Beckmann rearrangement

8 Key excerpts on "Beckmann rearrangement"

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  Organic Reaction Mechanisms 1982

  An annual survey covering the literature dated December 1981 through November 1982

  • A. C. Knipe, W. E. Watts, A. C. Knipe, W. E. Watts(Authors)
  • 2008(Publication Date)
  • Wiley

    (Publisher)

  The scope of the hydrazone rearrangement has been extendedsz8 to include a series of aromatic diketone monohydrazones. The migratory aptitudes of alkyl groups in the Beckmann rearrangement of 0-picryloximes, in the Criegee rearrangement of p- nitroperbenzoates, and in the isonitrile-nitrile rearrangement have been investigated.529 The same authors have showns30that the migratory aptitudes of polycyclic bridgehead groups, cycloalkyl groups, and P-J-, and &branched alkyl groups in the Beckmann-Chapmann rearrangement, indicate that at the transition state the migrating group resembles a penta-coordinated carbonium ion rather than a planar carbenium ion. The migratory tendencies of hydrogen and aryl groups in the photochemical Beckmann rearrangement of benzaldoximes have been compareds3’ with those in the photochemical rearrangement of 2-alkyl-3- aryloxaziridines. They are similar and appear to depend on the nature of the aryl substituent, thus implying that the photochemical Beckrnann rearrangement proceeds through an oxaziridine intermediate. A second-order photo-Beckrnann rearrangement of cyclodihydrocodeinone oxime has been used’ 32 to prepare secomorphinans,and a photo-Beckmann process has been as a key step in the syntheses of six- and eight-membered lactams of the B-homo- and A-nor-B,B- dihomocholestane series. The rearrangement of cholest-4-en-3-one oxime in refluxing CC14containing triphenylphosphine has been to yield 3-aza-A- homocholest-4a(5)-en-4-one. Beckmann rearrangements of ketoximes in the stigmastane series have been described.53J Baeyer-Villiger oxidations of 1-substituted cis-bicyclo [4.2.0]octanones (228) to the corresponding cis-octahydrobenzo [b]furan-2-ones (229) have been re- ported.536Interestingly, the acid-catalysed Beckmann rearrangement of oximes of ketones of the type (230) has been shown to afford the corresponding octahydroisoindolones (231) as major products.

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  Science of Synthesis: Knowledge Updates 2020/2

  • M. Christmann, Z. Huang, J. A. Joule, M. Christmann, Z. Huang, J. A. Joule(Authors)
  • 2020(Publication Date)
  • Thieme

    (Publisher)

  The combined organic layers were washed with brine, dried (Na 2 SO 4 ), filtered, and concentrated under reduced pressure. The crude product was purified by flash chro-matography (silica gel, petroleum ether/EtOAc 6:1) to provide the product as a colorless oil; yield: 642 mg (77%). 337 40.1. 1 Alkyl-and Cycloalkylamines 40.1. 1.4.3.2 Rearrangements from Carbon to Nitrogen 40.1. 1.4.3.2.1 Beckmann rearrangement The Beckmann rearrangement involves the transformation of an oxime to an amide by migration of a group from carbon to nitrogen (see Section 40.1.1.4.2.2). During the Gin laboratory’s elegant investigation into the synthesis of the alkaloid palau’amine, tricyclic ketone 110 was synthesized from decadiene 109 . Reaction of ketone 110 with hydroxyl-amine hydrochloride produces oxime 111 . Treatment with thionyl chloride induces the regioselective Beckmann rearrangement via cationic intermediate 112 , which affords lac-tam 113 (Scheme 27). [38] An alternative procedure involves the use of sulfuryl fluoride (SO 2 F 2 ) as the electrophilic reagent, which leads to Beckmann rearrangement through a similar mechanistic pathway. [39] Scheme 27 Beckmann rearrangement of a Tricyclic Ketone [38] H H OBn Cl EtO 2 C H H H OBn Cl H H H OBn Cl H H N H H OBn Cl H 109 110 111 113 NH 2 OH pyridine EtOH, H 2 O 90 o C SOCl 2 Et 2 O, 23 o C H H OBn Cl H N 112 H 2 O 54% 91% O HON O Microwave irradiation has also been used to promote the Beckmann rearrangement for the conversion of 2-(alkylamino)-3-acylquinolin-4-ones into oxazoloquinolines (Scheme 28). [40] Quinolinone 114 is mixed with hydroxylamine hydrochloride and pyridine; after exposure to microwave irradiation, Beckmann rearrangement results in nitrilium ion 115 , which is converted into acetamide 116 . Subsequent removal of the morpholine func-tional group afford oxazoloquinoline 117 . for references see p 371

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  Fine Chemicals through Heterogeneous Catalysis

  • R. A. Sheldon, Herman van Bekkum, R. A. Sheldon, Herman van Bekkum(Authors)
  • 2008(Publication Date)
  • Wiley-VCH

    (Publisher)

  @ I 6) * 80 75 L2233IL 0 1 2 3 4 5 6 7 Time on Stream /h Time on Stream /h Figure 5. Change in cyclohexanone oxime conversion and lactam selectivity with time on stream in the vapor phase Beckmann rearrangement over 12-MR zeolites. Di- luent: (a) methanol, (b) I-hexanol. (X) H-BEA, (A) H-LTL, (V) H-OFF-ERI. (El) H- USY (Si02/A1,0, = 62), (0) H-MOR, (0) H-MTW; 623 K, oximeidiluent/N2 molar ratio of 1/9/5.9 and W/F of 80 g cat h-' mol oxime-' [41]. 5. I Beckmann rearrangement 193 5.1.3 Mechanistic Considerations 5.1.3.1 Reaction Pathway The reaction pathway for the Beckmann rearrangement is depicted in Figure 6. It is commonly assumed that the Beckmann rearrangement reaction involves initial protonation at the oxygen atom of an oxime (I) giving an oxonium cation (IT), fol- lowed by a migration of an alkyl group concomitant with liberation of a water mo- lecule affording a nitrilium cation (111). The nitrilium cation (111) is hydrolyzed to form (IV) and, finally, its tautomer (V), an amide. The reaction is highly stereo- specific in that the R, group anti to the hydroxyl group of the oxime always mi- grates. This stereospecificity is also observed with the heterogeneously catalyzed reaction. In the reaction of acetophenone oxime (R, = phenyl, R2 = methyl) over H-Y at 573 K acetanilide and N-methylbenzamide were obtained in a ratio of 19:1 [32]. The small amount of benzamide was considered to arise from isomerization of oxime before rearrangement, rather than from migration of a syn methyl group. Aldoximes (R2 = H) dehydrate to the nitrile under conditions causing ketoximes to rearrange to the corresponding lactams [29]. By use of ab initio calculations energy surfaces of the isolated gas phase sys- tems of the Beckmann rearrangement were mapped out.

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  Organic Chemistry

  A Mechanistic Approach

  • Penny Chaloner(Author)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  N OH Me Ph (1) PCl 5 (2) H 2 O Me NHPh O FIGURE 18.17 Beckmann.rearrangements.are.stereospecific. 864 18.3 Migration to Electron-Deficient Nitrogen essentially by removing the carbonyl group (chalk up another amide to amine synthesis). The amide is reacted with bromine and sodium hydroxide. In the first step, the amide is deproton- ated and brominated at nitrogen. A further deprotonation gives an anion, which rearranges to RN=C=O, an isocyanate. This is attacked at carbon by the hydroxyl ion, to give a carbamic acid (RNHCOOH), which readily decarboxylates (Figure 18.18). Neither the isocyanate nor the carbamic acid is particularly stable, but they can both be isolated from the reaction, and when they are put back in again, they do convert to product—they are true intermediates. You may be wondering why this reaction is categorized with “migration to electron-deficient nitrogen.” Although the mechanism as drawn is correct, at one point, it was thought that loss of bromide ion preceded the migration of the alkyl or aryl group to nitrogen. This would give R NH 2 O NaOH R NH O Br Br R NHBr O NaOH N C H OH R NH 2 + CO 2 _ R H O O H R N O _ Br N C O HO – N C O H H OH R R O – FIGURE 18.18 Mechanism.of.the.Hofmann.degradation. NaOH, Br Ph CONH 2 Ph NH 2 CONH 2 NaOH, Br 2 NH 2 CONH 2 NaOH, Cl 2 NH 2 N CONH 2 Cl 2 , KOH N NH 2 FIGURE 18.19 Examples.of.the.Hofmann.degradation. Chapter 18 – Rearrangement Reactions 865 an intermediate containing a nitrogen atom with just one substituent and six electrons—called a nitrene, by analogy with carbenes. This clearly is electron deficient! Some examples of the reaction are given in Figure 18.19; alkyl, aryl, and even nitrogen atoms can migrate. The second example shows that the reaction goes with retention of stereochemistry, and from examples 3 and 4, we see that chlorine may be substituted for bromine.

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  Solid Acid Catalysis

  From Fundamentals to Applications

  • Hideshi Hattori, Yoshi Ono(Authors)
  • 2015(Publication Date)
  • Jenny Stanford Publishing

    (Publisher)

  Methanol is recovered at the end of the reactor and recycled. Figure 6.22 Flow diagram for Sumitomo’s Beckmann rearrangement process. In 1995, a new production route for cyclohexanone oxime by ammoximation was disclosed. In this process, a mixture containing NH 3 , H 2 O 2 , and cyclohexanone is allowed to react over TS-1 (titanosilicate with MFI structure). NH 3 reacts with H 2 O 2 to form hydroxylamine, which reacts with cyclohexanone without catalyst to form cyclohexanone oxime. NH 3 NOH NH 2 OH O TS– 1 + H 2 O 2 (6.65) Sumitomo Chemicals Co. combined this ammoximation process with the Beckmann rearrangement process to construct a new process for e -caprolactam production from cyclohexanone (Fig. 6.23) [275]. The by-product from the new process is only H 2 O. This is environmentally benign process. The ammoximation step is arried carried at 353 K; cyclohexanone conversion is 99.9%, with cyclohexanone oxime selectivity of 98.2% (based on cyclohexanone), cyclohexanone oxime yield being 93.2% (based on H 2 O 2 ). In the Beckmann rearrangement step carried out at 623 K, cyclohexanone oxime conversion is 99% and e -caprolactam selectivity is 95%. A fluidized bed reactor is employed for the 461 Beckmann rearrangement step because coke is accumulated on the catalyst during the reaction. The catalyst is regenerated continuously. The commercial operation started in 2003. O TS–1 NOH MFI zeolite + NH 3 + H 2 O 2 + 2H 2 O O NH Figure 6.23 Production of e -caprolactam through ammoximation and Beckmann rearrangement. 6.9 Acetalization The protection of functional groups such as aldehydes or ketones is one of the most important organic synthetic strategies for the production of multifunctionalized molecules. Acetalization offers a means of protection during manipulation of multifunctional organic molecules. Furthermore, acetals are molecules with industrial applications often involved in cosmetic formulations as fragrances, cosmetics, and polymer production.

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  Organic Reaction Mechanisms 1974

  An annual survey covering the literature dated December 1973 through November 1974

  • A. R. Butler, M. J. Perkins, A. R. Butler, M. J. Perkins(Authors)
  • 2008(Publication Date)
  • Wiley-Interscience

    (Publisher)

  Abnormal rearrangements of oximes have been encountered in attempts to acetylate the hydroxyiminocholestane derivative (127),154 and on treatment of the tetrahydro- cinnoline derivative (128) with acid.155 In the latter case a similar reaction was found under Schmidt conditions ; in the Beckmann case the intermediacy of (129)was proposed. Two competing anomalous pathways have been encountered on acid-catalysed rearrangement of (130) or its 0-benzoyl derivative, differing according to the site of protonation which initiates the reaction.lS* A theoretical model for the rearrangement step of the Baeyer-Villiger reaction has been discussed, and CNDO/2 and ab initio calculations appear to agree well with experi- ment.lS7 For the optimized transition-state geometry (131), there is little reorganization of the migrating group; this is consistent with the small a-deuterium isotope effects determined experimentally.158 The experimental /%deuterium isotope effect (deter- mined158 for benzyl migration in 3,3,3-trideuterio-l-phenylpropan-2-one) is consistent with the calculated development of carbonyl double-bond character at the migration transition state. Molecular Rearrangements 479 q,& R (180) A study of Lossen and I Hofmann rearrangements of dialkylhomophthalimide (isoquinoline-1,3-dione) derivatives (192) showed that the bulk of the kkyl group determined the direction of the rearrangement.15B In neither case was 180 incorporated from labelled water. Rearrangements Involving Ring-openings and Ring-closures Three-membered Rings Several reports have appeared of rearrangementa involving derivatives of cyclopropyl ketones or aldehydes. For example, the endo-pyrrolidineaminal(l33) isomerizes to the eso-isomer in a mildly acid-catalysed process at 80°, probably by way of the cyclo- propylidene enamine (134) ;I60 at 140°, further rearrangement to the homofulvenes (135) occurs, also by way of (134). Heating, followed by acidic work-up, transforms the aminel

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  Catalysis for Fine Chemicals

  • Werner Bonrath, Jonathan Medlock, Marc-André Müller, Jan Schütz(Authors)
  • 2021(Publication Date)
  • De Gruyter

    (Publisher)

  7  Rearrangement reactions

  7.1  Introduction

  Rearrangement reactions are a broad class of organic reactions in which the reactant undergoes a rearrangement to give a structural isomer of the original molecule via a migration of an H atom or a larger molecular fragment. From the view of atom economy and E-factor, rearrangement reactions fulfil the criteria of the modern type of chemistry and green chemistry, with all atoms of the starting material being present in the product structure.

  In many rearrangement reactions, the migration occurs directly to a neighbouring position. These rearrangements belong to the class of [1,2]-rearrangements or [1,2]-shifts. These reactions are often sigmatropic rearrangements meaning that a σ-bond migrates during the reaction. The nomenclature of rearrangement reactions is described by numbering the atoms directly attached to the bond that is broken with 1 and 1ʹ (Scheme 7.1 ). The following atoms in the direction of the rearrangement are labelled 2, 3 and so forth starting from 1 and 2ʹ, 3ʹ and so forth starting from 1ʹ. After the rearrangement the new σ-bond is connected to two atoms which characterise the rearrangement. The numbers are listed in square brackets and the prime is removed from the second number.

  Scheme 7.1: Naming and examples of sigmatropic rearrangements.

  Some of the most important industrial rearrangement reactions, such as [3,3]-sigmatropic rearrangements, are used in the synthesis of isoprenoid building blocks such as isophytol, β-ionone or aroma compounds such as methyl heptanone. These are the main focus of this chapter.

  7.2  Wagner–Meerwein rearrangements

  The Wagner–Meerwein rearrangement is a predominately acid-catalysed [1,2]-rearrangement in which a hydrogen, alkyl or aryl group migrates from one carbon to a neighbouring carbon to generate a new carbocation. This carbocation reacts with a nucleophile or a proton from a neighbouring atom is eliminated. The driving force of the reaction is that the initially formed carbocation has the tendency to rearrange to a thermodynamically more stable structure. In the terpene chemistry, the Wagner–Meerwein rearrangement is of importance in the manufacture of camphene from isoborneol (Scheme 7.2

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  Organic Reaction Mechanisms 1980

  An annual survey covering the literature dated December 1979 through November 1980

  • A. C. Knipe, W. E. Watts, A. C. Knipe, W. E. Watts(Authors)
  • 2008(Publication Date)
  • Wiley

    (Publisher)

  A further example of the occurrence of a benzidine-like rearrangement I H H SCHEME 1 in N,O-diarylhydroxylamines has been observed4 in hydrolytic studies of 7-nitro-2- phenyl- 1 ,Zbenzisoxazol-3-one. Treatment of this compound with base causes hydrolysis of the amide bond and subsequent benzidine-like rearrangement to give 4-amino-3-carboxy-4-hydroxy-5-nitrobiphenyl. Acid treatment on the other hand causes cleavage of the N-0 bond and rearrangement to 7-nitro-3-phenyl- benzoxazol-2-one. The novel naphth[3.2.1-cd]indole (4) has been prepared5 from a- methyl-/3-(acetoacety1)phenylhydrazine (3) by a unique transformation which includes an arylation and an N-N bond cleavage reminiscent of the benzidine rearrangement. A method for the introduction of a hydroxy group ortho to a phenolic hydroxy group by the rearrangement of 0-aryl-N-benzoylhydroxylamines, has been described,' while a radical-pair mechanism has been proposed7 to account for the observed rearrangements of 0-alkylsulphinyl-N-phenylhydroxylamines. Interestingly, significant amounts of o- and p-anisidines were formed on catalytic hydrogenation of o-nitrotoluene in H2SO4-MeOH solution,8 presumably by a Bamberger-type rearrangement of the intermediate arylhydroxylamine. The Wallach rearrangement of chloro-substituted azoxybenzenes has been examined;' azoxybenzene-SbC1, complexes have been shown to undergo on thermolysis selective ortho-Wallach rearrangement to yield o-hydroxy- azobenzenes, ' while new base-catalysed' ' and acid-catalysed' ' rearrangements of azoxybenzenes have been reported. A study of the effect of different factors on the kinetics of C-nitrosation of arylamines has been undertaken,I3 and a kinetic study of the denitrosation of nitrosamines in ethanol has supported for the process a rate- determining proton transfer to the nitro~amine'~ - in sharp contrast to the behaviour in water.

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