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7
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37449027605
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See for example:
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-
-
-
13
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37449018651
-
-
note
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The direct addition of an amine to an olefin is clearly the most economical and environmentally friendly access to substituted amines. Indeed, though substituted amines can be prepared industrially from alcohols, the alcohols themselves are typically obtained from the corresponding alkenes, hence adding one more step to the process. Moreover, the classic synthesis of amines by nucleophilic substitution generates large quantities of salts, which have to be disposed of in a suitable and ecologically benign manner.
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-
-
-
14
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0000324064
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These conditions are required, for example, for the addition of ammonia onto ethylene, catalysed by alkali metals:
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These conditions are required, for example, for the addition of ammonia onto ethylene, catalysed by alkali metals:. Howk B.W., Little E.L., Scott S.L., and Whitman G.M. J. Am. Chem. Soc. 76 (1954) 1899
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(1954)
J. Am. Chem. Soc.
, vol.76
, pp. 1899
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-
Howk, B.W.1
Little, E.L.2
Scott, S.L.3
Whitman, G.M.4
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15
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37449003889
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In these cases, release of internal strain energy or enhanced stabilising of the generated carbanion is responsible for the ease of amine addition. See for example:
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-
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22
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37449014207
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For example, the addition of ammonia to propene to form propylamine requires temperatures around 250 °C and pressures in the range of 800-1000 bars (yield: 29%).
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-
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25
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84987255164
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-
-1. Data obtained from:
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-1. Data obtained from:. Steinborn D., and Taube R. Z. Chem. 26 (1986) 349
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(1986)
Z. Chem.
, vol.26
, pp. 349
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Steinborn, D.1
Taube, R.2
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26
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37449003119
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For general references on hydroamination, see:
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31
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37449030764
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For alkali and alkaline earth metal-catalysed hydroamination of non-activated alkenes, see:
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34
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37449010434
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See Ref. 6c;
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36
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37449029218
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See Ref. 7b;
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41
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25844465776
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Khedkar V., Tillack A., Benisch C., Melder J.-P., and Beller M. J. Mol. Catal. A 241 (2005) 175
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(2005)
J. Mol. Catal. A
, vol.241
, pp. 175
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-
Khedkar, V.1
Tillack, A.2
Benisch, C.3
Melder, J.-P.4
Beller, M.5
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46
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37449001555
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For selected references on lanthanides and actinides-catalysed hydroaminations, see:
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57
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33645033199
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Riegert D., Collin J., Meddour A., Schultz E., and Trifonov A. J. Org. Chem. 71 (2006) 2514
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(2006)
J. Org. Chem.
, vol.71
, pp. 2514
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-
Riegert, D.1
Collin, J.2
Meddour, A.3
Schultz, E.4
Trifonov, A.5
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59
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37449030404
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note
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For example, most of the lanthanide-based catalysts can only be prepared using a glove-box or special Schlenck techniques. They are also exquisitely sensitive towards the slightest trace of oxygen and lose most of their activity in nucleophilic solvents.
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60
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37449027212
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note
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It is quite clear that intramolecular hydroamination reactions proceeded with a lower activation energy than their intermolecular counterparts. However, the ω-amino-alkene substrates cannot be considered as activated olefins, as described in Ref. 6.
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-
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62
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37449019766
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note
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Amine 8 has been specifically selected for this purpose, since it is a substrate that gives only poor yields of the corresponding pyrrolidine under the previously described conditions.
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-
-
-
63
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37449033191
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-
note
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This proton abstraction could be an inter- or an intramolecular process. Since it occurs at about the same rate, regardless of the ring size of putative intramolecular transition states, we favour the intermolecular pathway, taking place through the mixed amine-lithiated amide dimer.
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65
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37449011311
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See also: .
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-
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66
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0001043787
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For a splendid article discussing the various mechanistic possibilities involved in the hydroamination ring closing step, see:
-
For a splendid article discussing the various mechanistic possibilities involved in the hydroamination ring closing step, see:. Gagné M.R., Stern C.L., and Marks T.J. J. Am. Chem. Soc. 114 (1992) 275
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(1992)
J. Am. Chem. Soc.
, vol.114
, pp. 275
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-
Gagné, M.R.1
Stern, C.L.2
Marks, T.J.3
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70
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37449026838
-
-
note
-
The role played by the lithium cation is of paramount importance. By coordinating to the alkene π-system, it withdraws electron density from the olefin, hence facilitating the addition of the amine. Moreover, its coordination to the amine acidifies the hydrogen atoms attached on the nitrogen, easing the transfer of one of them to the developing carbanion. Finally, partial donation of the electron density gathered by lithium from the amine nitrogen and the C-C double bond to the amide nitrogen, increases its nucleophilicity, speeding up its addition on the alkene.
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-
-
-
71
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34250883890
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This is clearly evidenced by the various aggregation forms of lithiated amides in solvents of different polarity or coordinating abilities. For an excellent review, see: and references cited therein
-
This is clearly evidenced by the various aggregation forms of lithiated amides in solvents of different polarity or coordinating abilities. For an excellent review, see:. Collum D.B., McNeil A.J., and Ramirez A. Angew. Chem., Int. Ed. 46 (2007) 3002 and references cited therein
-
(2007)
Angew. Chem., Int. Ed.
, vol.46
, pp. 3002
-
-
Collum, D.B.1
McNeil, A.J.2
Ramirez, A.3
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72
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37449006616
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-
note
-
Since it is sold as a 1.6 M solution, using 16 mol % of n-BuLi is particularly convenient. However, in many cases, we have observed that lower amounts of n-BuLi are enough to bring the hydroamination to full conversion. For example, the double cyclisation of 40 to 42 and 43 proceeded in identical yields and diastereomeric ratios if 16, 10 or 5 mol % n-BuLi were employed.
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