Intermolecular photoreaction

During the photoreaction of ethyl methyl 1,4-phenylenediacrylate crystals (3 OEtMe), in which the distances of intermolecular double bonds are 3.891 A between two methyl cinnamate groups and 4.917 A between two... 

In the crystal of 7 OEt, two molecules form a molecular pair as is the case in the crystal of 7 OMe. Considering the intermolecular distances between the ethylenic double bonds (3.714 and 3.833 A within the pair, and 4.734 and 4.797 A between the pairs), each molecule can react only with its partner in the molecular pair and not with any molecule of another pair. Since paired molecules are related by centrosymmetry, two pairs of facing ethylenic double bonds should be equal in photoreactivity, affording two... 

The presence of Cu(I) salts promotes intermolecular photocycloaddition of simple alkenes. Copper(I) triflate is especially effective.182 It is believed that the photoreactive species is a 2 1 alkene Cu(I) complex in which the two alkene molecules are brought together prior to photoexcitation.183... 

Intermolecular addition of photochemically generated nitrenes and in particular acylnitrenes to alkenes provides a useful and widely applied route to aziridines.385 An analogous intramolecular photoreaction is thought to be involved in the conversion of the o-azidophenylethylfuran 461 into the pyrrolo[l,2-a]quinoline 462 as outlined in Scheme 13,386 and intramolecular addition to an azo group has been observed in the 8-azido-1-arylazonaphthalenes 463.387... 

Photochemical reactions of the pyrimidine polymers in solution were studied to determine the quantum yields of the intramolecular photodimerization of the pyrimidine units along the polymer chains. Photoreactions of the polymers were carried out in very dilute solutions to avoid an intermolecular(interchain) photodimerization. Quantum yields determined at 280 nm for the polymers (1-6 in Figure 1) are listed in Table I. The quantum yield of the 5-bromouracil polymer [poly(MAOU-5Br)] could not be determined because of side reactions of the base during the irradiation. 

Photochemical (2 + 2) and (4 + 4) photocycloaddition is well investigated and recent advances in this field easily predict the patterning of the photoreactivity. The intermolecular and intramolecular photocycloaddition of alkenes to benzene ring also has a citizenship in this field. On the other hand, most people believe the photocycloaddition of unsaturated compounds to naphthalene ring takes place at... 

C-P4-C can undergo intra- and intermolecular photoreactions. Irradiation of <5 X 10 4 M C-P4-C in an organic solvent such as benzene results primarily in intramolecular syn head-to-tail cyclomer (Fig. 12). Upon irradiation of more concentrated solutions, a large amount of oligomeric material was formed. For example, at concentration of 1 X 10-3 M, -20% of oligomers were present in the product mixture. As observed in the case of the N-P -N, irradiation of 1 X 10 2 mol/g-film C-P4-C in LDPE resulted in conversion to intramolecular cyclomer. As in the case of irradiations in homogeneous solutions, only the syn head-to-tail... 

B. Prass, J. P. Colpa, and D. Stehlik, Chem. Phys., 136,187 (1989). Intermolecular H-Tunnel-ing in a Solid State Photoreaction Promoted by Distinct Low Energy Fluctuation Modes. 

Ghosh, S., Raychaudhuri, S.R., and Salomon, R.G. (1987) Copper(I) catalysis of olefin photoreactions. 15. Synthesis of cyclobutanated butyrolactones via copper(I)-catalyzed intermolecular photocycloadditions of homoallyl vinyl or diallyl ethers. Journal of Organic Chemistry,... 

B.C., Turro, N.J. and Ramamurthy, V. (2007) Controlling photoreactions with restricted spaces and weak intermolecular forces exquisite selectivity during oxidation of olefins by singlet oxygen. Journal of American Chemical Society,... 

Sensitized intramolecular reaction of two 1,3-dienes (86) (Sch. 17) yields predominantly the [2+2] adduct 87, with small amounts of [4+4] adduct 89 and little, if any, [4+2] product 88 [58,59], consistent with Hammond results for intermolecular reactions of acyclic dienes (Sch. 4). Benzophenone-sensitized reaction yields a mixture of two isomers of 87. Heating this mixture to 200 °C converts both isomers of 87 to cyclo-octadiene 89 [58]. Unsensitized photoreaction of 86 in the presence of copper(I) triflate gives a significant amount of [4+2] adduct 88. Extended irradiation time converts much of 87 and 89 into 88, as well as producing secondary products [59]. Copper triflate-mediated photocycloaddition of a related tethered diene-monoalkene, gave only the [2+2] adduct [59]. 

Intermolecular photoreaction of an aryl halide with another aromatic compound may lead to the formation of biaryls. In this section several examples of such reactions will be discussed. In some cases, information concerning the reaction mechanism is available but the depth to which mechanisms have been investigated varies greatly. In many cases aryl radicals formed by homolysis of the carbon-halogen bond are the reactive species. Such radicals may also be produced via electron transfer, followed by departure of halide anion. In some cases aryl cations have been proposed as intermediates. Intermolecular bond formation may also be preceded by charge transfer within an exciplex or by formation of radical ion pairs. 

Since the concept of topochemically controlled reactions was established, various approaches to asymmetric synthesis using a solid-state reaction have been attempted, most actively by the research group at the Weismann Institute. Their studies have been concerned with the bimolecular reactions of chiral crystals in the solid state. In these studies, successful absolute asymmetric synthesis has been performed by using topochemically controlled four-centered photocyclodimerizations of a series of unsymmetrically substituted diolefin crystals. Research on reactivity in the crystalline state has been extended in recent years to a variety of new systems, and many absolute asymmetric syntheses have been provided. Successful examples of absolute asymmetric synthesis using chiral crystals are listed in Tables 2 to 4, which are divided into three categories intermolecular photoreaction in the solid state (Table 2), intramolecular photoreaction in the solid state (Table 3, A-D), and asymmetric induction in the solid-gas and homogeneous reactions (Table 4). 

We have used chiral cocrystals composed of two different molecules [10]. When one of the two components is chiral, a cocrystal of a chiral space group is necessarily obtained. Combination of an electron donor molecule with an electron acceptor molecule, or a photoinert molecule with a photosensitizer molecule, in a cocrystal can induce new photoreactivity as well as intermolecular photoreaction. 

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