N-N bond formation in Ugi processes: from nitric acid to libraries of nitramines

Article abstract of DOI:10.1039/c6cc10288c

The Ugi reaction has drawn considerable attention over the years leading to numerous libraries of heterocycles and various extensions changing the nature of the components of the coupling. We report here the use of nitric acid as carboxylic acids surrogates, displaying the first aminative Ugi-type reaction leading to nitramines.

Full text of DOI:10.1039/c6cc10288c

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Re
N-N bond formation in Ugi Processes: from nitric acid to
libraries of Nitramines
Valentina Mercalli,a,d Aude Nyadanu,a,c Marie Cordier,b Gian Cesare Tron,d* Laurence Grimaud,c* and
Aucune source spécifiée dans le
document actif.ceived 00th
January 20xx,
Laurent El Kaim.a*
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
forming tetrazoles in an electrocyclization process,6 electron-
The Ugi reaction has drawn considerable attention over the years
leading to numerous libraries of heterocycles and various
extensions changing the nature of the components of the
coupling. We wish to report here the use of nitric acid as
carboxylic acids surrogates, it displays the first aminative Ugi-type
reaction leading to nitramines.
poor phenols with a final Smiles rearrangement,7 squaric acid8
and hydroxy-tropolone9 which behave similarly.
Thiocarboxylic acids in Ugi reaction (Domling et al.[4]
)
R3
H
N
O
R2NH2
+
R3NC
+
R1CHO
NH
R1
R3
Mumm-type
rearrangement
R2
R4
R4
SH
R1
R2
O
N
O
S
R4
R1
The success encountered by the use of the Passerini and Ugi
reactions for the preparation of libraries of bioactive
compounds has led to a renewal of isocyanide chemistry in the
last two decades.1 The potential of the Ugi reactions, in
particular, has been widely explored through extensive
modifications of the initial partners of the coupling. For most
of these studies, the functional tolerance of the coupling
allowed addition of further reactive centers prone to cyclise
after an initial Ugi reaction (the so called Ugi post-
condensations).2 Extensions associated with modifications of
the Ugi reaction mechanism are less documented due to a
complex reaction cascade with each partner acting at the
different stages of the mechanism. This is particularly the case
of the acidic component which participates in the initial
electrophilic activation of the imine but also plays a key role in
the final formation of the Ugi adduct.3 Thus the replacement
of the carboxylic acid has only been proposed with a reduced
number of acids: thiocarboxylic acids still involving a Mumm
rearrangement,4 isocyanic and isothiocyanic acids leading to
hydantoin derivatives5 via a final cyclization, hydrazoic acid
R4
S
N
S-
N
R3
HN
R2
O
Ugi-Smiles couplings (El Kaïm, Grimaud et al.[5]
)
H
N
R3
R3
R2NH2
+
R3NC
+
R1
HN
Smiles
rearrangement
R2
N
Ar OH
R1
R1
O
ArO
ArO
N
N
R3
Ar
R2
HN
R2
R1CHO
Nitro-Ugi reaction (this work)
H
R3
R3
R2NH2
+
R1
N
HN
Nitrate-
Nitramine shift
R2
N
O2N OH
R1
R2
R1
R2
O
R3NC
+
O2NO
NO3
N
N
HN
O2N
R3
R1CHO
Scheme 1. Acidic surrogates in Ugi reactions.
a.Laboratoire de Synthèse Organique, CNRS, Ecole Polytechnique, ENSTA ParisTech-
UMR 7652, Université Paris-Saclay, 828 Bd des Maréchaux, 91128 Palaiseau.
France. laurent.elkaim@ensta-paristech.fr
In most of these extensions, the initial amine partner is
involved in a final N-C bond formation as observed in the N-
acylation step of the Mumm rearrangement or the N-arylation
of the Smiles rearrangement. Herein, we wish to report the
use of nitric acid leading to the first N-N bond formation with
the amine partner of the Ugi reaction (Scheme 1).
b.Laboratoire de Chimie Moléculaire, UMR 9168, Department of Chemistry, Ecole
Polytechnique, CNRS, 91128, Palaiseau Cedex, France
c. Ecole normale supérieure, PSL Research University, UPMC Univ Paris 06, CNRS,
Département de Chimie, PASTEUR, 24, rue Lhomond, 75005 Paris, France. 2.
Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, PASTEUR, 75005 Paris,
France. Laurence.grimaud@ens.fr
d.Dipartimento di Scienze del Farmaco, Università degli Studi del Piemonte
Orientale“A. Avogadro”, largo Donegani 2, 28100 Novara, Italy.
giancesare.tron@uniupo.it
Strong mineral acids are known to trigger both Ugi and
Passerini reactions but these acidic components have led to
very few useful synthetic applications. Indeed, the strong
activation of the carbonyl component is counterbalanced by
the instability of the isocyanide in the presence of strong acids
Electronic Supplementary Information (ESI) available: Details of experimental
procedures, 1H NMR and 13C NMR spectra for all unknown compounds.
See DOI: 10.1039/x0xx00000x
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together with the weak nucleophilicity of the associated were obtained with ammonium nitrate 5a13,14 which gave
counter-anion. The latter point lead to important competitions nitramine 3a in 69% isolated yields (Scheme 3). An even better
in the attack of the intermediate nitrilium by the stabilized 89% isolated yield was obtained when the same reaction was
anion, the solvent, water or even the intermediate amines in conducted in MeOH. The structure of 3a was further
the case of Ugi reactions.10 Thus strong mineral acids (HCl, confirmed through nitration of the amine 2a under standard
H2SO4, HNO3 or H3PO4) have been reported in the Passerini conditions (nitric acid, acetic anhydride).15
reaction but require a large excess of the carbonyl derivative
to form hydroxyamide derivatives in good yields.11 Whereas
their stoichiometric use in the Ugi reaction is not hampered by
the high acidity of the medium, the few available reports are
mostly limited to secondary amines12 or present important
competition with the Passerini reaction.10 These difficulties
together with the high synthetic potential of these acids
towards undisclosed N-S, N-P or N-N Ugi adducts was
challenging enough to re-evaluate some of these reactions.
Nitric acid with its single hydroxy group appeared as the best
candidate for this study.
When equimolar amounts of para-chlorobenzyl amine,
cyclohexyl isocyanide, isovaleraldehyde and nitric acid used as
a 70% aqueous solution were mixed in methanol (0.3 M), we
observed the formation of a white precipitate. After two
Scheme 3. Optimization using ammonium salts .
hours, the precipitate could be either separated by filtration
With this set of optimized conditions in hands, the scope of
and washing with diethyl ether to afford the ammonium
this new nitramine synthesis was further examined (Scheme
nitrate 1a obtained in 90% isolated yield or the mixture could
4).16
be directly treated by a sodium hydrogencarbonate solution to
R2NH3.NO3
O
NO2
N
O
afford after extraction with diethyl ether the amine 2a with
the same yield (Scheme 2). Working in dichloromethane or
acetonitrile instead of MeOH afforded 2a in comparable yields.
Other starting Ugi components afforded similar results when
the reaction was performed in CH2Cl2 with 70% nitric acid, 2b
and 2c were obtained after basic treatment without observing
any precipitation in the medium in these cases (Scheme 2).
Working in DMF was more rewarding as besides 2a obtained in
75% yield, the expected nitramine 3a could be isolated as a
side product in a poor 13% yield. Adding magnesium sulfate to
pre-formed
MeOH (1M)
rt
R3
R2
+
N
R1
H
H
R1
3b-r
R3NC
Cl
O
NO2
N
O
NO2
N
O
NO2
N
Cy
Cy
Cy
N
N
N
NH
H
H
H
3b
93%
3c
71%
Ph
3d
Ph
43% Ph
Cl
Cl
O
NO2
N
O
NO2
O
NO2
O
NO2
N
Cy
Cy
N
Cy
N
Cy
N
H
N
N
H
Cy
n-C6H13
N
H
H
3g
3f
3h
27%
the mixture just gave
concentrated nitric acid (90%) allowed us to reach 20%
(Scheme 2).
a
small increase and
a
more
3e
69%
49%
21%
Cl
Cl
OMe
Cl
Cl
Cl
O
NO2
N
Cl
O
NO2
N
O
NO2
Cy
.
Cy
N
N
n-Pent
N
H
N
H
H
3i
3j
i-Bu
3k
O
42%
32%
S
82%
O
NO2
O
NO2
n-Pent
N
N
H
Cy
n-Pent
N
N
H
3m
49%
3l
40%
3l
S
Cl
Cl
Cl
O
NO2
N
O
NO2
N
O
NO2
EtO
N
N
H
N
N
H
H
3o
34%
3p
86%
3n
O
i-Bu
i-Bu
MeO
78%
Ph
MeO
MeO
MeO
MeO
Cl
O
NO2
N
O
NO2
N
N
N
H
H
3q
3r
52%
i-Bu
i-Bu
Scheme 2. Ugi-type reaction with nitric acid in various solvents.
84%
Scheme 4. Scope of the nitramine synthesis.
We next started to evaluate the use of nitrate salts together
with various ammonium salts as starting amine to optimize
conditions with a lower amount of water in the solvent.
Whereas sodium nitrate together with ammonium chloride 4a
gave allowed to improve the yields in DMF, the best results
The reaction turned out to be efficient with both aliphatic (3a-
d) and aromatic aldehydes (3e-j The range of isocyanides
).
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successfully involved in this coupling is rather wide. Indeed, alkyl use as energetic materials and explosives21 but also display
(3a-m, 3q-r), benzyl (3n), aryl (3o) or isocyanoacetate (3p) some interesting applications as synthetic intermediates.22
derivatives gave the desired products in moderate to good yields. They can be easily reduced to hydrazine and nitrosamine
Surprisingly, no desired product could be isolated from the reaction derivatives.23 Their biological activities have been mostly
of the tert-butylisocyanide probably to its particular acidic exploited in the agrochemical field with some promising
sensitivity. The isolation and X-Ray analyses of compound 3l further herbicide and fungicide activities.24
confirmed the structure of the products formed in this new nitric
acid-promoted Ugi reaction.17 Concerning the amine partner in this
To conclude, we have re-examined the use of strong
coupling, the reaction proceeded smoothly with aliphatic (3e, 3m), mineral acids in isocyanide-based multicomponent reactions.
allylic (3c, 3r) and benzylic (3a-b, 3n-q) amines. However, no The use of nitric acid was just reported once before as catalyst
reaction was observed when using aniline, probably because of its in Passerini reactions with water as final nucleophilic trapping
lower nucleophilicity. Secondary amine such as pyrrolidine fail to agents. The use of stoichiometric amount of acid in the
afford the expected Ugi nitramide probably because of an absence of water insures an efficient trapping of the
unfavorable [1,3]-shift of the nitro group, the ketoamide 6 could be intermediate nitrilium by the moderately nucleophilic nitrate
just isolated in low yield (Scheme 5). Similarly, no distal nitration anion followed by an intramolecular nitration. The extension
could be observed with piperazine in contrast to the Ugi reaction of this approach to other families of strong acid (phosphonic
with carboxylic acids (Scheme 5). 18
and sulfonic acids) is under study in our research group as well
as the potential applications of the newly obtained Ugi
nitramines.
Notes and references
1
(a) J. Zhu, H. Bienaymé, (2005) Multicomponent reactions;
Wiley-VCH, Weinheim; (b) A. Dömling, I. Ugi, Angew. Chem.
Int. Ed. 2000, 39, 3168-3210; (c) H. Bienaymé, C. Hulme, G.
Oddon, P. Schmitt, Chem. Eur. J. 2000,
6
, 3321-3329; (d) A.
, 306-313; (e) I. Ugi,
, 53-66; (f) R. V. A.
Dömling, Curr. Opin. Chem. Bio. 2002,
B. Werner, A. Dömling, Molecules 2003,
6
8
Orru, M. de Greef, Synthesis 2003, 1471-1499; (g) C. Hulme,
V. Gore, Curr. Med. Chem. 2003, 10, 51-80; (h) A. Dömling,
Chem. Rev. 2006, 106, 17-89; (i) A. Dömling, K. Wang, W.
Wang, Chem. Rev. 2012, 112, 3083-3135; (j) Multicomponent
Reactions in Organic Synthesis, J. Zhu, Q. Wang, M.-X. Wang,
Eds., Wiley-VCH:Weinheim, Germany, 2014; (k) V. P.
Boyarskiy, N. A. Bokach, K. V. Luzyanin, V. Y. Kukushkin,
Chem. Rev., 2015, 115, 2698-2779; (l) A. Varadi, T. C. Palmer,
R. N. Dardashti, S. Majumdar, Molecules, 2016, 21, 19; (m)
M. Giustiniano, A. Basso, V. Mercalli, A. Massarotti, E.
Novellino, G. C. Tron, J. Zhu, Chem. Soc. Rev., 2016, ASAP,
DOI: 10.1039/C6CS00444J.
L. Banfi, A. Basso, R. Riva “Synthesis of heterocycles through
classical Ugi and Passerini reactions” in Topics in Heterocyclic
Chemistry, 2010, Spinger-Verlag: Berlin/Heidelberg, vol 23, p
1-40.
L. El Kaim, L. Grimaud, "Ugi and Passerini Reactions with
Carboxylic Acid Surrogates" In "Isocyanide Chemistry:
Application in Synthesis and Material Science" V. G.
Nenajdenko, Ed., Wiley-VCH Verlag GmbH, Weinheim,
Germany, 2012.
Scheme 5. Failed attempts with pyrrolidine and piperazine .
By analogy with the mechanism of the classical Ugi reaction,19 we
can propose a plausible pathway involving the intermolecular
trapping of the nitrilium by the nitrate anion. The resulting
nitroimidate could further evolve through a [1,4]-shift of the nitro
according to a Mumm-type transfer, to give the corresponding
nitramine as depicted in Scheme 6.20
2
3
4
(a) S. Heck, A
Kazmaier, S. Ackermann, Org. Biomol. Chem., 2005,
.
Dömling, Synlett, 2000, 424-426; (b) U.
, 3184-
3
3187; (c) J. Kolb, B. Beck, A. Dömling, Tetrahedron Lett.,
2002, 43, 6897-6901; (d) B. Henkel, B. Westner, A. Dömling,
Synlett, 2003, 2410-2412; (e) J. Kolb, B. Beck, M. Almstetter,
S. Heck, E. Herdtweck, A. Dömling, Mol. Div., 2003, 6, 297-
313; (f) M. Umkehrer, J. Kolb, C. Burdack, W. Hiller, Synlett,
2005, 79-82; (g) A.V. Gulevich, E.S. Balenkova, V.G.
Nenajdenko, J. Org. Chem., 2007, 72, 7878-7885.
(a) I. Ugi, F.K. Rosendhal, F. Bodesheim, Justus Liebigs Ann.
Chem., 1963, 666, 54-61; (b) I. Ugi, K. Offerman, Chem. Ber.,
1964, 97, 2276-2281; (c) A. I. Polyakov, L. A. Medvedeva, O.
A. Dyachenko, A. B. Zolotoi, L. O. Atovmyan, Khim.
Scheme 6. Plausible mechanism for the nitramine formation.
5
Nitramines are usually prepared through nitration of their
related amine derivatives.15 They are mostly known for their
Geterotsikl. Soedin., 1986, 1, 53-61; (d) K. M. Short, B. W.
Ching, A. M. M. Mjalli, Tetrahedron Lett., 1996, 37, 7489-
This journal is © The Royal Society of Chemistry 20xx
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7492; (e) R. Bossio, S. Marcaccini, R. Pepino, Liebigs Ann. 19 N. Chéron, R. Ramozzi, L. El Kaim, L. Grimaud, P. Fleurat-
Chem., 1993, 1229-1231.
Lessard, J. Org. Chem., 2012, 77, 1361-1366.
6
7
(a) I. Ugi, C. Steinbrückner, Chem. Ber., 1961, 94, 734-742.
For some more recent uses see: (b) T. Nixey, M. Kelly, C.
Hulme, Tetrahedron Lett., 2000, 41, 8729-8733; (c) C. F.
Marcos, S. Marcaccini, G. Menchi, R. Pepino, T. Torroba,
Tetrahedron Lett., 2008, 49, 149-152.
(a) L. El Kaim, L. Grimaud, J. Oble, Angew. Chem. Int. Ed.,
2005, 44, 7961-7964; (b) L. El Kaim, M. Gizolme, L. Grimaud,
J. Oble, J. Org. Chem. 2007, 72, 4169-4180; For reviews on
Ugi-Smiles reactions see: (c) L. El Kaïm, L. Grimaud, Mol. Div.
2010, 14, 855-867; (d) L. El Kaïm, L. Grimaud, Eur. J. Org.
Chem. 2014, 7749-7762.
K. Aknin, M. Gauriot, J. Totobenazara, N. Deguine, R. Deprez-
Poulain, B. Deprez, J. Charton, Tetrahedron Lett., 2012, 53, 22 (a) H. J. Shine, J. Zygmunt, M. L. Brownawell, J. S. Filippo, J.
458–461.
A. Massoudi, I. Amini, A. Ramazani, F. Z. Nasrabadi, Y.
Ahmadi, Bull. Korean Chem. Soc., 2012, 33, 39-42.
20 The use of N-hydroxysuccinimides in Passerini reaction was
recently published, though the reaction does not lead to N-N
bond formation, its mechanism might involve a related N-O
fragmentation: A. L. Chandgude, A. Domling, Org. Lett., 2016,
18, 6396-6399.
21 (a) E. F. Witucki, E. R. Wilson, J. E. Flanagan, M. B. Frankel, J.
Chem. Eng. Data, 1983, 28, 285-286; (b) T. Brill, Y. Oyumi, J.
Phys. Chem., 1986, 90, 6848-6853; (c) J. Song, Z. Zhou, X.
Dong, H. Huang, D. Cao, L. Liang, K. Wang, J. Zhang, F. Chen,
Y. Wu, J. Mater. Chem., 2012, 22, 3201-3209; (d) J. Zhang, C.
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8929-8936.
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8
9
Am. Chem. Soc., 1984, 106, 3610-3613; (b) O. Gorchs, M.
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10 I. W. McFarland, J. Org. Chem. 1963, 28, 2179-2181.
11 (a) I. Hagedorn, U. Eholzer, Chem. Ber., 1965, 98, 936-940;
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(c) B. Zeeh Tetrahedron, 1968, 24, 6663- 6669.
12 (a) For use of stoichiometric amount of HCl see 7a; (b) For
use of sulfonic acid and enamines see: C. Masdeu, J. L. Diaz,
23 (a) P. d. Armos, C. G. Francisco, R. Hernandez, E. Suarez,
Tetrahedron Lett., 1986, 27, 3195-3198; (b) X. Pan, Z. Liu,
Tetrahedron, 2014, 70, 4602-4610.
24 (a) B. Cross, R. Hill, W. H. Gastrock, Phenylnitramine
herbicides, US Pat., US 3844762, 1974; (b) B. Cross, D.H.
Dawe,
phenylnitramines, US Pat., US 4130645, 1978; (c) Y. Wang, Z.
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13 CAUTION: Though no explosion has been reported with
ammonium nitrate prepared from primary amines, great
care should be taken with small amines with one to three
carbons due to the known sensibility of ammonium nitrate
(NH4NO3)
14 All the ammonium nitrates displayed in this study were
prepared through dropwise addition of HNO3 70% (1 equiv)
to a solution of the amine (1 equiv) in the toluene (1 M). The
reactions were stirred at room temperature for 30 minutes.
The precipitates were filtrated off, washed with Et2O, and
used without further purifications. When no precipitate is
formed, the crude ammonium nitrate can be dried by
azeotropic removal of water with toluene, followed by
evaporation of solvent under reduced pressure.
15 H. E. Ungnade, L. W. Kissinger, J. Org. Chem. 1965, 30, 354-
359.
16 Typical procedure given for 3a: The ammonium nitrate salt
5a (204 mg, 1.0 mmol, 1 equiv) was added in MeOH (0.3 M),
followed by the addition of isovaleraldehyde (107 µL, 1.0
mmol, 1.0 equiv), and cyclohexylisocyanide (124 µL, 1.0
mmol, 1.0 equiv). The reaction was stirred at room
temperature under argon overnight. After evaporation of the
solvent, purification by column chromatography (eluents:
PE/EtOAc 9:1, 8:2) to afford 3a as amorphous solid (342 mg,
yield 89%). 1H NMR (400 MHz, CDCl3) δ (ppm) 7.32 – 7.26 (m,
4H), 6.18 (d, J = 8.0 Hz, 1H), 5.21 (t, J = 7.5 Hz, 1H), 5.05 (d, J
= 16.1 Hz, 1H), 4.88 (d, J = 16.1 Hz, 1H), 3.73 – 3.68 (m, 1H),
1.92 – 1.85 (m, 2H), 1.71 – 1.58 (m, 5H), 1.56 – 1.48 (m, 1H),
1.39 – 1.27 (m, 2H), 1.21 – 1.06 (m, 3H), 0.96 (d, J = 6.6 Hz,
3H), 0.90 (d, J = 6.6 Hz, 3H).13C NMR (100 MHz, CDCl3) δ
(ppm) 166.7, 134.0, 133.7, 129.2, 128.8, 61.8, 51.3, 48.8,
38.1, 32.7, 32.6, 25.4, 25.0, 24.7, 22.4, 22.3. IR (thin film)
3418, 3058, 2858, 1682, 1516, 1371, 1289, 899νmax/cm-1.
HRMS m/z: [M]+●calcd for C19H28ClN3O3: 381.1819; calcd for
[M-NO2]+●: 335.189016 Found: 335.1880 [M-NO2]+●.
17 The crystallographic data for compounds 3l can be obtained
free of charge under the reference CCDC 1524126 from the
Cambridge
www.ccdc.cam.ac.uk/data_request_cif.
Crystallographic
Data
Centre
at
18 G. B. Giovenzana, G. C. Tron, S. D. Paola, I. G. Menegotto, T.
Pirali, Ang. Chem. Int. Ed. 2006, 45, 1099-1102.
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