Sodium hydrogen sulfate: Safe and efficient

Abstract

(A) Bis- and tris(1H-indol-3-yl)methanes are synthesized in high yields by an electrophilic substitution reaction of indoles with carbonyl compounds under mild reaction conditions using silica-supported NaHSO4 and Amberlyst-15. (B) Silica gel supported sodium hydrogen sulfate was found to be an efficient catalyst for the selective removal of the N-Boc protecting group from aromatic amines, keeping aliphatic N-Boc intact. (C) A combination of NaHSO4 and NaNO2 in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of secondary amines to their corresponding nitroso derivatives under mild conditions. (D) Different p-hydroxybenzyl alcohols were subjected to NaHSO4-SiO 2 and it was shown that this catalyst can transformphydroxybenzyl alcohols to the corresponding p-hydroxybenzyl ethers and thioethers efficiently and selectively. (E) Cyclic and acyclic ketones, amides, and β-keto esters were converted to their α-brominated derivatives using NaHSO 4-SiO2 in the presence of NBS and with Et2O or CCl4 as solvent at room temperature. (F) 1,2-Dihydroquinolines were subjected to oxidation effectively and in short reaction times with Na 2Cr2O7-H2O and NaHSO4 as catalyst. The reactions proceed under mild conditions and with dichloomethane as solvent. (G) The reaction of ethyl glyoxylate with different heteroaromatic compounds in the presence of sodium salts was investigated. It was shown that NaHSO4 is effective and affords Friedel-Crafts addition products in good yield under aqueous conditions. © Georg Thieme Verlag Stuttgart.