Synthesis of 2,3,4,5-tetrasubstituted pyrroles and 1,4-dihydro-tetraarylpyrazines using acidic alumina as a heterogeneous catalyst

Recent Advances for the Synthesis of N‐Unsubstituted Pyrroles

“…Another three‐component condensation reaction of benzoin 11 derivatives with 1,3‐dicarbonyl compounds 20 , and ammonium acetate 2 using acidic Al 2 O 3 was developed as an efficient procedure for the production of new 2,3,4,5‐tetrasubstituted pyrroles 21 with high yields (Scheme 6). [9] …”

“…Another three-component condensation reaction of benzoin 11 derivatives with 1,3-dicarbonyl compounds 20, and ammonium acetate 2 using acidic Al 2 O 3 was developed as an efficient procedure for the production of new 2,3,4,5-tetrasubstituted pyrroles 21 with high yields (Scheme 6). [9] Tamaddon and Tadayonfard [10] synthesized a novel MGSFe catalyst, which was subsequently applied to a broad substrate scope on 1,3-dicarbonyls 20 and benzoin derivatives 11 in the multicomponent reaction with ammonium acetate 2 to obtain highly functionalized free-NH pyrroles 21 (Scheme 7).…”

A Critical Review on Advances in the Multicomponent Synthesis of Pyrroles

“…The reaction mixture was then cooled to room temperature and the precipitate formed was filtered and washed with water in order to remove the IL 4. 83 The resulting solid were recrystallized from ethanol to obtain the pure substituted pyrrole 64 in a metal free, eco-friendly, one pot five component sequential reaction was reported by S. Ambethkar which involved the coupling of acetophenone 65, N,Ndimethylformamide-dimethylacetal 66, substituted amine 67, arylglyoxal 68 and malononitrile 69 in methanol under reflux for 1.5 h to obtained novel pyrrole cyano-acetamides 70 in high yields (Scheme14). 84 The experimental result showed that solvent and temperature played significant role in the reaction productivity.…”

Catalyst-free four-component domino synthetic approach toward versatile multicyclic spirooxindole pyran scaffolds

“…13 There are many reports on multicomponent entries in the synthesis of spirooxindole-4H-pyrans from readily available starting materials including isatin, malononitrile, and 1,3dicarbonyl compounds. This class of reaction has been carried out under different conditions as follows: in the presence of ptoluenesulfonic acid (p-TSA) in aqueous media, 14 [BMIm]BF 4 as an ionic liquid catalyst at ambient temperature, 15 piperidine under ultrasound irradiation, 16 proline-derived thiourea catalyst, 3 CuFe 2 O 4 (10 mol%) as an inexpensive, magnetically recoverable, and reusable catalyst in reuxing water, 17 SBA-Pr-NH 2 as an efficient heterogeneous nanoporous solid basic catalyst in an aqueous medium, 18 a-amylase extracted from hog pancreas, 19 silica-bonded N-propyltriethylenetetramine as a heterogeneous solid base catalyst, 20 triethylamine in ethanol, 21 silica-bonded ionic liquids as a recyclable catalyst, 22 1 mol% of (DHQD) 2 28 Although various catalysts have been applied for the synthesis of these compounds, the role of catalysts is the same in these reactions and it was to catalyze the Knoevenagel condensation, Michael addition, and cyclization reactions. Each of the procedures has its own benets with at least one drawback, such as low yield, long reaction time, harsh reaction conditions, and use of toxic and expensive catalysts or solvents; hence, there is still a requirement for simple, efficient and economical methods.…”