01685nas a2200241   4500008004100000022001400041245013600055210006900191260007700260300001400337490000700351520076700358653001201125653001201137653001401149653002801163653002101191100002201212700002501234700002301259700002901282856013201311       2013                        eng d  a2192-650600aHighly efficient povidone-phosphotungstic acid catalyst for the tandem acetalization of aldehydes to bis- and tris(indolyl)methanes0 aHighly efficient povidonephosphotungstic acid catalyst for the t  aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcNOV  a1393-13990 v783 a<p>A novel, nonleachable hybrid of heteropoly acid and polyvinylpyrrolidone (or povidone) catalyzes the acetalization of aldehydes in methanol at room temperature followed by reaction with indole to give bis(indolyl)methanes (BIMs) and tris(indolyl)methanes (TIMs) in quantitative yields (90-97%). The catalyst was shown by pyridine FTIR spectroscopy to possess BrOnsted acidity, and the hybrid formation was confirmed by XRD and (PNMR)-P-31 studies. Friedel-Crafts alkylation of indole as well as the tandem synthesis of BIMs and TIMs were established with several types of carbonyl and indole substrates to give the corresponding products quantitatively. The catalyst was recycled efficiently for three successive runs without losing its original activity.</p>10aacetals10aAcidity10aaldehydes10aheterogeneous catalysis10aheteropoly acids1 aKamble, Sumit, B.1 aSwami, Rameshwar, K.1 aSakate, Sachin, S.1 aRode, Chandrashekhar, V.  uhttps://library.ncl.res.in/content/highly-efficient-povidone-phosphotungstic-acid-catalyst-tandem-acetalization-aldehydes-bis-0