Synthesis, electrochemical and photochromic behaviour of a series of (1,4-dithiafulven-6-yl)substituted 3H-naphtho[2,1-b]pyran derivatives

The synthesis and electrochemical and photochromic properties of new 3,3-diphenyl-8-(1,4-dithiafulven-6-yl)-[3H]-naphtho[2,1-b]pyran derivatives containing differently substituted dithiafulvenyl units are described. An example of electrochemical dimerization is shown which gives access to electroactive bichromophoric systems. Such systems could allow the study of the interplay of photochromic and electrochemical properties.     

Amine Exchange and Unexpected Ring‐Opening Reactions of Pyranone Derivatives: Synthesis of 3‐Amino‐Substituted Oxonaphthopyran‐carbaldehydes and Tetrahydropyrimidinethanones as New Potential Oligonucleotide Stabilization Agents

3‐[(3‐Aminopropyl)amino]‐1‐oxo‐1H‐naphtho[2,1‐b]pyran‐2‐carbaldehyde ( 10 ) was synthesized by nucleophilic substitution reaction of 2‐(3‐dimethylamino)‐1‐oxo‐1H‐naphtho[2,1‐b]pyran‐2‐carbaldehyde ( 9 ) and the monoprotected propane‐1,3‐diamine. The reaction with the unprotected reagent led to the unexpected 1‐(2‐hydroxynaphthalen‐1‐yl)‐2‐(tetrahydropyrimidin‐2(1H)‐ylidene)ethanone ( 6 ). Extension of this reaction to chromone 16 gave 1‐(2‐hydroxy‐3‐isopropyl‐6‐methylphenyl)‐2‐(tetrahydropyrimidin‐2(1H)‐ylidene)ethanone ( 7 ). The X‐ray crystal structures of 6 and 7 were also determined.     

Syntheses of thiopyrone and pyrone derivatives by photocyclization reaction of 3‐aryl‐2‐( Benzothien‐3‐yl)propenoic acids

Naphtho[1,2‐b][1]benzothiophene‐6‐carboxylic acids, 6H‐benzo[b]naphtho[2,3‐d]thiopyran‐6‐ones and 6H‐benzo[b]naphtho[2,3‐d]pyran‐6‐ones were synthesized in one step by the photocyclization reaction of 3‐aryl‐2‐([1]benzothien‐3‐yl)propenoic acids. The photocyclization reaction did not occur when the 3‐aryl group contained the electron‐withdrawing nitro group. The assignment of the ¹H and ¹³C nmr spectra of 6H‐benzo[b]naphtho[2,3‐d]thiopyran‐6‐one and 6H‐benzo[b]naphtho[2,3‐d]pyran‐6‐one by two‐dimensional nmr methods is described. The difference between the chemical shift values of H12 for these two compounds is attributed to different molecular geometries.     

Carbenoid induced irreversible ring opening of naphthopyrans

Contrary to expectation rhodium carbenoids do not undergo cycloaddition to the 2H-pyran unit of the isomeric naphthopyrans 3 and 5. With 3, a naphtho[2,1-b]pyran-8-ylacetate, 4 is formed and a novel merocyanine dye 6 results from a cycloaddition across the C-5-C-6 double bond of the naphtho[1,2-b]pyran 5. Tethering the carbenoid to the naphtho[1,2-b]pyran system 5, as in 10, results in a similar mode of addition and affords the intensely coloured tetracycle 11.     

Photophysics and kinetics of naphthopyran derivatives,part 2: Analysis of diarylnaphthopyran kinetics. Degeneracy of the kinetic solution

The photocoloring and fading kinetics of the photochromic 3,3‐diphenyl‐3H‐naphtho[2,1‐b]pyran (NPY) have been analyzed using a kinetic treatment for three related species recently developed by us (Int J Chem Kinet 2005, 37(3), 162). The concepts of identifiability and distinguishability are developed with respect to the elucidation of the NPY kinetics. We find that neither set of kinetic data on its own, nor the two data sets combined, allow the true mechanism to be distinguished. In addition, even for a chosen mechanism, there exist degenerate sets of parameters i.e. the solutions are also unidentifiable. A discussion of the limits and uniqueness of the results' interpretation is presented. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 717–727, 2005     

The reaction between 3,3-bis(methoxyphenyl)-3H-naphtho[2,1-b]pyran and 1,3-bis(methoxyphenyl)-1H-naphtho[2,1-b]pyran, 2,2-diphenyl-2H-chromen and 2,4-diphenyl-4H-chromen,and related compounds

The reaction between 3,3-bis(methoxyphenyl)-3H-naphtho[2,1-b]pyran and 1,3-bis(methoxyphenyl)-1H-naphtho[2,1-b]pyran under acid conditions gives a 7a,15a-dihydro-7a,15-bis(methoxyphenyl)-16-[2,2-bis(methoxyphenyl)-l-vinyl]dinaphtho-[2,1-b:2,1-g]-4H,5H-pyrano[2,3-b]-pyran.     

Phptotophysics and kinetics of naphthopyran derivatives,part 4: Investigation of [3H]‐naphthopyran kinetics considered as an ABC(2k, 6ϕ) system yielding a monoexponential trace

The elucidation of [3H]‐naphthopyran photochromic kinetics has been dealt with in this investigation by approximating the photocoloring traces as monoexponential. The experimental data have been analyzed, and 13 defining equations of the reactive dynamics have been established. These have been solved simultaneously as a system of nonlinear equations depending on the extinction coefficients and the six possible quantum yields of this ABC type system. The results of this new approach predict that both colored species are directly photochemically produced from the starting material. The most photochemically reactive photoisomer is the most thermally stable and is also the one characterized by the lowest extinction coefficient of the visible absorption band. The mechanism predicted for 3,3‐diphenyl‐3H‐naphtho[2,1‐b]pyran in toluene at 30°C obeys ABC(1k,6?) kinetics. © 2006 Wiley Periodicals, Inc. J Chem Kinet 38: 431–438, 2006     

Strategy to Construct Stair‐Shaped Partially Reduced Naphtho[1,2‐b]pyrano[2,3‐d]oxepines and Dinaphtho[1,2‐b,d]oxepines

A concise and efficient base‐induced synthesis of stair‐shaped, 4‐methylthio‐2‐oxo‐5,6‐dihydro‐2H‐naphtho[1,2‐b]pyran[2,3‐d]oxepine‐3‐carbonitriles ( 3 ) has been delineated by the reaction of 3,4‐dihydronaphtho[1,2‐b]oxepin‐5(2H)‐one ( 1 ) and methyl 2‐cyano‐3,3‐dimethylthioacrylate in DMSO using powdered KOH as a base at room temperature. Amination of 3 has been achieved by reaction with secondary amine in ethanol at reflux temperature to yield 4‐sec‐amino‐2‐oxo‐5,6‐dihydro‐2H‐naphtho[1,2‐b]pyran[2,3‐d]oxepine‐3‐carbonitriles ( 4 ). Reaction of 3 with aryl methyl ketone ( 5 ) in DMSO at room temperature using powdered KOH as a base produced stair‐shaped 5‐aryl‐7,8‐dihydro‐1,4‐dioxa‐2,3‐dioxodinaphtho[1,2‐b,d]oxepine ( 6 ) in good yields. However, reaction of 6‐aryl‐2H‐pyran‐2‐one‐3‐carbonitrile ( 8 ) with 3,4‐dihydronaphtho[1,2‐b]oxepin‐5(2H)‐one ( 1 ) did not give similar product, but in lieu 4‐aryl‐5,6‐dihydronaphtho[1,2‐b]oxepino[4,5‐b]pyran‐2‐ylidene)acetonitrile ( 9 ) was isolated and characterized.     

Synthesis and photochromic properties of substituted naphthopyran compounds

A group of 3,3-diaryl-3H-naphtho[2,1-b]pyran compounds with functional substituents at the 5- and 6-positions of the naphthopyran skeleton and the para positions at the 3-aryl moieties were prepared through condensation reactions between 2-naphthol derivatives and 1,1-diarylprop-2-yn-1-ol derivatives. The chemical structures of the compounds were confirmed by NMR and MS. The crystal structure of 3,3-diphenyl-6-morpholino-3H-naphtho[2,1-b]pyran (4b) was determined and the relationship between the pyran substructure and photochromism was discussed. The photochromic properties were studied as well, and decoloration kinetics of colored forms was fitted to the biexponential model. Among these compounds, 4b was considered to be the best one due to the large ΔOD of colored form, which is one of the most important properties used in the photochromic material.     

Photomodulable Materials. Synthesis and Properties of Photochromic 3H‐Naphtho[2,1‐b]pyrans Linked to Thiophene Units via an Acetylenic Junction

The synthesis of 3H‐naphtho[2,1‐b]pyrans linked to mono‐, di‐, or terthiophene via an acetylenic junction is described (Schemes 2 and 3). The synthetic approaches involve successive Sonogashira coupling reactions. The photochromic properties in solution of these novel materials were investigated under continuous irradiation.     

A new approach for the synthesis of some pyrazolo[5,1‐c]triazines and pyrazolo[1,5‐a]pyrimidines containing naphtofuran moiety

Naphtho[2,1‐b]furan‐2‐yl)(8‐phenylpyrazolo[5,1‐c][1,2,4]triazin‐3‐yl)methanone, ([1,2,4]triazolo[3,4‐c][1,2,4]triazin‐6‐yl)(naphtho[2,1‐b]furan‐2‐yl)methanone, benzo[4,5]imidazo[2,1‐c][1,2,4]triazin‐3‐yl‐naphtho[2,1‐b]furan‐2‐yl‐methanone, 5‐(naphtho[2,1‐b]furan‐2‐yl)pyrazolo[1,5‐a]pyrimidine, 7‐(naphtho[2,1‐b]furan‐2‐yl)‐[1,2,4]triazolo[4,3‐a]pyrimidine, 2‐naphtho[2,1‐b]furan‐2‐yl‐benzo[4,5]imidazo[1,2‐a]pyrimidine, pyridine, and pyrazole derivatives are synthesized from sodium salt of 5‐hydroxy‐1‐naphtho[2,1‐b]furan‐2‐ylpropenone and various reagents. The newly synthesized compounds were elucidated by elemental analysis, spectral data, chemical transformation, and alternative synthetic route whenever possible. J. Heterocyclic Chem., (2012).     

Investigation on the condensation of α and β ketoaldehydes with hydroxyaromatic compounds

Mechanism of the condensation reactions of methylglyoxal, phenylglyoxal and benzoylacetaldehyde with phenolic compounds have been discussed. It was observed that the reaction mechanisms changed depending on the type of the phenolic and also dicarbonyl compounds. While, methylglyoxal gave the angular methyl derivative of naphthofuraranonaphthofuran with 2‐naphthol, phenylglyoxal and its p‐chloro and p‐methoxy derivatives formed benzo[b]naphtho[2,1‐f]oxepine‐13‐ones. However, resorcinol behaved different and gave 2‐phenyl‐3‐(2,4‐dihydroxy)‐6‐hydroxy‐benzo[b]furans with phenylglyoxal derivatives. 2‐Phenyl‐4‐(2‐hydroxynaphmyl)‐4H‐naphtho[b]pyran was produced from the reaction of benzoylacetaldehyde and 2‐naphthol, but the reaction product was 3,9‐dihydroxy‐6‐phenyl‐6,12‐methano‐12H‐dibenzo[1,3]dioxocin when the same carbonyl compound reacted with resorcinol.     

Metallocenyl‐[2H]naphtho[1,2‐b]pyrans: metal effect on the photochromic behaviour

Previous studies have shown that the substitution by a ferrocenyl group in the 2‐position of naphthopyrans has a specific and an original effect on the photochromic behaviour. In this work, the synthesis and the photochromic properties of new naphthopyrans substituted in the 2‐position by three different metallocenyl groups (ferrocenyl, ruthenocenyl and osmocenyl) are presented. Whereas the ferrocenyl‐substituted derivatives under UV irradiation show two absorption bands, the ruthenocenyl and osmocenyl derivatives are characterized by only one absorption band under the same condition. The photochromic behaviour of these compounds is compared with that of their parent alkyl or phenyl 2‐substituted [2H]‐naphtho[1,2‐b]pyrans. Copyright © 2002 John Wiley & Sons, Ltd.     

Photochromic hybrid sol–gel films containing naphthopyrans

Abstract  

Several photochromic benzo- and naphthopyrans were embedded in hybrid organic–inorganic ureasilicate based films obtained by a sol–gel process. The resulting films, containing 0.1% (w/w) of the photochromic compound, were transparent and flexible and for naphthopyrans they were colourless or presented just a slight colouration. Under UV continuous irradiation the films developed a significant absorption in the visible region that fades in the dark with variable kinetics depending on the naphthopyran structure. 2,2-Diphenyl-3H-naphtho[2,1-b]pyran films showed a very fast colouration under UV light giving rise to coloured open forms, containing mainly the TC isomer (98%) along with a very small amount of the more stable TT isomer (2%), that practically returned to the initial absorbance in 1 min.     

An organic photochromic compound: (2S)‐2′‐ethoxy‐1,3,3‐trimethyl‐6′‐(piperidin‐1‐yl)spiro[indoline‐2,3′‐3′H‐naphtho[2,1‐b][1,4]oxazine]

In the course of our synthesis of hybrid photochromic compounds, the unexpected new organic photochromic title compound, C₂₉H₃₃N₃O₂, (I), was obtained. It is a derivative of the parent spirooxazine 1,3,3‐trimethyl‐6′‐(piperidin‐1‐yl)spiro[indoline‐2,3′‐3′H‐naphtho[2,1‐b][1,4]oxazine], (II). The 2′‐ethoxy group gives (I) different photochromic properties from its parent spirooxazine (II).     

Angular polycyclic thiophenes containing two thiophene rings. Part II

The syntheses of naphtho[1,2–6:7,6-b′]bisbenzo[b]thiophene ( 4 ), naphtho[1,2–6:7,8-b′]bisbenzo[b]thiophene ( 5 ), naphtho[2,1-b:7,6-b′]bisbenzo[b]thiophene ( 8 ), naphtho[2,1-b:7,8-b′]bisbenzo[b]thiophene ( 9 ), naphtho-[1,2–6:5,6-b′]bisbenzo[b]thiophene ( 14 ), naphtho[1,2–6:6,5-b]bisbenzo[b]thiophene ( 17 ) and naphtho[2,1–6:-6,5-b′]bisbenzo[b]thiophene ( 23 ) are reported.     

NMR proofs of the involvement of an allenyl-naphthol as a key-intermediate in the photochromic process of [3H]-naphthopyrans

The NMR characterization of an intermediate, proved to be involved in the photochromic process of fluoro-substituted-3,3-diphenyl-3H-naphtho[2,1-b]pyrans is reported. An o-allenyl-naphthol structure was deduced and a plausible reaction mechanism was proposed.     

Synthesis of 8-substituted naphtho[2,1-b]thiophenes with cationic side chains at position 4

A series of five 8-substituted α-[bis(2-hydroxyethyi)aminoethyl]naphtho[2,1-b]thiophenes 7 and a series of seven N-(3-dimethylaminopropyl)-8-substituted naphtho[2,1-b]thiophene-4-carboxamides 8 have been synthesized. The naphtho[2,1-b]thiophene-4-carboxylic acids 4 were prepared by photooxidative cyclization of α-(2-thienyi)-β-arylacrylic acids 3. The carboxylic acids 4 were converted by a conventional five step route involving α-bromoketone intermediates to the a-[bis(2-hydroxyethyl)aminomethyl]-8-substituted naphtho-[2,1-6]thiophene-4-methanols 7 and by a standard two-step amide preparation to the N-(3-dimethylaminopropyl)-8-substituted naphtho[2,1-6]thiophene-4-carboxamides 8 .     

Synthesis and Photochromic Behaviour of Naphthopyrans,Pyranoquinolines, Pyranoquinazolines and Pyranoquinoxalines

New chromenes annulated with different six-membered azaheterocycles were prepared, i.e., the 3H-pyra-no[3,2-f]quinolines 9/10 and 14 , the 8H-pyrano[2,3-h]isoquinoline 11 , the 8H-pyrano[3,2-f]quinazolme 12 , the 8-H-pyrano[3,2-f]quinoxaline 13 , and the 2H-pyrano[2,3-f]isoquinoline 15. The synthesis was achieved using conveniently substituted α,β-unsaturated aldehydes and organotitanium intermediates arising from azaheterocyclic phenols. Their photochromic behaviour (photocolouration yield, UV/VIS spectrum of photomerocyanines, rate constant of thermal bleaching) were studied besides those of corresponding naphthopyrans. The heterocycle effect and the role of substituents in the pyran moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. Diaryl-substituted azino-fused chromenes, especially isoquinoline derivatives, exhibit increased colourabilities and bathochromically shifted spectra for photomerocyanines which open up new prospects for photochromic applications.     

Photoswitch based on remarkably simple naphthopyrans

Photochromic switches built around 5-carbonyl-3,3-diphenyl-3H-naphtho[2,1-b]pyran unit have been synthesized. Their open forms are constituted of a 1:1 ratio of TC and TT-isomers according to ¹⁹F and ¹H NMR investigations. Electrocyclization of TT isomers back to the closed form is efficiently achieved upon visible irradiation whereas it has been found to be a particularly unfavoured thermal process. These simple 2H-chromenes could act as molecular photoswitch at ambient temperature.