Boron Reagents in Process Chemistry__Excellent Tools for Selective.PDF

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1、Chem.Rev.2006,106,2617-26502617BoronReagentsinProcessChemistry:ExcellentToolsforSelectiveReductionsElizabethR.BurkhardtandKarlMatos*BASFCorporation,1424Mars-EvansCityRoad,EvansCity,Pennsylvania16033ReceivedSeptember12,2005Contentsandhighselectivities,thesere

2、agentshavebecomeavaluablepartoftheorganicchemistrytoolboxandfoundtheirway1.IntroductionandScope2617intoanumberofcommercialapplications.2.Hydroboration2618Muchoftheexploratoryresearchonthesyntheticap-2.1.ConversiontoAlcohol2619plicationofboranechemistrywascon

3、ductedinthelabora-2.2.Suzuki-MiyauraSubstrateFormation2621toriesofH.C.Brown.Borane(BH3)isanelectrophilic2.3.AsymmetricHydroboration2622reducingagent;thatis,itisnotnucleophilicorhydridicin3.ReductiontoAlcohol2623nature.Thiselectrophilicityofboranecanbevieweda

4、s3.1.CarboxylicAcidReduction2623Lewisacidcharactersincetheboroniselectrondeficient.3.2.Aldehyde,Ketone,andEsterReduction2624Duetotheelectrophilicnatureofboraneandcomplexationwiththeelectron-richcenterofthefunctionalgroup,reduc-3.3.LactoneReductiontoLactol262

5、5tionswithboraneareveryselectiveandspecific.3.4.AmideReductiontoAlcohol2626Thecatalyticeffectofethersinthehydroborationreaction4.ReductiontoAmines2626ledtothedevelopmentofmorestableboraneligand4.1.AmideReduction2626complexes(BH3-L)asthepreferredboranesources

6、at4.2.NitrileReduction2628commercialscale.BoraneadductsofLewisbasessuchas4.3.NitroGroupReductiontoAmine2628tetrahydrofuran(THF),dimethylsulfide(DMS),andsome4.4.ReductiveAmination2628aromaticandhinderedamineshavebeenusedveryef-4.4.1.ViaAmineBoranes2629fective

7、lyforhydroborationofdoubleandtriplebondsaswell4.4.2.ViaSodiumTriacetoxyborohydride2630asinreductionsofotherfunctionalgroups.5.StereoselectiveReactionswithBoranesand2635ThestrengthoftheLewisbasedeterminesthereactivityBorohydridesoftheboranecomplex.Boranetetra

8、hydrofurancomplex5.1.StereoselectiveKetoneReduction2635(BTHF)isthemostreactive.Attheotherextreme,numerous5.2.DiastereoselectiveReductionof2636amineboranespossesslowreactivityeventowardprotonâ-Hy