Asymmetric Photoreactions Using Microscopic Spaces

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Photochemical reactions using microscopic spaces were investigated to develop highly efficient and stereoselective photoreactions. The following results were obtained.(1)Control of intramolecular photocycloaddition of 1-cyanonaphthalene derivatives was studied in microreactors. By using the microreactors and flow system, both the efficiency and regioselectivity in the intramolecular photocycloaddition increased compared with those under batch conditions. An increase of efficiency can be attributed to thorough absorption of light in the thin ditch. Highly regioselective photoreaction was explained by flowing out of the initial product.(2)Asymmetric induction in photochemical reactions was investigated using chirally modified zeolites. Enantiomeric excesses (ee) was dependent on the structures of chiral materials adsorbed in zeolite cavity, SiO_2 / Al_2O_3 ratio, alkali metal cations in zeolites, molar ratio of substrates and chiral sources, and conversion of the reaction.(3)Stereocontro … More l in Photoalkylation and photoreduction of electron-deficient alkenes by allylic silanes was examined. Diastereomeric excesses (de) of products changed depending on the structures and stoichiometry of the added carboxylic acids. High diastereoselectivity can be attained when equimolar carboxylic acids bearing bulky substituents or hydroxy group at β-position were added.(4)Oxidative photodimerization of conjugated dienes proceeded in the presence of catalytic amount of 9-cyanophenanthrene to give nucleophile-incorporated photodimers of dienes in high yields. When chiral compounds were used as dienes or proton donors, enantioselective formation of 9-cyano-9,10-dihydrophenanthrene was observed.(5)Hydrogen bonding was effective for stereoselective photoreactions. Highly diastereoselective photocycloadditions of vinyl ethers and furan derivatives to electron-deficient naphthalene derivatives occurred to give (2+2) and caged cycloadducts via intermolecular hydrogen bonding in the ground states. Less