Gallagher–Hollander degradation

In the Gallagher–Hollander degradation (1946) pyruvic acid is removed from a linear aliphatic carboxylic acid yielding a new acid with two carbon atoms fewer.[1] The original publication concerns the conversion of bile acid in a series of reactions: acid chloride (2) formation with thionyl chloride, diazoketone formation (3) with diazomethane, chloromethyl ketone formation (4) with hydrochloric acid, organic reduction of chlorine to methylketone (5), ketone halogenation to 6, elimination reaction with pyridine to enone 7 and finally oxidation with chromium trioxide to bisnorcholanic acid 8.
pyruvic acidcarboxylic acidbile acidacid chloridethionyl chloridediazomethanehydrochloric acidorganic reductionketone halogenationelimination reactionpyridinechromium trioxideJ. Biol. 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rearrangementChan–Lam couplingClaisen condensationClaisen rearrangementClaisen-Schmidt condensationCombes quinoline synthesisCorey–Fuchs reactionCorey–House synthesisCoupling reactionCross-coupling reactionCross dehydrogenative couplingCross-coupling partnerDakin–West reactionDarzens reactionDiels–Alder reactionDoebner reactionWulff–Dötz reactionEne reactionEnyne metathesisEthenolysisFavorskii reactionFerrier carbocyclizationFriedel–Crafts reactionFujimoto–Belleau reactionFujiwara–Moritani reactionFukuyama couplingGabriel–Colman rearrangementGattermann reactionGlaser couplingGrignard reactionGrignard reagentHammick reactionHeck reactionHenry reactionHeterogeneous metal catalyzed cross-couplingHigh dilution principleHiyama couplingHomologation reactionHorner–Wadsworth–Emmons reactionHydrocyanationHydrovinylationHydroxymethylationIvanov reactionJohnson–Corey–Chaykovsky reactionJulia olefinationJulia–Kocienski olefinationKauffmann olefinationKnoevenagel condensationKnorr pyrrole 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reactionWeinreb ketone synthesisWittig reactionWurtz reactionWurtz–Fittig reactionZincke–Suhl reactionHomologation reactionsHooker reactionKiliani–Fischer synthesisMethoxymethylenetriphenylphosphoraneBamford–Stevens reactionBoord olefin synthesisChugaev eliminationCope reactionCorey–Winter olefin synthesisDehydrohalogenationGrieco eliminationHofmann eliminationHydrazone iodinationAzo couplingBartoli indole synthesisBoudouard reactionCadogan–Sundberg indole synthesisDiazonium compoundEsterificationHaloform reactionHegedus indole synthesisHurd–Mori 1,2,3-thiadiazole synthesisKharasch–Sosnovsky reactionLeimgruber–Batcho indole synthesisMukaiyama hydrationNenitzescu indole synthesisOxymercuration reactionReed reactionSchotten–Baumann reactionUllmann condensationWilliamson ether synthesisYamaguchi esterificationBarbier–Wieland degradationBergmann degradationEdman degradationEmde degradationHofmann rearrangementIsosaccharinic acidMarker degradationRuff degradationStrecker degradationVon 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rearrangementAchmatowicz reactionAlkyne zipper reactionAllen–Millar–Trippett rearrangementAllylic rearrangementAlpha-ketol rearrangementAmadori rearrangementAza-Cope rearrangementBaker–Venkataraman rearrangementBamberger rearrangementBanert cascadeBeckmann rearrangementBenzilic acid rearrangementBoekelheide reactionBrook rearrangementCarroll rearrangementCope rearrangementCornforth rearrangementCriegee rearrangementCurtius rearrangementDemjanov rearrangementDi-π-methane rearrangementDimroth rearrangementDivinylcyclopropane-cycloheptadiene rearrangementDowd–Beckwith ring-expansion reactionElectrocyclic reactionFavorskii rearrangementFerrier rearrangementFischer–Hepp rearrangementFries rearrangementFritsch–Buttenberg–Wiechell rearrangementGroup transfer reactionHalogen dance rearrangementHayashi rearrangementHofmann–Martius rearrangementIreland–Claisen rearrangementJacobsen rearrangementLobry de Bruyn–Van Ekenstein transformationLossen rearrangementMcLafferty rearrangementMeyer–Schuster rearrangementMislow–Evans rearrangementMumm rearrangementMyers allene synthesisNazarov cyclization reactionNeber rearrangementNewman–Kwart rearrangementOverman rearrangementOxy-Cope rearrangementPericyclic reactionPinacol rearrangementPummerer rearrangementRing expansion and contractionRupe reactionSchmidt reactionSemipinacol rearrangementSigmatropic reactionSkattebøl rearrangementSmiles rearrangementSommelet–Hauser rearrangementStevens rearrangementStieglitz rearrangementTiffeneau–Demjanov rearrangementVinylcyclopropane rearrangementWagner–Meerwein rearrangementWallach rearrangementWestphalen–Lettré rearrangementWillgerodt rearrangementWolff rearrangementRing forming reactions1,3-Dipolar cycloadditionAnnulationAzide-alkyne Huisgen cycloadditionBaeyer–Emmerling indole synthesisBischler–Möhlau indole synthesisBischler–Napieralski reactionBlum–Ittah aziridine synthesisBobbitt reactionBohlmann–Rahtz pyridine synthesisBorsche–Drechsel cyclizationBucherer carbazole synthesisCamps quinoline synthesisChichibabin pyridine synthesisCook–Heilbron thiazole synthesisCycloadditionDavis–Beirut reactionDe Kimpe aziridine synthesisDebus–Radziszewski imidazole synthesisDieckmann condensationFeist–Benary synthesisFerrario–Ackermann reactionFiesselmann thiophene synthesisFischer indole synthesisFischer oxazole synthesisFriedländer synthesisGewald reactionGraham reactionHantzsch pyridine synthesisHemetsberger indole synthesisHofmann–Löffler reactionIodolactonizationIsay reactionJacobsen epoxidationKnorr quinoline synthesisKröhnke pyridine synthesisLarock indole synthesisMadelung synthesisNiementowski quinazoline synthesisNiementowski quinoline synthesisPaal–Knorr synthesisPaternò–Büchi reactionPechmann condensationPetrenko-Kritschenko piperidone synthesisPictet–Spengler reactionPomeranz–Fritsch reactionPrilezhaev reactionPschorr cyclizationReissert indole synthesisSimmons–Smith reactionSkraup reactionUrech hydantoin synthesisVan Leusen reactionWenker synthesis4+4 Photocycloaddition(4+3) cycloaddition6+4 CycloadditionAza-Diels–Alder reactionBradsher cycloadditionCheletropic reactionConia-ene reactionCyclopropanationDiazoalkane 1,3-dipolar cycloadditionEnone–alkene cycloadditionsHexadehydro Diels–Alder reactionIntramolecular Diels–Alder cycloadditionInverse electron-demand Diels–Alder reactionKetene cycloadditionMcCormack reactionMetal-centered cycloaddition reactionsNitrone-olefin (3+2) cycloadditionOxo-Diels–Alder reactionPauson–Khand reactionPovarov reactionPrato reactionRetro-Diels–Alder reactionStaudinger synthesisTrimethylenemethane cycloadditionVinylcyclopropane (5+2) cycloadditionBamberger triazine synthesisBarton–Zard reactionBernthsen acridine synthesisBoger pyridine synthesisEinhorn–Brunner reactionErlenmeyer–Plöchl azlactone and amino-acid synthesisHantzsch esterHerz reactionLehmstedt–Tanasescu reactionPellizzari reactionRobinson–Gabriel synthesis