Intramolecular charge-transfer-induced chemiluminescent decomposition of 1,2-dioxetanes bearing a phenylmethanide anion

Dioxetanes (1) bearing a phenyl moiety substituted with a methylene or methine having an electron-withdrawing group(s) (-CH₂-Ew or -CH(X)-Ew) and dioxetane (2) bearing a 3-(1-cyanoethenyl)phenyl group were synthesized. Treatment of dioxetanes (1) with tetrabutylammonium fluoride (TBAF) caused their decomposition with accompanying emission of light with maximum wavelength at 530-758 nm. The Michael addition of a bis(methoxycarbonyl)methanide anion to dioxetane (2) produced initially an unstable dioxetane bearing a phenylmethanide anion, decomposition of which gave light with maximum wavelength at 710-740 nm. Intramolecular cyclopropanation without decomposition of the dioxetane ring took place concurrently for the Michael reaction-induced decomposition of 2 with the bis(methoxycarbonyl)chloromethanide anion.     

Alkaline metal ion-enhanced chemiluminescence of bicyclic dioxetanes bearing a hydroxyaryl group with an ‘even’ substitution pattern

Bicyclic dioxetane 5 bearing a 3-hydroxynaphthalen-2-yl group and its analogs 14 and 15 decomposed to give light with efficiencies of only 0.002-0.005% in a tetrabutylammonium fluoride (TBAF)/THF system, which was as expected for dioxetanes with a so-called ‘even’ substitution pattern. However, the chemiluminescence efficiencies (Φ^CL) markedly increased when these dioxetanes were decomposed with alkaline metal t-butoxide in THF. This enhancement of Φ^CL by alkaline metal ion was most likely due to the highly ordered conformation of an aromatic ring by chelate formation of the metal ion with both an oxido anion and oxygen atom of a tetrahydrofuran ring in an intermediary dioxetane like 12. Alkaline metal ion-enhanced chemiluminescence was similarly observed for dioxetane 6 bearing a 2-hydroxyphenyl group.     

Reactions of azulenes with 1,2-diaryl-1,2-ethanediols in methanol in the presence of hydrochloric acid: comparative studies on products, crystal structures, and spectroscopic and electrochemical properties

Although reaction of guaiazulene (1a) with 1,2-diphenyl-1,2-ethanediol (2a) in methanol in the presence of hydrochloric acid at 60 °C for 3 h under aerobic conditions gives no product, reaction of 1a with 1,2-bis(4-methoxyphenyl)-1,2-ethanediol (2b) under the same reaction conditions as 2a gives a new ethylene derivative, 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene (3), in 97% yield. Similarly, reaction of methyl azulene-1-carboxylate (1b) with 2b under the same reaction conditions as 1a gives no product; however, reactions of 1-chloroazulene (1c) and the parent azulene (1d) with 2b under the same reaction conditions as 1a give 2-[3-(1-chloroazulenyl)]-1,1-bis(4-methoxyphenyl)ethylene (4) (81% yield) and 2-azulenyl-1,1-bis(4-methoxyphenyl)ethylene (5) (15% yield), respectively. Along with the above reactions, reactions of 1a with 1,2-bis(4-hydroxyphenyl)-1,2-ethanediol (2c) and 1-[4-(dimethylamino)phenyl]-2-phenyl-1,2-ethanediol (2d) under the same reaction conditions as 2b give 2-(3-guaiazulenyl)-1,1-bis(4-hydroxyphenyl)ethylene (6) (73% yield) and (Z)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-1-phenylethylene (7) (17% yield), respectively. Comparative studies of the above reaction products and their yields, crystal structures, spectroscopic and electrochemical properties are reported and, further, a plausible reaction pathway for the formation of the products 3-7 is described.     

Reaction of azulene with 1,2-bis[4-(dimethylamino)phenyl]-1,2-ethanediol in a mixed solvent of methanol and acetonitrile in the presence of hydrochloric acid: a facile one-pot synthesis and properties of new triarylethylenes possessing an azulen-1-yl group

Reaction of azulene (1) with 1,2-bis[4-(dimethylamino)phenyl]-1,2-ethanediol (2) in a mixed solvent of methanol and acetonitrile in the presence of 36% hydrochloric acid at 60 °C for 3 h gives 2-(azulen-1-yl)-1,1-bis[4-(dimethylamino)phenyl]ethylene (3) (8% yield), 1-(azulen-1-yl)-(E)-1,2-bis[4-(dimethylamino)phenyl]ethylene (4) (28% yield), and 1,3-bis{2,2-bis[4-(dimethylamino)phenyl]ethenyl}azulene (5) (9% yield). Besides the above products, this reaction affords 1,1-di(azulen-1-yl)-2,2-bis[4-(dimethylamino)phenyl]ethane (6) (15% yield), a meso form (1R,2S)-1,2-di(azulen-1-yl)-1,2-bis[4-(dimethylamino)phenyl]ethane (7) (6% yield), and the two enantiomeric forms (1R,2R)- and (1S,2S)-1,2-di(azulen-1-yl)-1,2-bis[4-(dimethylamino)phenyl]ethanes (8) (6% yield). Furthermore, addition reaction of 3 with 1 under the same reaction conditions as the above provides 6, in 46% yield, which upon oxidation with DDQ (=2,3-dichloro-5,6-dicyano-1,4-benzoquinone) in dichloromethane at 25 °C for 24 h yields 1,1-di(azulen-1-yl)-2,2-bis[4-(dimethylamino)phenyl]ethylene (9) in 48% yield. Interestingly, reaction of 1,1-bis[4-(dimethylamino)phenyl]-2-(3-guaiazulenyl)ethylene (11) with 1 in a mixed solvent of methanol and acetonitrile in the presence of 36% hydrochloric acid at 60 °C for 3 h gives guaiazulene (10) and 3, owing to the replacement of a guaiazulen-3-yl group by an azulen-1-yl group, in 91 and 46% yields together with 5 (19% yield) and 6 (13% yield). Similarly, reactions of 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene (12) and 1,1-bis{4-[2-(dimethylamino)ethoxy]phenyl}-2-(3-guaiazulenyl)ethylene (13) with 1 under the same reaction conditions as the above provide 10, 2-(azulen-1-yl)-1,1-bis(4-methoxyphenyl)ethylene (16), and 1,3-bis[2,2-bis(4-methoxyphenyl)ethenyl]azulene (17) (93, 34, and 19% yields) from 12 and 10 and 2-(azulen-1-yl)-1,1-bis{4-[2-(dimethylamino)ethoxy]phenyl}ethylene (18) (97 and 58% yields) from 13.     

Synthesis and properties of 7,7-bis(heteroazulen-3-yl)-8,8-dicyano-1,4-quinodimethanes

The synthesis and properties of a novel type of 7,7-bis(heteroazulen-3-yl)-8,8-dicyano-1,4-quinodimethanes (9a-c) are studied. The synthetic method is based on a TFA-catalyzed electrophilic aromatic substitution on the heteroazulenes with 4-(dicyanomethyl)benzaldehyde to afford the corresponding methane derivatives, followed by oxidative hydrogen abstraction with DDQ. The polarization of 9a-c is evaluated by the inspection of their ¹³C NMR and IR spectra. Based on the investigation of the UV-Vis spectra of 9a-c and protonated cations 10a-c, conformational changes of the heteroazulene-moiety and (dicyanomethyl)phenyl group are suggested. In the CV measurements of 9a-c, two reversible reduction waves are observed, indicating the stabilizing ability of heteroazulenes toward the corresponding radical and anion species. Furthermore, 9a-c exhibit two irreversible oxidation waves, which suggest a conformational change in the radical cation during the redox process. The conformational change is rationalized on the basis of the MO calculations.     

Base-induced decomposition of dioxetanes bearing a 3-hydroxyphenyl moiety substituted with a proton-donating group at the 4-position: effect of intramolecular hydrogen bonding on decomposition rate and chemiluminescence efficiency

Bicyclic dioxetanes bearing a 3-hydroxyphenyl moiety substituted with an amidomethyl group (3a-c) or a hydroxymethyl group (4) were synthesized. On treatment with tetrabutylammonium fluoride in CH₃CN, they decomposed rapidly with accompanying emission of blue light. Their decomposition rates and chemiluminescence efficiencies were found to be affected by the intramolecular hydrogen bonding between the phenoxy anion and the adjacent proton-donating group.     

Cyclodimerization of phenyliodoacetylene with elemental tellurium: New pathway to 1.3-ditellurofulvenes

Thermal reaction between PhCCI and powdered Te afforded a mixture of (E)-4-iodo-2-(iodo(phenyl)-5-phenyl-1,3-ditellurofulvene (1) and (Z)-4-iodo-2-(iodo(phenyl)-5-phenyl-1-(diiodo),3-ditellurofulvene (2), which was subsequently reduced to (Z)-4-iodo-2-(iodo(phenyl)-5-phenyl-1,3-ditellurofulvene (3). Formation of 1 and 3 as the thermodynamically most stable products has been rationalized using density functional theory (DFT) calculations. Molecular structures of 1-3 were established crystallographically. In the solid state the coordination sphere of both tellurium atoms in 2 is extended by weak intermolecular Te?π interactions with the solvate molecule of toluene which completes the pseudo-trigonal bipyramidal coordination geometry around each Te atom and assembles 2 into the chains along the crystallographic c-axis.     

Manganese(III) acetate based oxidative cyclizations of 3-oxopropanenitriles with conjugated alkenes and synthesis of 4,5-dihydrofuran-3-carbonitriles containing heterocycles

4,5-Dihydrofuran-3-carbonitriles 3a-i were obtained through oxidative cyclizations of 3-oxo-3-phenylpropanenitrile 1a, 3-oxo-3-thien-2-ylpropanenitrile 1b, 3-(2-furyl)-3-oxopropanenitirle 1c, 3-(1-benzofuran-2-yl)-3-oxopropanenitrile 1d, and 4,4-dimethyl-3-oxopropanenitrile 1e mediated manganese(III) acetate with 1,1-diphenyl-1-butene 2a and 1,2-diphenyl-1-pentene 2b. The treatments of these 3-oxopropanenitriles with 2-thienyl substituted alkenes such as 2-[(E)-2-phenylvinyl]thiophene 2c, 2-[(E)-1-methyl-2-phenylvinyl]thiophene 2d, and 2-(1-phenylvinyl)thiophene 2e formed 5-(2-thienyl)-4,5-dihydrofuran-3-carbonitriles 3j-r in good yields (45-93%). As a result, 2-thienyl substituted alkenes formed products in higher yields than phenyl substituted derivatives.     

Rotamer-dependent chemiluminescence in the intramolecular charge-transfer-induced decomposition of bicyclic dioxetanes bearing a hydroxyaryl group

Base-induced chemiluminescent decomposition of acylamino-substituted dioxetane 1b bearing a 3-hydroxyphenyl group proceeded according to dual phase kinetics due to syn-anti isomerism of the aryl group. For dioxetane 7 bearing a 6-hydroxynaphthalen-2-yl group, syn- and anti-rotamers were each isolated and their structures were determined by X-ray single crystallographic analysis. Both rotamers underwent base-induced decomposition accompanied by the emission of red light to exclusively give the same keto imide 8. However, a marked difference in chemiluminescence efficiency was observed between anti-7 and syn-7.     

Solvent-free reactions of N,N′-thiocarbonyldiimidazole with ferrocenylcarbinols

The efficient and simple routes for the synthesis of various ferrocenyl derivatives from ferrocenylcarbinols and N,N′-thiocarbonyldiimidazole (TCDI) are described. It involves grinding the two substrates in a Pyrex tube with a glass rod at room temperature. The reaction of ferrocenylmethanol (1a) provided S,S-bis(ferrocenylmethyl)dithiocarbonate (1b), whose crystal structure and a plausible mechanism for its formation are also reported. The reaction of 1-ferrocenyl-1-phenylmethanol (2a) and 1-ferrocenylbutanol (2b) gave the products 2c and 2d, respectively. The reaction of ω-ferrocenyl alcohols 4-ferrocenylphenol (3a) and 6-ferrocenylhexan-1-ol (3b) yielded the products 3c and 3d, respectively. Reaction of 1,1′-ferrocenedimethanol (3e) afforded 3f in moderate yield, and by contrast, it was not similar to 1b. Reaction of [4-(trifluoromethyl)phenyl]methanol (4a) provided the thiocarbonate 4b in good yield.     

Structurally original oxathioethers macrocycles containing an exocyclic double-bond: synthesis,characterization, reactivity,and coordination

New oxathioethers macrocycles have been synthesized and characterized. Each macrocycle consists in structurally defined ether and thioether moieties and an exocyclic double-bond (2a–c) or a hydroxymethyl group (3a–c). Macrocycles (2a–c) have been synthesized by reaction of dianions of thioethers diols (1a–c) with 3-chloro-2-chloromethylprop-1-ene. Their hydroboration/oxidation led to corresponding primary alcohols (3a–c). Structures of compounds (2b) and (3a) have been determined by X-ray diffraction. The reactivity of the hydroxyl group allowed the preparation of oxathioethers macrocycles bearing a polyether chain or a benzyl group (4a,b) and the synthesis of new bicyclic sandwich-type compounds (5a,b). The ability of these functionalized macrocycles to coordinate to palladium has been investigated.     

Synthesis of 2,3-disubstituted benzofurans and indoles by π-Lewis acidic transition metal-catalyzed cyclization of ortho-alkynylphenyl O,O- and N,O-acetals

The PtCl₂-catalyzed cyclization reaction of ortho-alkynylphenyl acetals 1 in the presence of COD (1,5-cyclooctadiene) produces 3-(α-alkoxyalkyl)benzofurans 2 in good to high yields. For example, the reaction of acetaldehyde ethyl 2-(1-octynyl)phenyl acetal (1a), acetaldehyde ethyl 2-(cyclohexylethynyl)phenyl acetal (1c), and acetaldehyde ethyl 2-(phenylethynyl)phenyl acetal (1f) in the presence of 2 mol % of platinum(II) chloride and 8 mol % of 1,5-cycloocatadiene in toluene at 30 °C gave the corresponding 2,3-disubstituted benzofurans 2a, 2c, and 2f in 91, 94, and 88% yields, respectively. Moreover, the reaction of N-methoxymethyl-2-alkynylanilines 3 was catalyzed by PdBr₂, affording the corresponding 2,3-disubstituted indoles 4 in moderate yields. For example, the reaction of N-methoxymethyl-2-(1-pentynyl)-N-tosylaniline (3a) and N-methoxymethyl-2-(phenylethynyl)-N-tosylaniline (3b) in the presence of 10 mol % of PdBr₂ in toluene at 80 °C gave 3-methoxymethyl-2-propyl-1-tosylindole (4a) and 3-methoxymethyl-2-phenyl-1-tosylindole (4b) in 33 and 33% yields, respectively.     

Tetracyclic 1,6-methano-[10]annulenes a novel class of steroidal annulenes

Reaction of 19-hydroxyandrosta-4,6-diene-3,17-dione (8b) and the corresponding Δ⁷-compound (8c) with diethyl-(2-chloro-1,1,2-trifluoroethyl)-amine affords 5β,19-cyclo-Δ^1,6- and 5β,19-cyclo-Δ^1,7-3-ketones (4b) and (4c) respectively. Solvolysis experiments with the 19-tosylates of the 19-hydroxy-Δ^4,6- and Δ^4,7-3-ketones (8b) and 8c) are described as alternate approaches to (4b) and (4c). Exposure of 5β,19-cyclo compounds (4b) and (4c) to acetic anhydride-acetic acid-p-toluenesulfonic acid yields the respective 3-acetoxycycloheptatrienes (5a) and (6a). The latter substance (6a) is converted into the novel tetracyclic 1,6-methano-[10]annulene (2a) on exposure to N-bromosuccinimide in boiling carbon tetrachloride. Synthesis of the corresponding 3-methoxy- and 3-desoxy-1,6-methano-[10]annulenes (2b) and (2c) are also described. The NMR spectra of (2a), (2b) and (2c) and related intermediates are discussed.     

Synthesis and photochromic reactivity of a diarylethene dimer linked by a phenyl group

A diarylethene dimer linked by a phenyl group was synthesized and the photochromic behavior was examined. Upon irradiation with ultraviolet light (λ=313 nm), a hexane solution of the diarylethene dimer (1a) turned purple blue. Upon further prolonged irradiation the color changed to blue. The purple-blue and blue colors are due to the formation of a dimer having one open- and one closed-ring forms (1b) and a dimer having two closed-ring forms (1c), respectively. Both 1b and 1c returned to 1a by irradiation with visible light (λ>500 nm). The photochromic reactivity was evaluated by measuring quantum yields of the photocyclization and photocycloreversion reactions. The photocyclization quantum yield was 0.50. The cycloreversion quantum yield from 1c to 1b (0.0026) was lower than that from 1b to 1a (0.0094).     

An efficient electrochemical method for a unique synthesis of new derivatives of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one

The electrochemical oxidation of catechols (1a-c) has been studied in the presence of 6-methyl-1,2,4-triazine-3-thion-5-one 3 in aqueous sodium acetate, using cyclic voltammetry and controlled-potential coulometry. A plausible mechanism for the oxidation of catechols and their reaction with 3 is presented. All the catechol derivatives (1a-c) were converted into 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives (6a-c) through a Michael-type addition reaction of 3 to anodically generated o-quinones. The electrochemical syntheses of 6a-c were successfully performed in one pot in an undivided cell using an environmentally friendly method with high atomic economy.     

Synthesis and properties of 5-[bis(1-heteroazulen-3-yl)methylidene]pyrimidine-2,4,6(1,3,5H)-triones

The synthesis and properties of a novel type of 5-[bis(1-heteroazulen-3-yl)methylidene]pyrimidine-2,4,6(1,3,5H)-triones (13a-c) and (14a-c) are studied. The synthetic procedure is based on addition of bis(1-heteroazulen-3-yl)methyl cations with barbituric acid and subsequent oxidation by o-chloranil. Structural characteristics of 13a-c and 14a-c were clarified on inspection of the ¹³C NMR spectral data and X-ray crystal analysis. Based on the investigation of the UV-vis spectra of 13a-c and 14a-c and their protonated cations, conformational change of the heteroazulene-moiety and the barbituric acid-moiety is suggested. In the CV measurements of 13a-c and 14a-c, two reversible reduction waves are observed, indicating the stabilizing ability of heteroazulenes toward the corresponding radical and anion species. Furthermore, 13a-c and 14a-c exhibit one irreversible oxidation wave and the corresponding reduction wave appearing in a far negative region, which suggested a conformational change in the radical cation during the redox process. The conformational change is rationalized on the basis of the MO calculations.     

Rhodium(III) and palladium(II) complexes of some P-heterocycles; synthesis and X-ray structures

Deoxygenation of the syn-3-phosphabicyclo[3.1.0]hexane 3-oxides bearing a 3-phenyl or a 3-(4-methylphenyl) substituent (1a,b) by trichlorosilane took place already at mild condition and resulted in the corresponding phosphines (2a,b) with retention of configuration at phosphorus, while in the case of 3-(2-methylphenyl)-3-phosphabicyclo[3.1.0]hexane (2c), the inversion of the phosphorus atom was observed in solution under ambient conditions that was evaluated by quantum chemical calculations. A further phosphine ligand (5) was obtained by the reduction of 4-dichloromethylene-1,4-dihydrophosphinine oxide (4). The phosphine ligands (2 and 5) were used in the preparation of Rh(III) complexes (3 and 6). A Pd(II) complex of type PdCl₂(5)₂ (7) was also prepared. The stereostructures of a series of Rh(III) complexes of 3-aryl-3-phosphabicyclo[3.1.0]hexanes (3b-syn, 3c-syn and 3c-anti) were elucidated by single crystal X-ray analysis confirming the relative position of the dichlorocyclopropane and the P-substituent.     

Regiochemistry of an ambident cyclic ketene-N,O-acetal nucleophile and its anion toward electrophiles

The five-membered cyclic ketene-N,O-acetal, 2-oxazolidin-2-ylidene-1-phenylethanone 1, and its anion 2, formed on deprotonation, are ambident nucleophiles. Compound 1 was synthesized by benzoylation of 2-methyl-2-oxazoline to give a ring-opened N,C,O-trisbenzoylation product, 9, followed by N,O-double debenzoylation using methanolic KOH. Compound 1 reacted with benzoyl chloride to give N,C,O-trisbenzoylated 9, and reacted with phenyl chloroformate to give the similar ring-opened carbonic acid 3-[(2-chloro-ethyl)-phenoxycarbonyl-amino]-3-oxo-1-phenyl-propenyl ester phenyl ester, 13. In contrast, ambident anion 2 reacted with benzoyl chloride to give the β,β-bisbenzoylated cyclic ketene-N,O-acetal, 16, and reacted with phenyl chloroformate to give the novel heterocycle 3-(2-hydroxy-ethyl)-6-phenyl-[1,3]oxazine-2,4-dione, 17.     

Microwave-assisted synthesis of novel bis(2-thioxothiazolidin-4-one) derivatives as potential GSK-3 inhibitors

(5Z,5′Z)-3,3′-(1,4-Phenylenebis(methylene)-bis-(5-arylidene-2-thioxothiazolidin-4-one) derivatives (5a-r) have been synthesized by the condensation reaction of 3,3′-(1,4- or 1,3-phenylenebis(methylene))bis(2-thioxothiazolidin-4-ones) (3a,b) with suitably substituted aldehydes (4a-f) or 2-(1H-indol-3-yl)2-oxoacetaldehydes (8a-c) under microwave conditions. The bis(2-thioxothiazolidin-4-ones) were prepared from the corresponding primary alkyl amines (1a,b) and di-(carboxymethyl)-trithiocarbonyl (2). The 2-(1H-indol-3-yl)-2-oxoacetaldehydes (8a-c) were synthesized from the corresponding acid chlorides (7a-c) using HSnBu₃.     

Synthesis and photophysical properties of porphyrins with fluorenyl pendant arms

Symmetrical-A₄-porphyrins bearing four fluorene donor moieties TOFP (5,10,15,20-tetra(4-(2 methyloxyfluorenyl)phenyl)porphyrin) as well as eight fluorene arms OOFP (5,10,15,20-octa(3,5-(2-methyloxyfluorenyl)phenyl)porphyrin) were synthesized and characterized. Preliminary photophysical properties are reported. In comparison to the reference tetraphenylporphyrin TPP, the luminescence properties are slightly improved. The fluorescence quantum yields of tetrafluorenylporphyrin TOFP (1) and octafluorenylporphyrin OOFP (2) are 0.10 and 0.13, respectively.