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The Boger pyridine synthesis is a
cycloaddition
In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of th ...
approach to the formation of pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...
s named after its inventor Dale L. Boger
Dale Lester Boger is an American medicinal and organic chemist and former chair of the Department of Chemistry at The Scripps Research Institute in La Jolla, CA.
Dale Boger was born on August 22, 1953, in Hutchinson, Kansas. He studied chemist ...
, who first reported it in 1981. The reaction is a form of inverse-electron demand Diels-Alder reaction in which an enamine
An enamine is an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine. Enamines are versatile intermediates.
:
The word "enamine" is derived from the affix ''en''-, used as the suffix of alkene, and th ...
reacts with a 1,2,4-triazine
Triazines are a class of nitrogen-containing heterocycles. The parent molecules' molecular formula is . They exist in three isomeric forms, 1,3,5-triazines being common.
Structure
The triazines have planar six-membered benzene-like ring but ...
to form the pyridine nucleus. The reaction is especially useful for accessing pyridines that would be difficult or impossible to access via other methods and has been used in the total synthesis
Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes ...
of several complicated natural products.
Mechanism
The enamine is generally generated ''in situ'' from catalytic amine (such as pyrrolidine) and a ketone. The enamine then reacts as the dienophile with a 1,2,4-triazine. The initial adduct then expels nitrogen, and the pyridine is rearomatized with loss of the amine.
References
Pyridine forming reactions Heterocycle forming reactions Organic reactions Name reactions {{organic-chem-stub