Undergo Beckmann Rearrangement Research Articles

A General Method to Access Underexplored Ylideneamino Sulfates as Interrupted Beckmann-Type Rearrangement Intermediates.

The Beckmann rearrangement of ketoximes to their corresponding amides, using a Brønsted acid-mediated fragmentation and migration sequence, has found wide-spread industrial application. We postulated that the development of a methodology to access ylideneamino sulfates using tributylsulfoammonium betaine (TBSAB) would afford isolable Beckmann-type intermediates and competent partners for subsequent rearrangement cascades. The ylideneamino sulfates generated, isolated as their tributylammonium salts, are sufficiently activated to undergo Beckmann rearrangement without additional reagent activation. The generation of sulfuric acid in situ from the ylideneamino sulfate giving rise to a routine Beckmann rearrangement and additional amide bond cleavage to the corresponding aniline was detrimental to reaction success. The screening of bases revealed inexpensive sodium bicarbonate to be an effective additive to prevent classic Brønsted acid-mediated fragmentation and achieve optimal conversions of up to 99%.

Observations arising from a Beckmann rearrangement-Mannich cyclization approach to the azepinobisindole alkaloid iheyamine A

An overview of an iterative Beckmann rearrangement-Mannich cyclization approach to the azepinobisindole alkaloid iheyamine A is described. In a preliminary model study, the (E)-oxime 10 underwent Beckmann rearrangement to give the bisindolylacetamide 4 followed by an intramolecular Mannich cyclization affording 2-(indolin-2-yl)indole 5 containing the heterocyclic framework of the iheyamine alkaloids. However, the 2-(indolin-2-yl)indole 5 could not be converted into the azepinobisindole core of iheyamine A. When the same Beckmann-Mannich approach was applied toward the natural product itself, a result was obtained that contrasted the model study. The (E)-oxime 3 did not undergo Beckmann rearrangement, but instead an intramolecular Mannich cyclization whereby the electron rich C4 site attacked the intermediate iminum ion, generating the 4-(indolin-2-yl)indole 25 bearing the heterocyclic framework of the slime mould pigment arcyriacyanin A. Although this route did not result in the synthesis of iheyamine A being accomplished, some interesting observations related to the venerable Beckmann rearrangement and Mannich cyclization reactions are described.

Keggin-type Bronsted dodecatungstophosphoric acid: a quasi homogenous and reusable catalyst system for liquid phase Beckmann rearrangement

A variety of ketoximes, prepared from corresponding ketones, undergo Beckmann rearrangement using H3PW12O40 (DTPA) in acetonitrile under reflux to yield N-substituted amides and lactams in good to excellent yields (72–96%). The present method provides an efficient, clean, eco-friendly, and simple synthesis. The catalyst is cheap, moisture tolerant, recoverable, and reusable without much loss of its activity.

ChemInform Abstract: Preparation and Beckmann Rearrangement of O-(Chlorooxalyl) Oximes.

Oximes 1 react with phosgene or oxalyl chloride to give O-(chloroformyl)- 2, or O-(chlorooxalyl)oximes 8, which undergo Beckmann rearrangement with antimony pentachloride to afford nitrilium hexachloroantimonates 3 in high yields. With di- or triphosgene (4 or 6) oximes 1 form mixtures of O-(chloroformyl)-2 and O-(trichloromethoxyformyl)oximes 5. The O-(chlorooxalyl)oximes 8 are further characterized as esters 10 and amides 11. With N,N-dimethylformamide the nitrilium salts 3 react to give N-acyl formamidinium salts 12

Efficient Iodine-Mediated Beckmann Rearrangement of Ketoximes to Amides under Mild Neutral Conditions

Aryl ketoximes readily underwent Beckmann rearrangement to give N-substituted amides in excellent yields on electrophilic activation by elemental iodine in anhydrous acetonitrile under reflux. The main advantages of this environmentally friendly protocol include a high selectivity as a result of the absence of any accompanying deprotection to form the parent ketones as byproducts, mild neutral conditions, procedural simplicity, and particularly ease of isolation of the products.

20-hydroxyecdysone oximes and their rearrangement into lactams

(E)-Oximes derived from 20-hydroxyecdysone diacetonides and 7,8-dihydro analog were converted into the corresponding lactams (6-oxo-5a-aza-5a-homo derivatives) via Beckmann rearrangement. 14,15-Anhydro-20-hydroxyecdysone (Z)-oxime under analogous conditions (reaction with p-toluenesulfonyl chloride in acetone in the presence of Na2CO3) gave rise to 20-hydroxyecdisone 20,22-acetonide (Z)-O-tosyloxime which did not undergo Beckmann rearrangement.

Neurosteroids: 7-aza-allopregnanolone—a poor substitute for allopregnanolone

7-Nor-20-oxopregn-5-en-3β-yl acetate was converted into (20 R)-5β,6β-epoxy-7-nor-5β-pregnane-3β,20-diyl diacetate in three steps. Stereospecific migration of the 6α-hydride ion led to a 6-oxo derivative with a 5α-configuration. The ( Z)-oxime of this ketone underwent Beckmann rearrangement to yield a lactam with the nitrogen in position 7. Lithium aluminium hydride reduction yielded the dihydroxy amine, which was either oxidised or Boc-protected and then oxidised to 7-aza-5α-pregnane-3,20-dione. Its regioselective reduction produced 7-aza-3α-hydroxy-5α-pregnan-20-one—a poor inhibitor for the binding of [ 35 S]TBPS to the GABA A receptor. The corresponding lactam—7-aza-3α-hydroxy-5α-pregnane-6,20-dione—was inactive.

Fragmentations and Rearrangements of α‐Hydroxyiminoalkylphosphonates

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Fragmentations and Rearrangements of α-Hydroxyiminoalkylphosphonates

This article reviews the unique reactivities of � -hydroxyiminoalkylphosphonates, which result from the proximity and the interaction between the hydroxyimino and the phosphonic groups. The reaction course of � -hydroxy- iminoalkylphosphonates depends markedly on the type of groups linked to the phosphorus and on the stereochemistry of the oxime function. (Z)-� -Hydroxyiminoalkylphosphonates and phosphinates undergo, upon heating, fragmentation to a nitrile and a phosphate or phosphonate, while (E)-� -hydroxyiminoalkylphosphonates and -phosphinates undergo Beckmann rearrangement to N-acylphosphoramidates or N-acylphosphonamidates, respectively. In contrast to the diesters, � -hydroxyiminoalkylphosphonic acids (and monoesters) are unstable and fragment to metaphosphates, which can perform in situ phosphorylation of appropriate groups. Kinetic and mechanistic studies of the fragmentations of � - hydroxyiminobenzylphosphonates to metaphosphoric acid and esters are reviewed. The fragmentation of � -hydroxyimino- benzylphosphonic acid monoesters to metaphosphate esters requires acid catalysis and slows down at about pH 3. In contrast, � -hydroxyiminobenzylphosphonic acid undergoes fragmentation in aqueous solutions at a wide range of pH, from strongly acidic up to about pH 9. The � -hydroxyiminophosphonate fragmentation methodology was applied to phosphorylation of silica gel, which can potentially be useful as chromatographic stationary phase. A variety of stable precursors of � - hydroxyiminophosphonates that can be induced to fragment thermally, photochemically or by base catalysis is described. (E)-� -Hydroxyiminobenzylphosphonamidates of various types have been found to undergo Beckmann rearrangement to yield N-acylphosphordiamidates upon heating in nonpolar solvents such as toluene, or fragmentation to metaphosphonamidate by heating in polar solvents. The fragmentation of (E)-� -hydroxyiminobenzyl- phosphonates to metaphosphates is considered a special case of the Beckmann fragmentation.

Beckmann rearrangement of E, E-cinnamaldoxime on rare earth exchanged (Ce 3+, La 3+, and RE 3+) HFAU-Y zeolites: An efficient green process for the synthesis of isoquinoline

In this paper, a novel application of solid acid catalysts in the Beckmann rearrangement of E, E-cinnamaldoxime in the synthesis of an important heterocyclic compound; isoquinoline is reported. E, E-Cinnamaldoxime under ambient reaction conditions on zeolite catalysts underwent Beckmann rearrangement to produce isoquinoline in yields of ca. 86–95%. Cinnamonitrile and cinnamaldehyde were formed as by-products. LaH-Y zeolite produces maximum amount of the desired product (yield 95.6%). However, the catalysts are susceptible for deactivation due to the basic nature of the reactants and products, which neutralize the active sites. H-Y zeolite is more susceptible (22% deactivation in 10 h) for deactivation compared to the cerium-exchanged counterpart (18% deactivation in 10 h). Thus, the optimal protocol allows isoquinoline to be synthesised in excellent yields through the Beckmann rearrangement of cinnamaldoxime. The reaction is simple, effective, does not involve any other additives, and environmentally benign.

RuCl3 Catalyzed Facile Conversion of Arylalkyl Ketoximes to Amides.

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RuCl3 Catalyzed Facile Conversion of Arylalkyl Ketoximes to Amides

A variety of aromatic ketoximes undergo Beckmann rearrangement upon treatment with a catalytic amount of RuCl3 in refluxing acetonitrile to furnish the corresponding amides in excellent yield and high selectivity.

Beckmann rearrangement in the solid state: reaction of oxime hydrochlorides

Several ketoxime hydrochlorides undergo Beckmann rearrangement upon heating below their melting points for 5–48 h, in excellent yields (generally >70%). The absence of a reaction solvent and of by-products (except for HCl) makes for a very simple work-up. Aldoxime hydrochlorides apparently undergo dehydration to the corresponding nitriles under the above conditions. Dibenzyl ketoxime hydrochloride unexpectedly furnished a pyrazine derivative (67%), presumably via further reaction of the intermediate nitrilium ion in the crystal lattice.

BASE CATALYSED LOSSEN REARRANGEMENT OF N-SULPHONYLOXY-2,3-NORBORN-5-ENEDICARBOXIMIDE

N-Sulphonyloxy-2,3-norborn-5-enedicarboximide 1 underwent Lossen rearrangement with some nucleophilic reagents, but it failed to undergo Beckmann rearrangement.

Acylphosphonamidates and α‐hydroxyiminophosphonamidates. Synthesis of N‐acylphosphordiamidates by Beckmann rearrangement. Crystal structure of (E)‐α‐hydroxyiminobenzyl‐1‐pyrrolidinylphosphinate

Reaction of methyl benzoylphosphonochloridate (3) with a secondary or primary series of amines yielded methyl benzoylphosphonamidates, 4a-e. The latter compounds reacted with hydroxylamine to yield a-hydroxyiminobenzylphosphonamidates (5a-e), largely as (E)-isomers. The structure of methyl (E)-a-hydroxyimino-benzyl-1-pyrrolidinylphosphinate (5b) was determined by single-crystal X-ray crystallography. Heating oximes 5a-e in boiling toluene caused them to undergo Beckmann rearrangement to N-benzoylphosphordiamidates 6a-e. © 1996 John Wiley & Sons, Inc.

ChemInform Abstract: Beckmann Rearrangement of (Z)‐ and (E)‐Oximes of 2‐Aryl‐4,5,6,7‐tetrahydro‐6,6‐dimethyl‐2H‐benzo(d)(1,2,3)triazol‐4‐ones and 4,5,6,7‐Tetrahydro‐6,6‐dimethylbenzo(c)(1,2,5)oxadiazol‐4‐ones.

AbstractThe title compounds (III) and (IV) are prepared from (I) but only (Z)‐oximes (III) undergo Beckmann rearrangement to give azepinones (V) (accompanied by ca. 5% (I) and 2‐3% of starting material (III)).

Preparation and Beckmann Rearrangement ofO-(Chlorooxalyl)oximes

Oximes 1 react with phosgene or oxalyl chloride to give O-(chloroformyl)- 2, or O-(chlorooxalyl)oximes 8, which undergo Beckmann rearrangement with antimony pentachloride to afford nitrilium hexachloroantimonates 3 in high yields. With di- or triphosgene (4 or 6) oximes 1 form mixtures of O-(chloroformyl)-2 and O-(trichloromethoxyformyl)oximes 5. The O-(chlorooxalyl)oximes 8 are further characterized as esters 10 and amides 11. With N,N-dimethylformamide the nitrilium salts 3 react to give N-acyl formamidinium salts 12

Reactions of oximes with trimethylsilyl iodide: dehydration and beckmann rearrangement

Aldoximes are dehydrated in good yields to nitriles and certain ketoximes undergo Beckmann rearrangement when treated with trimethylsilyl iodide.

ChemInform Abstract: THE BECKMANN REARRANGEMENT OF 3β‐CHLORO‐5α‐CHOLESTAN‐7‐ONE OXIME AND RELATED COMPOUNDS AND THE SCHMIDT REACTION OF THE CORRESPONDING KETONES

The chromic acid oxidation of cholesteryl chloride gave 3β- chlorocholest-5-en-7-one, which on hydrogenation gave 3β-chloro-5α- cholestan-7-one. The Schmidt reaction of this ketone afforded a single lactam, 3β-chloro-7a-aza-B-homo-5α-cholestan-7-one. The Beckmann rearrangement of its oxime by means of thionyl chloride or p- toluenesulphonyl chloride and pyridine gave the same lactam. The structure of the lactam was established by its conversion into a known lactam by reduction. 3β-Chlorocholest-5-en-7-one oxime on treatment with thionyl chloride or the corresponding O-tosyloxime on passing through a column of alumina underwent Beckmann rearrangement to give a single lactam, 3β-chloro-7α-aza-B-homocholest-5-en-7-one.

Reactions of oximes halides. Part III. α-benzil monoxime and acetyl monoxime with phenyl boron dichloride and boron tri-fluoride, -chloride and -bromide

Abstract Reaction of boron trifluoride with α-benzil monoxime (bmoH) gave BF 3 , bmoH. With boron trichloride and tribromide the oxime gave BX 2 (bmo) (X = Cl or Br) and with phenyl boron dichloride it gave PhBCl(bmo). Analogous complexes were obtained from acetyl monoxime (amoH). The complexes BX 2 (bmo) were unaffected by water but were hydrolysed by warm alkali; all the other complexes were hydrolysed by water. The adduct BF 3 , bmoH underwent Beckmann fragmentation on heating at 120 °C/0.1 mm but at 120dg/460 mm the adduct underwent Beckmann rearrangement; the other complexes underwent Beckmann fragmentation on heating. Mass spectrometric studies indicate that the complexes BCl 2 (bmo) and BX 2 (amo) are dimeric in the vapour state.