Tetrahydropyridines (or piperideines) are

heterocycle A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, proper ...

s with the formula . Three isomers exist, which differ by the location of the double bond. None of the parent species occur widely, so they are mainly of theoretical interest. Although the parent tetrahydropyridines are rare, many substituted tetrahydropyridines are known.

Preparation and occurrence

2,3,4,5-Tetrahydropyridine, a colorless liquid, is commercially available. It is an imine. Illustrating another isomer of tetrahydropyridine,

6-acetyl-2,3,4,5-tetrahydropyridine 6-Acetyl-2,3,4,5-tetrahydropyridine is an aroma compound and flavor that gives baked goods such as white bread, popcorn, and tortillas their typical smell, together with its structural homolog 2-acetyl-1-pyrroline. 6-Acetyl-2,3,4,5-tetrahydrop ...

occurs naturally. Partial reduction of pyridinium salts gives N-alkyltetrahydropyridines. Treatment of N-methylpyridinium with

borohydride Borohydride refers to the anion , which is also called tetrahydroborate or more commonly tetrahydrobiopterin, and its salts. Borohydride or hydroborate is also the term used for compounds containing , where ''n'' is an integer from 0 to 3, for ex ...

reagents gives 1-methyl-1,2,3,6-tetrahydropyridine. A modified Ireland-Claisen rearrangement leads to tetrahydropyridines via a silyl ketene acetal intermediate. Ring-closing olefin metathesis has also been used to establish the tetrahydropyridine ring system. {{center,

References

Imines Tetrahydropyridines