Hanztsch reaction

More recently, Shen et al. reported on a green and efficient three-component one-pot synthesis of 2-aryl-pyridines with the same starting materials as the Hanztsch reaction, under solvent-, catalyst-, and heat-free conditions. This methodology does... 

Catalyst Heterogeneous, 12-tungstophosphoric acid (H3PWi204o)/Si02 (40 wt% PW/Si02> Keywords Aromatic aldehydes, 1,3-dicarbonyls, ammonium acetate, 40 wt% PW/Si02, heterogeneous catalysis, solvent-free, room temperature, 1,4-dihydropyridines, Hanztsch reaction... 

Various approaches have been used to prepare pyrroles on insoluble supports (Figure 15.1). These include the condensation of a-halo ketones or nitroalkenes with enamines (Hantzsch pyrrole synthesis) and the decarboxylative condensation of N-acyl a-amino acids with alkynes (Table 15.3). The enamines required for the Hanztsch pyrrole synthesis are obtained by treating support-bound acetoacetamides with primary aliphatic amines. Unfortunately, 3-keto amides other than acetoacetamides are not readily accessible this imposes some limitations on the range of substituents that may be incorporated into the products. Pyrroles have also been prepared by the treatment of polystyrene-bound vinylsulfones with isonitriles such as Tosmic [28] and by the reaction of resin-bound sulfonic esters of a-hydroxy ketones with enamines [29]. 

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