Dess–Martin periodinane mediated efficient one-pot oxidation of aldehydes to acyl azides

  • 格式:pdf
  • 大小:133.56 KB
  • 文档页数:3

TETRAHEDRON

LETTERS

TetrahedronLetters44(2003)3543–3545Pergamon

Iodine(V)reagentsinorganicsynthesis.Dess–Martinperiodinane

mediatedefficientone-potoxidationofaldehydestoacylazides

D.SubhasBose*andA.V.NarsimhaReddy

OrganicChemistryDivisionIII,FineChemicalsLaboratory,IndianInstituteofChemicalTechnology,Hyderabad500007,India

Received16January2003;revised17February2003;accepted3March2003Abstract—Amild,efficientandgeneralmethodfortheone-steppreparationofacylazidesfromaldehydesusingDess–Martinperiodinaneandsodiumazideisdescribed.©2003ElsevierScienceLtd.Allrightsreserved.

Thedrivingforceforthedevelopmentofnewmethod-

ologiesinorganicsynthesishasbeentheneedfor

simpleandefficientstrategiestoobtaincomplexnatural

productsandtheiranalogs.Acylazidesarevaluable

syntheticintermediatesinpreparativeorganicchem-

istry.1Theyareusefulforthepreparationofamides

andheterocycliccompounds.Theyundergofacilether-

malrearrangementtoisocyanatesfromwhichure-

thanes,thiourethanes,amines,ketenimines,

carbodiimidesandureascanbeconvenientlyprepared.

Acylazidesareusuallypreparedfromacidderivatives

suchasacidhalidesandacylhydrazides.2Eventhough

severalmethodsareavailabletoaccomplishthistrans-

formation,3themajorityinvolvetheconversionofcar-

boxylicacidstoacidchloridesoranhydrides,whichare

thenreactedwithazidereagents.Thereareafew

reportsonthedirectconversionofcarboxylicacidsto

acylazidesbyusingacidactivatorssuchasethylchlo-

roformate,4diphenylphosphorylazide(DDPA),5NCS-

Ph3P,6triphosgene,7andcyanuricchloride.8Inviewof

this,investigationsinthisfieldhavebeenmainly

focusedonthepreparationofacylazidesdirectlyfrom

aldehydesbyusingcombinationsofchromicanhydride-

trimethylsilylazide,9andtriazidochlorosilane-activated

MnO2.10

Oxidationofcarbonylcompoundstothecorresponding

acylazidesisanimportantsyntheticprocedure,andthe

developmentofselectiveandefficientreagentsforthis

conversion,especiallywhenotheroxidizablefunctional

groupsarealsopresent,hasinterestedorganicchemistsforalongtime.Inthiscontext,notwithstandingthe

availabilityofmanypreparativemethods,therestric-

tionsthataccompanysomeofthemmakenew,mild,

andselectiveprocedureshighlydesirable.

Inrecentyears,hypervalentiodinereagentshaveoccu-

piedanimportantplaceintherealmofnaturaland

syntheticorganicchemistrybecauseoftheirpotential

applicationsintheconstructionofcarbon󰀁heteroatom

andcarbon󰀁carbonbonds.11Oneofthefield’smost

significantadvances,thediscoveryoftheDess–Martin

periodinane(DMP)reagent,121,1,1-triacetoxy-1,1-dihy-

dro-1,2-benziodoxol-3(1H)-one,openedthedoortoa

mildoxidationprocedureallowingamyriadofalcohols

tobeconvertedtothecorrespondingcarbonylcom-

pounds.Itswidespreaduseoverthepastdecadeattests

toitsbenignnatureanditsuncannyabilitytosucceed

inthemostdifficultofoxidationcircumstances.Aspart

ofourongoingprogramonthesynthesisanddevelop-

mentofnewmethodologiesinorganicsynthesis,13we

describeanew,efficientandpracticalrouteforthe

one-stepconversionofaldehydesintothecorrespond-

ingacylazidesbyusingDess–Martinperiodinaneand

sodiumazideinCH2Cl2at0°Cinhighyields(Scheme

1).Moreover,theacylazidescanbeisolatedwithout

Scheme1.Keywords:aldehydes;Dess–Martinperiodinane;acylazides;oxida-tion.*Correspondingauthor.Fax:(040)27160387;e-mail:dsb@iict.ap.nic.in

0040-4039/03/$-seefrontmatter©2003ElsevierScienceLtd.Allrightsreserved.doi:10.1016/S0040-4039(03)00623-3D.S.Bose,A.V.N.Reddy/TetrahedronLetters44(2003)3543–35453544

Curtiusrearrangementleadingtoanalkylisocyanate

becausethereactionconditionsaresomild.Tothebest

ofourknowledge,however,thegeneralityandappli-

cabilityofDMPinthepreparationofacylazidesfrom

aldehydesisnotknown.Theproductswerecharacter-

izedbyIR,1HNMRandmassspectralstudieswhich

wereconsistentwithliteraturedata.14Caution:Azido

compoundsmayrepresentanexplosionhazardwhen

beingconcentratedundervacuumorstoredneat.Asafety

shieldandappropriatehandlingproceduresare

recommended.

Toexplorethegeneralityandscopeofthisprocess,

diversealdehydeswerestudiedtoillustratethisnovel

andgeneralmethodforthesynthesisofacylazidesand

theresultsaresummarizedinTable1.Basedonthe

susceptibilityofthealdehydicC󰀁Hbondstohomolytic

rupture,15thereactionmayproceedviainsitugener-

ated1,1,1-tris(azido)-1,1-dihydro-1,2-benziodoxol-

3(1H)-one,whichisformedbyligandexchange

followedbyhomolyticdecompositiontogeneratean

azidoradical.16Thestartingaldehydemaythenbe

azidonatedviaH-abstractionandcoupling.Theeffectofsubstituentswasobservedbycomparing

theresultswithastronglyelectrondonatingarylgroup

(entry2,Table1)andanelectronwithdrawingexample

(entry5,Table1).Aliphaticaldehydeswerealsooxi-

dizedtothecorrespondingacylazides,butinthese

casesafairamountofacylaziderearrangedtothealkyl

isocyanateatroomtemperature.Whenthetemperature

waskeptbelow0°C,therearrangementwascompletely