1.3- dicarbonyl compounds reaction with

X-ray photoelectron spectroscopy, 139 Diazo ligands, 100 Dicarbonyl compounds reaction with amines aza macrocycles from, 902... 

Other Electrophiles. In addition to carbonyl compounds, ester enolate (1) also reacts with other electrophiles. With nitrones, the product is dependent upon the structure of the nitrone a,N-dialkyl nitrones provide alkenes, while a-aryl-A-alkyl nitrones or aW-diaryl nitrones usually give aziridines. With the phenylhy-drazone of a 1,2-dicarbonyl compound, reaction with (1) provides a convenient preparation of 3(2f/)-P3 dazinones (eq 3). ... 

Ureas are commonly employed in the syntheses of 2-hydroxypyrimidines. An example is the reaction of 1,3-dicarbonyl compounds 19 with urea (20) in the presence of HC1 to produce pyrimidines 21 though no yields were given <00JMC3995>. 

Hydroxycoumarin can be considered as an enol tautomer of a 1,3-dicarbonyl compound conjugation with the aromatic ring favours the enol tautomer. This now exposes its potential as a nucleophile. Whilst we may begin to consider enolate anion chemistry, no strong base is required and we may formulate a mechanism in which the enol acts as the nucleophile, in a simple aldol reaction with formaldehyde. Dehydration follows and produces an unsaturated ketone, which then becomes the electrophile in a Michael reaction (see Section 10.10). The nucleophile is a second molecule of 4-hydroxycoumarin. 

The standard syntheses for pyrazoles (17) and isoxazoles (19) involve the reactions of (3-dicarbonyl compounds (18) with hydrazines and hydroxylamine, respectively. These reactions take place under mild conditions and are of very wide applicability the substituents Y can be H, R, Ar, CN, C02Et, etc. 

The reaction of 1,2-dicarbonyl compounds (477) with amidrazones (478) is the best method for the synthesis of alkyl-, aryl- or hetaryl-substituted 1,2,4-triazines (481) (78HC(33)189). Mixtures result unless the dione (477) is symmetrical. 

The reaction of 1,2-dicarbonyl compounds (452) with amidrazones (453) is the best method for the synthesis of alkyl, aryl or hetaryl substituted 1,2,4-triazines (78HC(33)189, p. 195). No limitation of this synthetic principle is reported, except that it is, of course, preferable for the dione (452) to be symmetrical. The best reaction procedure is to add the dicarbonyl compound to a solution of the free amidrazone, or amidrazonium salt in the presence of one mole of base, and allow a reaction time of about 12 h. Since the first step of this reaction, i.e. condensation of the hydrazono group with one carbonyl group, is fast, while the second, i.e. condensation of the amide group with the other carbonyl, is slow, the intermediate (454) has been isolated in a few cases. This method has been used also for the synthesis of compounds containing more than one 1,2,4-triazine nucleus, and for the parent 1,2,4-triazine (1) (68CB3952). 

The reaction of 1,3-dicarbonyl compounds (515) with azodicarboxamidine (516) affords l-amidino-3-amino-1,2-dihydro-1,2,4-triazines (517) (73AP697, 73AP801). 

Cyclization to a morpholinolactone (59) occurs in the hydrolysis reaction of the di-A-hydroxylethylated compound (60). Compound (59) is rapidly hydrolysed by water to (61) but in file presence of equimolar amounts of amines (RNH2) or ammo acid derivatives (62) forms.56 A novel reaction of cyclic 2-diazo-l,3-dicarbonyl compounds (63) with lactones (64) affords the products (65) in the presence of rhodium acetate, Rh2(OAc)4.57 Lewis acid-promoted intramolecular additions of allylsilanes to lilac tones gave substituted cyclopentanes.58 A proposed transition state guided efforts to improve the stereoselectivity of the reaction. The reaction of a series of /1-lactone derivatives, such as (66)-(68), has been studied and they have been ling cleaved the reaction outcome is both Lewis acid and structure dependent.59... 

The 1-(3,4-dimethoxyphenyl)-4-methyl-5-ethyl-7,8-dimethoxy-577-2,3-benzodiazepine 63, a known anxiolytic agent, is prepared by the reaction of a monoketal derivative of a 1,5-dicarbonyl compound 62 with hydrazine or its hydrate or its salt <2003W02003050092A2> (Equation 7). 

A range of other related 2,4-dicarbonyl compounds react with dicyanogen to give products derived from initial electrophilic attack upon the 3-position. For example, the reaction with C6F5NHCOCH2COR is promoted by [Ni(acac)2], and the major products are the free ligands 5.4 and 5.5. The copper(n) complexes of 5.4 and 5.5 are obtained directly from the reaction of dicyanogen with copper(n) complexes of C6F5NHCOCH2COR. 

Figure 2.9. Glucose can enolize and reduce transition metals thereby generating superoxide free radicals (02" ), hydroxyl radicals ( OH), hydrogen peroxide (H202) and reactive dicarbonyl compounds. Adapted with permission from Wolff, S. P. (1996). Free radicals and glycation theory. In The Maillard Reaction. Consequences for the Chemical and Life Sciences, Ikan, R., ed., John Wiley Sons, Chichester, UK, 73-88.

Alkylidene-4,5-dihydrofurans.1 Reaction of 2-alkenyl 1,3-dicarbonyl compounds (1) with I2 effects cyclization to iodoalkyldihydrofurans (2). Dehydroiodin-ation (DBU) of 2 results in 5-alkylidene-4,5-dihydrofurans (3), which undergo acid-catalyzed isomerization to furans (4). 

Reaction of 201 with 1,3-dicarbonyl compounds, or with aliphatic and cyclic ketones 203 in the presence of dilute sulfuric acid, gave the 3//-l,2,3-triazolo[4,5-6]pyridines 204 (79CPB2861). The mechanism of transformation involves ring fission to 202, followed by reaction with 203 to give 204, a type of Friedlaender synthesis (see Scheme 42). 

Pyrazoles and isoxazoles from 1,3-diketones. The standard syntheses for pyrazoles 41 and isoxazoles 43 involve the reactions of -dicarbonyl compounds 42 with hydrazines and hydroxylamine, respectively (Scheme 31). These reactions take place under mild conditions and are of very wide applicability the substituents R can be H, alkyl, aryl, GN, G02Et, etc. For example, 4-alkoxypyrazoles 45 can be prepared from diketones 44 and hydrazine (Scheme 32) <2002SL1170>, while diketooximes 46 react with excess hydrazine in ethanol to give 4-amino-3,5-disubstituted pyrazoles 47 in generally good yields (Scheme 33) <2004TL2137>. 

In a related reaction, condensation of 1,3-dicarbonyl compounds (323) with methylene bis-imidazolidine (324) gave substituted imidazo[l,2-a]pyridines (325) (78LA1491). The reactions of aldehydes (326) with ethyl 2-imidazolidinyleneacetate (327), or those of aldehydes (326) and jS-dicarbonyl compounds with imidazolidines (330) gave similar structures (328) and (331) (78LA1476, 73GEP2210633). 

Reaction of 2-(4-nitrophenylsulfonyloxy)-l, .3-dicarbonyl compounds 31 with a base (e.g., tri-ethylamine or l,8-diazabicyclo[5.4.0]undec-7-ene) gives 1,2,3-tricarbonyl compounds32 in high yield. The tricarbonyl compound can be further reacted, without isolation, with benzene-1,2-di-aminc to give quinoxalines 33 in excellent yields. ... 

The condensation of a, dicarbonyl compounds (49) with aj3-diamino compounds (50), which proceeds through the dihydropyrazine (51), has been much used for the synthesis of alkyl- and arylpyrazines (52). These reactions are usually carried out in methanol, ethanol, or ether in the presence of sodium or potassium hydroxide. The dihydropyrazines may be isolated, or oxidized directly to the pyrazine. Dehydrogenating agents that have been employed include oxygen in aqueous alkali (329), air in the presence of potassium hydroxide (330), sodium amylate in amyl alcohol (330a), alcoholic ferric chloride (24), and copper chromite catalyst at 300° (331) (see also Section 1). Pyrazines prepared by this method and modifications described below are listed in Table II.8 (2, 6, 24, 60, 80,195, 329-382) and some additional data are provided in Sections VI. 1 A, VlII.lA(l), and IX.4A(1). 

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