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'''Hydroamination''' is the addition of an N-H bond of an amine across the C=C or C≡C bonds of an [[alkene]] or [[alkyne]]. This process is a highly [[atom economy|atom economical]] method of preparing substituted amines, which are attractive targets for organic synthesis and the pharmaceutical industry.<ref name="jain">Jain, A. [http://pharmaxchange.info/press/2012/08/hydroamination-direct-addition-of-amines-to-alkenes-and-alkynes/ Hydroamination- Direct Addition of Amines to Alkenes and Alkynes]</ref><ref>{{cite journal | author = Kai C. Hultzsch | title =Catalytic asymmetric hydroamination of non-activated olefins | format = Review | journal = [[Organic & Biomolecular Chemistry]] | year = 2005 | volume = 3 | pages = 1819–1824 | doi = 10.1039/b418521h | pmid = 15889160 | issue = 10}}</ref><ref>{{cite journal | author = Hartwig, J. F. | url = http://www.iupac.org/publications/pac/2004/pdf/7603x0507.pdf | title = Development of catalysts for the hydroamination of olefins | journal = [[Pure Appl. Chem.]] | year = 2004 | volume = 76 | pages = 507–516 | doi = 10.1351/pac200476030507 | issue = 3}}</ref><ref>{{cite journal | author = Shi, Y. H.; Hall, C.; Ciszewski, J. T.; Cao, C. S.; Odom, A. L. | title = Titanium dipyrrolylmethane derivatives: rapid intermolecular alkyne hydroamination | journal = [[Chemical Communications]] | year = 2003 | volume = 5 | pages = 586–587 | doi =10.1039/b212423h | issue = 5}}</ref><ref>{{cite journal | author = Pohlki, F., Doye, S. | title = The catalytic hydroamination of alkynes | journal = Chemical Society Reviews | volume = 32 | pages = 104–114 | doi = 10.1039/b200386b | year = 2003 | pmid = 12683107 | issue = 2}}</ref><ref>{{cite journal | author = Odom, A. L. | title = New C–N and C–C bond forming reactions catalyzed by titanium complexes | journal = [[Dalton Trans.]] | year = 2005 | volume = 2 | pages = 225–233 | doi = 10.1039/b415701j | pmid = 15616708 | issue = 2}}</ref>
'''Hydroamination''' is the addition of an N-H bond of an amine across the C=C or C≡C bonds of an [[alkene]] or [[alkyne]]. This process is a highly [[atom economy|atom economical]] method of preparing substituted amines, which are attractive targets for organic synthesis and the pharmaceutical industry.<ref name="jain">Jain, A. [http://pharmaxchange.info/press/2012/08/hydroamination-direct-addition-of-amines-to-alkenes-and-alkynes/ Hydroamination- Direct Addition of Amines to Alkenes and Alkynes]</ref><ref>{{cite journal | author = Kai C. Hultzsch | title =Catalytic asymmetric hydroamination of non-activated olefins | type = Review | journal = [[Organic & Biomolecular Chemistry]] | year = 2005 | volume = 3 | pages = 1819–1824 | doi = 10.1039/b418521h | pmid = 15889160 | issue = 10}}</ref><ref>{{cite journal | author = Hartwig, J. F. | url = http://www.iupac.org/publications/pac/2004/pdf/7603x0507.pdf | title = Development of catalysts for the hydroamination of olefins | journal = [[Pure Appl. Chem.]] | year = 2004 | volume = 76 | pages = 507–516 | doi = 10.1351/pac200476030507 | issue = 3}}</ref><ref>{{cite journal | author = Shi, Y. H.; Hall, C.; Ciszewski, J. T.; Cao, C. S.; Odom, A. L. | title = Titanium dipyrrolylmethane derivatives: rapid intermolecular alkyne hydroamination | journal = [[Chemical Communications]] | year = 2003 | volume = 5 | pages = 586–587 | doi =10.1039/b212423h | issue = 5}}</ref><ref>{{cite journal | author = Pohlki, F., Doye, S. | title = The catalytic hydroamination of alkynes | journal = Chemical Society Reviews | volume = 32 | pages = 104–114 | doi = 10.1039/b200386b | year = 2003 | pmid = 12683107 | issue = 2}}</ref><ref>{{cite journal | author = Odom, A. L. | title = New C–N and C–C bond forming reactions catalyzed by titanium complexes | journal = [[Dalton Trans.]] | year = 2005 | volume = 2 | pages = 225–233 | doi = 10.1039/b415701j | pmid = 15616708 | issue = 2}}</ref>


[[Image:Hydroamination-2.svg|center|400px]]
[[Image:Hydroamination-2.svg|center|400px]]

Revision as of 12:49, 11 September 2013

Hydroamination is the addition of an N-H bond of an amine across the C=C or C≡C bonds of an alkene or alkyne. This process is a highly atom economical method of preparing substituted amines, which are attractive targets for organic synthesis and the pharmaceutical industry.[1][2][3][4][5][6]

The hydroamination reaction is approximately thermodynamically neutral; there is a high activation barrier due to the repulsion of the electron-rich substrate and the amine nucleophile. The reaction also has a highly negative entropy, making it unfavorable at high temperatures. Consequenly, catalysts are necessary for this reaction to proceed.[1][7][8]

The development of a catalysts for hydroamination remains an active area, especially for alkenes. Progress has been reported on the hydroamination of alkynes and alkenes using lanthanides and late transition metals. Although there have been many reports of the catalytic hydroamination reaction with group IV metals, there are far fewer describing enantioselective catalysis.

Base catalyzed hydroamination

Strong bases catalyze hydroamination, an example being the ethylation of piperidine using ethylene:[9]

Hydroamination of ethylene with piperidine proceeds with no transition metal catalyst, but requires a strong base.

Such base catalyzed reactions proceed well with ethylene but higher alkenes are less reactive.

Hydroamination catalyzed by group (IV) complexes

Titanium and zirconium complexes catalyze inter-molecular hydroamination of alkynes and allenes.[1] Both stoichiometric and catalytic variants were initially examined with zirconocene bis(amido) complexes. Titanocene amido and sulfonamido complexes catalyze the intra-molecular hydroamination of aminoalkenes via a [2+2] cycloaddition that forms the corresponding azametallacyclobutane, as illustrated in Figure 1. Subsequent protonolysis by incoming substrate gives the α-vinyl-pyrrolidine (1) or tetrahydropyridine (2) product. There is substantial experimental and theoretical evidence for the proposed imido intermediate and mechanism with neutral group IV catalysts.

Figure 1. The catalytic hydroamination of aminoallenes to form chiral α-vinyl-pyrrolidine (1) and tetrahydropyridine (2) products. L2 = Cp2 or bis(amide).

References

  1. ^ a b c Jain, A. Hydroamination- Direct Addition of Amines to Alkenes and Alkynes
  2. ^ Kai C. Hultzsch (2005). "Catalytic asymmetric hydroamination of non-activated olefins". Organic & Biomolecular Chemistry (Review). 3 (10): 1819–1824. doi:10.1039/b418521h. PMID 15889160.
  3. ^ Hartwig, J. F. (2004). "Development of catalysts for the hydroamination of olefins" (PDF). Pure Appl. Chem. 76 (3): 507–516. doi:10.1351/pac200476030507.
  4. ^ Shi, Y. H.; Hall, C.; Ciszewski, J. T.; Cao, C. S.; Odom, A. L. (2003). "Titanium dipyrrolylmethane derivatives: rapid intermolecular alkyne hydroamination". Chemical Communications. 5 (5): 586–587. doi:10.1039/b212423h.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Pohlki, F., Doye, S. (2003). "The catalytic hydroamination of alkynes". Chemical Society Reviews. 32 (2): 104–114. doi:10.1039/b200386b. PMID 12683107.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ Odom, A. L. (2005). "New C–N and C–C bond forming reactions catalyzed by titanium complexes". Dalton Trans. 2 (2): 225–233. doi:10.1039/b415701j. PMID 15616708.
  7. ^ Müller, T. E. Beller, M. (1998). "Metal-Initiated Amination of Alkenes and Alkynes". Chemical Reviews. 98 (2): 675–704. doi:10.1021/cr960433d. PMID 11848912.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ M. Beller, J. Seayad, A. Tillack and H. Jiao (2004). "Catalytic Markovnikov and anti-Markovnikov Functionalization of Alkenes and Alkynes: Recent Developments and Trends". Angewandte Chemie, International Edition. 43 (26): 3368–3398. doi:10.1002/anie.200300616. PMID 15221826.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ J. Wollensak and R. D. Closson (1973). "N-Methylpiperidine". Organic Syntheses. 43: 45; Collected Volumes, vol. 5, p. 575.
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