Kabachnik–Fields reaction
{{Short description|Chemical reaction}}
In organophosphorus chemistry, the Kabachnik–Fields reaction is a three-component organic reaction forming α-aminomethylphosphonates from an amine, a carbonyl compound, and a dialkyl phosphonate, (RO)2P(O)H (that are also called dialkylphosphites).{{cite journal|title=The Kabachnik-Fields reaction: mechanism and synthetic use|author1=Keglevich, Gyorgy |author2=Balint, Erika |journal=Molecules|year=2012|volume=17|issue=11|pages=12821–12835|doi=10.3390/molecules171112821|pmid=23117425|pmc=6268146|doi-access=free}} Aminophosphonates are synthetic targets of some importance as phosphorus analogues of α-amino acids (a bioisostere). This multicomponent reaction was independently discovered by {{ill|Martin Kabachnik|ru|Кабачник, Мартин Израилевич}}{{cite journal |last1=Kabachnik |first1=Martin I. |last2=Medved |first2=T. Ya. |year=1953 |title=New method for the synthesis of 1-aminoalkylphosphonic acids Communication 1 |trans-title= |url=https://doi.org/10.1007/BF01178856 |journal=Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science |language=English |volume=2 |issue=5 |pages=769–777|doi=10.1007/BF01178856 |url-access=subscription }}{{Cite journal |last1=Medved |first1=T. Ya. |last2=Kabachnik |first2=Martin I. |year=1954 |title=New method for the synthesis of amino-phosphonic acids. Communication 2. Reaction of ketones with dialkyl phosphites and ammonia |url=https://doi.org/10.1007/BF01177621 |journal=Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science |volume=3 |issue=2 |pages=255–261|doi=10.1007/BF01177621 |url-access=subscription }} and Ellis K. Fields{{cite journal| last=Fields | first=Ellis K. | year=1952 | title=The synthesis of esters of substituted amino phosphonic acids | journal=Journal of the American Chemical Society | volume=74 | issue=6 | pages=1528–1531 | doi=10.1021/ja01126a054}} in 1952. The reaction is very similar to the two-component Pudovik reaction, which involves condensation of the phosphite and a preformed imine.
The first step in this reaction is the formation of an imine, followed by a hydrophosphonylation step where the phosphonate P–H bond across the C=N double bond.{{cite journal| last=Zefirov | first=Nikolay S. |author2=Elena D. Matveeva | date=2008-01-18 | title=Catalytic Kabachnik-Fields reaction: New horizons for old reaction | journal=Arkivoc | volume=2008 | issue=i | pages=1–17 | url=http://www.arkat-usa.org/get-file/22930/?wikipedia-format=.pdf | accessdate=2009-12-08 | doi=10.3998/ark.5550190.0009.101| doi-access=free}} The starting carbonyl component is usually an aldehyde and sometimes a ketone. The reaction can be accelerated with a combination of dehydrating reagent and Lewis acid.
Enantioselective variants of the Kabachnik–Fields reaction have been developed, for example employing α-methylbenzylamine provides a chiral, non-racemic α-aminophosphonate.{{cite journal|author1=Gilmore, F. |author2=McBride, A. |journal=J. Am. Chem. Soc.|year=1972|volume=94|pages= 4361|doi=10.1021/ja00767a065|pmid=5036657|title=Synthesis of an optically active -aminophosphonic acid|issue=12}}
