Carbonyl reagents

The usual carbonyl reagents (hydrazines, semicarbazone, hydroxyl-amine) do not give the normal derivatives, but lead to ring contraction and formation of pyrazoles or isoxazoles. However, a semicarbazone and an oxime of 2,6-diphenylpyrone has been obtained by Arndt et al., indirectly, through the intermediacy of the more reactive 4-thiopyrone. 

In general, the carbonyl derivatives of isothiazole behave normally and condense readily with carbonyl reagents. The aldehydes reduce ammoniacal silver nitrate and undergo the Cannizzaro reaction. ... 

The reaction of these aldehydes, derived from periodate oxidation, with carbonyl reagents has also been investigated. Studies 147 148 were made on oxidized laminarin, a (1 —> 3)-linked polysaccharide, in which only the terminal residues had been oxidized. The addition of phenylhydrazine acetate detached the remainder of the terminal residue as glyoxal phenyl-osazone. When the aldehydic compounds derived from the periodate oxidation of raffinose and trehalose818a were reacted with p-nitrophenylhydrazine, the authors were surprised to find that one molecule of oxidized raffinose, containing six aldehydic functions, reacts with only three molecules of the reagent, and that the four aldehydic functions of the oxidized trehalose molecule react with only two. The reactions of periodate-oxidized carbo-... 

Carbohydrate lactones have been used as the carbonyl reagent in the Reformatsky reaction. Thus, 2,3 5,6-di-O-cyclohexylidene-D-mannono-1,4-lactone [44, obtained by oxidation of the mannofuranose derivative (49)] reacted with ethyl bromoacetate and zinc to give the protected 2-deoxy-3-octulosonic acid ethyl ester (45a) in 69% yield (50). Ketonic hydrolysis with potassium hydroxide in aqueous methanol, followed by acidification and heating, afforded the 1-deoxyheptulose derivative 45b. Similarly, starting from compound 44, the 1-C-substituted allyl and propar-gyl lactols were prepared on reaction with allyl or propaigyl bromides in the presence of zinc (51). 

It has recently been shown (H naff, 1963 Bell and Evans, 1966) that under suitable conditions the reaction of various carbonyl reagents (e.g. 

It has been shown by H naff (1963) that the rate of reaction of several carbonyl reagents (bisulphite, hydrazine, phenylhydrazine, semi-carbazide and hydroxylamine) with aqueous formaldehyde solutions is independent of the nature and concentration of the reagent, and is therefore determined by the rate of dehydration of methylene glycol. He obtained catalytic constants for hydrogen and hydroxide ions, and a detailed study of acid-base catalysis has been made by the same method by Bell and Evans (1966). 

Both esters can be distinguished by their reactions with carbonyl reagents. A phenylhydrazone is formed only by the compound with a free carbonyl group. 

Attempts were made in my laboratory to determine carbonyl groups with various carbonyl reagents, e.g., hydroxylamine, semicarbazide or dinitrophenylhydrazine. With hydroxylamine, oximes were formed to an extent that was equivalent to the difference between NaOEt and NaOH consumption. Errors due to binding of hydroxylammonium ions, which would show up in nitrogen determinations as well, were prevented either by methylation of the acidic groups with diazomethane or by ion exchange with dilute sodium hydroxide oximes are stable towards dilute alkali. However, only half the quantity of carbonyl groups reacted with semicarbazide or with dinitrophenylhydrazine. 

Nitrobenzyl phosphoric esters, which are photolyzed to the free acids (compare Scheme 3), are used in nucleotide synthesis and are very efficiently cleaved (90-98%) at >320 nm in the presence of a polymeric carbonyl reagent ((P)-N(CH3)-CONHNH2) to remove the aromatic photoproducts an example is given in Scheme 30. 

In 1963, Heck reported the ring opening of propylene oxide by the carbonylating reagent tetracarbonylhydridocobalt(I) in the presence of carbon monoxide, which results in a stable acyl cobalttetracarbonyl compound (Fig. 15). However, no polymeric products were reported, which would result from multiple ring opening and CO insertion processes [58, 59]. 

Carbonyl reagents, such as semicarbazide and phenelzine (27), are inactivators of SSAO. In a strategy that includes two inactivating structural motifs (allylamine and hydrazine), a series of allyl hydrazines including the series 28a-c as well as the fluoroallyl analogue 29 were prepared. Compounds 28a-c were potent irreversible inhibitors of SSAO, and compounds 28a,c had particularly good selectivity with respect to MAO inhibition. The presence of the vinyl fluoride in 29 had little effect on potency but did result in a loss in selectivity [82]. 

Ring keto groups are attacked by the usual carbonyl reagents. Compounds such as tetrahydropyran-2-one (67), with the keto function adjacent to the heteroatom, behave as cyclic esters, and are ring-opened by hydroxide ion. Condensation reactions with (67) at C-3 can also be performed. 

GABA synthesis inhibitors act on the enzymes involved in the decarboxylation and transamination of GABA. Glutamic acid decarboxylase (GAD), the first enzyme in GABA biosynthesis, is inhibited easily by carbonyl reagents such as hydrazines [e.g., hydrazinopropionic acid (4.164) or isonicotinic acid hydrazide (4.165)], which trap pyridoxal, the essential cofactor of the enzyme. A more specific inhibitor is allylglycine (4.166). All of these compounds cause seizures and convulsions because they decrease the concentration of GABA. 

Boron-bonded p -borazine complexes of transition metals have been prepared by two different approaches (a) nucleophilic substitution of B,fi, fi"-trichloro-borazine with an anionic metal carbonyl reagent and (b) oxidative addition of a B-Br bond of 5,5, B"-tribromoborazine to a zerovalent group 10 complex (see examples in Scheme 9.2). 

Ortho-esters at position 1,2- of sugars are more easily prepared than the corresponding acetals as an exchange of both functional groups is possible, 1,2-O-alkylidene derivatives can be prepared by the reaction of these ortho-esters with the appropriate carbonyl reagent in strictly anhydrous conditons and in the presence of an acid [87]. 

Benzofuran-3(2/f)-ones (396) exist in the keto form but undergo ready enolization. Acetylation with acetic anhydride and sodium acetate affords 3-acetoxybenzo[6]furans, but reaction under acidic conditions usually supplies these products admixed with 3-acetoxy-2-acetylbenzo[6]furans. Alkylation usually furnishes a mixture of O- and C-alkylated products. 3-Acetoxy-6-methoxy-4-methylbenzo[6]furan, on Vilsmeier reaction, supplies the 3-chlorobenzo[6]furan-2-carbaldehyde, the product expected from an enolizable ketone (72AJC545). Benzofuran-3(2//)-ones react normally with carbonyl reagents. Grignard reagents react in the expected way and dehydration of the intermediate affords a 3-substituted benzo[6]furan. The methylene group is reactive so that self condensation, condensation with aldehydes and ketones and reaction with Michael acceptors all occur readily. 

Many poisonous substances as well as useful drugs react with PLP-requiring enzymes. Thus, much of the toxic effect of the "carbonyl reagents" hydroxylamine, hydrazine, and semicarbazide stems from their formation of stable derivatives analogous to Schiff bases with PLP. 

Acylcuprate reagents.1 The reaction of cuprates of the type R2(CN)CuLi2 with carbon monoxide at -110° results in carbonylated reagents, possibly with the composition (RCO)R(CN)CuLi2. In any case, these cuprates effect 1,4-acylation of a,p-enones and -enals to provide 1,4-dicarbonyl compounds. 

In conclusion, we have shown that due to the diffusional problems, monodirectional large pore zeolites are very inefficient to perform bimolecular reactions involving carbonylic reagents in the liquid phase. By contrast, catalysis by tridirectional Y and fl zeolites show similar features, with a high catalytic activity which increases with the acid strength of the acid sites. 

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