Silica gel-supported polyphosphoric acid

Silica-gel supported polyphosphoric acid (PPA/Si02) has been developed as a reusable catalyst-oxathio- and dithio- acetals were synthesized by using PPA/Si02. The recovered catalyst can be reused nine successive times, after drying each time at 100 °C for 2 h under reduced pressure [60],... 

Davoodnia and coworkers set up a simple and efficient procedure for the synthesis of 14-aryl-147f-dibenzo[fl, ]xanthenes using a one-pot condensation reaction of P-naphthol and aryl aldehydes catalyzed by silica gel-supported polyphosphoric acid (PPA/SiOj) (Khojastehnezhad et al, 2011). Xanthene derivatives occupy a prominent position in medicinal chemistry (Wang et al., 1997) and have been investigated for their agricultural bactericide activity (Handique and Baruah, 2002), antiinflammatory effect (Sirkecioglu et al, 1995), and antiviral activity. 

Aoyama, T., Takido, T., Kodomari, M. 2004. Silica gel-supported polyphosphoric acid (PPA/ Si02) as an efficient and reusable catalyst for conversion of carbonyl compounds into oxathioacetals and dithioacetals. Synlett 13 2307-2310. 

Khojastehnezhad, A., Davoodnia, A., Bakavoli, M., Tavakoli-Hoseini, N., Zeinali-Dastmalbaf, M. 2011. Silica gel-supported polyphosphoric acid (RRA/SiOj) An efficient and reusable heterogeneous catalyst for facile synthesis of 14-Aryl-14//-dibenzo[a/ xanthenes under solvent-free conditions. Chinese Journal of Chemistry 29 297-303. 

A. Davoodnia, S. AUameh, S. FazH, N. TavakoH-Hoseini, One-pot synthesis of 2-amino-3-cyano-4-arylsubstituted tetrahydrobenzo[b]pyrans catalysed by silica gel-supported polyphosphoric acid (PPA-Si02) as an efficient and reusable catalyst, Chem. Pap. Slovak Acad. Sci 65 (2011) 714-720. 

The only 5//-1,3,6-triazonine system which has been reported and is fully supported by spectral data and elemental analysis is obtained by reaction of the imine 1 with chloroacetic acid and polyphosphoric acid.22 From a mixture of products, 2-chloro-6-(chloromethyl)-13-phenyl-dibenzo[e/, h [, 3,6]triazonine (2) was separated by silica-gel flash chromatography in poor yield. 

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