Synthesis and characterization of N,N-di(prop-2-ynyl)-p-toluidine

Article abstract of DOI:10.1007/s10870-010-9792-9

In order to investigate the intramolecular [4 + 2] cycloaddition, we prepared some new tertiary N-(5-substituted-2-furfuryl)-N-prop-2-ynyl-p- toluidines [Hergold-Brundic et al., Acta Cryst C56:e520, 2000; Mance and Jakopcic, Mol Divers 9:229, 2005; Mance,

Full text of DOI:10.1007/s10870-010-9792-9

J Chem Crystallogr (2010) 40:1045–1048
DOI 10.1007/s10870-010-9792-9
ORIGINAL PAPER
Synthesis and Characterization of N,N-di(prop-2-ynyl)-p-toluidine
•
Gordana Pavlovic Ana Dunja Mance
´
Received: 18 February 2009 / Accepted: 13 May 2010 / Published online: 4 June 2010
Ó Springer Science+Business Media, LLC 2010
Abstract In order to investigate the intramolecular [4 ? 2]
cycloaddition, we prepared some new tertiary N-(5-substi-
Introduction
´
tuted-2-furfuryl)-N-prop-2-ynyl-p-toluidines [Hergold-Brundic
ˇ ´
et al., Acta Cryst C56:e520, 2000; Mance and Jakopcic, Mol
Intramolecular Diels–Alder reaction (IMDA) of tertiary
N-alkenyl- and N-alkynyl-N-aryl-N-5-substituted-2-furfur-
ylamines is a useful procedure to convert simple furans via
epoxyisoindolines to substituted isoindolines [1] as the
potentially useful nitrogen containing heterocycles.
Besides our interest in some biological activity of such
tertiary amines and their [4 ? 2] cycloaddition products it
was found that the course of cycloaddition can be greatly
affected by the appropriate substitution.
Divers 9:229, 2005; Mance, ‘‘unpublished results’’] by the
alkylation of secondary N-(5-substituted-2-furfuryl)-p-tol-
ˇ
uidines with the propargyl-bromide [Mance and Sindler-
Kulyk, Synth Commun 26:923, 1996]. In the course of
preparation of N-(5-methoxy-2-furfuryl)-N-prop-2-ynyl-
p-toluidine [Mance, ‘‘unpublished results’’], besides the
main product (compound 1) (Scheme 1) we obtained
N,N-di(prop-2-ynyl)-p-toluidine (compound 2) as the col-
ourless crystals. The title compound 2, N,N-di(prop-2-ynyl)-
p-toluidine, C13H13N, crystallizes in monoclinic C 2/c
Here the attention was focused to the synthesis of the new
tertiary furfurylamines with the triple bond [2] as a dieno-
phylic part of the molecule and the substituents at furanic
diene with the potentially favorable electronic effects.
˚
space group with unit cell parameters: a = 19.5319(9) A,
˚
˚
b = 7.5230(3) A, c = 15.9000(7) A, b = 112.554(5)°, V =
3
2157.64(18) A , Z = 8. The crystal structure is dominated
˚
by van der Waals forces only. The bond distances around
Experimental Section
amine N atom correspond to r dominated bonds (1.467(2),
˚
1.462(2) and 1.419(2) A). The angles sum around amine N
Preparation
atom is in accord with sp3 hybridization (343°).
Starting from 2.2 g (0.01 mole) of freshly chromatographed
N-(5-methoxy-2-furfuryl)-p-toluidine, 1.3 g (0.011 mole)
prop-2-ynyl bromide and 2.1 g of anhydrous sodium car-
bonate under stirring and cooling in a nitrogen atmosphere at
room temperature for 20 h, the residue was extracted with
ether, treated with 5% aqueous sodium hydroxide and puri-
fied by column chromatography on silica gel using petro-
leum ether/ether (10:1) as the eluent. Besides the main
product N-(5-methoxy-2-furfuryl)-N-prop-2-ynyl-p-tolui-
dine (unpublished results) (Scheme 1) we obtained 0.4 g
(15.7%) N,N-di(prop-2-ynyl)-p-toluidine (2) as colour-
less crystals (mp.: 54–55 °C); IR (KBr) cm-1: m = 3280
(H–C:C); 1H NMR (C6D6) d/ppm: 6.96 (d,2H, J = 8.5 Hz)
and 6.77 (d,2H, J = 8.5 Hz) for p-phenylene CH protons;
Keywords Tertiary amines Á N, N-di(prop-2-ynyl)-p-
toluidine Á Synthesis Á IR Á NMR and XRD
´
G. Pavlovic (&)
Department of Applied Chemistry, Faculty of Textile
´
Technology, University of Zagreb, Prilaz Baruna Filipovica 28a,
10000 Zagreb, Croatia
e-mail: gpavlov@ttf.hr
A. D. Mance
Faculty of Chemical Engineering and Technology,
Department of Organic Chemistry, University of Zagreb,
´
Marulicev trg 19, 10000 Zagreb, Croatia
123

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J Chem Crystallogr (2010) 40:1045–1048
Scheme 1 Reaction scheme for
preparation of N,N-di(prop-2-
ynyl)-p-toluidine
CH3
CH2NH
CH
R
O
R = -OCH3
CH2Br
C
CH
CH
C
C
CH2
CH2
CH2
R
CH3
N
O
CH3
N
CH2
HC
C
2
1
3.82 (d,4H, J = 2.3 Hz) for propargyl CH2 protons and 1.81
(t,1H, J = 2.3 Hz) for propargyl CH proton; 2.12 (s,3H) for
p-phenylene CH3. 13C NMR (C6D6) d/ppm: 79.98 (s), 73.20
(d),41.04 (t) for propargyl C atoms; 146.66 (s), 117.25 (d),
130.25 (d), 129.61 (s) for p-phenylene C atoms; 20.86 (q) for
p-phenylene CH3.
Table 1 General and crystal data and summary of intensity data
collection and structure refinement for compound N,N-di(prop-2-
ynyl)-p-toluidine
Formula
C13H13
N
Mr
183.24
Crystal system, colour and habit
Space group
Monoclinic, colourless prism
C 2/c (No. 15)
Crystal dimensions (mm)
Unit cell parameters
T/K
0.47 9 0.32 9 0.28
X-Ray Diffraction Experiment
296
The general and crystallographic data for compound is
listed in Table 1. The main geometrical features are listed
in Table 2.
˚
a (A)
19.5319(9)
7.5230(3)
15.9000(7)
112.554(5)
2157.64(18)
8
˚
b (A)
˚
c (A)
The data collection was carried out on Xcalibur four-
circle kappa geometry single-crystal diffractometer with
Oxford Diffraction Xcalibur Sapphire 3 CCD detector with
b/°
V (A )
3
˚
˚
k(MoKa) = 0.71073 A. Data collection has been performed
Z
Dc (g cm-3
)
1.128
by applying the CrysAlis Software system, Version 1.171.26
[3]. The Lorentz-polarization effect was corrected and the
intensity data reduced by the CrysAlis RED application of
the CrysAlis Software system, Version 1.171.26 [3].
Coordinates of the non-hydrogen atoms were deter-
mined by direct methods with the SHELXS program [4].
The coordinates and anisotropic thermal displacement
parameters for all non-hydrogen atoms were refined by the
least-squares methods based on F2 using the SHELXL97
program [4].
l (mm-1
)
0.066
F(000)
784
h range for data collection (°)
h,k,l range
4–27
-25:25; -9:9; -20:20
x scan
Scan type
No. measured reflections
No. independent reflections (Rint
No. refined parameters
12785
)
2332, 0.028
136
No. observed reflections, I C 2r(I) 1809
Hydrogen atoms belonging to the alkynyl group atoms
C3 and C6 are found in the difference Fourier map at the
final stages of refinement as a small electron-density
g1, g2 in w
0.0649, 0.8872
R, wR [I C 2r(I)]
R, wR [all data]
Goodness of fit on F2, S
0.0538, 0.1278
0.0747, 0.1380
1.06
3
˚
(*0.4 e/A ) and refined freely (C3–H1 and C6–H16C
˚
0.92(3) and 0.94(2) A, respectively; angles C2–C3–H1
-3
)
˚
Min., max. electron density (e A
-0.17, 0.17
0.001
176(1)° and C5–C6–H16C 176(1)°. Hydrogen atoms bon-
ded to the other carbon atoms were introduced at calculated
Maximum D/r
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J Chem Crystallogr (2010) 40:1045–1048
1047
˚
Table 2 Selected interatomic distances (A) and valence angles (°)
Selected bond distances
N1–C7
N1–C4
1.4192(19)
1.462(2)
1.467(2)
1.171(3)
1.173(3)
N1–C1
C2–C3
C5–C6
Bond angles
C7–N1–C4
C7–N1–C1
C4–N1–C1
C3–C2–C1
C6–C5–C4
112.36(11)
114.76(11)
115.52(12)
178.6(2)
Fig. 1 ORTEP drawing of N,N-di(prop-2-ynyl)-p-toluidine with the
atomic numbering scheme. The thermal ellipsoids are drawn at the
50% probability level at 296 K
179.43(19)
positions and refined by applying the riding model (Uiso(H) =
the average value found for the X–C:C–X fragment
˚
(1.183 A; X = any atom) [10] as well as with the corre-
1.2 Ueq for C(phenyl) and C(methylene); 1.5 for C(methyl).
˚
The distances were 0.93, 0.97 and 0.96 A, for C(phenyl)–
sponding value found in the structure of N-(4-methyl-
phenyl)-N-(5-nitro-2-furfuryl)-N-prop-2-ynylamine solved
H, C(methylene)–H and C(methyl)–H, respectively).
The molecular graphics were done using PLATON [5]
and MERCURY [6] programmes.
˚
by us, too (1.183(2) A) [10]. The angles sum around amine
N1 atom is in accord with sp3 hybridization (angles range
108–114° for Nsp3; mean valence angle at Nsp2 is larger
than 117.5° [10]. The N1–C1 and N1–C4 bonds values of
˚
1.467(2) and 1.462(2) A, respectively, has a pure r char-
Results and Discussion
˚
acter, while the N1–C7 bond (1.419(2) A) is shortened to
some extent, with some p character, due to the sp2 char-
acter of the C7 atom in relation to sp3 character of the C1
and C4 atoms of methylene groups. The corresponding
values in N-(4-methylphenyl)-N-(5-nitro-2-furfuryl)-N-
prop-2-ynylamine structure [7] are 1.443(2) and
General Aspects of Preparation
In the course of preparation some new tertiary N-(5-
substituted-2-furfuryl)-N-prop-2-ynyl-p-toluidines [2, 7, 8]
by the alkylation of secondary N-(5-substituted-2-furfuryl)-
p-toluidines with the propargyl-bromide we observed the
rearrangement of the prepared tertiary amines and some
alkyl exchange products. The reaction is greatly depending
on the polar effects of the furan substituents [1, 9].
˚
1.456(2) A.
˚
The bonds values of C1–C2 (1.466(2) A) and C4–C5
3
(1.463(2) A) are in agreement for Csp –Csp mean bond
˚
˚
˚
value (1.466 A) [10]. The value of 1.507(3) A for C10–
˚
C13 bond corresponds with the mean value of 1.506 A for
Csp3–Car bonds [10].
The formation of the by-product could be explained by
the reaction of the formed tertiary amine with the propar-
gyl-bromide giving quaternary salt followed by the dis-
placement of 5-methoxy-2-furfuryl-bromide from the salt,
facilitated by the resonance stabilization. The greater
excess of the propargyl-bromide enhanced the yield of the
rearranged product. In the preparation of N-(5-methoxy-2-
furfuryl)-N-prop-2-ynyl-p-toluidine [2] with the almost
equimolar quantity of the reactants, we isolated N,N-
di(prop-2-ynyl)-p-toluidine as by-product in 15.7% yield.
Crystal Structure Description
The ORTEP drawing of the molecular structure of N,N-
di(prop-2-ynyl)-p-toluidine is depicted in Fig. 1.
The C:C bond values in the propynyl moieties are
˚
1.173(3) and 1.171(3) A, for C5:C6 and C2:C3,
respectively (Fig. 1; Table 2). They are in agreement with
Fig. 2 Crystal packing of N,N-di(prop-2-ynyl)-p-toluidine viewed
down b axis
123

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J Chem Crystallogr (2010) 40:1045–1048
under the framework of the scientific programme ‘‘Ligands, com-
plexes, proteins-synthesis and structure-properties relationship’’.
The molecules are linked together only by van der
Waals forces (Fig. 2). Since, there is no possible proton
acceptors, the potential alkynyl acid protons are not
involved into hydrogen bonds formation as it is established
by spectroscopic analysis, too [11–13].
References
ˇ
ˇ ´
´
1. Mance AD, Borovicka B, Jakopcic K, Pavlovic G, Leban I (2002)
J Heterocycl Chem 39:277; references cited therein
2. Mance AD, unpublished results
Supplementary Material
3. Oxford Diffraction Ltd (2004) CrysAlis software (Version
1.171.26.). Abingdon, Oxfordshire OX14 4RX, UK
4. Sheldrick GM (2008) Acta Cryst A64:112
CCDC 720753 for N,N-di(prop-2-ynyl)-p-toluidine con-
tains the supplementary crystallographic data for this
paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre (CCDC), 12
Union Road, Cambridge CB2 1EZ, UK; fax: ?44(0)1223-
336033; email: deposit@ccdc.cam.ac.uk]. Structure factors
table is available from the authors.
5. Spek L (2003) J Appl Cryst 36:7
6. Macrae CF, Bruno IJ, Chisholm, JA, Edgington, PR, McCabe P,
Pidcock E, Rodriguez-Monge L, Taylor, R, van de Streek JP,
Wood A (2008) J Appl Crystallogr 41:466
´
´ ˇ ´
7. Hergold-Brundic A, Pavlovic G, Mance AD, Jakopcic K (2000)
Acta Cryst C56:e520
ˇ ´
8. Mance AD, Jakopcic K (2005) Mol Divers 9:229
9. Mance AD, Sindler-Kulyk M (1996) Synth Commun 26:923
ˇ
10. Allen FH, Kennard O, Watson DG, Brammer L, Orpen AG
(1987) J Chem Soc Perkin Trans II S1
11. Calabrese JC, McPhail A T, Sim GA (1970) J Chem Soc B:282
12. Steiner Th (1995) Z Kristallogr 210:459
13. Steiner Th, Schreurs AMM, Kanters JA, Kroon J, van der Maas J,
Lutz B (1997) J Mol Struct 436
Acknowledgement The Ministry of Science and Technology of the
Republic of Croatia, Zagreb (Grant No. 0125012 and 098-1191344-
2943) supported this work. G.P. gratefully acknowledges for diffrac-
tion time to record data to the scientific project 119-1193079-1332
123