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6 For recent examples, see: (a) H. R. Tan, H. F. Ng, J. Chang and
J. Wang, Chem. – Eur. J., 2012, 18, 3865; (b) A. C. Razus, C. Nitu,
V. Tecuceanu and V. Cimpeanu, Eur. J. Org. Chem., 2003, 4601.
7 Y.-G. Zhang, J.-K. Xu, X.-M. Li and S.-K. Tian, Eur. J. Org. Chem.,
2013, 3648.
8 For a recent review on catalytic methods for imine synthesis, see:
(a) R. D. Patil and S. Adimurthy, Asian J. Org. Chem., 2013, 2, 726. For
select examples, see: (b) D. Ghislieri, A. P. Green, M. Pontini,
S. C. Willies, I. Rowles, A. Frank, G. Grogan and N. J. Turner, J. Am.
Chem. Soc., 2013, 135, 10863; (c) A. E. Wendlandt and S. S. Stahl, Org.
Lett., 2012, 14, 2850; (d) H. Lange, M. J. Capener, A. X. Jones,
C. J. Smith, N. Nikbin, I. R. Baxendale and S. V. Ley, Synlett, 2011, 869.
9 For other ‘‘boomerang’’ reactions, see: (a) I. V. Alabugin and B. Gold,
J. Org. Chem., 2013, 78, 7777; (b) A. Ohtaka, E. Sakaguchi, T. Yamaguchi,
G. Hamasaka, Y. Uozumi, O. Shimomura and R. Nomura, ChemCatChem,
proton NMR revealed an imine : alkene ratio of 0.7 : 1.0, which did
not change with extended reaction times. We hypothesize that the
deamination, under these reaction conditions, exists in equilibrium
and the alkene is irreversibly trapped by the peroxide, thus driving
the reaction to completion.
We have demonstrated that synthetically valuable inter-
mediates, a-dicyano- or a-cyano-a-esterepoxides, can be rapidly
and efficiently generated in a continuous manner by trapping
of ketimines and aldimines, formed upon photooxidation of
the corresponding amine by singlet oxygen, with malononitrile or
methyl cyanoacetate. The epoxidation occurs by hydrogen peroxide,
a waste product of 1O2-oxidation of amines and requires no
additional acids, bases, or oxidants. This rapid increase in
molecular complexity is not limited to activated amines and is
not sensitive to substitution in the alpha position. Further
studies in this area are currently underway.
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2013, 5, 2167; (c) H. Clavier, F. Caijo, E. Borre, D. Rix, F. Boeda, S. P. Nolan
and M. Mauduit, Eur. J. Org. Chem., 2009, 4254.
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10 F. Levesque and P. H. Seeberger, Org. Lett., 2011, 13, 5008.
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11 D. Kopetzki, F. Levesque and P. H. Seeberger, Chem. – Eur. J., 2013,
19, 5450.
12 For photoredox functionalization of nitrogen-containing com-
pounds, see: (a) L. Shi and W. Xia, Chem. Soc. Rev., 2012, 41, 7687;
(b) J. Xuan and W.-J. Xiao, Angew. Chem., Int. Ed., 2012, 51, 6828;
(c) J. W. Tucker, Y. Zhang, T. F. Jamison and C. R. J. Stephenson,
Angew. Chem., Int. Ed., 2012, 51, 4144.
Notes and references
1 For select examples, see: (a) S. Tagliapietra, G. Cravotto, 13 D. B. Ushakov, K. Gilmore, D. Kopetzki, D. T. McQuade and
E. C. Gaudino, S. Visentin and V. Mussi, Synlett, 2012, 1459; (b) G. P. H. Seeberger, Angew. Chem., Int. Ed., 2014, 53, 557.
Bentabed-Ababsa, S. Hamza-Reguig, A. Derdour, L. R. Domingo, 14 The amide presumably forms by addition of hydroxide, formed
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J. A. Saez, T. Roisnel, V. Dorcet, E. Nassare and F. Mongin, Org.
upon epoxidation with hydrogen peroxide to the a-dicyanoepoxide,
see: J. M. Harrison and T. D. Inch, Tetrahedron Lett., 1981, 22, 679.
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Biomol. Chem., 2012, 10, 8434; (c) L. R. Domingo and J. A. Saez,
J. Org. Chem., 2011, 76, 373; (d) J. Volmajer, R. Toplak, S. Bittner and 15 For the unreactive nature of diethyl malonate in comparison with
A. M. Le Marechala, ARKIVOC, 2003, 14, 49; (e) G. Bentabed-Ababsa,
A. Derdour, T. Roisnel, J. A. Saez, P. Perez, E. Chamorro,
L. R. Domingo and F. Mongin, J. Org. Chem., 2009, 74, 2120; ( f ) G.
malononitrile and ethyl cyanoacetate, see: J. S. Yadav, B. V. S. Reddy,
A. K. Basak, B. Visali, A. V. Narsaiah and K. Nagaiah, Eur. J. Org.
Chem., 2004, 546.
Bentabed, M. Rahmouni, F. Mongin, A. Derdour, J. Hamelin and 16 pKa values in DMSO according to Bordwell pKa table (http://
J. P. Bazureau, Synth. Commun., 2007, 37, 2935. For photocatalytical
C–O cleavage and subsequent [3+2]-cycloaddition with alkenes, see:
(g) J. Pan, W. Zhang, J. Zhang and S. Lu, Tetrahedron Lett., 2007,
48, 2781.
28.8, diethylmalonate 16.4, nitromethane 17.2, malononitrile 11.1,
ethylcyanoacetate 13.1.
17 For example, see: (a) S. J. Deshpande, P. R. Leger and S. R. Sieck,
Tetrahedron Lett., 2012, 53, 1772; (b) S. Fioravanti, L. Pellacani,
P. A. Tardella, A. Morreale and G. Del Signore, J. Comb. Chem.,
2006, 8, 808 and references cited therein.
2 For select examples, see: (a) M. Seifi and H. Sheibani, ARKIVOC, 2013,
ˇ
4, 191; (b) A. Majcen-Le Marechal, P. Le Grel, A. Robert, J. Biskup,
V. Ferk and R. Toplak, ARKIVOC, 2001, 5, 119; (c) F. Roger, M.-G. Le
Pironnec, M. Guerro, P. Gougeon, P. Gall, P. le Grel and M. Baudy- 18 J. H. Park, K. C. Ko, E. Kim, N. Park, J. H. Ko, D. H. Ryu, T. K. Ahn,
Floc’h, Synthesis, 1999, 1341; (d) S. Boukhris and A. Souizi, Tetrahe- J. Y. Lee and S. U. Son, Org. Lett., 2012, 14, 5502.
dron Lett., 2000, 41, 2559; (e) A. O. Amanetoullah, M. M. Chaabouni 19 For an example of oxidative Mannich reaction, see: J.-I. Matsuo,
and A. Baklouti, Synth. Commun., 1996, 26, 1155. Y. Tanaki and H. Ishibashi, Org. Lett., 2006, 8, 4371.
3 (a) A. Majcen-Le Marechal, A. Robert and I. Leban, Tetrahedron, 20 THF-peroxide can also be produced by extended irradiation of THF and
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1990, 46, 453; (b) M. Guillemet, A. Robert and M. Baudy-Floc’h,
Tetrahedron Lett., 1995, 36, 547.
4 E. Knoevenagel, Ber. Dtsch. Chem. Ges., 1898, 2596.
5 (a) A. Foucaud and M. Bakouetila, Synthesis, 1987, 854; (b) A. Robert,
S. Jaguelin and J. L. Guinamant, Tetrahedron, 1986, 42, 2275;
(c) H. Hopf and M. Kruetzer, Angew. Chem., 1990, 102, 425;
(d) J. M. Harrison and T. D. Inch, Tetrahedron Lett., 1981, 22, 679.
oxygen gas (see: N. Tada, T. Ishigami, L. Cui, K. Ban, T. Miura and A. Itoh,
Tetrahedron Lett., 2013, 54, 256). While product formation was observed
upon reaction of the classically prepared Knoevenagel product with
THF-peroxide under our conditions with the addition of Hu¨nig’s base
(no product was observed in its absence), when peroxide-free THF was
used for photooxidation, similar yields of cyanoepoxide was obtained,
suggesting THF-peroxide is not a significant factor in this reaction.
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