In view of its unique photocatalytic properties, decatungstate (W(10)O(32)(4-)) is rapidly emerging as a promising tool in organic chemistry. This tutorial review surveys recent developments in the chemistry of decatungstate, including mostly synthetic, and to a lesser extent mechanistic aspects. We have chosen to present several representative examples that illustrate the diverse uses of decatungstate in organic synthesis. Thus, the decatungstate-mediated radical functionalization of several classes of organic compounds such as alkanes, alkenes, alcohols, aldehydes and sulfides, under both aerobic and anaerobic conditions, represents reactions of fundamental and practical interest in academia and industry. Several new discoveries concerning the heterogenization of decatungstate for the development of sustainable methods with broad applications in catalysis, such as the photooxidation or photodegradation of various organic substrates, are also presented.

Herein, we show that mesoporous titania-supported gold nanoparticle assemblies (Au/MTA) catalyze the activation of NaBH4 and 1,1,3,3-tetramethyl disiloxane (TMDS) compounds, which act as transfer hydrogenation agents for the reduction of nitroarenes to the corresponding anilines in moderate to high yields. On the other hand, nitroalkanes are reduced to the corresponding diazo and hydrazo compounds under the studied conditions. The substantial measured primary kinetic isotope effects found here suggested that B–H bond cleavage occurs in a rate-determining step and [Au]–H active hybrids are formed, which are responsible for the reduction of nitroarenes to the corresponding amines. Formal Hammett-type kinetic analysis of a range of para-X-substituted nitroarenes lends support to this hypothesis. Nitro compounds substituted with electron-withdrawing groups were reduced faster than the corresponding compounds with electron-donating groups. The presence of water enhanced the catalytic activity of Au/MTA in aprotic solvents. Nuclear magnetic resonance studies support the formation of the corresponding hydroxylamines as the only intermediate products. On the basis of the high observed chemoselectivities and the fast and clean reaction processes, these catalytic systems, i.e., Au/MTA-NaBH4 and Au/MTA-TMDS, show promise for the efficient synthesis of aromatic amines at industrial levels.

Gold nanoparticles supported on TiO(2) (~1%) catalyse in high yields the selective cycloisomerisation of aryl propargyl ethers into the corresponding 2H-chromenes, under heterogeneous conditions. 2H,2'H-3,3'-Bichromenes resulting from a catalytic oxidative dimerization pathway are also formed as by-products.

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Gold nanoparticles supported on TiO(2) (1.2 mol %) catalyze, for the first time under heterogeneous conditions, the cycloisomerization of a series of 1,6-enynes in high yields. In several cases, the product selectivity differs significantly as compared to homogeneous Au(I)-catalysis. Based on product analysis and stereoisotopic studies it is proposed that the major or exclusive pathway involves a 5-exo cyclization mode to form stereoselectively gold cyclopropyl carbenes that undergo a single cleavage pathway, in contrast to homogeneous Au-catalysis where the double cleavage pathway operates substantially.

Ph 3 PAuNTf 2 (≈1 mol-%) catalyzes the selective cycloisomerization of substituted aryl propargyl ethers into 2H-chromenes in excellent yields. Benzofuran byproducts are formed only in the case of electron-deficient arenes, in up to 7 % relative yield. The Ph 3 PAuNTf 2 -catalyzed cyclization of

A family of benzotriazole based coordination compounds, obtained in two steps and good yields from commercially available materials, formulated as [Cu(L)(MeCN)]·2ClO·MeCN (1), [Cu(L)(NO)]·MeCN (2), [Zn(L)(HO)]·2ClO·2MeCN (3), [Cu(L)Cl] (4), [Cu(L)Cl] (5), [Cu(L)Br]·4MeCN·CuBr (6), [Cu(L)(MeCN)]·2BF (7), [Cu(L)(CFSO)] (8), [Zn(L)(MeCN)]·2CFSO (9), [Cu(L)(HO)]·4CFSO·4MeCO (10), and [Cu(L)(CFSO)]·2CFSO·MeCO (11), are reported. These air-stable compounds were tested as homogeneous catalysts for the A coupling synthesis of propargylamine derivatives from aldehyde, amine, and alkyne under a noninert atmosphere. Fine tuning of the catalyst resulted in a one-dimensional (1D) coordination polymer (CP) (8) with excellent catalytic activity in a wide range of substrates, avoiding any issues that would inhibit its performance.

Gold nanoparticles supported on titania catalyse, even at a ppm loading level, the quantitative reduction of nitroarenes into anilines and nitroalkanes into alkylhydroxylamines by the ammonia· borane complex. No dehalohalogenation was seen in the case of chloro-or bromonitroarenes, while ester, cyano, or carboxylic acid functionalities also remain intact. The nitroarene to aniline reduction pathway does not require nitrosoarenes as intermediate products.