Yoshikatsu Ito

Control of solid-state photodimerization of trans-cinnamic acid by double salt formation with diamines

By double salt formation, diamines can steer the solid-state [2+2] photodimerization of trans-cinnamic acid (1). Thus, the yields for the photodimerization were significant only in three double salts, i.e., the ones with tn and t- and c-chxn, which are assumed to have an overlap structure. The resultant photodimer is generally β-truxinic acid, although in one case, e-truxillic acid was formed. α-Truxillic acid was not produced from any of the double salts studied. The X-ray crystal structures of three double salts of low photoreactivity (1·en, 1·pen, 1·hen) were consistent with Schmidts rule.

CONTROL OF THE SOLID-STATE PHOTODIMERIZATION OF SOME DERIVATIVES AND ANALOGS OF TRANS-CINNAMIC ACID BY ETHYLENEDIAMINE

Some of double salts derived from ethylenediamine (en) and a variety of trans-cinnamic acids and their analogs underwent photodimerization in the solid state, giving predominantly β-truxinic dimers. X-Ray studies demonstrate that (a) the conformation of en is gauche for the highly photoreactive double salts (o-1b·en and m-1e·en), whereas it is anti for lessphotoreactive o-1a·en or photoinert 1d·en and (b) for highly reactive o-1b·en and m-1e·en, the monomer acid molecules are arranged in an overlap configuration and a reactive monomer pair is hydrogendashbonded to the same en molecule.

Compelled Orientational Control of the Solid-State Photodimerization of trans-Cinnamamides: Dicarboxylic Acid as a Non-covalent Linker

Abstract The 2:1 hydrogen-bonded cocrystals 1a·ox, 1a·su, 1a·pht, 1a·fu, 1b·ox, 1c·ox, 1d·ox between trans-cinnamamides (1a–1d) and dicarboxylic acids (ox, su, gl, fu, pht) were prepared and characterized by IR and powder X-ray techniques. The crystal structures of 1a·pht, 1a·ox and 1a·fu were solved by single crystal X-ray diffraction. Phthalic acid (pht) caused β-type photodimerization of trans-cinnamamide (1a) in the cocrystal and functioned as a non-covalent linker like gauche 1,2-diamines in photodimerization of trans-cinnamic acids. Oxalic acid (ox) enforced 1a to take a bilayer structure that is suitable for β-type photodimerization. In the case of fumaric acid (fu), cross photodimerization with 1a occurred to give a cycloadduct 4. For the cocrystals 1a·pht and 1a·fu, pedal-like motion was assumed to occur prior to the dimerization.

Coerced photodimerization reaction in the solid state through amine salt formation

Abstract Photodimerization of fumaric or several γ-form trans -cinnamic acids proceeded successfully in the solid state through amine salt formation with ammonia or some aromatic heterocyclic amines (especially, imidazole). It appears that this success is due to a small size or a planar structure of the amine. A layered or a channel-type clathrate crystal structure was revealed, respectively.

Single-crystal-to-single-crystal photodimerization of 4-chlorocinnamoyl-O,O'-dimethyldopamine.

[2+2]Photodimerization of the title compound, C(19)H(20)ClNO(3), has been observed in situ by single-crystal X-ray diffraction. Pairs of monomers related by centers of symmetry have parallel C=C bonds at a C.C distance of 4.155 (17) A. Irradiation of a single crystal with a mercury lamp achieves 100% conversion to the dimer. Redetermination of the structure during the course of the reaction revealed a linear correlation between the percent conversion to the dimer and the decrease in the cell Volume. The displacement parameters for the pure dimer structure are substantially smaller than those for the pure monomer structure. The dimerization reaction is also induced by irradiation with X-rays, the induction being stronger with Cu Kalpha than with Mo Kalpha radiation.

Efficiency for solid-state photocyclization of 2,4,6-triisopropylbenzophenones

Abstract Quantum yields for photocydization of 2,4,6-triisopropybenzophenones in the solid state were estimated by using an usual merry-go-round apparatus. The results suggest that the π,π ☆ excited state is responsible for the reaction.

Photocatalytic cleavage of 1,2-diols by a cofacially hindered water-soluble iron(III) porphyrin

Abstract The photocatalytic decompositions of 1,2-diols by newly synthesized [meso-tetrakis(3,5-dichloro-1-methyl-4-pyridiniumyl)porphyrinato] iron(III) FeIIICl2MPyP were compared with those by [meso-tetrakis(1-methyl-4-pyridiniumyl)porphyrinato]iron(III) FeIIITMPyP, Cofacially hindered FeTCl2MPyP was more robust and substrate-specific than FeTMPyP.

Efficient photochemical oxetane formation from 1-methyl-2,4,5-triphenylimidazole and benzophenones

Abstract In contrast to simple imidazoles, 1-methy1–2,4,5-triphenylimidazole ( 1 ) produced stable oxetane photoadducts 3b - e with good efficiency upon irradiation in the presence of benzophenone derivatives 2b - e in acetonitrile solution. Irradiation in the solid-phase was also studied. The oxetanes 3b - e readily underwent cycloreversion by acid catalysis or by heating.

SOLID‐STATE PHOTOCHEMISTRY OF INDOLES WITH NAPTHALENE AND PHENANTHRENE

Abstract— Solid‐state irradiation of mixed crystals prepared by meltinga 1:3 molar mixture of indole and phenanthrene followed by resolidifying the melt gave an adduct 2a in 13.5% yield. An adduct 2b was obtained by irradiation of the mixed crystals of 3‐methylindole and phenanthrene. Irradiation of the same mixtures of indoles and phenanthrene in solution gave no photoproduct. Irradiation of the mixed crystals of indole and naphthalene gave a similar photoadduct 3a, which was also formed in solution. The 1:1 mixed crystals of indole and phenanthrene and of indole and naphthalene were characterized by various spectroscopic methods. Among them powder X‐ray diffraction spectral analysis and differential scanning calorimetry revealed that the former mixed crystal is a simple mixture of microcrystals of indole and phenanthrene, while the latter forms a molecular compound.

Photoinduced reactions. LXX. Photochemistry of 2-isoxazolines

Abstract Upon irradiation at 253·7 nm, 2-isoxazolines undergo three types of formal [2 + 2] cycloreversions, in addition to 1,2-bond cleavage followed by further transformation. To determine whether the localized excitation of a particular chromophore is responsible for each type of reaction, the effects of sensitizer, quencher and excitation wave-length were examined with selected 2-isoxazolines. It is suggested that for 2-isoxazolines having a phenyl ketoxime group and a 4-aryl and/or 5-aryl group an excited singlet state of the 4- or 5-aryl group is responsible for the formation of some products, while an excited singlet state of the phenyl ketoxime group is responsible for others.