Tetrahydropyridine

Tetrahydropyridines (or piperideines) are heterocycles with the formula C₅H₉N. 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.

Tetrahydropyridine

Three isomers of tetrahydropyridine
Identifiers
CAS Number	2,3,4,5: 505-18-0 1,2,3,4: 37497-65-7 1,2,3,6: 694-05-3
3D model (JSmol)	2,3,4,5: Interactive image 1,2,3,4: Interactive image 1,2,3,6: Interactive image
ChEBI	CHEBI:26145 2,3,4,5: CHEBI:47858 1,2,3,4: CHEBI:47859 1,2,3,6: CHEBI:47860
ChemSpider	2,3,4,5: 61469 1,2,3,4: 8351589 1,2,3,6: 12226
EC Number	1,2,3,6: 211-766-2
KEGG	2,3,4,5: C06181
PubChem CID	2,3,4,5: 68161 1,2,3,4: 10176084 1,2,3,6: 12750
UNII	1,2,3,6: 26RLS9D255
UN number	2410
CompTox Dashboard (EPA)	2,3,4,5: DTXSID20198514 1,2,3,4: DTXSID40436364 1,2,3,6: DTXSID0075289
InChI 2,3,4,5: InChI=1S/C5H9N/c1-2-4-6-5-3-1/h4H,1-3,5H2 Key: DWKUKQRKVCMOLP-UHFFFAOYSA-N 1,2,3,4: InChI=1S/C5H9N/c1-2-4-6-5-3-1/h2,4,6H,1,3,5H2 Key: VSWICNJIUPRZIK-UHFFFAOYSA-N 1,2,3,6: InChI=1S/C5H9N/c1-2-4-6-5-3-1/h1-2,6H,3-5H2 Key: FTAHXMZRJCZXDL-UHFFFAOYSA-N
SMILES 2,3,4,5: C1CCN=CC1 1,2,3,4: C1CC=CNC1 1,2,3,6: C1CNCC=C1
Properties
Chemical formula	C5H9N
Molar mass	83.134 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation and occurrence

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine causes permanent symptoms of Parkinson's disease.

(–)-Mitragynine is a naturally occurring tetrahydropyridine.

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 occurs naturally.

Partial reduction of pyridinium salts gives N-alkyltetrahydropyridines. Treatment of N-methylpyridinium with borohydride reagents gives 1-methyl-1,2,3,6-tetrahydropyridine.^[1][2]

A modified Ireland-Claisen rearrangement leads to tetrahydropyridines via a silyl ketene acetal intermediate.^[3]

Ring-closing olefin metathesis has also been used to establish the tetrahydropyridine ring system.^[4]