Crystalline derivatives preparation ketones

Certain nucleophilic species add to carbonyl groups to give tetrahedral intermediates that are unstable and break down to form a new double bond. An important group of such reactions is that between compounds containing primary amino groups and ketones or aldehydes. Scheme 8.2 lists some of the more familiar classes of such reactions. At one time, a principal interest in these reactions was for the preparation of crystalline derivatives of ketones and aldehydes for characterization, but more recently, these types of reactions have been studied in detail because they are models of processes that are of importance in biological reactions. In... 

Imine formation from such reagents as hydroxylamine and 2,4-dinitro-phenylhydrazine is sometimes useful because the products of these reactions— oximes and 2,4-dinitrophenylhydrazones (2,4-DNPs), respectively—are often crystalline and easy to handle. Such crystalline derivatives are occasionally prepared as a means of purifying and characterizing liquid ketones or aldehydes. 

Crystalline derivatives of aliphatic nitriles may be prepared by an application of the Hoesch reaction. Equimolecular proportions of phloroglucinol and the nitrile react in dry ethereal solution in the presence of anhydrous zinc chloride and hydrogen chloride to give an imine hydrochloride, which is converted into a solid alkyl trihydroxyphenyl ketone by hydrolysis. The alkyl 2,4,6-trihydroxy-phenyl ketones are usually highly crystalline solids of sharp melting point and are purified by recrystallisation from hot water. Many contain water of crystallisation which can be removed by drying in vacuo at about 100 °C the melting points of both the hydrated and anhydrous compound should be determined. 

You should already be familiar with approximately half of the reactions listed in Table 9.2 from your introductory class. Moreover, you have probably tried to prepare an oxime, a phenylhydrazone, a 2,4-dinitrophenylhydrazone, or a semicarbazone. These compounds serve as crystalline derivatives with sharp and characteristic melting points for identifying aldehydes and ketones and for distinguishing them. When spectroscopic methods for structure elucidation were not available, such a means of identification was very important. 

Most steroid ketones react readily with tolnene- Siilphonyl hydrazide -CH3 C6H4 S03 NH NH2) to form crystalline derivatives ( tosylhydrazones ) which are valuable intermediates for the preparation of olefins and fully-saturated unsubstituted products. Three modes of reaction of tosyl-hydrazones have become important. 

N-nitrosonor codeine can also be prepared from nor codeine on reduction with zinc-dust and acetic acid it yields norcodylliydrazine [xnx], which forms crystalline derivatives with aldehydes and ketones [356], Norcodylhydrazine can be oxidized to the tetrazone [l], C34H3606N4, by mercuric acetate [356]. 

Upon boiling colupulone in methanol hydrogen chloride 12 N 10 3 during 3.5 h, two crystalline derivatives with molecular formula C20H28O4 s " obtained (1,2). The compound with a melting point of 83°C (190, Figs. 107 and 113) is synthesized by reaction of phlorisobutyrophenone with two equivalents of 3-methyl-2-butenyl bromide in dry chloroform (3). The neutral character of the tricyclic molecule is ascribed to the presence of an o.-hydroxyaryl ketone (4,5). Compound 190 can also be prepared by... 

The Henegar modification of the Friedlander reaction has been recently reported. The A-Boc protected derivative of o-aminobenzaldehyde (25, in this case prepared via directed ortho metallation of 24) is a stable, crystalline compound that can be stored for extended periods (in contrast with 4, which typically is freshly prepared). Treatment of 25 with ketone 26 in acetic acid results in deprotection of the aniline in situ and subsequent formation of 27, an intermediate in the synthesis of mappicine. 

Representatives of this new type of meso-ionic system (502) have been prepared by cyclodehydration of the acid derivatives 503 using trifluoroacetic anhydride. For example, the acid 503, R = p.ClCgH4, gave the red crystalline meso-ionic l,3-oxathiol-5-one (502, R =p.Cl.CgH4, R = CF3.CO) which is readily hydrolysed to the ketone (504, R = j3.Cl.CgH4). The trifluoroacetyl group in the 4-position appears to be essential for the stability of the meso-ionic system (502). 

In the case of D-psicose14 and D-sorbose80 the fceto-pentaacetates, as well as some of their derivatives, have been prepared by the diazomethane synthesis. The only crystalline product which was isolated from the low temperature acetylation of D-psicose137 was the fceto-pentaacetate. /ceabsorption spectrum indicated the presence of the ketonic group and its structure was further verified by catalytic hydrogenation,102 followed by acetylation, in which case both L-iditol and... 

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