Dess–Martin periodinane mediated efficient one-pot oxidation of aldehydes to acyl azides
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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
applicationsintheconstructionofcarbonheteroatom
andcarboncarbonbonds.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
susceptibilityofthealdehydicCHbondstohomolytic
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