Dimedone properties

If an unknown compound gives a positive test with the 2 4-dinitrophenylhydrazine reagent, it then becomes necessary to decide whether it is an aldehyde or a ketone. Although the dimedone reagent (Section 111,70,2) reacts only with aldehydes, it is hardly satisfactory for routine use in class reactions. It is much simpler to make use of three other reagents given below, the preparation and properties of which have already been described (Section 111,70). 

This approach has been extended to cyclic 1,3-dicarbonyls for the synthesis of tetrahydrobenzopyrane derivatives, also known as tetrahydrochromenes, which have attracted much attention due to their wide range of biological properties. Thus, a mixture of an aromatic aldehyde, dimedone, and malonitrile in aqueous media catalyzed either by (5)-proline [123] or tetramethylammoniura hydroxide (TMAH) [124] gave the bicyclic heterocycle in excellent yields (Scheme 35). 

Ferrocene derivatives coupled with heterocyclic systems have attracted special attention in recent years because of their interesting organic and inorganic properties. Recently, an efficient and rapid route for the synthesis of 4-aryl-2-ferrocenyl-quinolines 70 has been described by Tu and co-workers [116] through a microwave-assisted MCR of acetylferrocene with an aromatic aldehyde and dimedone in the presence of ammonium acetate in DMF. This novel procedure provides the target hetero-metallic compounds in excellent yields without the need of any purification (Scheme 54). 

Organ and co-workers [120] described a unique approach to MCRs using a microwave-assisted, continuous flow process for the synthesis of new series of tetrahydro-pyrazolo[3,4-6]quinolin-5(6//)-ones 79. An aldehyde, dimedone, and 5-amino-3-methyl-l//-pyrazole were reacted, yielding the desired compound 79 in moderate to excellent yields. It was proved that the electronic properties of the substituted benzaldehydes have an important impact on the conversions as with electron-donating groups rather low yields were obtained (Scheme 60). 

When the Knoevenagel adducts formed from aldehydes with dimedone were reacted with dihydropyridazine-dione 156 (Scheme 30), pyridazino indazole triones 157 were obtained under solvent-free conditions in moderate yields [67]. The compounds were tested for their antibacterial properties against E. coli (ATCC 25922), P aeruginusa (ATCC 85327), Bacillus subtilis (ATCC 465) and S. aureus (ATCC 25923) (Table 11). Compounds 158-160 were found to be more active than Amoxicillin against E. coli but less potent than Norfloxacin. None of the reported compounds was active against S. aureus. 

The oxidizing properties of chlorate are utilized in its spectrophotometric determination. Chlorate admixtures in perchlorates have been determined by its colour reaction with benzidine [44] and J(5-thiosemicarbazone dimedone (e= 1.910 at 417 nm) [45]. Chlorate in water has been determined with o-tolidine [46]. At a suitably high chloride concentration in 3-7 M H2SO4, chlorate reacts quantitatively with Cf to form CI2, which decreases the absorbance of Methyl Orange [47]. 

Aminoandrostanes (453) open the ring of maleic anhydride to give the N-steroidal maleamic acids (454). which react with acetic anhydride-sodium acetate to give the 17-yl maleimides (456) via the labile isomaleimides (455). Chiroptical properties of steroidal amine-dimedone condensation products are reported on p. 292. 

F. Hansske and F. Cramer, Reaction of the ribose moiety of adenosine and AMP with periodate and 5,5-dimethylcyclohexane-l,3-dione (dimedone), Carbohydr. Res., 41 (1975) 366-369. P. N. Lowe and B. R. Beechey, Preparation, structure, and properties of periodate-oxidised ATP, a potential affinity-labelling reagent, Bioorg. Chem., 11 (1982) 55-71. 

Dimedone and dihydroresorcinol condensation products of a-amino acids (24) can be obtained from the corresponding amino acid esters with subsequent hydrolysis. The optical properties of these materials have been investigated over a period of several years (Crabbe and Halpern, 1965 Crabbe et a/.. 

The chiroptical properties of dimedone and dihydroresorcinol condensation compounds with the NH2-terminal amino acid of di- and tripeptide esters have been reported (Crabbe et a/., 1968). These chromophoric deriv-vatives (73) exhibit uv maxima at 274-278 nm (a = ca. 20,000). The corre-... 

These include the SSA-catalyzed synthesis of heterocyclic compounds such as xanthenes, coumarins, oxazoles, and so on. Xanthenes are of great therapeutic and biological interest on account of their many biological activities such as anti-inflanunatory, antiviral, antibacterial properties, and so on. Seyyed Hamzeh et al. (2008) carried out the SSA-catalyzed synthesis of aryl-14 f-dibenzo[fl,y]xanthenes from aldehydes and P-naphthol and 1,8-dioxo-octahydro-xanthenes from aldehydes and 1,3-dicarbonyl componnd such as dimedone under solvent-free conditions (Schemes 5.25, 5.26). Reactions were carried out at 80°C. Nazeruddin et al. (2011) documented an effective method for 9,10-dihydro-12-aryl-8 f-benzo[a]xanthenes-ll(12 f)-one derivatives in excellent yield and short reaction time using SSA under solvent-free conditions (Scheme 5.27). 

Five separate reports have appeared on the preparation, properties, and reactions of selenium ylides. The reaction of dimedone with dichloro-diphenylselenium afforded a selenonium salt, which was converted into the ylide (170) by chromatography on alumina. Based on this reaction, the... 

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