Frustrated Lewis Pairs (FLP’s):
Catalysis with Focus on Hydrogena;on
LONG LIT: 6/29/17
VAN TRAN
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Intro
! LP’sfirstdescribedbyGilbertN.Lewis–1923! Electronpairdonor&electronpairacceptorinterac?on
! 1942:H.C.Brown–sterics
! 1959:G.WiGg/1966:Tochtermann–specialreac?vity
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Hydrogen Ac;va;on Beginnings ! DouglasStephan
! Reversible,intramolecular(2006)
! Irreversible,intermolecular(2007)
! Erker&Stephan(2007)
*DFTcalculated
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Cataly;c Hydrogena;on
! GoodforbulkyN! GoodforbasicN
! GoodforbulkyN! Protona?onfirstforbasicN! ForregularN,needLAaddi?ve
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Cataly;c Hydrogena;on 1 ! Bulky(N)imines
! SubstrateasLB(imines&aziridines)
! Enamines&imines
LA-LBadductpreventsproductinhibi?onBulkynitrogenprevents
productinhibi?on
Iminesw/electronpoornitrogenrequirePMes3
addi?veasLB(e.g.protectednitriles)
! Protectedimines&nitriles
Reduc?onofenamines&bulkierimines.
Reduc?onofenamines&iminesatambienttemperature.
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Cataly;c Hydrogena;on 2 ! N-Heterocycles–Stephan
! Metallocenes(enamines)–Erker
ActsasFLPcatalystforhydrogena?onofimines&silyl
enolethers.
! Silylenolethers–Erker
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Cataly;c Hydrogena;on 3 ! Olefins
WeakLBcreatesstrongH+source.
Intermediateswithstabilizedca?ons.
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Cataly;c Hydrogena;on 4 ! Olefins
! Carbonylstoalcohols
! Alkynestocisalkenes
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Cataly;c Hydrogena;on 5 ! Transferhydrogena?on
! ammoniaborane
! diisopropylamine
Concerted2Htransfer.
Stepwisehydrobora?onthenH+transfer.
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General Principles ! H2spli)ngac.vityisbasedonmatchinginterac?onb/wLA&LB
! Sterics:encountercomplex! Electronics:differenceinLewisacidity/basicity! Condi?ons:temperature&pressuredependent
! Mechanismissubstratedependent! Protona.onfirst:
! Basicsubstrates(unprotectedimines)! BasicityofLBisimportant(rela?vetosubstrate)
! WeakLBforolefins(stabilizedca?onintermediate)! Hydridetransferfirst:
! Polarizedpibonds! Pre-coordinatedtoaddedLA! Conjugatedolefins
! Hydrobora.onfirst:! Reac?vepibonds(alkynes)! Non-polarizedpibonds
! Concerted2Htransfer:! Notcommon,ohenforBH3NH3transferhydrogena?on
! Bulkierand/orweakerLA"beierFGtolerance
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Cataly;c Asymmetric Hydrogena;on
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Cataly;c Asymmetric Hydrogena;on
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! Chiralboranes/borates–Klankermayer(2008-2010)
! Phosphoniumhydridoborates–Klankermayer(2012)
! Chiralphosphines–Stephan(2011)! Lessthan25%eewith20%(S,S)-diop
Cataly;c Asymmetric Hydrogena;on 1
Loweree(≤76%)thanchiralborates,butmorestablereagent.
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! Ansa-ammoniumborates–Repo(2011)
Cataly;c Asymmetric Hydrogena;on 2
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! Ansa-ammoniumborates–Repo(2011)
Cataly;c Asymmetric Hydrogena;on 2
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! Ansa-ammoniumborates–Repo(2011)
! Lowerbasicity! ReleasesH2faster&atlowertemp.! Moreac?vecatalystforbasicsubstrates.
! Impliesprotona?onisratedeterminingforbasic&bulkysubstrates.
! Fornon-bulkysubstrates,dissocia?onofprdfromLAisratedetermining.
Cataly;c Asymmetric Hydrogena;on 2
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! Ansa-ammoniumborates–Repo(2011)
! Axiallychiralammoniumboronate–Repo(2015)
! Chiralsulfonamide–Du(2016)
Cataly;c Asymmetric Hydrogena;on 3
Racemizesunderreac?oncondi?ons.
≤37%ee≤17%ee
Imines:34-92%yield32-83%ee
Enamines:42-95%yield47-99%ee
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! Axiallychiraldienesasprecursors–Du(2013-2016)
Cataly;c Asymmetric Hydrogena;on 4
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! Carbonyls–Piers(1996)
! Iminesasymmetric–Mewald&Klankermayer(2011-2012)
! Heterocycles
Cataly;c Hydrosilyla;on ! Imines–Piers(2000)
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! Cataly?cC-Hac?va?onboryla?on–Fontaine(2015)
! Carbon-basedLA–Stephan(2013)
! Perfluoroalkyla?on
Miscellaneous
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! Reduc?veetherifica?on–Soos(2017)
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Thank You!
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