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1、P1:FCH/FFXP2:FCH/FFXQC:FCH/FFXT1:FCHBY023-Tierney-v2.clsDecember24,20047:504Microwave-assistedreductionsTIMOTHYN.DANKSandGABRIELEWAGNER4.1.IntroductionReductionsoforganicfunctionalgroupsplayacentralroleinsynthesis.However,theirapplicationisoftenlimitedandispoorl
2、ycompatiblewiththesynthesisofsensitiveproductsbecauseoftheharshconditionsused.Similartomanyothertypesoftransfor-mationsinorganicchemistry,hightemperatureandlongreactiontimesarecommon,andmanyreactionssufferfromtheformationofby-products.Theimprovementofcurrentlyex
3、istingreductionschemestowardsfaster,moreselective,economicallyandecologicallyacceptableproceduresisthereforeanimportantissue.Inthiscontext,theapplicationofmicrowaveheatingwasshowntohaveastronglybeneficialimpactonalargevarietyofsyntheticprocedures.Oftenreactiontim
4、escanbedrasticallyreduced,thusleadingtooverallmilderreactionconditions,higheryieldsandpurerproducts.Inmanyexamplestheapplicationofmicrowaveirradiationhasalsoallowedfortheuseofmilderandmoreenvironmentallyacceptablereagents1−7.Theuseofmicrowaveirradiationisthusexp
5、ectedtoimprovereductionsoffunctionalgroupsinasimilarsense.Anumberofreductionsinorganicchemistryrequiretheuseofgasesunderhighpressure,forexample,catalytichydrogenationreactionswithhydrogen.Althoughtheuseofgasesinthelaboratoryandonasmallscaledoesnotnecessarilycre-
6、ateaseveresafetyhazard,thereactionsrequirededicatedequipment,suchasau-toclavesorgascylinders,andanoxygen-freeatmosphere.Theintroductionofsolidhydrogendonorsallowsforhydrogenationreactionsbeingperformedinnormalre-actionvessels,andthishasfacilitatedtheuseofmicrowa
7、veheatinginsuchtypeofreactionsandallowedtobenefitfromthegeneraladvantagesofmicrowave-assistedreactions.Solvent-freereactionsplayanimportantroleinmicrowave-enhancedchemistry8−11,andespeciallythedevelopmentof‘dry’reactionsonmineralsupportsinconjunctionwithmicrowave
8、irradiationhavehadastrongimpactonthedevelopmentofsafeandefficientreductionschemes.Indryreactionconditions,themicrowaveenergyisdirectlyabsorbedbythesolidsupportortherea
