Phthalimides photochemistry

Investigations of phthalimide photochemistry in the authors laboratories have concentrated on SET-induced excited-state reactions with a-trialkylsilyl substituted ethers, thioethers, and amines. These efforts have uncovered several interesting photochemical reactions. For example, in an early effort simple, a-silyl-substituted ethers, thioethers, and amines were observed to undergo efficient photoaddition reactions with phthalimide and its N-methyl derivative (Scheme 5.4) [20]. In these processes, thermodynamically/kinetically driven SET from the a-silyl donors 13 to excited phthalimide leads to formation of ion radical pairs 16 (Scheme 5.5). Solvent (MeOH) promoted desilylation of the cation radicals 16 and protonation of the phthalimide anion radicals 15 then provides radical pairs 17, the direct precursor of adduct 14. 

The Use of Phthalimide Photochemistry in Macrocyclec Polyamide, Polyether, and Polythioether Synthesis... 

For other recent reviews of phthalimide photochemistry, see Griesbeck, AG., Chimia, 52, 272-283, 1998 Griesbeck, A.G., Photochemical Activation of Amino Acids. From the Synthesis of Enantiomer-icaUy Pure P,Y-Unsaturated Amino Adds to Macrocychc Ring Systems, Liebigs Ann., 1951-1958,1996. Yoon, U.C., Kim, H.J., and Mariano, P.S., Eledron Transfer Induced Photochemical Reactions in Imide Systems. Photoaddition of a-Trimethylsilyl Substituted Heteroatom Containing Compounds to Phthalimides. Heterocycles, 29,1041-1064. 1989. 

The photochemistry of imides, especially of the N-substituted phthalimides, has been studied intensively by several research groups during the last two decades [233-235]. It has been shown that the determining step in inter- and intramolecular photoreactions of phthalimides with various electron donors is the electron transfer process. In terms of a rapid proton transfer from the intermediate radical cation to the phthalimide moieties the photocyclization can also be rationalized via a charge transfer complex in the excited state. 

The photochemistry of phthalimide systems was thoroughly investigated by many groups over the last two decades. This chromophore shows a broad spectrum of reactivity leading mainly to cycloaddition and photoreduction products by either intermolecular or intramolecular processes. In the presence of electron donors, the electronically excited phthalimide could also undergo electron transfer and act as an electron acceptor. 

Phthalimide, JV-thio-metal complexes, 800 Phthalocyanines, 863-870 chelate complexes, 374 demetallation, 863 IR spectra, 861 mass spectra, 861 metallation, 863 NMR, 861 photochemistry, 869 reactions, 863 at metal, 869 redox chemistry, 870 spectra, 860 synthesis, 861 two-metal complexes, 868 Phytic acid zinc complexes, 985 2-Picoline... 

Less intensively investigated than phthalimides was the photochemistry of maleimides, succinimides, and glutarimides. 

Oelgemoller M (2000) Photochemistry of Phthalimides Photodecarboxylative Addition of Carboxylates and PET-Induced Macrocyclizations, Europ. Photochem. Assoc. Newsl. 69 11-23. 

Related photochemistry has also been examined with other functional groups such as phthalimides, which also abstract nearby hydrogens with the photoexcited carbonyl group. - Furthermore, since the hydrogen abstraction is performed by the half-vacant nonbonding orbital of a photoexcited ketone carbonyl, related chemistry is observed if the electron is removed electrochemically, not just photoexcited into a Tr -orbital. Electrochemical functionalization of nearby carbons has been reported in which, after hydrogen atom abstraction by an oxidized ketone, the resulting radical is electrochemically oxidized further to the carbon cation, which reacts with solvent (Scheme 7). ... 

Interest in the photochemistry of the phthalimide systems has continued. The phthalimide derivatives (316) are phot ochemically reactive and on irradiation in acetone yields the cyclized products (317). The reaction involves hydrogen abstraction to yield the biradical (318) which subsequently bonds to afford the observed products. A recent study has examined the behaviour of the anion (319) in an attempt to reduce electron transfer processes. In t-butanol irradiation affords the solvent addition product (320) as the principal product presumably by a free radical path. Minor products (321) and (322) are also formed but are probably artefacts of the work-up procedure. Irradiation of (319) in methanol with added cyclohexene follows a different reaction path. In this system the reaction with methanol is minor while the dominant reaction is addition of the alkene to afford the adduct (323) in 20 % yield. The Dewar benzene derivative (324) is photocheraically unstable and irradiation affords t etramet hyl cyclobutadiene. ... 

Photoadditions to phthalimides and related imides have again attracted much interest and it has been clearly shown that variation in the arene structure causes a change in the site of addition. Detailed studies of the photochemistry of N-methyl-9,10-phenanthrenedicarboximide (113) have been reported. Stereo-... 

Imines conjugated with electron-withdrawing carbonyl or aryl functions at nitrogen or carbon appear to more readily participate in cycloadditions. This was shown for 6-azauracil derivatives io2,103 ancj 3-ethoxyisoindole 9104-105, both reactions are thought to proceed via the triplet state of the electronically excited imines. The isoindole photochemistry, to some extent, resembles the reactions of phthalimides described in Section 1.6.1.4.3.8. For example, the azetidine 10 can be converted to the azepinedione derivative 11 using acid. 

Phthalimides and Related Compounds - 4-Amino-./V-methylphthalimide has been studied by laser flash photolysis. The photophysical parameters have been established by this approach and this study has supported the results obtained from steady state irradiations. Intramolecular photoelectron transfer photochemistry of the A-[(JV-acetyl-./V-trimethylsilyl-methyI)amidoalkyl]phthali-mides has been demonstrated. The yields obtained on irradiation in methanol range from low to medium. 

Machida M, Takechi H et al (1982) Photochemistry of the phthalimide system. 32. Photoreaction of N-(w-indol-3-ylalkyl)phthalimides intramolecular oxetane formation of the aromatic imide system. Tetrahedron Lett 23 4981 982... 

Takechi H, Machida M et al (1994) Photochemistry of the phthalimide system XLIV. Intramolecular photoreactions of phthalimide-alkene systems. Macrocyclic synthesis through the remote Patemo-Buechi reaction of phthalimide with indole derivatives. Chem Pharm Bull 42 188-196... 

To understand the primary photochemistry of 6F-PIs in air, Hoyle et al. [I72-I74] used V-phenylphthalimide as a model compound, since this model probably reflects the structural units in 6F-PIs where conjugation between the diimide groups is prevented by the C(CF3)3 bridge. Upon irradiation with a Pyrex filtered medium pressure mercury lamp, this model in an air-saturated acetonitrile solution rapidly decomposes to form phthalic anhydride (quantum yield major product, phthalimide (0 = 2X and a trace amount of nitrobenzene (this originates probably from... 

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