Hantzsch multicomponent condensation

In a related example involving the use of the same instrument (Fig. 12.6) in the Hantzsch multicomponent condensation, the serial synthesis of 24 dihydropyridine... 

H. Masrouri, F. Movahedi, Monatsh. Chem. 2010, 141, 317-322. ZnO-nanoparticle-promoted synthesis of poly hydroquinoline derivatives via multicomponent Hantzsch reaction, (d) F. K. Behbahani, H. S. Alaei, J. Chem. Sci. 2013,125, 623-626. L-Proline-catalysed synthesis of functionalized unsymmetrical dihydro-lH-indeno[l,2-b]pyri-dines. (e) S. K. Singh, K. N. Singh, J. Heterocycl. Chem. 2010, 47, 194—198. Glycine-catalyzed easy and efficient one-pot synthesis of polyhydroquinolines through hantzsch multicomponent condensation under controlled microwave. 

A one-pot synthetic method for pyridines on a multigram scale was achieved from a condensation between 2 moles of a jS-keto ester and 1 mole of aldehyde under MWI using bentonite clay as a support and ammonium nitrate as the source of ammonia and oxidant. However, good yields of C-4 substituted pyridines 155 could only be obtained when the aldehydes were aliphatic, but only 5% yield of 155 (R = Ph) and 75% yield of 156 were obtained when benzaldehyde was used. A number of 1,3-dicarbonyl compounds including jS-keto esters were used as building blocks for the multicomponent Hantzsch synthesis (95T6511) whereby symmetrical 155 and 157 and nonsymmetrical pyridines 158 were synthesized (Scheme 32) (98TL1117). 

Ramachary and Reddy developed one of these sequences using an amino acid-catalyzed three-component reductive alkylation (TCRA) as the first reaction of their MCC. This multicomponent reaction involved an aldehyde 21, a malonate 22, and the Hantzsch ester 24 under amino acid catalysis starting with a Knoevenagel condensation, which was followed by hydrogenation of the formed olefin 23 to form... 

Hantzsch s reaction is a multicomponent organic reaction between an aldehyde, a P-keto ester, and a nitrogen donor such as ammonium acetate or ammonia. It provides rapid access to dihydropyridine and polyhydroquinoline derivatives, which constitute an important class of calcium channel blockers. Zinc oxide nanoparticles have been used for one-pot four-component synthesis of Hantzsch s polyhydroquinolines (7) and 1,4-dihydropyridines (5) in higher yields and short reaction times by the condensation of aldehydes (1), dimedone (2), active methylene compounds (4,6), and ammonium acetate (3) under solvent-free conditions at room temperature (Kassaee et al. 2010) (Scheme 9.1). 

Keywords Aldehydes, dimedone, active methylene compounds, ammonium acetate, solvent-free, catalyst-free, room temperature, grinding, one-pot multicomponent synthesis, Hantzsch condensation, polyhydroquinolines... 

---