Nickel complexes as efficient catalysts in multicomponent synthesis of tetrahydropyridine derivatives

5‐Sulfosalicylicacid an organocatalyst for the synthesis of highly functionalized piperidines through the multicomponent reaction

“…[ 3,4 ] They have been identified as antihypertensive, [ 5 ] an antihistaminic, [ 6 ] anticancer, [ 7,8 ] antibacterial, [ 9–11 ] antidiabetic, [ 12,13 ] anti‐HIV, [ 14 ] anti‐inflammatory, [ 15 ] anti‐insecticidal, [ 16 ] and antimalarial [ 17 ] (Figure 1). There are multiple reports on one‐pot five‐component methods for the synthesis of highly derivatized piperidines using catalysts such as citric acid, [ 18 ] thiamine hydrochloride, [ 19 ] TMSI, [ 20 ] nickel complexes, [ 21 ] nano‐BF 3 /cellulose, [ 22 ] copper (II) triflate, [ 23 ] Fe 3 O 4 /SiO 2 /TiO 2 nanocomposites, [ 24 ] NO 2 ‐Fe(III)PcCl@C, [ 25 ] cyanuric chloride, [ 26 ] L‐proline nitrate, [ 27 ] 2,6‐pyridine dicarboxylic acid (2,6‐PDCA), [ 28 ] bromodimethylsulfonium bromide (BDMS), [ 29 ] tetrabutylammonium tribromide (TBATB), [ 30 ] thiourea dioxide, [ 31 ] BF 3 ·SiO 2, [ 32 ] Bi(NO 3 ) 3 ·5H 2 O, [ 33 ] LaCl 3 ·7H 2 O, [ 34 ] para ‐sulfonic acid calixarenes, [ 35 ] citric acid, [ 36 ] iodine, [ 37 ] cerium ammonium nitrate (CAN) [ 38 ] and BF 3 etherate. [ 39 ] Even though some of these protocols have shown progress in the synthesis of these heterocyclic molecules, many of them have some drawbacks, such as poor yield, extreme reaction conditions, prolonged reaction time, use of toxic organic solvents, side product generation, excessive use of catalyst etc.…”