Derivatives Oximes

A number of oxime derivatives of rifaldehyde have been prepared. Many of these derivatives exhibit good activity against rifampicin-resistant organisms (151,152). 

It is estimated that thiophene reacts with phenyl radicals approximately three times as fast as benzene. Intramolecular radical attack on furan and thiophene rings occurs when oxime derivatives of type (112) are treated with persulfate (8UCS(Pt)984). It has been found that intramolecular homolytic alkylation occurs with equal facility at the 2- and 3-positions of the thiophene nucleus whereas intermolecular homolytic substitution occurs mainly at position 2. 

Ketones are more stable to oxidation than aldehydes and can be purified from oxidisable impurities by refluxing with potassium permanganate until the colour persists, followed by shaking with sodium carbonate (to remove acidic impurities) and distilling. Traces of water can be removed with type 4A Linde molecular sieves. Ketones which are solids can be purified by crystallisation from alcohol, toluene, or petroleum ether, and are usually sufficiently volatile for sublimation in vacuum. Ketones can be further purified via their bisulfite, semicarbazone or oxime derivatives (vide supra). The bisulfite addition compounds are formed only by aldehydes and methyl ketones but they are readily hydrolysed in dilute acid or alkali. 

Note that the acetonitrile oxide cyclooligomers (e.g. 13) are not true oxime derivatives. Such derivatives have been prepared from biacetyl, however . Derivatives related to 14, below, were prepared and found not to be good complexing agents. They were, nevertheless, capable of phase transferring either sodium or potassium permanganate into dichloromethane. 

The reduction of oxime derivatives (section IV-C) is useful for the preparation of steroidal amines labeled with a deuterium on the nitrogen-bearing carbon atom... 

Preparation and use of amphiphilic oximes, derivatives of pyridine, pyridazine, pyrimidine, and pyrazine 98CFY469. 

Oxime-(9-sulfonic acid potassium salts of pyrido[3,2,l-(/]quinazolines 180 (X = H2, O) were obtained from 7-oxo derivatives 179 (X = H2, O) by reacting with hydroxylamino-O-sulfonic acid, then with K2CO3 (98EJM763). Reaction of 2,3,6,7-tetrahydro-l//,5//-pyrido[3,2,l-//]quinazo-line-l,3,7-trione with HONH2 HCI in boiling EtOH in the presence of NaOAc afforded 7-oxime derivative (01MI28). 

Unlike the Beckmann rearrangement, the outcome of the Neber rearrangement does not depend on the configuration of the starting oxime derivative E- as well as Z-oxime yield the same product. If the starting oxime derivative contains two different a-methylene groups, the reaction pathway is not determined by the configuration of the oxime, but rather by the relative acidity of the a-methylene protons the more acidic proton is abstracted preferentially. ... 

It was observed that while the ester (3) and ketone (4) derivatives of p-/erf-butyl calix[4]arene extracted negligibly small amounts of Cu " and Cr " ions, its oxime derivative efficiently extracted these ions. Furthermore, 5 was found to be more effective than 6 in extracting Cr ion. 

Some benzannulated azocine systems can be obtained via Beckmann rearrangement of the corresponding benzocycloheptatrienone oxime derivatives.27... 

A possible extension of the modified Neber reaction would be the synthesis of sulfonyl-substituted 2ff-azirines following the chemistry shown in Scheme 17 [27]. Unexpectedly, the oxime derived from -keto sulfones could not be converted into the oxime tosylate. Therefore, a different route to these requisite starting materials was designed, viz., via the corresponding sulfides 30 which were then oxidized with peracid to the sulfones 31. 

Horvath, K. and Molnar-Perl, I. (1997). Simultaneous quantitation of mono-, di- and trisaccharides by GC-MS of their TMS ether oxime derivatives II. In honey. Chromatographia 45,328-335. 

Quantitation is performed by the calibration technique. Construct a new calibration curve with methomyl oxime standard solutions (0.2, 0.4, 0.6, 0.8 and 1.0 xgmL in acetone) for each set of analyses. Plot the peak area against the injected amount of methomyl oxime on logarithmic paper. As the amount of alanycarb is measured in terms of its oxime derivative, a conversion factor of 3.8 (the molecular weight ratio of alanycarb to methomyl oxime) should be applied to obtain the net amount. The injection volume should be kept constant as the peak area varies with the injection volume in flame photometric detection. Before each set of measurements, check the GC system by injecting more than one standard solution containing ca 2-10 ng of methomyl oxime. 

Recently, Suzuki-type reactions in air and water have also been studied, first by Li and co-workers.117 They found that the Suzuki reaction proceeded smoothly in water under an atmosphere of air with either Pd(OAc)2 or Pd/C as catalyst (Eq. 6.36). Interestingly, the presence of phosphine ligands prevented the reaction. Subsequently, Suzuki-type reactions in air and water have been investigated under a variety of systems. These include the use of oxime-derived palladacycles118 and tuned catalysts (TunaCat).119 A preformed oxime-carbapalladacycle complex covalently anchored onto mercaptopropyl-modified silica is highly active (>99%) for the Suzuki reaction of p-chloroacetophenone and phenylboronic acid in water no leaching occurs and the same catalyst sample can be reused eight times without decreased activity.120... 

An exothermic reaction, sufficiently violent to expel the flask contents, occurs after an induction period of 15-30 s when acetic anhydride is added to a solution of the nitroso compound in acetic acid. 4,4/-Azobis(A,A-dimethylaniline), isolated from the reaction tar, may have been formed in a redox reaction, possibly involving an oxime derived from the nitroso compound. 

A similarly high performance has been reported for oxime-derived (125) and benzylsulfide-derived (126) palladacycles.438 These precatalysts are effective in the cross-coupling of arylboronic acids,438,439 organotin compounds,440 and terminal acetylenes441 with aryl iodides and bromides, and of activated aryl chlorides. SC-palladacycles can effect the Suzuki-Miyaura reaction even at room temperature. 

Hydrazones are also useful substrates in the preparation of pyrazoles. Reaction of N-monosubstituted hydrazones with nitroolefins led to a regioselective synthesis of substituted pyrazoles <060L3505>. lf/-3-Ferrocenyl-l-phenylpyrazole-4-carboxaldehyde was achieved by condensation of acetylferrocene with phenylhydrazine followed by intramolecular cyclization of the hydrazone obtained under Vilsmeier-Haack conditions <06SL2581>. A one-pot synthesis of oxime derivatives of l-phenyl-3-arylpyrazole-4-carboxaldehydes has been accomplished by the Vilsmeier-Haack reaction of acetophenone phenylhydrazones <06SC3479>. 

In a recent article by Botella and Najera, controlled mono- and double-Heck arylations in water catalyzed by an oxime-derived palladacycle were described [22], When the reaction was carried out under microwave irradiation at 120 °C in the presence of dicyclohexylmethylamine with only 0.01 mol% of palladium catalyst (palladium acetate or palladacycle), monoarylation took place in only 10 min with a very high turnover frequency (TOF) of > 40000 (Scheme 6.3). As regards diarylation, 1 mol% of the palladacycle catalyst and 2 equivalents of iodobenzene had to be utilized to obtain moderate to good yields of diarylated product. Whereas microwave heating at 120 °C provided a 31% yield after 10 min, a 66% isolated yield of product was obtained by heating the reaction mixture under reflux for 13 h at 100 °C. Here, the... 

Scheme 6.3 Mono- and double-Heck arylations in water using oxime-derived palladacycles.

This protocol could be extended to a range of different ,/i-unsaturated carbonyl compounds and either activated or deactivated aryl iodides [22], An application of related Heck chemistry to the synthesis of methylated resveratrol (3,4, 5-trihydroxy-( )-stilbene) is shown in Scheme 6.4 [23]. The phytoalexin resveratrol exhibits a variety of interesting biological and therapeutic properties, among them activity against several human cancer cell lines. Botella and Najera have shown that the trimethyl ether of resveratrol (Scheme 6.4) can be rapidly prepared by microwave-assisted Heck reaction of the appropriate aryl iodide and styrene derivatives, using the same oxime-derived palladacycle as indicated in Scheme 6.3. 

Alonso DA, Najera C, Pacheco C (2002) Oxime-derived palladium complexes as very efficient catalysts for the Heck-Mizoroki reaction. Adv Synth Catal 344 172-183... 

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