Editing Pyridine (section)

===Hydrogenation and reduction===
[[File:Piperidin Reaktionsschema.svg|class=skin-invert-image|left|thumb|Reduction of pyridine ('''1''') to piperidine ('''2''') with [[Raney nickel]]]]

[[Piperidine]] is produced by [[hydrogenation]] of pyridine with a [[nickel]]-, [[cobalt]]-, or [[ruthenium]]-based catalyst at elevated temperatures.<ref>{{Ullmann|last1=Eller |first1=K. |last2=Henkes |first2=E. |last3=Rossbacher |first3=R. |last4=Hoke |first4=H. |title=Amines, aliphatic}}</ref> The hydrogenation of pyridine to piperidine releases 193.8&nbsp;kJ/mol,<ref name="Cox">{{cite book|last1=Cox |first1=J. D. |last2=Pilcher |first2=G. |date=1970 |title=Thermochemistry of Organic and Organometallic Compounds |publisher=Academic Press |location=New York |pages=1–636 |isbn=0-12-194350-X}}</ref> which is slightly less than the energy of the hydrogenation of [[benzene]] (205.3&nbsp;kJ/mol).<ref name="Cox"/>

Partially hydrogenated derivatives are obtained under milder conditions. For example, reduction with [[lithium aluminium hydride]] yields a mixture of 1,4-dihydropyridine, 1,2-dihydropyridine, and 2,5-dihydropyridine.<ref>{{cite journal|last1=Tanner|first1=Dennis D.|last2=Yang|first2=Chi Ming|title=On the structure and mechanism of formation of the Lansbury reagent, lithium tetrakis(''N''-dihydropyridyl) aluminate|journal=The Journal of Organic Chemistry|volume=58|pages=1840|year=1993|doi=10.1021/jo00059a041|issue=7}}</ref> Selective synthesis of 1,4-dihydropyridine is achieved in the presence of organometallic complexes of [[magnesium]] and [[zinc]],<ref>{{cite journal|last1=De Koning|first1=A.|title=Specific and selective reduction of aromatic nitrogen heterocycles with the bis-pyridine complexes of bis(1,4-dihydro-1-pyridyl)zinc and bis(1,4-dihydro-1-pyridyl)magnesium|journal=Journal of Organometallic Chemistry|volume=199|pages=153|year=1980|doi=10.1016/S0022-328X(00)83849-8|issue=2|last2=Budzelaar|first2=P. H. M.|last3=Boersma|first3=J.|last4=Van Der Kerk|first4=G. J. M.}}</ref> and (Δ3,4)-tetrahydropyridine is obtained by electrochemical reduction of pyridine.<ref>{{cite journal | last=Ferles | first=M. | title=Studies in the pyridine series. II. Ladenburg and electrolytic reductions of pyridine bases | journal=Collection of Czechoslovak Chemical Communications | publisher=Institute of Organic Chemistry & Biochemistry | volume=24 | issue=4 | year=1959 | doi=10.1135/cccc19591029 | pages=1029–1035}}</ref> [[Birch reduction]] converts pyridine to dihydropyridines.<ref>{{cite journal |doi=10.1021/ol0065930|title=Partial Reduction of Electron-Deficient Pyridines |year=2000 |last1=Donohoe |first1=Timothy J. |last2=McRiner |first2=Andrew J. |last3=Sheldrake |first3=Peter |journal=Organic Letters |volume=2 |issue=24 |pages=3861–3863 |pmid=11101438 }}</ref>