Phthalimides and Related Compounds

1 Phthalimides and Related Compounds - A detailed study of the formation of the ylide (219) from irradiation of the phthalimide derivatives (220) has been reported. Suau et a/. have examined the irradiation of phthalimide in the presence of a low concentration of hydroxide ion and alkenes (221). The 

The naphthalimide (227) imdergoes a SET process with arylalkenes such as p-xylene. The initial process yields a radical cation/radical anion pair within 

1 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. 

Lactams such as (258) can be synthesized from the phthalimides (259) by irradiation. Again the reactions are controlled by single electron transfer processes that are usually encountered in the photochemical reactions of phthalimides. The outcome of the reaction is a conventional proton transfer from the benzylic site within the zwitterionic biradical formed on irradiation. Cyclization within the resultant 1,5-biradical affords the final product. Griesbeck and his coworkers have studied the photochemical reactivity of the phthalimide derivatives (260). These compounds on irradiation under triplet sensitized conditions undergo decarboxylation and cyclization. The reaction involves SET and the key intermediates are shown as (261) and (262). The biradical anion (262) is the species that either cyclizes to afford (263) or abstracts hydrogen to yield (264). The reaction is controlled by a variety of factors that have been reported in some detail. Some photochemical reactions of phthaloylcysteine derivatives have been described. Typical of the processes are the decarboxylations of the derivative 

Photochemical reactions of phthalimides and related systems continues to produce new and interesting results. A Ethybuccinimide is converted into the azepinedione (309) in 64% yield on irradiation with a low pressure Hg lamp. AtMethylglutarimide adds photochemically to 2-methylpropene to yield the oxetan (310).  

A detailed account of the photobehaviour of the phthalimide (311) with alkenes has supplemented earlier reports. The reactions encountered are either a 2tt+2ct addition yielding benzazepinediones or electron transfer from the alkene to the phthalimide followed by intermolecular trapping. In another study TV methylphthalimide derivatives (312) undergo electron transfer reactions on irradiation in alcoholic solution. Reaction between the radical anion and radical cation yields adducts e.g. (313) as well as the more conventional products of addition to the carbonyl group. The identity of these new structures was verified by X-ray crystallography.  

As can be seen from the foregoing, phthalimide photocyclizations have provided useful synthetic routes to a variety of heterocyclic products. Machida et al. have used the reaction to yield the spiro compounds (325) from the irradiation (in methanol) of the phthalimide derivatives (326). The products are presumed to be formed via bond formation in the biradical produced by the addition of methanol to the radical cation/r ulical anion pair. The indoles (327) undergo photochemical (2-f-2)-addition with A methyl phthalimide to afford the oxetan adducts (328). This work has also been the subject of a patent application.  

The xanthate (340) undergoes decarbonylation to afford the alkyl xanthate (341) when irradiated in benzene solution. 

Photo-addition of alkenes to A methylnaphthalene dicarboxamides in benzene has been studied. The structure of the arene moiety in the imide was important in determining the reaction path. Mainly cyclobutane and oxetan formation occurred. The dicarboximide (342) undergoes photochemical cyclization with incorporation of methanol to yield the two products (343) and (344) in 55 and 16% respectively. This type of cyclization appears to be quite general for such systems and is also reported for the imides (345) and (346). A variety of products resulting from aminolysis, reduction, and radical coupling is produced on irradiation of the phthalimide (347) in diethylamine.  

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With cyclic systems such as succinimide and related compounds coplanarity is to be expected and now much greater separations are found. Succinimide shows bands at [ 157] 1781 and 1715 cm", and other compounds behave similarly [156, 157]. The frequency ranges are quite wide 1790—1735 and 1745—1680 cm". As with the anhydrides it is the antisymmetric mode which has the lower frequency and has the greater intensity in the infra-red. Sizeable frequency shifts in this band can occur if the nitrogen atom is also substituted [158]. It is at 1738 cm" in phthalimide, at 1720 cm" ... 

Direct preparation of an aziridine from an alkene is possible by reaction of the alkene with a nitrene or metal nitrenoid species. Nitrenes can be generated thermally or photochemically from azides, although their reaction with alkenes to give aziridines is often low yielding and is complicated by side reactions. Oxidation of iV-amino-phthalimide or related hydrazine compounds (e.g. with Pb(OAc>4 or by electrolysis) and reaction with an alkene has found some generality. The metal-catalysed reaction of nitrenes with alkenes has received considerable study. A variety of metal catalysts can be used, with copper(II) salts being the most popular. For example, styrene was converted to its A-tosyl aziridine 72 by reaction with [A-(tosyl)imino]phenyliodinane (PhI=NTs) and copper(II) triflate (5.75). ... 

Because the reactions of related in -cyclohexadienyl complexes are synthetically valuable, the reactions of this ligand have been studied extensively. An outline of how this chemistry can be conducted on the Fe(CO)j fragment is shown in Equation 11.51. A variety of cyclohexadienes are readily available from Birch reduction of substituted aromatics. Coordination and abstraction of a hydride, typically by trityl cation, leads to cationic cyclohexadienyl complexes. These cyclohexadienyl complexes are reactive toward organolithium, -copper, -cadmium, and -zinc reagents, ketone enolates, nitroal-kyl anions, amines, phthalimide, and even nucleophilic aromatic compounds such as indole and trimethoxybenzene. Attack occurs exclusively from the face opposite the metal, and exclusively at a terminal position of the dienyl system. This combination of hydride abstraction and nucleophilic addition has been repeated to generate cyclohexa-diene complexes containing two cis vicinal substituents. The free cyclohexadiene is ttien released from the metal by oxidation with amine oxides. ... 

Either direct or sensitized photolysis of 3-(V-phthalimido)adamantane-l-carboxylic acid leads to population of the triplet excited state, which decarboxylates in the presence of a base, giving V-(l-adamantyl)phthali-mide. The intermediate radical adds regiospecffically to electron deficient alkenes. This type of reaction can be extended to related compounds, where the electron donor (carboxylate) and the acceptor (phthalimide) are separated by a rigid spacer. The photodecarboxylation of phthalimides... 

In addition to phthalimide and substituted derivatives, related compounds such as 1,8-naphthimide, succinimide, saccharine, or piperidien-2,6-dione could be used successfully [21]. 

Related to the above-mentioned compounds, in the sense that they contain a tin atom linked to an acid nitrogen atom, are N-triethylstannyl-phthalimide and A -triethylstannylsaccharin prepared directly from triethyltin hydroxide and phthalimide or saccharin, respectively (91). All these compounds are reasonably stable to hydrolysis. They can be kept in contact with the atmosphere without decomposition. 

Therefore, the solvent used for successful electrosynthesis of PcCu should be inert in relation to PA and, on the other hand, should have electroconductivity. The compounds used as promoters [41] could theoretically serve as such solvents. Tetramethylurea (TMU) and l-methyl-2-pyrolidinone were chosen by the authors of Ref. 32 among other promoters used in the work [41]. The first one has a nature close to that of the principal precursor (urea), and thus should not influence the reaction course negatively. The TMU has sufficient conductivity to permit electrolysis in its medium, and reasonable viscosity. The boiling point of 174-178 C is ideal for such research, since conventional syntheses of Pc from urea and PA are carried out at similar temperatures. The results of TMU use as a solvent are presented in Table 5.7. The results seem promising, and this solvent is recommended to study Pc formation in its medium in further research work. In the case of l-methyl-2-pyro-lidinone, no phthalocyanine formation was observed. No phthalocyanine was observed also in the following systems (1) urea, PA, TBA, TMU (without copper) (2) urea, PA, TBA, TMU, Sb, or Mg (anodes (3) TMU, urea (or without urea), phthalimide, TBA (in all cases with or without electrolysis). 

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