Seralite SRC-120 resin catalyzed synthesis of bis(indolyl)methanes using indoles and low/high boiling point carbonyl compounds under solvent free conditions

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

“…Silica gel is an intriguing solid support, since it is a low cost, commercially available and non-hazardous support, that can be employed in tandem with various traditional catalysts [70]. Some examples in literature are ZrOCl 2 •8H 2 O/SiO 2 [71], P 2 O 5 /SiO 2 [72], LiHSO 4 /SiO 2 [73], (PhCH 2 PPh 3 ) + Br − /SiO 2 [74], H 2 SO 4 /SiO 2 [75], ZnCl 2 /SiO 2 [76], heteropoly-11-tungsto-1-vanadophosphoric acid, H4[PVV W11O40] (HPV) (20%) supported on natural clay (HPVAC-20) [77], V 2 O 5 /SiO 2 [78], strongly acidic cation exchange resin (Seralite SRC-120) [79] or HCl/SiO 2 [80]. Among all the protocols mentioned above, it is worth mentioning that Hojati et al, in 2013, developed a simple, novel and efficient procedure for the synthesis of BIMs, utilizing 1,3dibromo-5,5-dimethylhydantoin (DBDMH) as the catalyst (Scheme 3).…”