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Reductive amination of carbonyl compounds and nitro compounds represents a straightforward way to attain imines or secondary amines, but it is difficult to control the product selectivity. Herein, we report the selective formation of C−N or C=N bond readily manipulated through a solvent‐induced hydrogen bond bridge, facilitating the swift photocatalytic reductive coupling process. The reductive‐coupling of nitro compounds with carbonyl compounds using formic acid and sodium formate as the hydrogen donors over CdS nanosheets selectively generates imines with C=N bonds in acetonitrile solvent; while taking methanol as solvent, the C=N bonds are readily hydrogenated to the C−N bonds via hydrogen‐bonding activation. Experimental and theoretical study reveals that the building of the hydrogen‐bond bridge between the hydroxyl groups in methanol and the N atoms of the C=N motifs in imines facilitates the transfer of hydrogen atoms from CdS surface to the N atoms in imines upon illumination, resulting in the rapid hydrogenation of the C=N bonds to give rise to the secondary amines with C−N bonds. Our method provides a simple way to control product selectivity by altering the solvents in photocatalytic organic transformations. [ABSTRACT FROM AUTHOR]

Reductive amination of carbonyl compounds and nitro compounds represents a straightforward way to attain imines or secondary amines, but it is difficult to control the product selectivity. Herein, we report the selective formation of C-N or C=N bond readily manipulated through a solvent-induced hydrogen bond bridge, facilitating the swift photocatalytic reductive coupling process. The reductive-coupling of nitro compounds with carbonyl compounds using formic acid and sodium formate as the hydrogen donors over CdS nanosheets selectively generates imines with C=N bonds in acetonitrile solvent; while taking methanol as solvent, the C=N bonds are readily hydrogenated to the C-N bonds via hydrogen-bonding activation. Experimental and theoretical study reveals that the building of the hydrogen-bond bridge between the hydroxyl groups in methanol and the N atoms of the C=N motifs in imines facilitates the transfer of hydrogen atoms from CdS surface to the N atoms in imines upon illumination, resulting in the rapid hydrogenation of the C=N bonds to give rise to the secondary amines with C-N bonds. Our method provides a simple way to control product selectivity by altering the solvents in photocatalytic organic transformations., (© 2024 Wiley-VCH GmbH.)

Catalytic ammoxidation of alcohols into nitriles is an essential reaction in organic synthesis. While highly desirable, conducting the synthesis at room temperature is challenging, using NH 3 as the nitrogen source, O 2 as the oxidant, and a catalyst without noble metals. Herein, we report robust photocatalysts consisting of Fe(III)-modified titanium dioxide (Fe/TiO 2 ) for ammoxidation reactions at room temperature utilizing oxygen at atmospheric pressure, NH 3 as the nitrogen source, and NH 4 Br as an additive. To the best of our knowledge, this is the first example of catalytic ammoxidation of alcohols over a photocatalyst using such cheap and benign materials. Various (hetero) aromatic nitriles were synthesized at high yields, and aliphatic alcohols could also be transformed into corresponding nitriles at considerable yields. The modification of TiO 2 with Fe(III) facilitates the formation of active • O 2 - radicals and increases the adsorption of NH 3 and amino intermediates on the catalyst, accelerating the ammoxidation to yield nitriles. The additive NH 4 Br impressively improves the catalytic efficiency via the formation of bromine radicals (Br • ) from Br - , which works synergistically with • O 2 - to capture H • from C α -H, which is present in benzyl alcohol and the intermediate aldimine (RCH═NH), to generate the active carbon-centered radicals. Further, the generation of Br • from the Br - additive consumes the photogenerated holes and OH • radicals to prevent over-oxidation, significantly improving the selectivity toward nitriles. This amalgamation of function and synergy of the Fe(III)-doped TiO 2 and NH 4 Br reveals new opportunities for developing semiconductor-based photocatalytic systems for fine chemical synthesis.