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Notes and references
1 (a) F. Alonso, I. P. Beletskay and M. Yus, Chem. Rev., 2004,
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2 For a review on the synthesis of homopropargylic amines,
see: (a) R. Bloch, Chem. Rev., 1998, 98, 1407; (b) C.-H. Ding
and X.-L. Hou, Chem. Rev., 2011, 111, 1914. For selected
recent examples on the synthesis of homopropargylic
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Sci., 2011, 2, 807; (d) D. R. Fandrick, C. S. Johnson,
K. R. Fandrick, J. T. Reeves, J. Tan, H. Lee, J. J. Song,
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3 For some selected papers: (a) Y. Yamamoto, W. Ito and
K. Maruyama, J. Chem. Soc., Chem. Commun., 1984, 1004;
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Scheme 3 A protective group-free synthesis of piperidin-4-ol from
benzylic azide. a CH3COCl (1.2 equiv.), Et3N (2 equiv.), CH2Cl2, rt, 5 h. b
[Au(PPh3)]+NTf2 (5 mol%), MsOH (1.2 equiv.), 4 A˚ M.S., rt, 20 min;
ꢂ
catecholborane (6 equiv.), rt, 10 h.
addition to the primary alkyl azide substrates shown above,
secondary cyclohexyl azide 13 proved to be efficient substrate
even though the reaction was somewhat slower than the aliphatic
primary alkyl azides. When the reaction was performed in the
presence of 3 mol% catalyst for 24 h, the product 23 was obtained
in 72% yield (entry 9). Thus, tertiary carbinylamines can be also
accessed by this method. Finally, homopropargylic amine 24 was
afforded in 85% yield with ꢁ4 : 1 syn-stereoselectivity.13
As discussed above, the homopropargylic amines have been
used as versatile intermediates in synthetic organic chemis-
try(Scheme 3). For example, the product 24 could be used as
important precursors for the synthesis of various amino-
deoxysugars via metal-catalyzed/mediated cycloisomerization
reaction.14 In addition, the homopropargylic amines generated
via the proposed method can be merged with other metal-
catalyzed processes to access more structurally and stereo-
chemically diverse nitrogen heterocycles in a highly efficient
manner.15,16 As an example, we explored the synthesis of 2,6-
dialkyl-4-hydroxy-piperidine 26 by combining the current
protocol with the gold(I)-catalyzed in situ cycloisomerization-
reduction protocol developed by Zhang.15 While the synthesis
of acetylated homopropargylic amine precursor 25 in Zhang's
study requires the use of tert-butylsulnyl group for the
installation of the allenyl group, the current protocol can
eliminate these additional steps. Thus, the current synthesis
signicantly improved the step efficiency of this catalytic
reaction.
4 For some selected papers: (a) H. C. Brown, U. R. Khire,
G. Narla and U. S. Racherla, J. Org. Chem., 1995, 60, 544;
(b) S. S. Nikam and K. K. Wang, J. Org. Chem., 1985, 50, 2193.
5 For some selected papers: (a) M. T. Robak, M. A. Herbage and
J. A. Ellman, Chem. Rev., 2010, 110, 3600; (b) F. Chemla and
F. Ferreira, Synlett, 2006, 2613; (c) A. Voituriez, F. Ferreira,
´
A. Perez-Luna and F. Chemla, Org. Lett., 2007, 9, 4705; (d)
A. Voituirez, F. Ferreira and F. Chemla, J. Org. Chem., 2007,
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7 (a) M. Yus, J. Gonzalez-Gomez and F. Foubelo, Chem. Rev.,
2011, 111, 7774; (b) P.-O. Delaye, J.-L. Vasse and
J. Szymoniak, Org. Lett., 2012, 14, 3004; (c) M. Fujita,
T. Nagano, U. Schneider, T. Hamada, C. Ogawa and
S. Kobayashi, J. Am. Chem. Soc., 2008, 130, 2914.
8 J. H. Lee, S. Gupta, W. Jeong, Y. H. Rhee and J. Park, Angew.
Chem., Int. Ed., 2012, 51, 10851.
9 (a) Y. Do, J. Han, Y. H. Rhee and J. Park, Adv. Synth. Catal.,
2011, 353, 3363; (b) Y. Do, I.-C. Hwang, M.-J. Kim and
J. Park, J. Org. Chem., 2010, 75, 5740.
10 (a) M. Sugiura, K. Hirano and S. Kobayashi, J. Am. Chem. Soc.,
2004, 126, 7182; (b) B. Dhudshia, J. Tiburcio and
A. N. Thadani, Chem. Commun., 2005, 5551.
11 We investigated the homopropargylic amine synthesis
mediated by the condensation of benzaldehyde with
ammonia. Using liquid ammonia or aqueous ammonia
at low temperature (below rt) with allenylboronate 3a
following the protocol described in ref. 10a showed
poor conversion, generating the product 4a in ꢁ40%
yield with the recovery of benzaldehyde (>30% yield).
In summary, we have developed a new and efficient one-pot
synthesis of homopropargylic amines from various alkyl
azides. This result signicantly expands the utility of
N-unsubstituted imines in amine synthesis. Variation of alle-
nylmetal species as well as the asymmetric version of the
proposed homopropargylic amine synthesis is now under
progress in our laboratory, and the result will be reported in
due course.
Acknowledgements
This work was supported by the National Research Foundation
funded by the Korean government (NRF-2013R1A2A2A01068684
and NRF-2012-007235).
20634 | RSC Adv., 2014, 4, 20632–20635
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