Dimedone method

PdCl2(Ph3P)2, dimedone, THF, 95% yield. This method is also effective for removing the allyloxycarbonyl group from alcohols and amines. 

Unique methods based on new principles have been developed within the past 10 years. Threonine (27,28,249) is oxidized by lead tetraacetate or periodic acid to acetaldehyde, which is determined by photometric analysis of its p-hydroxydiphenyl complex or iodometric titration of its combined bisulfite. Serine is oxidized similarly to formaldehyde, which is determined gravimetrically (207) as its dimedon (5,5-dimethyldihydro-resorcinol) derivative or photometric analysis (31) of the complex formed with Eegriwe s reagent (l,8-dihydroxynaphthalene-3,5-disulfonic acid). It appears that the data obtained for threonine and serine in various proteins by these oxidation procedures are reasonably accurate. [Block and Bolling (26) have given data on the threonine and serine content of various proteins. ]... 

The assay for formaldehyde is today mainly performed by either of two general methods. The one most widely used depends on the reaction of 5,5-dimethyl-1,3-cyclohexanedione (Dimedon) with formaldehyde when applied after the destruction of excess periodate, it proceeds quantitatively,... 

A method for the determination of formaldehyde in the presence of acetaldehyde was developed by Nicolet and Shinn.88,100 103 After the excess periodate had been destroyed, these workers swept the acetaldehyde (from the neutral reaction mixture) into a sodium bisulfite solution by means of a stream of carbon dioxide. The acetaldehyde was measured by conventional, bisulfite methods, and the residual formaldehyde was precipitated with Dimedon. This procedure was applied to protein hydroly-zates and to terminal deoxy structures of carbohydrates.88,280 ... 

To carry out MCRs of aminoazoles with aldehydes and cyclic CH-acids, the methods of green chemistry were also applied. For example, treatments of 3-methylisoxazol-5-amine and aromatic aldehydes with 1,3-cyclohexanedione, dimedone, 1,3-indanedione, or titronic acid were proceeded in water under micro-wave irradiation at 120°C [100] (Scheme 31). As a result, clean, efficient, and convenient procedures for the generation of polycyclic-fused isoxazolo[5,4-b] pyridines 71 were developed. An interesting fact is that, in the case of 1,3-cyclohexanedione, dihydropyridine s were obtained while in aU other cases only hetero-aromatized derivatives were isolated. No reason for this experimental fact was discussed in the article. 

A more general method for carbohydrates that can be used equally well on handsections and on sections of plastic embedded materials uses the Periodic acid SchifFs (PAS) reaction or one of its variants [29] for vicinal hydroxyl groups [22,23]. Sections are treated with 1%W/V Periodic acid at room temperature for 10 minutes and rinsed. The aldehydes created by this treatment are detected with SchifFs reagent (decolorized para-rosaniline) by immersion for 30 minutes. A red color (or fluorescence with excitation at 540 nm) indicates vicinal hydroxyl groups in starch and many other carbohydrates. If the specimen has been fixed with aldehydes then an aldehyde-blocking step must precede this reaction [22]. The best treatment is immersion for 24 hr in a saturated solution of dimedone. 

Another method for deallylation is the Pd-catalyzed transfer of the allyl group to reactive nucleophiles. Sodium 2-ethylhexanoate [141], morpholine [142], dimedone [143] and AA-dimethylbarbituric acid [144] are used as allyl scavengers. It is claimed that benzenesulfinic acid 331 or sodium toluenesulfinate are the best allyl scavengers [145]. 

Phenylation and arylation have also been performed in bifunctional compounds such as malonates, /1-diketones and /1-ketoesters (Table 8.4). Diethyl malonate was arylated at room temperature affording mixtures of mono- and bis-arylated products, whereas isopropylidene malonate (Meldrum s acid) underwent bis arylation directly. Dimedone, the all carbon analogue of Meldrum s acid, was also mono-and bis-phenylated, with some concomitant O-phenylation [33], Generally, / -diketones show often ambident reactivity but the O-arylated product is normally the minor one an exception was noted in the triketone (PhCO)2CHCOPh which underwent mainly O-phenylation (68%) [33], Several dianions from /1-diketones have been arylated in high yields at the a-position, in a procedure superior to other methods [35]. 

Ogawa and Fritz (1985) developed a method for the identification of acrolein in water. A known volume of water is passed over a column of zeolite that traps the acrolein. The column is then eluted with acetonitrile, and derivatization using DNP follows. By following this procedure, a sample that can be analyzed by HPLC is obtained. Other derivatizing agents that have been used successfully for the monitoring of acrolein in the environment include dimedon, phenylhydrazone, 4-hexylresorcinol, and 3-methyl-2-benzothiazolone (Altshuller and McPherson 1963 Peltonen et al. 1984). 

Condensation of primary dimedone enaminones with formaldehyde according to Greenhill and coworkers26,27 give, in neutral medium, methylenbisenaminones, whereas acidic conditions produce spirocompounds. Structure A is given by Greenhill27 for the spiro-product, but structure B (equation 20) also seems reasonable. Modern spectroscopic methods should be used to solve this problem. Similar products are obtained in the Mannich reaction of enaminones derived from indan-l,3-dione33. 

A new series of polyhydroquinolines 64 has been prepared by Shingare and co-workers [111] using nanosized Ni as a heterogeneous catalyst in a one-pot synthesis via Hantzsch condensation by reacting an aldehyde, dimedone, ethyl aceto-acetate and ammonium acetate in a domestic microwave oven. Ni (80 0.5 nm), having a higher surface to volume ratio, has given the best results in terms of short reaction times and excellent product yields. This method has demonstrated that Ni, in the form of nanoparticles, is a potential alternative catalyst for the Hantzsch... 

Condensation of 5,5-dimethylhexan-l,3-dione (dimedone) with amino acid esters leads to Af -5,5-dimethyl-3-oxocyclohex-l-enyl derivatives 128 as particularly stable enamines that are converted into the free acids by saponification, for coupling by carbodiimides, carbonyldiimidazole, or Woodward s reagent K, or are transformed into the hydrazides for coupling via the azide method (Scheme... 

Dimedone (0.7 g, 5.0 mmol) was added to a solution of 4,4 -(bicyclo[n.l.0]alkanediyl)dimorpholine (5.0mmol. Method A) or 4-[(n-t-3)-methoxybicyclo[n.l.0]alkyl)morpholine (5.0mmol. Method B) in MeCN (15 mL). The solution was stirred for 24 h at 20 °C. The resulting colorless precipitate was isolated by suction, washed with EtjO and dried in vacuo. 

A convenient one-pot method for the synthesis of acridine derivatives was carried out by supporting a mixture of dimedone, aromatic aldehydes, and ammonium bicarbonate (02SC2181) or ammonium acetate (99H21), as a nitrogen donor, on neutral or better basic alumina and catalytic amount of DMF to give upon MW irradiation good yields of 356 (R = Ar, R1 = H) within very short time (99H21). The reaction can... 

Dimedone provides diazo dimedone (135) with -benzoic acid sulfonylazide (84%) and with p-tolyl sulfonylazide (96%). Weak nucleophilic base such as 1,8-diazabicyclo[5.4.0]undecen-7-ene (DBU) has been used as catalyst for the diazo transfer reactions of 1,3-diketones (136 -139).55 A highly efficient methodology in solid state has been developed for the synthesis of a-diazo carbonyl/sulfonyl compounds from 1,3-diketones using tosyl azide. This method avoids any aqueous workup and diazo compounds are obtained via a column filtration over silica gel. 0... 

Of course, derivatization methods can also be used for the identification of organic acids. For example, volatile fatty acids in urine and plant protein hydrolysates were esterified with phenyldiazomethane and the resulting benzyl esters were separated by glass capillary GC [254]. Janos et al. [255] described a method for the analysis of dimedone derivatives of formaldehyde and other aliphatic aldehydes on capillary columns. Phenolic amines, 3-methoxycatecholamines, indoleamines and related amines can be determined as their N,0-ethyloxycarbonyl derivatives [256]. The reaction of dithiols and certain monothiols with phenylarsine oxide was used for derivatization prior to GC [257]. Destructive GC methods for the identification of microorganisms were described in refs. 258-261. 

Protected amino acids and peptides in the form of aminomethylene-dimedone derivatives are formed and cleaved very readily. The cleavage with hydrazine in DMF proceeds at room temperature. This protection method is suitable for solid-phase peptide synthesis. 

The nitrosation method is not recommended for a-aminoketones, but it works well for 2-amino-l,3-dicarbonyl compounds, as found by Wolff (1902) for the preparation of 3-diazopentane-2,4-dione (2.31). Cyclic diazo-a, a -diketones, such as 2-diazocyclohexane-l,3-dione (2.32, R=H) and its 5,5-dimethyl derivative (diazo-dimedone, 2.32 R=CH3), can be synthesized without major difficulties (Eistert et al., 1959 Stetter and Kiehs, 1965). The parent compound, diazomalonodialdehyde (2.33) was prepared only in 1973 by Arnold and Sanliova. The smooth formation of diazo-a,a -diketones and the decreased tendency for proton addition at the central C-atom can be explained by the resonance structures 2.31 a-c. 

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