Selective bond cleavage using a photoredox reaction is a powerful technique in the chemical conversion of biomass such as lignin since it enables us to produce value-added aromatic compounds by controlling the activation of certain chemical bonds. Also, a water-based environment would be preferred for the sake of an eco-friendly reaction, additionally having the advantage of utilizing water-originated species such as • OH and H 2 O 2 . However, a direct cleavage of the C−C bond is still challenging due to the difficulties in tailoring redox potentials of catalysts relevant to covalent bond decoupling. Herein, we investigate a selective C−C bond cleavage of the β-O-4 lignin model compound using giant Keplerate polyoxometalates as photocatalysts. The redox potentials of photocatalysts are varied by changing metal compositions, and the correlation between redox potential and covalent bond decoupling is elucidated, probing each set of active radicals by HOMO and LUMOs. Especially, Mo 132 shows a highly selective C−C bond cleavage with hydroxyl groups in the lignin model and produces phenyl formate�a effective CO surrogate for the synthesis of various organic compounds�as the main product (97.8% of product selectivity) in a water-based condition. Furthermore, Mo 132 decomposes other aromatic polymer models, indicating the potential of photocatalytic C−C bond decoupling of polymers under a benign environment.

Tandem Radical Cyclization Reaction of N-Aziridinyl Imines to (3.3.3) Propellanes: Formal Total Syntheses of dl-Modhephene.-The first synthesis of propellane rings via tandem radical cyclization reactions is described. This strategy is applied to the synthesis of the precursors (VIII) and (XIII) of modhephene (XIV). -(LEE, H.-Y.; KIM, D.-I.; KIM, S.; Chem.

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