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The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multi-component organic reaction between an aldehyde such as formaldehyde, 2 equivalents of a β-keto ester such as ethyl acetoacetate and a nitrogen donor such as ammonium acetate or ammonia.
Hantzsch ester refers to an organic compound with the formula HN(MeC=C(CO 2 Et)) 2 CH 2 where Me = methyl (CH 3) and Et = ethyl (C 2 H 5). It is a light yellow solid. The compound is an example of a 1,4-dihydropyridine. It is named after Arthur Rudolf Hantzsch who described its synthesis in 1881.
Acetoacetic ester synthesis is a chemical reaction where ethyl acetoacetate is alkylated at the α-carbon to both carbonyl groups and then converted into a ketone, or more specifically an α-substituted acetone. This is very similar to malonic ester synthesis. Acetoacetic ester synthesis equation
The Hantzsch pyridine synthesis typically uses a 2:1:1 mixture of a β-keto acid (often acetoacetate), an aldehyde (often formaldehyde), and ammonia or its salt as the nitrogen donor. First, a double hydrogenated pyridine is obtained, which is then oxidized to the corresponding pyridine derivative.
At large scale, ethyl acetoacetate is industrially produced by treatment of diketene with ethanol. [2] The small scale preparation of ethyl acetoacetate is a classic laboratory procedure. [3] It involves Claisen condensation of ethyl acetate. Two moles of ethyl acetate condense to form one mole each of ethyl acetoacetate and ethanol. [4]
2,6-Lutidine has been evaluated for use as a food additive owing to its nutty aroma when present in solution at very low concentrations. Due to the steric effects of the two methyl groups, 2,6-lutidine is less nucleophilic than pyridine.
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In organic chemistry, the Mannich reaction is a three-component organic reaction that involves the amino alkylation of an acidic proton next to a carbonyl (C=O) functional group by formaldehyde (H−CHO) and a primary or secondary amine (−NH 2) or ammonia (NH 3). [1] The final product is a β-amino-carbonyl compound also known as a Mannich base.