Carbonyl-hydrazones

Reductive coupling of dialdehydes may also be accomplished by use of samarium(II) iodide514. The reactions is stereoselective and has been used to prepare myo-inositol derivatives (equation 132)515. The equivalent reaction, using low-valent titanium species as catalysts, results in a mixture of products516. The production of cyclic /1-amino alcohols may be accomplished in good yields, and with a high degree of cis selectivity by the treatment of carbonyl hydrazones with samarium(II) iodide (equation 133)517. This reaction is effectively equivalent to an aza-Barbier reaction. 

Table 3 Wolff-Kishner Reduction of Carbonyl Hydrazones Using the Henbest Modification...

Styrene and cyclohexene by reactions with O3 during sampling. Roberts et al. reported formation of monoaromatics, w-alkanes, and aldehydes when Tenax was exposed to O3. Unsaturated compounds adsorbed on Tenax have been observed to react with nitrogen oxides, CI2, and O3 to produce a mixture of OxHCs. ° Decomposition of the Tenax by O3 can also occur to produce benzaldehyde, phenol, and acetophenone however, graphitized carbon sorbents appear more robust. " Interferences of O3 with carbonyl sampling by 2,4-DNPH-coated cartridges include depletion of the 2,4-DNPH, degradation and formation of carbonyl hydrazones, and formation of unknown 2,4-DNPH products. 

The set of twenty two compounds included carbonyl, hydrazone, and oxime derivatives, most of which were active on several tumor cell lines, albeit generally less potently than the natural parent compounds. Computer modeling of the new derivatives suggested that the introduction of a double bond in ring C led to more rigid, as well as more active, structures, Fig. (10). It was hypothesized that the less flexible unsaturated ring C caused a better orientation of the ester group and more closely... 

Carbonyl hydrazones also participate in reactions with hydrogenphosphonate esters, as is illustrated by the formation of the hydrazine derivative 209. The outcome of the reaction between diethyl hydrogenphosphonate and an aromatic aldazine, typically 210, depends on the ratio of reactants. With the reactants in the ratio 1 1, the initial step is the formation of the use of a mixture of the hydrogenphosphonate and sodium... 

Aldehydes and ketones may be converted into the corresponding primary amines by reduction of their oximes or hydrazones (p. 93). A method of more limited application, known as the Leuckart Reaction, consists of heating the carbonyl compound with ammonium formate, whereby the formyLamino derivative is formed, and can be readily hydrolysed by acids to the amine. Thus acetophenone gives the i-phenylethylformamide, which without isolation can be hydrolysed to i-phenylethylamine. 

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

Other interesting regioselective reactions are carried out within the synthesis of nitrofurantoin. Benzaidehyde semicarbazone substitutes chlorine in chloroacetic ester with the most nucleophilic hydrazone nitrogen atom. Transamidation of the ester occurs with the di-protic outer nitrogen atom. Only one nucleophilic nitrogen atom remains in the cyclization product and reacts exclusively with carbonyl compounds. 

Carbonyl deductions. The classical Wolff-Kishner reduction of ketones (qv) and aldehydes (qv) involves the intermediate formation of a hydrazone, which is then decomposed at high temperatures under basic conditions to give the methylene group, although sometimes alcohols may form (40). 

Hydrazones are formed from mono- and Ai,A/-disubstituted hydrazines. Hydrazine itself can give either hydrazones or azines, depending mainly on the ratio of carbonyl component to hydrazine. The ease of formation of these compounds depends on the nature of the carbonyl constituent ... 

Pyridazine aldehydes and ketones with the carbonyl group at the ring or in a side chain react in the usual manner. They form hydrazones, semicarbazides, oximes, etc. Side-chain aldehydes can be easily oxidized to pyridazinecarboxylic acids with silver nitrate and side-chain ketones are oxidized to carboxylic acids by treatment with potassium permanganate or hydrogen peroxide. 

Acyl-, 4-alkoxycarbonyl- and 4-phenylazo-pyrazolin-5-ones present the possibility of a fourth tautomer with an exocyclic double bond and a chelated structure. The molecular structure of (138) has been determined by X-ray crystallography (Table 5). It was shown that the hydroxy group participates in an intramolecular hydrogen bond with the carbonyl oxygen atom of the ethoxycarbonyl group at position 4 (8OCSCII21). On the other hand, the fourth isomer is the most stable in 4-phenylazopyrazolones (139), a chelated phenyl-hydrazone structure. 

SMITH MIDDLETON RQZEN Fhionnation Conversion ol carbonyls to CF2 compounds by SF4 (Smith) or dielhylammosullur Influonde (OAST) (Middleton) or by IF on hydrazones (Rozen)... 

The carbonyl group forms a number of other very stable derivatives. They are less used as protective groups because of the greater difficulty involved in their removal. Such derivatives include cyanohydrins, hydrazones, imines, oximes, and semicarbazones. Enol ethers are used to protect one carbonyl group in a 1,2- or 1,3-dicarbonyl compound. 

In order to characterize them and more readily separate them from interfering accompanying substances carbonyl compounds (aldehydes, ketones) can be converted to hydrazones at the start. The reagent mainly employed is 2,4-dinitro-phenylhydrazine in acidic solution [70], This yields osazones with aldoses and ketoses. Some examples are listed in Table 15. 

Dinitrophenylhydrazine reacts with carbonyl groups with the elimination of water to yield hydrazones (I) and with aldoses or ketoses to yield colored osazones (II). 

Carbonyl cyanide-p-trifluoro-metho5 henyl hydrazone... 

Chloroformates or carbonyl chloride react with 2-piperidone hydrazones to give triazolopyridine-3-ones (86JAP(K)69776), and there are further examples of the production of 3-thiols from a hydrazine and carbon disulfide (83USP4419516, 88EUP254623). 

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