2- hydrazone, crystal

More recently, Enders group has described the X-ray crystal structure of the chiral hydrazone anion (19). This internally chelated chiral hydrazone crystallizes as the bis(tetrahydrofuran) monomeric adduct. The lithium in this structure is 17° out of the C—C— N plane and is predominantly associated with the anionic nitrogen (and the chelating methoxy group). Interactions with the =CH2 carbon are minimal. Earlier studies by Bauer and Seebach had examined the association behavior of (19). They found that in THF this azaallyllithium reagent was monomeric. While there is no or ri -interaction with the azaallyl anion, the lithium in this structure is tetracoordinate and prochiral. Preferential coordination of lithium to an electrophile such as a carbonyl oxygen with selective replacement of one THF moiety could be involved in some of the asymmetric aldol reactions discussed below. 

Biilow and Ganghofer330 obtained dimethyl mesoxalate phenylhydrazone by adding a diazonium salt solution prepared from aniline (12 g), 30% hydrochloric add (36 g), ice + water (150 g), and 98% sodium nitrite (10 g) to a cold solution of dimethyl malonate (20 g) in ethanol (100 g), followed by saturated aqueous sodium acetate solution slowly to incipient turbidity. The hydrazone crystallized during 24 hours storage in a refrigerator and had m.p. 62° after recrystallization from ethanol. 

Colan The trivial name given to di-phenylethyne (diphenyl acetylene), CflHs C = C CeHs- Obtained as volatile colourless crystals, m.p. 6TC, by HgO oxidation of benzil bis-hydrazone. 

Dinitrophenylhydra2ones usually separate in well-formed crystals. These can be filtered at the pump, washed with a diluted sample of the acid in the reagent used, then with water, and then (when the solubility allows) with a small quantity of ethanol the dried specimen is then usually pure. It should, however, be recrystallised from a suitable solvent, a process which can usually be carried out with the dinitrophenylhydrazones of the simpler aldehydes and ketones. Many other hydrazones have a very low solubility in most solvents, and a recrystallisation which involves prolonged boiling with a large volume of solvent may be accompanied by partial decomposition, and with the ultimate deposition of a sample less pure than the above washed, dried and unrecrystal-lised sample. 

Dissolve 0-2 g. of fructose in 10 ml. of water, add 0-6 g. of cw-methyl-phenylhydrazine and sufficient rectified spirit to give a clear solution. Since the fructose may not be quite pure, warm the mixture slightly, allow to stand, preferably overnight, so that any insoluble hydrazones may separate if present, remove them by filtration. Add 4 ml. of 50 per cent, acetic acid to the filtrate it will become yellow in colour. Heat the solution on a water bath for 5-10 minutes, and allow to stand in the dark until crystalUsation is complete it may be necessary to scratch the walls of the vessel to induce crystalUsation. Filter the crystals and wash with water, followed by a little ether. RecrystaUise the orange-coloured methylphenylosazone from benzene m.p. 152°. 

The free selenazole hydrazines are solids, sometimes well crystallized compounds. They show the typical properties of hydrazines. Thus they reduce Fehling s solution on warming and liberate silver, even in the cold, from ammoniacal silver nitrate solution. Further, they react with carbonyl compounds for example, benzylidene hydrazones are formed with benzaldehyde. These are identical with the hydrazones formed by direct condensation from benzaldehyde selenosemicarbazone and the corresponding a-halogenocarbonyl compound. 2-Hydrazino-4-phenylselenazole has also been reacted with acetophenone. The 2-a-methylbenzylidenehydrazone of 4-phenyl-selenazole (2, K = CJl, R" = H, R" = NH—N CMe-aH ) forms golden yellow plates mp 171°C. ... 

In about 5-10 minutes a clear solution resulted, whereupon slow crystallization occurred and the temperature rose to about 6°-7°C. The crystallization was permitted to continue overnight at 5°C, and the very fine precipitate was then isolated by centrifugation and in the centrifuge washed with water, ethanol, and ether, yielding the dihydrate of DL-seryl-(2,3,4-trihydroxy-benzylidene) hydrazide hydrochloride, which melted at 134°-136°C and was poorly soluble in cold water, but very readily dissolved in hot water. The condensation was also effected in absolute ethanol yielding the anhydrous form of the hydrazone, which melted at 225°-228°C. 

Ethyl chloroglyoxylate (2-vinylphenyl)hydrazone (14a 0.253 g, 1 mmol) in benzene (10 mL) was treated with Et,N (0.500 g, 5 mmol) in benzene (2mL). The mixture was heated under reflux for 5 h, cooled, diluted with H20 (50 mL) and extracted with henzene. The organic phase was washed with sat. hrine, dried (MgSOt) and evaporated yield 0.197 g (91 %) blood-red crystals mp 107-108X. 

The hydrazone 12 (10 mmol) was dissolved in EtOH (80 mL) with warming and the stirred cooled solution was treated with cyanogen bromide (1.06 g, 10 mmol) and kept for 3 d. The solvent was removed and the residue was triturated with acetone. The resultant solid was collected, dissolved in warm MeOH and the solution was treated with coned IIBr. Et20 was added to incipient turbidity, whereupon the product crystallized. 

Fig. 1.7. Crystal structure of lithium salt of SAMP hydrazone of 2-acetylnaphthalene. Two molecules of THF are present. Reproduced from Angew. Chem. Int. Ed. Engl., 27, 1522 (1988), by permission of Wiley-VCH.

HadZi used IR spectroscopy to study some azophenols and azonaphthols (112). The phenylazophenols were found to be phenolic in the solid state. On the other hand the molecule of 4-phenylazo-l-naphthol is present in the crystal as the hydrazone tautomer. Had2i suggested that in l-phenylazo-2-naphthol and 2-phenylazo-1 -naphthol both tautomers are present. Similar suggestions have been made by others (113,114). 

Given the very small amount of protein present in a single crystal relative to the concentrations of DCL components, it is clear that amplification in the usual sense cannot occur. It is conceivable, however, that the protein structure influences equilibrium distribution of hydrazones in microcosm within the crystal. Conversely, it is possible that any DCC equilibrium is irrelevant, and that the hydrazone binding being observed by X-ray diffraction is due to a diffusion equilibrium of essentially static components between solution and solid state. 

Degradation of pentapropionyl-D-glucononitrile. (Sodium methoxide.Y - Five grams of pentapropionyl-n-glucononitrile was dissolved in 7 ml. of chloroform cooled to —6° and then a cool solution of 0.84 g. of sodium in 10 ml. of methanol was added. A jelly-like mass was produced that was kept in the ice-salt bath for five minutes. Fourteen milliliters of water and 2.5 ml. of acetic acid were then added. The water phase was separated and evaporated in vacuo 20 ml. of ethanol was added and the solvent evaporated again the operation was repeated once more. The final residue was dissolved in 26 ml. of water, and to 13 ml. 1 g. of diphenylhydrazine was added the solution was then heated in a water bath. When crystals of n-arabinose diphenyl-hydrazone appeared, heating was stopped, and after four hours in the cold the crystals were collected yield 54% (calcd. as n-arabinose), m. p. 204-205°. 

Degradation of octaacetyllactobiononitrile. (Sodium ethoxide.y To 750 ml. of chloroform containing the impure octaacetyllactobiononitrile prepared from 200 g. of lactose, a solution of 15 g. of sodium in 750 ml. of methanol was added the solution was maintained at a low temperature and was shaken continuously. A jelly-like mass precipitated. When the precipitation was ended, 750 ml. of water and 50 ml. of acetic acid were added. The chloroform layer was separated and the water phase was evaporated in vacuo to a thick sirup. This was dissolved in 400 ml. of 96% ethanol, 65 g. of a,ai-benzylphenylhydrazine was added and the solution was heated in a water bath for thirty minutes. Assisted by seeding, crystallization of the hydrazone of the 3-( 9-D-galactopyranosyl)-D-arabinose was completed in five hours. The crystals were filtered and washed well with 80% ethanol yield 60-67 g., m. p. 223-225°. 

The pyrazolo[3,4-( ][l,2,3,4]tetrazine derivative 49 has been reported to be formed by treatment of the hydrochloride salt of the amine 48 with sodium nitrite in aqueous ethanol at room temperature. Only a single example was described. Compound 49 was obtained as red crystals (m.p. >300°C). The product is presumed to form from the diazonium cation 50 which cyclizes via the hydrazone tautomer 51 (Scheme 2) <1998MI11>. 

In certain cases, especially for neutral substrates, the formation of covalent p,n-pairs, instead of salts, may be necessary to achieve optical resolution by crystallization. Suitable derivatives are esters of camphanic acid (1) or chrysanthemic acid (2) with racemic alcohols, or esters of menthol (3) and 1-phenylethanol (5) with racemic acids, or hydrazones of menthylhydrazine (4) with racemic aldehydes and ketones. 

The structures of two (p-bromophenyl)hydrazones have been determined from projection data. The first was that of D-ribose,112 in which the D-ribose is acyclic, in a sickle18 conformation, and C-l, C-2, C-3, and C-4 are coplanar. Rotation of C-5 out of this plane relieves the 0-2, 0-4 interaction that would be present in the extended conformation and brings 0-5 close to 0-2, so that an intramolecular hydrogen-bond can be formed this is the first (and, thus far, the only) case of an intramolecular hydrogen bond in a crystal of a monosaccharide derivative. The hydroxyl groups on C-2, C-3, and C-4 form three intermolecular hydrogen-bonds. 

Intramolecular hydrogen-bonding between two oxygen atoms in the same monosaccharide is of minor importance in a crystal lattice. Only one example is at present known, namely, in D-ribose (p-bromo-phenyl)hydrazone.l,z... 

Both tosylhydrazones95-287-288 and oximes289 292- 336 were formed in good yields from the corresponding cyclobutanones under standard conditions. The tosylhydrazone of 4-isopropyli-dene-7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one was reported288 to first crystallize at — 20 °C as a thermally labile stereoisomer which isomerized to a 1 5 mixture of the two possible stereoisomeric hydrazones 1 at room temperature. In deuteriochloroform at room temperature, the half life of the least stable isomer was approximately 8 hours. The exact configuration of each stereoisomer was not stated. 

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