Imides photoreactions

The influence of solvent on the nature and efficiencies of imide photoreactions has been demonstrated <1999JOC4411>. While irradiation of an acetonitrile solution of silylpropyl imide 140 results in quantitative conversion to the [2+2] photodimer (Equation 41), similar treatment of the imide in H2O-CH3CN mixtures produces only the functionalized pyrrolizidine. 

Systematic studies of the photoreactions of cyclic imides and in particular of phthalimide derivatives have been the subject of a review.278 One of the... 

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 fully unsaturated 1,3-benzodiazepine (135) is formed in a formally similar process by a photoreaction of the 1-substituted isoquinoline iV-imide (132) (80CPB2602). The same principle has been applied to the preparation of thieno-, furo- and pyrrolo-fused 1,3-diazepines (80CC454, 81 PB1539>. 

Kubo et al. reported the photoreaction of imide (268) with 2,3-dimethylbu-tadiene to give naphthazepinediones (269,270), which gave rise to the in-... 

Sakamoto et al. reported an intramolecular [2+2] thietane formation in the solid state (Scheme 7). [26] Achiral A-(thiobenzoyl)methacrylamide 39 formed (E,Z)-conformation of the imide moiety, crystallized in a chiral space group Phhh, and the photolysis of single homochiral crystals at room temperature resulted in the formation of an optically active thietane-fused 3-lactam (40,75%) with 10% ee. The solid-state photoreaction proceeded even at -45°C to give higher ee value, 40% ee (conv. 30%, yield 70%). 

Sakamoto et al. also demonstrated an absolute oxetane synthesis in the solid-state photolysis of Y-( ,(3-unsaturatcd carbonyl)benzoylformamides 43. [28] The X-ray analysis of Y-isopropyl substituted imide 43a revealed that the crystal system was monoclinic and the space group P2. Crystals of 43a were powdered and photolyzed at 0°C. The imide undergoes the [2+2] cycloaddition to afford the bicyclic oxetane 44a, which is a mixture of diastereomers, namely, syn- and anh-isomers at the C-7 position. In this reaction optically active. syn-oxctanc 44a with 37% ee (84% chemical yield) and racemic anti-44a were obtained. The solid-state photoreaction proceeded even at -78°C, and optically active syn-44n which showed ee value as high as >95% ee, (conv 100%, chemical yield 89%) was formed in a higher diastereomeric ratio (syn/anti = 6.5). Under identical conditions A-bcnzyl substituted 43b was irradiated in the solid state. 

In the first case, achiral IV-methacryloylthiobenzanilide 39 formed (E,Z)-conformation of the imide moiety and crystallized in a chiral fashion. The solid-state photoreaction gave optically active 3-lactam 40. The dynamic molecular rearrangement for cyclization was elucidated on the basis of direct comparison of the absolute configuration of both the starting material and the photoproduct (Scheme 11).[25][38]... 

Kricheldorf and Probst [58] have studied a series of photoreactive cholesteric copoly(ester-imide)s incorporating p-PDA, N-(4-carboxyphenyl)trimellit-imide, 25, and chiral diols such as 26. Their intention was to develop chiral... 

The fully-unsaturated 1,3-benzodiazepine 310 is formed by a photoreaction of the 1-substituted isoquinoline 7V-imide 309 (Scheme 169) <1980CPB2602>. The same principle has been applied to prepare thieno-, furo-, and pyrrolo-fused 1,3-diazepines <1980CC454, 1981CPB1539>. The imidazolo-fused l,3-benzodiazepin-2-ones 313 can be prepared by the reaction of 5-amino-4-(cyanoformimidoyl)imidazoles 311 with tosyl isocyanate. The mechanism of this reaction includes a 1-exo-dig cyclization of intermediates 312 followed by a Dimroth rearrangement to give the thermodynamic products 313 (Scheme 170) <1996JHC855, CHEC-III(13.05.9.2.2)174>. 

In contrast to the photoreaction of 39a and 39b, the solid state photocycliza-tions of 39c and 39h-j to give the oxetanes did not occur. The x-ray analyses of these imides indicate that all molecules are apparently in unfavorable orientation for the intramolecular cyclization, what was termed as (E,Z) conformation at the imide chromophores. 

Instead of the amide (350), the corresponding methyl imidate also could be used for the photoreaction. In this case, the labeling studies uniquely identified the process as a di-7t-methane rearrangement with initial vinyl-to-vinyl coupling " ... 

The photoaddition of phthalimides and related dicarbox-imides to alkenes has been the subject of detailed study over the years. In the presence of added methanol, the photoreactions of dicarboximides with alkenes also result in the formation of methanol-incorporated products. The efficiency of alcohol trapping by the N-methylphthalimide-alkene radical ion pair, which is involved in... 

Unsaturated compounds also yield cyclobutane derivatives in cycloaddition photoreactions sensitized by benzophenone,61,62 examples being cycloaddition of maleic anhydride and various alkyl and halo maleic anhydrides and male-imides.63 65... 

Useful reviews on the photochemistry of imides, the photoreactions of alkaloids, and selected aspects of photochemically induced preparative heterocyclic chemistry have been published. 

Many photoreactions of aryl azides can be interpreted as arising via unstable ring-fused azirines. The formation of the 6,7-diaminobenzothiazoles (117) and the 6-amino-8//-thiazolo[5,4-c]azepines (118) on irradiation of the corresponding 6-azidobenzothiazoles (119) in diethylamine can be explained in this way, as shown in Scheme 14. An alternative explanation for the photodecomposition of phenyl azide (120) at low temperatures has recently been advanced and involves the formation of an intermediate l-azacyclohepta-l,2,4,6-tetraene (121). Further evidence for this pathway is to be found in a study of the photodecomposition of phenyl azide in acetic acid the azepin-2-one (122) is believed to arise in this way, as shown in Scheme 15. The formation of the same azepin-2-one on irradiation of phenyl azide in the presence of naked acetate anion has been reported the nature of the intermediate in this transformation is still open to question, but both benzazirine and l-azacyclohepta-l,2,4,6-tetraene intermediates are considered possible. In contrast, irradiation of the azide (123) in an argon matrix at lOK affords, on the basis of spectral evidence, the cyclic carbodi-imide (124). " 2-... 

The 1-substituted isoquinoline A-imide (62), however, shows a new photoreaction instead of forming a 1,2-diazepine via closure at the 3-position, it cyclizes to (63), which apparently rearranges further to (64) before opening to give a 1//-1,3-benzodiazepine (65)." The 1-unsubstituted analogue, however, gives... 

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... 

Novolacs are thermoplastic materials, that need to be transformed by crosslinking reactions to get insoluble, nonmelting, thermally stable thermosets. Different crosslinking agents have been used for thermal curing, for instance l,3,5,7-tetiaazatricyclo[3.3.3. P Jdecane (hexamethylenetetramine), oxiranes (epoxides), diisocyanates, urea, melamine, urea methanal resins, melamine metfaanal resins, and imide precursors. Furthermore, photoreactive compounds crosslink novolacs with methacrylate and methacryloylchloride resins, respeetively by itradialion [1]. 

Lee et reported the preparation of new soluble and intrinsically photosensitive poly(amide-co-imide)s containing p-phenylenediacryloyl moiety. The copolymers were formed from p-phenylenediacryloyl chloride, aromatic dianhydrides and two equivalents of aromatic diamines. The products were subsequently imidized by reactions with the poly(amide-co-amic acid), acetic anhydride, and pyridine. The polymers were stable up to 350 C, showed good solubility in polar aprotic solvents, and became insoluble after the irradiation due to the photodimerization of phenylenediacryloyl moiety. The photoreactivity increases with the irradiation temperature. ... 

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