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A novel planar chiral flavinium salt, 3-benzyl-5-ethyl-10-(8-phenylnaphthalen-1-yl)isoalloxazinium perchlorate (2b), which bears a phenyl cap that covers one side of the isoalloxazinium skeleton plane, has been prepared as a potential catalyst for the enantioselective H 2 O 2 oxidation of sulfides. The rate of H 2 O 2 oxidation of sulfides in the presence of racemic 2b is comparable to that of the reaction catalysed by 5-ethyl-3,10-dimethylisoalloxazinium perchlorate, which indicates that the bulky shielding substituent does not influence the catalytic activity of the flavinium unit. The turnover fre-

New organosilica precursors containing two triethoxysilyl groups suitable for the organosilica material formation through the sol-gel process were designed and synthesised. These precursors display alkyne or azide groups for attaching targeted functional groups by copper-catalysed azide-alkyne cycloaddition (CuAAC) and can be used for the preparation of functional organosilicas following two strategies: 1) the functional group is first appended by CuAAC under anhydrous conditions, then the functional material is prepared by the sol-gel process; 2) the precursor is first subjected to the sol-gel process, producing porous, clickable bridged silsesquioxanes or periodic mesoporous organosilicas (PMOs), then the desired functional groups are attached by means of CuAAC. Herein, we show the feasibility of both approaches. A series of bridged bis(triethoxysilane)s with different pending organic moieties was prepared, demonstrating the compatibility of the first approach with many functional groups. In particular, we demonstrate that organic functional molecules bearing only one derivatisation site can be used to produce bridged organosilanes and bridged silsesquioxanes. In the second approach, clickable PMOs and porous bridged silsesquioxanes were prepared from the alkyne- or azide-containing precursors, and thereafter, functionalised with complementary model azide- or alkyne-containing molecules. These results confirmed the potential of this approach as a general methodology for preparing functional organosilicas with high loadings of functional groups. Both approaches give rise to a wide range of new functional organosilica materials.

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