Synthesis of borasiloxane-based macrocycles by multicomponent condensation reactions in solution or in a ball mill

Article abstract of DOI:10.1039/c2cc37538a

Large macrocycles containing imine and borasiloxane links are obtained in polycondensation reactions of 4-formylbenzeneboronic acid, t-Bu ₂Si(OH)₂, and diamines. The multicomponent reactions can be performed in solution or - advantageously - by mechanochemical syntheses in a ball mill.

Full text of DOI:10.1039/c2cc37538a

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Synthesis of borasiloxane-based macrocycles by
multicomponent condensation reactions in solution or
in a ball mill†‡
Cite this: Chem. Commun.,
2013, 49, 45--47
Received 16th October 2012,
Accepted 8th November 2012
Mirela Pascu, Albert Ruggi, Rosario Scopelliti and Kay Severin*
DOI: 10.1039/c2cc37538a
www.rsc.org/chemcomm
Large macrocycles containing imine and borasiloxane links are
obtained in polycondensation reactions of 4-formylbenzeneboronic
acid, t-Bu2Si(OH)2, and diamines. The multicomponent reactions can
be performed in solution or – advantageously – by mechanochemical
syntheses in a ball mill.
Condensation reaction of polyamines with polyaldehydes can
be used to construct molecularly defined nanostructures1 and
covalent organic frameworks.2 Imine links are highly successful
in this context because they are dynamic covalent bonds,3
which allow error correction processes to occur during the
synthesis. We and others have shown that imines can be used
in combination with boronic acid–diol condensations.4,5 The
parallel utilization of imines and boronate esters permits the
construction of complex nanostructures such as macrocycles or
cages in multicomponent reactions from simple building
blocks. In extension of this work, we have explored whether
imines could be combined with other types of condensation
reactions. The condensation of silane diols with boronic acids
appeared to be a potentially suited coupling reaction. This
reaction is known to give cyclic borasiloxanes of the general
formula (R2SiO)2(R0BO)2.6 Diboratetrasiloxanes have been
employed in polymer chemistry,7 but their utilization in struc-
tural supramolecular chemistry is mostly unexplored.8 Below
we show that large organic macrocycles with borasiloxane and
imine linkages are indeed accessible in simple polycondensation
reactions. We also demonstrate that the macrocycles are best
made by mechanochemical syntheses in a ball mill.
To test the compatibility of diboratetrasiloxanes with imine
condensations, we have synthesized dialdehyde 1 in 65% yield
by reacting t-Bu2Si(OH)2 with 4-formylbenzeneboronic acid in
´
´
´ ´
Institut des Sciences et Ingenierie Chimiques, Ecole Polytechnique Federale de
Lausanne (EPFL), Lausanne, Switzerland. E-mail: kay.severin@epfl.ch;
Fax: +41 (0)21 6939305; Tel: +41 (0)21 6939302
Scheme 1 Step-wise and one-pot synthesis of macrocycles 2 and 3.
† This article is part of the ChemComm ‘Mechanochemistry: fundamentals and
applications in synthesis’ web themed issue.
‡ Electronic supplementary information (ESI) available. CCDC 905956. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c2cc37538a
toluene (Scheme 1). Borasiloxane 1 was characterized spectro-
scopically as well as by single crystal X-ray diffraction (see ESI‡).
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 45--47 45

Communication
ChemComm
cages with imine and boronate ester linkages can be obtained
by polycondensation reactions in a ball mill.5b,13 These results
prompted us to explore whether macrocycle 2 could also be
obtained by ball-milling. The reaction was performed using a
MM200 Retsch mill operating at 30 Hz. Ball milling of the
boronic acid, the silane diol and the diamine for 2 ꢁ 45 min
gave a white powder. 1H NMR spectroscopic analysis of this
powder revealed that macrocycle 2 had formed in high yield
(490%; see ESI‡). Washing with dry diethyl ether gave pure 2 in
an isolated yield of 85% (Scheme 2). Macrocycle 3 could be
prepared in a similar fashion. The crude product was less pure
(see ESI‡), but a simple recrystallization gave 3 in 65% yield.
These results are evidence that borasiloxanes are accessible by
ball-milling. Furthermore, they show that the mechanochemical
syntheses of borasiloxane macrocycles can be achieved with high
yields, outperforming more classical solution-based methods.
In summary, we have described the synthesis of large
macrocycles with imine and borasiloxane linkages. The macro-
cycles are obtained in simple multicomponent condensation
reactions of t-Bu2Si(OH)2, 4-formylbenzeneboronic acid, and
diamines. It is conceivable that related reactions with polyfunc-
tional building blocks (e.g. triamines) can be used to generate
borasiloxane-based cages or networks. Our work is also further
evidence for the utility of mechanochemistry in structural
supramolecular chemistry.14
Fig. 1 The structures of macrocycles 2 (left) and 3 (right) as determined by
molecular modeling. Color coding: C: grey; N: blue, O: red; B: green; Si: cyan.
Hydrogen atoms are not shown.
The eight-membered (SiOBO)4 ring of crystalline 1 is nearly flat
with the coplanar 4-formylbenzene rings pointing in opposite
directions. The bond lengths and angles of 1 are similar to
9
what has been observed for (t-Bu2SiO)2(p-BrC6H4BO)2 and
(t-Bu2SiO)2(PhBO)2.10
Subsequently, the dialdehyde 1 was combined with the
diamines 4,40-bis(aminomethyl)biphenyl and (1R,2R)-1,2-diamino-
cyclohexane. The latter diamine was chosen because it has been
used previously with good success for the synthesis of imine
macrocycles (‘trianglimines’).1,11 The diamine with the biphenyl
spacer, on the other hand, was expected to result in an expanded
structure. Condensation of 1 with the diamines in organic
solvents gave macrocycles 2 and 3 in moderate yields (2:33%;
3:50%). The products were characterized by NMR spectroscopy
(1H, 13C, 29Si), elemental analysis, and mass spectrometry (see
ESI‡). Attempts to obtain single crystals for crystallographic
analysis were unfortunately not successful. In order to estimate
the size of 2 and 3, we have performed molecular modeling
using the crystallographic data of 1 for calibration (see ESI‡).
The 81-membered macrocycle 2 displays a diameter (max.
Cꢀ ꢀ ꢀC distance) of approximately 2.4 nm, and the 57-membered
macrocycle 3 of around 1.5 nm (Fig. 1).
This work was supported by a Marie-Curie fellowship (M.P.
IEF-2009-252716), by the Swiss National Science Foundation
and by the EPFL.
Notes and references
1 (a) M. E. Belowich and J. F. Stoddart, Chem. Soc. Rev., 2012, 41, 2003;
(b) N. M. Rue, J. Sun and R. Warmuth, Isr. J. Chem., 2011, 51, 743;
(c) M. Mastalerz, Angew. Chem., Int. Ed., 2010, 49, 5042;
(d) N. B. Borisova, M. D. Reshetova and Y. A. Ustynyuk, Chem. Soc.
Rev., 2007, 107, 46; (e) P. A. Vigato, S. Tamburini and L. Bertolo,
Coord. Chem. Rev., 2007, 251, 1311; ( f ) M. J. MacLachlan, Pure Appl.
Chem., 2006, 78, 873.
Next, we have examined whether it is possible to obtain
macrocycle 2 in a one-pot reaction from t-Bu2Si(OH)2, 4-formyl-
benzeneboronic acid and 4,40-bis(aminomethyl) biphenyl. This
three-component reaction indeed gave the desired product,
albeit in low isolated yield (20%). The 1H NMR spectrum of
the crude product showed that macrocycle 2 had formed as the
major product, but the recrystallization procedure employed
for purification resulted in significant loss of material.
The mechanochemical synthesis of compounds by grinding
solids in a mortar or – advantageously – in a ball mill is rapidly
gaining popularity.12 We have recently shown that nanometer-sized
2 (a) S.-Y. Ding and W. Wang, Chem. Soc. Rev., 2012, DOI: 10.1039/
c2cs35072f; (b) X. Feng, X. Ding and D. Jiang, Chem. Soc. Rev., 2012,
41, 6010.
3 (a) E. Moulin, G. Cormos and N. Giuseppone, Chem. Soc. Rev., 2012,
41, 1031; (b) P. T. Corbett, J. Leclaire, L. Vial, K. R. West, J.-L. Wietor,
J. K. M. Sanders and S. Otto, Chem. Rev., 2006, 106, 3562–3711;
(c) S. J. Rowan, S. J. Cantrill, G. R. L. Cousins, J. K. M. Sanders and
J. F. Stoddart, Angew. Chem., Int. Ed., 2002, 41, 898.
4 (a) R. Nishiyabu, Y. Kubo, T. D. James and J. S. Fossey, Chem.
Commun., 2010, 46, 1124; (b) K. Severin, Dalton Trans., 2009,
5254–5264; (c) N. Fujita, S. Shinkai and T. D. James, Chem.–Asian
¨
J., 2008, 3, 1076; (d) H. Hopfl, Struct. Bonding, 2002, 103, 1.
5 (a) B. Icli, E. Solari, B. Kilbas, R. Scopelliti and K. Severin, Chem.–Eur.
¨
J., 2012, 18, 14867–14874; (b) B. Icli, N. Christinat, J. Tonnemann,
C. Schu¨ttler, R. Scopelliti and K. Severin, J. Am. Chem. Soc., 2009,
131, 3154; (c) N. Christinat, R. Scopelliti and K. Severin, Angew. Chem.,
Int. Ed., 2008, 47, 1848; (d) M. Hutin, G. Bernardinelli and
J. R. Nitschke, Chem.–Eur. J., 2008, 14, 4585; (e) N. Christinat,
R. Scopelliti and K. Severin, J. Org. Chem., 2007, 72, 2192.
6 (a) A. G. Avent, S. E. Lawrence, M. M. Meehan, T. G. Russell and
T. R. Spalding, Collect. Czech. Chem. Commun., 2002, 67, 1051;
(b) M. A. Beckett, D. E. Hibbs, M. B. Hursthouse, K. M. A. Malik,
P. Owen and K. S. Varma, J. Organomet. Chem., 2000, 595, 241;
(c) B. J. Brisdon, M. F. Mahon, K. C. Molloy and P. J. Schofield,
J. Organomet. Chem., 1992, 436, 11.
7 (a) W. Liu, M. Pink and D. Lee, J. Am. Chem. Soc., 2009, 131, 8703;
(b) H. S. J. Behbehani, B. J. Brisdon and B. McEnaney, Polym. Adv.
Technol., 1994, 5, 653.
Scheme 2 Synthesis of macrocycles 2 and 3 by mechanochemistry.
46 Chem. Commun., 2013, 49, 45--47
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ChemComm
Communication
´
8 A borasiloxane of the formula (t-BuSi)2(RBO2)3 has been employed
as a link in a covalent organic framework. See: J. R. Hunt,
Chem., 2003, 1, 1157; (e) J. Gawronski, H. Kolbon, M. Kwit and
A. Katrusiak, J. Org. Chem., 2000, 65, 5768.
ˆ ´
ˇˇ ´
C. J. Doonan, J. D. LeVangie, A. P. Cote and O. M. Yaghi, J. Am. 12 S. L. James, C. J. Adams, C. Bolm, D. Braga, P. Collier, T. Friscic,
Chem. Soc., 2008, 130, 11872.
9 A. G. Avent, S. E. Lawrence, M. M. Meehan, T. G. Russell and
T. R. Spalding, Collect. Czech. Chem. Commun., 2002, 67, 1051.
F. Grepioni, K. D. M. Harris, G. Hyett, W. Jones, A. Krebs, J. Mack,
L. Maini, A. G. Orpen, I. P. Parkin, W. C. Shearouse, J. W. Steed and
D. C. Waddell, Chem. Soc. Rev., 2012, 41, 413.
10 A. Mazzah, A. Haoudi-Mazzah, M. Noltemeyer and H. W. Roesky, 13 For the synthesis of simple imines and boronate esters by mechano-
Z. Anorg. Allg. Chem., 1991, 604, 93.
11 For selected examples see: (a) H. F. Nour, M. F. Matei, B. S. Bassil,
U. Kortz and N. Kuhnert, Org. Biomol. Chem., 2011, 9, 3258;
chemistry see: (a) M. Schnu¨rch, M. Holzweber, M. D. Mihovilovic
and P. Stanetty, Green Chem., 2007, 9, 139; (b) G. Kaupp,
M. R. Naimi-Jamal and V. Stepanenko, Chem.–Eur. J., 2003,
9, 4156; (c) G. Kaupp and M. R. Naimi-Jamal, Eur. J. Org. Chem.,
2002, 1368; (d) G. Kaupp, J. Schmeyers and J. Boy, Tetrahedron, 2000,
56, 6899; (e) J. Schmeyers, F. Toda, J. Boy and G. Kaupp, J. Chem.
Soc., Perkin Trans. 2, 1998, 989.
´
(b) M. Kwit, A. Plutecka, U. Rychlewska, J. Gawronski,
A. F. Khlebnikov, S. I. Kozhushkov, K. Rauch and A. de Meijere,
Chem.–Eur. J., 2007, 13, 8688; (c) N. Kuhnert, N. Burzlaff, C. Patel
and A. Lopez-Periago, Org. Biomol. Chem., 2005, 3, 1911;
ˇˇ ´
(d) N. Kuhnert, G. M. Rossignolo and A. Lopez-Periago, Org. Biomol. 14 T. Friscic, Chem. Soc. Rev., 2012, 41, 3493.
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Chem. Commun., 2013, 49, 45--47 47