Photochemistry of purine 3-oxides in hydroxylic solvents

UV irradiation of the potent oncogen hypoxanthine 3-oxide in aqueous solution induces elimination of and rearrangement of the nitrogen-bound oxygen. The extent of each reaction shows a complex variation over the pH range 0–7. The variations in quantum yield for product formation are shown to result from the presence in the neutral molecule of tautomeric species with differing photochemistries that ionize in the excited state (pK_a^* ～ 3.5) just above the protonation pK_a (1.2). The photochemical reactivity of each ionic and each tautomeric form was assigned by comparing the effect of pH changes between 0 and 11 on the quantum yields for formation of each photoproduct from hypoxanthine 3-oxide with those of two model compounds, 1-hydroxyhypoxanthine and 6-methoxypurine 3-oxide. Photoreduction of the 3-oxides occurs via the triplet state. This process has a relatively consistent low quantum yield (Φ = 0.005 to 0.04) for most ionic and tautomeric forms of both purine 1-oxides and purine 3-oxides. Photorearrangement is a much more efficient process for purine 3-oxides (Φ = 0.3) than for purine 1-oxides (Φ = 0.04).     

Facile hydrogenation of aromatic nuclei with sodium borohydriderhodium chloride in hydroxylic solvents

Sodium borohydride-rhodium chloride in hydroxylic solvent was proved to be very useful for the reduction of aromatic nuclei to the corresponding saturated cycles under mild conditions.     

Preferential solvation of Brooker's merocyanine in binary solvent mixtures composed of formamides and hydroxylic solvents

The ET polarity values of 4-[(1-methyl-4(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (Brooker's merocyanine) were collected in mixed-solvent systems comprising a formamide [N,N-dimethylformamide (DMF), N-methylformamide (NMF) or formamide (FA)] and a hydroxylic (water, methanol, ethanol, propan-2-ol or butan-1-ol) solvent. Binary mixtures involving DMF and the other formamides (NMF and FA) as well as NMF and FA were also studied. These data were employed in the investigation of the preferential solvation (PS) of the probe. Each solvent system was analyzed in terms of both solute-solvent and solvent-solvent interactions. These latter interactions were responsible for the synergism observed in many binary mixtures. This synergistic behaviour was observed for DMF-propan-2-ol, DMF-butan-1-ol, FA-methanol, FA-ethanol and for the mixtures of the alcohols with NMF. All data were successfully fitted to a model based on solvent-exchange equilibria, which allowed the separation of the different contributions of the solvent species in the solvation shell of the dye. The results suggest that both hydrogen bonding and solvophobic interactions contribute to the formation of the solvent complexes responsible for the observed synergistic effects in the PS of the dye.     

Polarographic study of acridine and 9-chloroacridine and its derivatives in dimethylformamide

Polarographic data on the reduction of acridine (I) and its 9-chloro (II), 2-methoxy-9-chloro (III), 4-methoxy-9-chloro (IV), 2-methyl-9-chloro (V), 4-methyl-9-chloro (VI), 2,9-dichloro (VII), and 4,9-dichloro (VIII) derivatives and a mechanism for the reduction are presented. In dimethylformamide (DMF) the polarographic reduction of acridine I takes place in two steps with participation of one electron in each step and the intermediate formation of an anion radical. Acridine II is reduced in four steps: The second and fourth waves correspond to the reduction of the heteroring, while the first and third waves are associated with detachment of a chlorine atom. The addition of phenol as a proton donor facilitates the reduction but does not affect the number of electrons consumed by the depolarizer during its reduction. A linear correlation between E_1/2 and the corresponding constants of quinoline is observed for acridines II, III, V, and VII; this made it possible to calculate the previously unknown constants for acridines that contain a substituent in the 4 position. The E_1/2 ¹ values for acridine II and its derivatives correlate with the rate constants for chemical dehalogenation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1660–1665, December, 1978.     

Hydrogen bonding of aromatic amines in hydroxylic solvents 2. Absorption and emission spectroscopy of substituted 7-aminocoumarins and 7-aminocarbostyrils

The absorption and fluorescence spectra of 7-aminocoumarins and 7-aminocarbostyrils with different degrees of alkylation were studied in 2-propanol (IP), polyfluorinated alcohols and water. The spectral properties of substituted 7-aminocoumarins and 7-aminocarbostyrils in hexafluoro-2-propanol (HFP) are very different from those in 2-propanol due to the strong hydrogen-bonding (HB) interaction between the solute and the solvent (HFP). The spectral behaviour can be explained in terms of the strength of the HB interaction which depends on the degree of alkylation of the amino group and the electron affinity of the electron-accepting moiety. The absorption spectra indicate that a structural change at the amino nitrogen is induced on formation of strong hydrogen bonds.     

The mechanism of solvolysis of methyl perchlorate in hydroxylic solvents: calculation of the cavity terms

From standard Gibbs energies of transfer, corrected for cavity or nonelectrostatic effects, it is concluded that the solvolysis of methyl perchlorate takes place through a looser-than-usual S_N2 transition state with a charge separation of about 0.52 units.     

Reaction of 9-chloroacridine with heterocyclic compounds containing an active methyl group

9-Chloroacridine reacts with 4-picoline to form 1-(9-acridinyl)-4-(9-acridinylmethylidene)-1,4-dihydropyridine, whose structure was proved by chemical transformations. A number of such compounds were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1090–1093, August, 1971.     

Synthesis and Antibacterial Activity of New N9-Substituted Acridine-9-amines

Russian Journal of General Chemistry - A method for the synthesis of N9-substituted acridine-9-amines by reacting 9-chloroacridines with 2-(2-methyl-5- nitro-1H-imidazol-1-yl)ethanamine was...     

Demethoxylation and O-Demethylation of Pseudaconine and Isotalatizidine

Thenorditerpenoidalkaloidsnotonlyhaveimportantpharmacologicalactivities,butalsomaysetoffalotofinterestingchemicalreactionsl'2.Inthecourseofourstudiesonsearchforhighactivity,lowtoxicitycompoundsandconversionoftheskeletons,aseriesofmodificationsofthesealkaloidshavebeenreported'.Inthepresentpaper,wereportsomechemicalreactionsincludingthedemethoxylation,O-demethylationandoxidation,ofthenorditerpenoidalkaloidspseudaconine1andisotalatizidine7.Treatmentofthenorditerpenoidalkaloidscontainingmethoxylgr…     

Synthesis and characterization of oxadisilole-fused acridines,dioxatrisilole-fused acridines and benzo[b]acridines

Oxadisilole-fused acridines, dioxatrisilole-fused acridines and benzo[b]acridines were synthesized through nucleophilic additions and aromatization reactions of arynes with 2-aminoaryl ketones or 2-aminoaryl aldehydes in good yields at room temperature. The photophysical, redox and thermal properties of these compounds were characterized. These compounds show potential applications as strong deep-blue or green emitters for OLED because of high fluorescence quantum yields and good thermal stabilities.     

Acetylene chemistry. Part 29. A convenient synthesis of 9-(n-alkynyl)acridinamines via a nucleophilic displacement reaction between 9-chloroacridine and N-alkynyl amines

Three new 9-(N-alkynyl)acridinamines 5, 6 and 7 have been synthesized from 9-chloroacridine using a simple aromatic nucleophilic substitution reaction.     

Novel trends in the chemistry of acridines. New fluorescent bioreagents and synthons on the basis of 9-isothiocyanatoacridines

9-Isothiocyanatoacridines containing a reactive NCS group, together with a biologically active acridine skeleton, were used for the synthesis of new acridine heterocycles. Their reactivity with aliphatic and aromatic amines as well as 15 amino acids was quantified by kinetic measurements. Sodium D-alkyl-N-(9-acridinyl)iminothiocarbonates obtained by addition of sodium alkoxides to the title compounds gave three types of products with organic halogen reagents. The reaction of above iminothiocarbonates with alkyl halides led to the fluorescent S-alkyl derivatives, whereas bromoacetyl bromide and alkyl bromoacetates afforded the 3-(9acridinyl)-1, 3-thiazolidine-2,4-diones and a new heterocycle, spiro[dihydroacridine-9(IOH), 4'-thiazoline], respectively.Department of Organic Chemistry, P. J. Safarik University, 04167 Kosice, Slovak Republic. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1376–1379, October, 1995. Original article submitted July 1, 1995     

Spectrophotometric determination and computational evaluation of the rates of hydrolysis of 9-amino-substituted acridines

Aminoacridines have a long history in the drug and dye industries and display a wide range of biological and physical properties. Despite the historical relevance of 9-aminoacridines, there have been few studies investigating their stability. 9-Aminoacridines are known to hydrolyze at the C9-N15 bond, yielding acridones. In this study, the pH-dependent hydrolysis rates of a series of 9-substituted aminoacridines are investigated. In addition, ground-state physical properties of the compounds are determined using ab initio quantum mechanics calculations to gain insight into the forces that drive hydrolysis. An analysis of the bond orders, bond dissociation energies, and conformational energies show that the rate of hydrolysis depends on two main factors: delocalization across the C9-N15 bond and steric effects. The computational results are applied to explain the change in experimental rates of hydrolysis going from primary to secondary and to tertiary substituted 9-aminoacridines. In the case of tertiary substituted amines, the calculations indicate the C9-N15 bond is forced into a more gauche-like conformation, greatly diminishing delocalization (as shown by reductions in bond orders and bond energy), which leads to rapid hydrolysis. A model of intramolecular hydrogen bonding is also presented, which explains the increased rate of hydrolysis observed for highly substituted compounds under acidic conditions.     

Synthesis of 9-Substituted Berberine Derivatives with Microwave Irradiation

Hyperglycemia is frequently accompanying with hyperlipidemia. To explore the potent drugs with dual-activity and dual-site effects that could reduce blood glucose and blood lipid at the same time, fibrate group with lipid-lowering effect on the 9th position of berberine(BBR) was introduced using the drug design combination principle and the multi-target collaborative treatment method. Moreover, the molecular structure of BBR was modified, and six 9-substituted derivatives of BBR were designed and synthesized, among which, five compounds have never been reported before. In addition, the molecular structures of these derivatives were identified using liquid chromatography-mass spectrometry(LC-MS), ¹H nuclear magnetic resonance(¹H NMR) and ¹³C NMR, respectively. Furthermore, the microwave irradiation experimental technique was applied in the synthesis reaction using the novel microwave synthesizer, which accelerated the reaction rate, enhanced the reaction yield, reduced the reaction by-products, and simplified the post-processing steps. In the meantime, the 9-position regioselective demethylation of BBR was explored through quantum chemical calculation during the synthesis of berberrubine. The computations were consistent with the experimental results, which contributed to deducing the mechanism of its selective methylation.