Niobium pentachloride catalyst

The acylation of aromatic ethers by acyl chlorides is highly regioselective in the presence of 10 mol% Sml3.53 Some aromatic compounds are efficiently acylated by acid anhydrides catalysed by niobium pentachloride with silver perchlorate.54 Arenes of a range of reactivity are acylated by acetic anhydride in a fluorous biphasic system catalysed by Hfps SCLCgFn L (1 mol%)55 The catalyst is easily recoverable and can usually be used again without decrease in activity. 

Arai, S., Sudo, Y., and Nishida, A. 2005. Niobium pentachloride-silver perchlorate as an efficient catalyst in the Friedel-Crafts acylation and Sakurai-Hosomi reaction of acetals. Tetrahedron 61 4639 4642. 

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