandlife. Withouthispositiveaswellasnegativemotivation,thisdocumentwouldnothaveseen m thelightofday. IwouldalsoliketothankallmygroupmembersespeciallyMs.Lynn UsherandMs.MariaEstrellawithwhomIhadtoworkonadailybasis.Theyhadthe patienceandkindnesstooverlookmyfaultsandhelpmeduringthecourseofthiswork. SpecialthanksgotoClaudeRobothamforbeingtherewhenever1neededhishelp. I wouldalsoliketothankDr.KanikaSharmaandDr.CherianZachariah,foralltheirhelp andsupport. IV TABLEOFCONTENTS Page ACKNOWLEDGMENTS iii ABSTRACT vii CHAPTER 1 CHEMISTRYOFHALOGENATEDCYCLOPROPENES 1 Introduction 1 CycloadditionReactionsofTetrahalocyclopropenes 3 SynthesisofCycloproparenesusingHalogenatedCyclopropenes 10 HalogenatedCyclopropenesin1,3-DipolarReactions 13 ThermalRearrangementsofTetrahalocyclopropenes 16 ReactionsInvolvingCyclopropeniumionsfromHalogenatedCyclopropenes 20 NucleophilicSubstitutionswithTetrahalocyclopropenes 28 Conclusion 33 2 DIELSALDERREACTIONOFTETRABROMOCYCLOPROPENEAND2,5- DIMETHYLFURAN STRUCTUREANDREARRANGEMENTSTUDIES 34 : Introduction 34 KineticData,ResultsandDiscussion 38 Experimental 42 3 FUNCTIONALIZATIONOFTETRAHALOCYCLOPROPENE CYCLOADDUCTSBYSILVERPROMOTEDREACTIONS 45 Introduction 45 ResultsandDiscussion 48 SilverPromotedAdditionofOxygenNucleophiles 48 SilverMediatedAdditionofCarbonNucleophiles 50 AdditionofOrganometallicReagentstoDihaloenones103aand103c 58 SilverMediatedIntramolecularCyclizationofTetrabromooxa[3.2.1]bicyclic Systems 66 ConclusionsandFutureWork 77 4 EXPERIMENTAL 78 v APPENDIX A KINETICSOFREARRANGEMENT:EXPERIMENTALDATA 123 B SPECTRAOFSELECTEDCOMPOUNDS 127 C X-RAYCRYSTALLOGRAPHICDATA 197 LISTOFREFERENCES 233 BIOGRAPHICALSKETCH 240 vi AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy SILVERMEDIATEDFUNCTIONALIZATIONOF[3.2.1]BICYCLICSYSTEMS OBTAINEDFROMTETRAHALOCYCLOPROPENES By RAVISHANKARORUGUNTY August2003 Chair: DennisL.Wright MajorDepartment: Chemistry Thetetrahalobicyclo[3.2.1]octa-2,6-dienesareobtainedbytheDielsAlderreaction offuranandcyclopentadienewithtetrabromoortetrachlorocyclopropene. These oxabicyclicandcarbocyclicsystemsareversatilesyntheticintermediatesthatare analogoustothecompoundsobtainedfrom [4+3]oxyallyladditiontofuranor cyclopentadiene. Treatingthesecompoundswithcationicsilveraffordsthe perhalogenatedoxabicycliccationthatcanbeefficientlytrappedbyelectronrich aromaticsystems. Furtherinvestigationswithregardstothereactivityofthesecations werestudiedandthegeneralityofthissilverpromotedarylationwasexplored. Reaction ofthesecationswithwaterproducesthecorrespondingdihaloenones. Thebicyclic ketonesthatarethusobtainedareversatilesynthonsinthattheycanbetreatedwith variousnucleophilestoaffordhighlysubstitutedbicycliccompoundsingoodyields. AdditionofGrignardreagentsgivessolelythe1,2additionproductsinhighyieldswhile theadditionofcupratesgives1Aadditionproducts. PalladiumcatalyzedSuzuki Vll couplingsofthesedibromoenoneshavealsobeeninvestigatedandfoundtoundergo Suzukicouplingsspecificallyatthebetapositionformingtheproductinveryhighyields thusmakingtheseoxabicyclicsystemsveryusefulsynthons. Theintramolecularcationic cyclizationshavealsobeenstudied. Duringthecourseoftheseinvestigationsthe reactionbetween2,5-dimethylfuranandtetrabromocyclopropeneaffordedtheprimary unrearrangedadduct. Thiscompoundwasusedtostudytheratesofrearrangement,in varioussolvents,byNMRandtheimplicationsoftheseresultstothemechanismof rearrangementhavebeendiscussed. vm CHAPTER 1 CHEMISTRYOFHALOGENATEDCYCLOPROPENES Introduction Thesynthesisofhalogenatedcyclopropanesandcyclopropeneswasfirstreported inaseriesofpapersbyTobeyandWest.lad Theseauthorsshowedthatthethermal decarboxylationofsodiumtrichloroacetateindimethoxyethaneproduces dichlorocarbene,whichreactswithtrichloroethylenetoaffordpentachlorocyclopropane (1). Pentachlorocyclopropanewassubsequentlyconvertedtotetrachlorocyclopropene(2) bytreatmentwithaqueouspotassiumhydroxide. Sodiumtrichloracetate 18MAqKOH 1,2-Dimethoxyethane 80°C Scheme1.1.SynthesisofHalogenatedcyclopropenes Tetrachlorocyclopropenewasreadilyconvertedtotetrabromocyclopropene(3)by treatmentwithstoichiometricamountsofborontribromide. Thesehalogenated 1 2 cyclopropenes,2and3,wererespectivelyconvertedtol,2-dichloro-3,3- difluorocyclopropene(4)andl,2-dibromo-3,3-difluorocyclopropene(5)bytreatment withSbF3(Schemel.l). Theformationofthevarioushalogenatedcyclopropenes,3,4 and5,wereexplainedontheformationofthecorrespondingcyclopropeniumcationthat undergoeshalogensubstitution. Thel,2-dichloro-3,3-difluorocyclopropene(4)and1,2- dibromo-3,3-difluorocyclopropene(5)havebeenconvertedtothemonoanddiiodo cyclopropenesrespectivelyusingpotassiumiodideinDMF.2a — ClX^/F l)(CF3),PF-,/120C XFvv,F Zndust.Ethanol Cl Cl ci Scheme1.2.Synthesisofmono,diiodocyclopropenes.andtetrafluorocyclopropenes. TetrafluorocyclopropenewasfirstsynthesizedbyCamaggietal.2b Thesynthesis involvedthereactionofdifluorocarbeneand1,2-dichlorodifluoroethylenetoproduce1.2- dichlorotetrafluorocyclopropane(9). Reductivedechlorinationofthiscyclopropanewith zincdustaffordedtetrafluorocyclopropene(10). Thetetrafluorocyclopropenewasfound tohavesimilarreactionsasotherhalogenatedcyclopropenes. TetraiodocyclopropenehasbeenreportedbyWeissetal.2c Thecompoundwas synthesizedbytreatingtetrachlorocyclopropenewithtrimethylsilyliodideat0°Corboron
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