Beckmann Fragmentation of Camphor-4-carboxylic and Camphor-4-acetic Acid Oximes

The synthesis of chlorosilanes from alkoxysilanes, silanols, and hydrosilanes with bulky substituents

Thermochemistry of ulexite

Thermochemistry of rubidium calcium octaborate dodecahydrate

Thermochemistry of NaRb[B 4O 5(OH) 4]·4H 2O

Thermochemistry of dipotassium calcium octaborate dodecahydrate

Thermochemistry of dicesium calcium tetraborate octahydrate

Background: Thiosemicarbazone derivatives containing mono- or disaccharide moieties have remarkable anti-microorganism and antioxidant activities both in vivo and in vitro, therefore thiosemicarbazone derivatives containing simultaneously monosaccharide or disaccharide moieties have been synthesized. The conventional catalysts used in reactions of aldehydes or ketones with amines in general involve only several typically organic and mineral acids, such acetic acid or hydrochloric acid. The use of strong acidic catalysts in carbohydrate chemistry often have some disadvantages associated with prolonged reaction times, harsh and harmful reaction conditions, and sometimes, the difficulty in product separations. This problem needs to be resolved in synthesis of carbohydrate derivatives because of their susceptibility towards the strong acids. Therefore, we are especially interested in developing the use of inexpensive, simple and efficient catalysts in the synthesis of thiosemicarbazones having peracetylated mono- and disaccharide moieties. Methods: The synthesis of some substituted benzaldehyde N-(hepta-O-acetyl-β-D-lactosyl)thiosemicarbazones using different acidic and basic catalysts. The synthetic reaction was carried out under conventional and microwave-assisted heating conditions. The antibacterial activity of these thiosemicarbazones against some typical bacteria screened by using the MIC evaluation method. Results: Reaction conditions, including catalysts (piperidine, hydrochloric and acetic acids) and heating methods (such as conventional and microwave-assisted ones), have been investigated for the synthesis of benzaldehyde N-(hepta-O-acetyl- β-D-lactosyl)thiosemicarbazones. Based on optimal conditions found in the synthesis of benzaldehyde N-(hepta-O-acetyl- β-D-lactosyl)thiosemicarbazone, the other substituted thiosemicarbazones were synthesized by condensation reactions of N-(hepta-O-acetyl-β-D-lactosyl)thiosemicarbazide with corresponding different substituted benzaldehydes. Almost all obtained thiosemicarbazones exhibited remarkable antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Enterobacter and Escherichia coli. Conclusion: The optimal conditions were found for synthesis of thiosemicarbazones having β-lactose moiety under conventional and microwave-assisted heating conditions. Almost all quantitative yields, simple isolation and purification procedures of these products made it to become a useful procedure for the synthesis of these compounds. Almost all synthesized thiosemicarbazones exhibited the remarkable antibacterial activity. Keywords: Antibacterial, microwave-assisted synthesis, substituted benzaldehydes, thiosemicarbazide, thiosemicarbazone, β-lactose.

Treatment of 3-acetyl-4-hydroxy-6-methyl-1H-2-pyridone (V) with hydroxylamine gives its oxime (VI) whose treatment with polyphosphoric acid at room temperature results in the Beckmann rearrangement to afford 3-acetamido-4-hydroxy-6-methyl-1H-2-pyridone (VIII). Further heating of VIII with polyphosphoric acid results in its transition to 2, 6-dimethy1-5H-oxazolo[4, 5-c]pyridin-4-one (IX), which is also obtained on heating VI with polyphosphoric acid directly. IX also transits to VIII when left with hydrochloric acid at room temperature, while hydrolysis of IX with heating gives 3-amino-4-hydroxy-6-methyl-1H-2-pyridone (X). Treatment of dehydroacetic acid oxime (XIV) with polyphosphoric acid gives 3-acetamido-4-hydroxy-6-methyl-2H-pyran-2-one (XVI) and 2, 6-dimethyl-4H-pyrano[3, 4-d]oxazol-4-one (XVII), and the latter transits to IX on treatment with ammonia. Marcus and others5) reported that the reaction of XIV and diketene gave its cyclized product, 3, 6-dimethyl-4H-pyrano[3, 4-d]isoxazol-4-one (XV) but re-examination of this reaction showed that the product is a cyclized oxazolo compound (XVII) via the Beckmann rearrangement.

Abstract1, 1′‐Spirobis(3H‐2, 1‐benzoxatellurole) ‐3, 3′‐dione [10‐Te‐4(C202)] (1c) with five‐membered spirorings was prepared, and its molecular structure was determined by X‐ray crystallographic analysis. The two types of arrangement of the ligands about the central tellurium atom show considerably distorted trigonal bipyramidal (TBP) geometries. The tellurane 1c undergoes a ring‐opening reaction on treatment with aqueous sodium hydroxide to afford the telluroxide 10, which reacts with aqueous hydrochloric acid at room temperature to give again the tellurane 1c in quantitative yield. © 1995 John Wiley & Sons, Inc.

The extraction of uranium(VI) from aqueous hydrochloric or nitric acid, and the extraction of protactinium from hydrochloric acid by 1-(4-tolyl)-2-methyl-3-hydroxy-4-pyridone (HY) dissolved in chloroform has been studied. At pH >4, uranium (VI) is quantitatively extracted while at pH < 1 practically all the uranium remains in the aqueous phase. At hydrochloric acid concentrations lower than 1M, protactinium(V) is quantitatively extracted while at hydrochloric acid concentration higher than 5M practically all the protactinium remains in the aqueous phase. This difference in extraction of uranium and protactinium was utilized for their separation. From 0.5M hydrochloric acid, protactinium is quantitatively extracted, and separated from uranium.

Rare earth exchanged Na–Y zeolites, H-mordenite, K-10 montmorillonite clay and amorphous silica-alumina were effectively employed for the continuous synthesis of nitriles. Dehydration of benzaldoxime and 4-methoxybenzaldoxime were carried out on these catalysts at 473 K. Benzonitrile (dehydration product) was obtained in near quantitative yield with benzaldoxime whereas; 4-methoxybenzaldoxime produces both Beckmann rearrangement (4-methoxyphenylformamide) as well as dehydration products (4-methoxy benzonitrile) in quantitative yields. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream (TOS) studies show decline in the activity of the catalysts due to neutralization of acid sites by the basic reactant and product molecules and water formed during the dehydration of aldoximes.

Abstract12‐Aminododecanoic acid and 11‐aminoundecanoic acid, monomer precursors for nylon‐12 and nylon‐11, respectively, have been synthesized from vernolic (cis‐12,13‐epoxy‐cis‐9‐octadecenoic) acid via a reaction sequence that includes the formation of 12‐oxododecanoic acid oxime. Saponification of vernonia oil, followed by a low‐temperature recrystallization at −20°C, gave 51% vernolic acid (97% purity, m.p. 23–25°C). Hydrogenation afforded cis‐12,13‐epoxystearic acid (m.p. 52–54°C, lit. m.p. 52–54°C), which upon oxidation with periodic acid in tertiary butyl alcohol gave 12‐oxododecanoic acid with an isolated yield of 71.0%. Reaction of the oxoacid with hydroxylamine hydrochloride gave 12‐oxododecanoic acid oxime, which was catalytically reduced to give 12‐aminododecanoic acid with a yield greater than 85% and a melting point of 184–186°C (lit. m.p. 185–187°C). 11‐Aminoundecanoic acid was prepared from the 12‐oxododecanoic acid oxime via a three‐step reaction sequence that involved a Beckmann rearrangement, Hofmann degradation, and hydrolysis. Thus, the aldoxime acid was hydrolyzed in the presence of nickel acetate tetrahydrate to give 11‐carbamoylundecanoic acid (48% yield, m.p. 129–131°C, lit. m.p. 129–130°C). The amide was then treated with a solution of sodium methoxide and bromine at 70–80°C to give 11‐(methoxycarbonylamino)undecanoic acid at 75% yield (m.p. 84–86°C; elemental analysis, calculated for C13H25NO4: C, 60.19; H, 9.73; N, 5.40; O, 24.68%; found C, 60.02; H, 9.81; N, 5.26; O, 24.91%), which upon alkaline hydrolysis and subsequent neutralization gave 11‐aminoundecanoic acid at 34% yield (m.p. 189–192°C, lit. m.p. 190°C). Mass spectrometric and 13C nuclear magnetic resonance data of the previously unreported 11‐(methoxycarbonylamino)undecanoic acid is provided.

1. Effective rate constants (kef) for the hydrolysis of ethyl isovalerate in aqueous solutions containing from 4.95 to 41.3 mass % HCl, or from 2.52 to 94.0 mass % H2SO4, have been determined spectrophotometrically at 25°C. 2. The quantity kef increases with increasing acid concentration in aqueous HCl solutions. In aqueous sulfuric acid solutions, kef passes through a maximum at 49.8–55.9% H2SO4 and a minimum at 74.9% H2SO4. 3. In the hydrochloric acid and sulfuric acid solutions in question here (up to 74.9% H2SO4), the hydrolysis of ethyl isovalerate proceeds through an activated complex containing one un-ionized ester molecule and one hydronium ion carrying at least one solvation water molecule. The water molecule functions here as a nucleophilic agent. 4. The data obtained can be interpreted quantitatively by assuming that ionizatioa results in the formation of a protonized form of the ester and an unreactive complex in which the carbonyl group oxygen is bound to the hydronium ion. 5. Hydrolysis proceeds through the protonized form of the ester in sulfuric acid solutions with concentrations in excess of 74.9%.

: For the first time, a sonochemical method has been developed for the structural rearrangement of [5,6]-open mono- and poly adducts of fullerene C60 containing spirocyclic fragments of camphor analogs into [6,6]-closed isomers. The isomerization reaction occurs with quantitative yield under mild conditions: 1 hour at room temperature. A probable mechanism of sonochemical isomerization has been proposed. Mono- and poly adducts of C60 fullerene containing spirocyclic fragments of camphor analogues were obtained in the reaction of metal complex catalysis by the Pd(acac)2–2PPh3–4Et3Al system with the participation of fullerene and diazo compounds.

Bergmann and Stein (1) have described a procedure for the isolation and purification of naturally occurring L-leucine based upon the precipitation and recrystallization of the slightly soluble salt of this amino acid with naphthalene-β-sulfonic acid. The product obtained was stated to be 97 per cent pure and to be free from methionine, a common contaminant of less pure preparations of L-leucine (2). We have found that L-leucine so prepared contains significant amounts of those amino acids which are oxidized by bromine in acid solution, and that a naphthalene sulfonate of superior purity can be obtained if the crude leucine is first treated with bromine water. The use of the preliminary bromine oxidation and of more dilute solutions than were used by Bergmann and Stein for the recrystallization of the naphthalene-β-sulfonate gave L-leucine preparations of exceptional purity when judged by qualitative tests and solubility determinations. Characteristic physical constants of L-leucine so prepared are given elsewhere in this paper. In the determination of the optical rotation of α-amino acids in aqueous acid solutions, it has been assumed at times that the concentration of the aqueous acid is not critical provided sufficient acid has been added to assure formation of the amino acid cation. Dunn et al. (3) have pointed out that the specific rotation of solutions of L- and D-alanine in hydrochloric acid is dependent upon the hydrochloric acid concentration, and the data presented in Fig. 1 clearly show a similar dependency in the case of either hydrochloric or sulfuric acid solutions of L-leucine.