Science of Synthesis

Adolfsson, H., Science of Synthesis, (2008) 37, 229.

The high oxophilicity of titanium strongly inhibits the use of homogeneous titanium catalysts in combination with aqueous hydrogen peroxide as terminal oxidant. Thus, the only properly working systems are based on less hydrolytically sensitive heterogeneous catalysts. The development of the titanium(IV)–silicate catalyst (TS-1) represents a breakthrough for reactions performed with hydrogen peroxide.[‌8‌] This hydrophobic molecular sieve demonstrates excellent properties (i.e., high catalytic activity and selectivity) for the epoxidation of small linear alkenes in methanol. The substrates are adsorbed into the micropores of the TS-1 catalyst, which efficiently prevents the inhibition by water.[‌4‌] After the epoxidation reaction, the TS-1 catalyst can easily be separated and recycled. To enlarge the scope of this epoxidation method and thereby allow for the oxidation of a wider range of substrates, several different titanium-containing silicate zeolites have been prepared. Consequently, the scope has somewhat been improved, although the best epoxidation results using titanium silicates as catalysts are obtained with smaller, non-branched substrates.

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