2382-08-3

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Photoinduced cycloadditions of N-methyl-1,8-naphthalenedicarboximide 1 with phenylacetylenes 2a-2c, cyclopropylacetylene 2d, diphenylacetylenes 2e-2f and 1-phenylpropyne 2g were investigated. In the case of phenylacetylenes 2a, 2b and cyclopropylacetylene 2c, photoreaction with 1 takes place at the naphthalene C(1)C(2) bond to give the cyclobutene products. For 4-methoxyphenylacetylene 1c, the cyclobutene 3c is obtained together with the 4-benzo[a]thebenidinone 4c derived from a primary oxetene product formed by [2+2] addition of the imide carbonyl with the alkyne. Similar to 2c, photocycloaddition of 1 with 2e and 2f gave the cyclobutenes 7e, 7f, 8f and the 4-benzo[a]thebenidinone products 9e, 9f and 10f, respectively, derived from the corresponding oxetenes. Photoreaction of 1 with 2g gave cyclobutene 7g and benzo[a]thebenidinone 9g. Sensitization experiment and internal heavy atom effect study showed that these reactions proceed from the ππ* singlet excited state of 1. Estimation of the free energy change for electron transfer between 11* and the alkynes and the calculation of charge and spin density distribution in the anion radical of 1 and the cation radical of the alkynes suggested that the cyclobutene products are formed by direct [2+2] cycloaddition of 11* with the alkyne, while the formation of the oxetene products is the result of electron transfer interaction between 11* and the alkyne. The regioselectivity in the oxetene formation is accounted for by charge and spin density distribution in the anion radical of 1 and the cation radical of the alkyne.

In earlier studies we have shown that irradiation of MeCN solutions of N-[(trimethylsilyl)methyl]phthalimide and N-phthaloylglycine in the presence of electron-deficient olefins (e.g., methyl acrylate) results in the production of cycloadducts. In addition, irradiation of these substances in aqueous MeCN leads to formation of N-methylphthalimide. Laser flash photolysis and fluorescence spectroscopy have now been employed to investigate the mechanistic details of these novel excited-state processes. The results of this effort show that azomethine ylides are the key reactive intermediates in these processes. In addition, the investigations provide information about the dynamics of several ylide decay pathways and the nature of the excited states responsible for the ylide-forming silyl-migration (singlet and triplet) and decarboxylation (triplet) reactions. Pulsed irradiations of MeCN solutions of N-[(trimethylsilyl)methyl]phthalimide (1) and N-phthaloylglycine (2) give rise to transients whose absorption and decay properties are consistent with their assignment as azomethine ylides. Kinetic analysis of the decay of the ylides in the presence of dipolarophiles, methyl acrylate and acrylonitrile, provides the rates of the dipolar cycloaddition reactions. Reactions of methyl acrylate with the ylides produced by pulsed irradiation of N-[(trimethylsilyl)methyl]phthalimide (1) and N- phthaloylglycine (2) occur with respective bimolecular rate constants of 8.9 x 106 and 2.7 x 107 M-1 s-1. Methanol promotes the decay of the N- [(trimethylsilyl)methyl]phthalimide-derived ylide by a process which is second order in MeOH and has a kinetic OD-isotope effect of 4.3. In contrast, quenching of this ylide by acetic acid is first order in AcOH. The results suggest that the mechanism for MeOH-promoted decay involves initial and reversible formation of a silylate complex via nucleophilic addition of MeOH to the ylide. This is then followed by rate-limiting proton transfer from MeOH to the carbanionic center in the silylate complex either in concert with or preceding desilylation. The mechanism for AcOH-induced ylide decay has these steps reversed; i.e., rate-limiting proton transfer precedes AcOH- induced desilylation. Also, MeOH catalyzes the decay of the ylide derived by irradiation of N-phthaloylglycine by a process which is first order in MeOH and has a kinetic OD-isotope effect of 1.5. Finally, the observations (1) of complete loss of fluorescence of the 1,8- and 2,3-naphthalimide chromophores upon changing the N-substituent from methyl to (trimethylsilyl)methyl and (2) that ylide formation from 1 can be xanthone triplet sensitized suggest that the ylide-forming, silyl-transfer reactions of the (silylmethyl)phthalimides can occur in both the singlet and triplet excited-state manifolds.

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In this work we investigate the excited-state structure and dynamics of the two molecules 1,8-naphthalimide (NI) and N-methyl-1,8-naphthalimide (Me-NI) in the gas phase by picosecond time- and frequency-resolved multiphoton ionization spectroscopy. The energies of several electronically excited singlet and triplet states and the S1 vibrational wavenumbers were calculated. Nonadiabatic dynamics simulations support the analysis of the radiationless deactivation processes. The origin of the S1 ← S0 (ππ?) transition was found at 30 082 cm-1 for NI and at 29 920 cm-1 for Me-NI. Furthermore, a couple of low-lying vibrational bands were resolved in the spectra of both molecules. In the time-resolved scans a biexponential decay was apparent for both Me-NI and NI. The fast time constant is in the range of 10-20 ps, whereas the second one is in the nanosecond range. In accordance with the dynamics simulations, intersystem crossing to the fourth triplet state S1 (ππ?) → T4 (nπ?) is the main deactivation process for Me-NI due to a large spin-orbit coupling between these states. Only for significant vibrational excitation internal conversion via a conical intersection becomes a relevant deactivation pathway. (Figure Presented).

The rapid development of fluorescent probes for monitoring target enzymes is still a great challenge owing to the lack of efficient ways to optimize a specific fluorophore. Herein, a practical two-dimensional strategy was designed for the development of an isoform-specific probe for CYP3A4, a key cytochrome P450 isoform responsible for the oxidation of most clinical drugs. In first dimension of the design strategy, a potential two-photon fluorescent substrate (NN) for CYP3A4 was effectively selected using ensemble-based virtual screening. In the second dimension, various substituent groups were introduced into NN to optimize the isoform-selectivity and reactivity. Finally, with ideal selectivity and sensitivity, NEN was successfully applied to the real-time detection of CYP3A4 in living cells and zebrafish. These findings suggested that our strategy is practical for developing an isoform-specific probe for a target enzyme.

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N-Alkyl and N-aryl-isoindolinones were prepared by a dioxane-mediated oxidation of isoindoline precursors. The transformation exhibits unique chemoselectivity for isoindonlines. A chiral tertiary (3°)-benzylic position was not racemized during oxidation, and methyl indoprofen was prepared by late stage oxidation. Mechanistic studies suggest a selective H atom transfer, which avoids many known oxidation (by-)products of isoindolinones.

Ascorbic acid (AA) is a vital nutritional factor in many fruits and plants, and abnormal levels of AA are closely associated with several diseases. Therefore, the development of convenient methods for monitoring AA levels in biological systems is of great importance. In this work, we designed and synthesized three chemosensors for the rapid turn-on detection of AA via a new strategy for the azido-ascorbic acid reaction. The chemosensors were based on a 1,8-naphthalimide moiety with the azide group at different sites (probes 1, 2, and 3). The experimental results demonstrated that probe 2 showed high selectivity toward AA, having an experimental limit of detection of 74 nM. Its reduction was easier than that of probe 3 with a 3-substituted azide group. Moreover, probe 2 was successfully used for imaging of AA in garlic slice tissue for the first time.

The use of self-assembled aromatic molecules through π-π interactions has allowed the preparation of the silicoaluminophosphate (SAPO) form of the LTA, SAPO-42, with controlled Si content as isolated Si sites in the framework, and high thermal stability. Different SAPO-42 zeotypes can be synthesized with different acidity, morphology, and crystal size, depending on the selected quinolinium derived aromatic molecule as OSDA and the amount of fluoride content in the synthesis gels.

A novel copper-catalyzed oxidation of arene-fused cyclic amines to the corresponding cyclic imides has been developed. The reaction can be used to synthesize 1,3-disubstituted TPD in high yields.

N-methyl naphthalimide can be readily cyclomanganated at the 2-position, directed by the adjacent amide O atom. Di-cyclomanganation also occurs readily to attach Mn(CO)4 groups at both 2, 7 positions. An X-ray structure determination of the mono-substituted example confirmed the five-membered metallocyclic ring. Cleavage of the Mn-C bond by HgCl2 or ICl generates 2-substituted HgCl or I derivatives respectively. Reaction of the mono-cyclomanganated N-methyl naphthalimide with phenylacetylene gives an (η5-cyclohexadienyl)Mn(CO)3 complex where the cyclohexadienyl ring has formed by two PhCCH adding in a formal [2 + 2 + 2] process across the C(1)-C(2) bond of the naphthalimide, breaking the aromaticity of the naphthalene ring as shown by a single crystal structure determination.

The UV and IR spectra of N-methyl-1,8-naphthalimide in benzene showed a two-step consecutive complexation (hydrogen bond formation) with trifluoroacetic acid (TFA). The equilibrium constant K1 for the first complexation in benzene was determined from the UV spectrum to be 48 M-1. The fluorescence intensities of the imide in benzene were found to be remarkably enhanced by the addition of TFA. Furthermore, photochemical cyclobutane formation of the imide with styrene in benzene was enhanced by the addition of TFA. Enhancement of the fluorescence intensity and the photoreaction of the imide by complexation with TFA was explained by a decrease of the efficiency of the intersystem crossing from 1(ππ*) to 3(nπ*), that results from an increase in the energy of the 3(nπ*) level due to the complexation.

Iodoarenes (iodobenzene and 2-iodothiophene) and iodoalkenes (1-iodocyclohexene, 1-iodo-4-tert-butylcyclohexene, 1-iodo-2-methylcyclohexene and 1-iodo-1-(1-naphthyl)ethene) were used as substrates in palladium-catalysed aminocarbonylation with N,O-dimethylhydroxylamine. The corresponding Weinreb amides were prepared in high isolated yields (up to 87%) when forcing conditions (40-60 bar of CO, 50 °C) were used. The aminocarbonylation provides the Weinreb amides as pure products in a chemoselective reaction. No formation of ketocarboxamides, due to double CO insertion, except for 2-iodothiophene, was observed even at 60 bar of CO pressure.

1,8-N-alkyl-naphthalimides substituted with electron withdrawing groups were readily prepared in high yields using ultrasound in aqueous media.

The direct coupling reactions of 1,8-naphthalimide compounds efficiently occurred at 130 or 170 °C without the intervention of the leuco form dyes in the presence of base complex reagent, t-BuOK/1,5-diazabicyclo[4.3.0]non-5-ene (DBN), to give the corresponding perylene dyes in good yields with >95% purities. A possible mechanistic speculation for these oxidative coupling reactions is briefly discussed.

The reaction of 3-bromobenzanthrone and 4-bromonaphthalic acid derivatives with a reduction system NiCl2-2,2′bipyridyl (or 1,10-phenathroline)-Zn gives rise to compounds containing perylene fragment. Under similar conditions was established a possibility to transform substituted 1,1′-binaphthyls into the corresponding perylene derivatives.

This invention relates to a process for preparing perylene pigment compositions by reaction of (a) a perylene tetracarboxylic compound; (b) about 0.01 to about 20% by weight, relative to the perylene tetracarboxylic compound, of a non-pigmentary cyclic anhydride or imide of formula (I) STR1 wherein W is O or NR1 (where R1 is hydrogen, a metal, or optionally substituted alkyl, cycloalkyl, aralkyl, or aryl), R2, R3, and R4 are various combinations of substituents and/or fused-on rings, and the dotted line is an optional double bond representing R2 --C=C--R3 or R3 --C=C--R4 ; and (c) ammonia or a primary alkyl, aralkyl, or aryl amine; optionally in the presence of (d) a solvent and/or (e) one or more dispersants.

An investigation of the photochemistry of N-(silylmethyl)phthalimides and related α-phthaloylacetic acids and 2-phenylethanol derivatives has uncovered new excited state processes resulting in the formation of azomethine ylide intermediates. Irradiation of N-[(trimethylsilyl)methyl]phthalimide in MeCN promotes C to O silyl transfer to generate the corresponding azomethine ylide which is efficiently trapped by reaction with water to yield the N-methylphthalimide or by dipolar cycloaddition with acetone, methyl acrylate, or acrylomtrile. Cycloadditions with the latter two dipolarophiles are both regioselective and endo-stereoselective. These processes can be triplet photosensitized by use of acetophenone. The related N-[(trimethylsilyl)methyl]-1,8-naphthalimide reacts in a similar manner upon irradiation in MeCN solutions containing the dipolarophiles methyl acrylate and acrylonitrile to produce cycloadducts which undergo spontaneous elimination of TMSOH, yielding α,β-unsaturated ester or nitrile products. The ylide formed by irradiation of the (silylmethyl)phthalimide is trapped in a stereospecific (retention) manner by the dipolarophiles trans-hex-4-en-3-one, dimethyl maleate, and dimethyl fumarate. The effect of aryl ring substitution on the regiochemical course of the photoinduced C to O silyl migration process was probed by use of the 4-methoxy-and 4-carbomethoxyl-N-(silylmethyl)phthalimides. Irradiation of the former substance in an MeCN solution containing acrylonitrile gives rise to a single adduct whose structure suggests that silyl migration to oxygen of the carbonyl meta to the OMe substituent is highly favored. In contrast, the 4-carbomethoxyphthalimide is converted under these conditions to a mixture of regioisomeric adducts. Thus, silyl migration in the excited state of this substance is nonselective. In accord with hints found in earlier observations made by Kanaoka (Chem. Pharm. Bull. 1982, 30, 1263), N-phthalimide derivatives of the α-amino acids glycine, alanine, and phenylalanine undergo similar ylide forming photoreactions upon irradiation in MeCN solutions. The azomethine ylides produced by photodecarboxylation of these substances are efficiently trapped by dipolarophiles, and the overall photoreactions starting with the alanine and phenylalanine derivatives are highly stereoselective. Finally, the N-phthalimide derivative of 2-amino-1-phenylethanol also is transformed to a related ylide upon irradiation in MeCN. The nature, regiochemical and stereochemical course, and mechanistic interpretation of these new azomethine ylide forming photoreactions are discussed in this publication.

The photophysical properties of two rigidly linked naphthalene-trialkylamine compounds have been examined in a series of solvents using transient absorption spectroscopy and time-resolved spectrofluorimetry.In alkane solvents, excitation of either compound populates a locally excited (naphthalene-like) singlet state (LESS) which fluoresces strongly and which retains a relatively long lifetime.In polar aprotic solvents, the lifetime of the LESS is substantially reduced owing to formation of an intramolecular charge-transfer state (CTS), which corresponds to full electron transfer across the molecule.The rate of formation of the CTS, under such conditions, is extremely fast and comparable to the reorientation time of the solvent.Deactivation of the CTS, which occurs on the nanosecond timescale, involves fluorescence, population of a locally excited triplet state, and charge recombination to restore the ground state.The rate of formation of the CTS is markedly slower in alkanol solvents that can hydrogen bond to the N atom on the donor and, in such cases, charge transfer involves an additional activation energy of ca. 0.12 eV.Under these conditions, it appears that the controlling feature involved in formation of the CTS concerns breakage of a hydrogen bond, whereas in aprotic solvents the intrinsic barrier is likely to be associated with the modest structural changes that might accompany charge transfer.The rates of formation and deactivation of the CTS are discussed briefly in terms of current electron-transfer theory.

Irradiation of N-trimethylsilylmethylphthalimide and its 1,8-naphthalimide analog leads to generation of azomethine ylids by C to O TMS -transfer processes.

Irradiation of N-methyl-1,8-naphthalimide (NMN) in the presence of α-methylstyrene (α-MS) or 1,1-diphenylethylene in methanol gives novel tetracyclic imides.The mechanism proposed involves photostimulated electron transfer from the alkene to 1,8-NMN and radical coupling addition of methanol to the resultant radical cation-radical anion pair at the 4-position of the aromatic ring to give an unisolable intermediate with an α,β-unsaturated carbonyl moiety.Absorption of a second photon by this chromophore gives rise to the final product.The predicted regiochemistry and stereochemistry of the reaction were established by using pentadeuterio-α-methylstyrene (16), thus providing strong evidence for the mechanism.

The anhydrides and imides of 4-(Br,Cl,NO2)-substituted naphthalic acid react with mono- and dialkylaminopropionitriles with substitution of the halogen atoms or nitro group by the alkylamino and dialkylamino groups and the formation of acrylonitrile.The eliminated halogen combines with the reagents in the form of a salt, which retards the formation of the main product.The rates of reaction of 4-bromonaphthalic anhydride with amines decreases with the amines in the order: (CH3)2NCH2CH2CN > (C2H5)2NCH2CH2CN > HN(C2H5)2 > N(C2H5)3.The nature of the substituted halogen (Br, Cl) and the substituent in the imide ring (H, CH3, C6H5) of the N-substituted 4-halogenonaphthalimides has little effect on the initial formation rate of the reaction product.The transition from o-xylene to isoamyl alcohol is accompanied by an increase of 2-3 orders of magnitude in the initial reaction rate.