Reaction of 1,2-dibromoethane with primary amines: Formation of N,N′-disubstituted ethylenediamines RNH-CH2CH2-NHR and homologous polyamines RNH-[CH2CH2NR]n-H

Article abstract of DOI:10.1016/S0040-4020(03)01149-9

The reaction of primary amines RNH₂ (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH₂CH₂-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Pipe

Full text of DOI:10.1016/S0040-4020(03)01149-9

Tetrahedron 59 (2003) 7565–7570
Reaction of 1,2-dibromoethane with primary amines: formation of
N,N0-disubstituted ethylenediamines RNH–CH2CH2–NHR
and homologous polyamines RNH–[CH2CH2NR]n–H
*
Michael K. Denk, Mike J. Krause, Debyani F. Niyogi and Nachhattarpal K. Gill
Department of Chemistry and Biochemistry, University of Guelph, 50 Stone Road, Guelph, Ontario N1G 2W1, Canada
Received 6 May 2003; revised 18 July 2003; accepted 18 July 2003
Abstract—The reaction of primary amines RNH2 (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N0-disubstituted
ethylenediamines R–NH–CH2CH2–NH–R (1) in yields ranging from 10% (1a; R¼Me) to 70% (1d, R¼tBu; 1e, R¼Ph). Piperazines and
N-substituted polyethyleneimines were identified (1H NMR, 13C NMR and EI-MS) as side products of the reaction and isolated by fractional
distillation. The piperazines 2 are formed in yields of 3–10% and can be separated from the diamines 1 in all cases, except for R¼Me and Ph.
The polyamine homologues RNH–[CH2CH2NR]n–H (3–5) were isolated in yields ranging from 0.1% (n¼4, R¼iPr) to 14% (n¼2, R¼iPr).
The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
reaction of ethylenediamine with alkylating agents like
methyl iodide is known to give mixtures of polyalkylated
compounds.9,10 The introduction of N-protective groups8,11
can in principle solve this problem but also adds protection
and deprotection as two additional synthetic steps.9a,11
The N,N0-disubstituted ethylenediamines 1 and their
homologous diethylenetriamines and tetramines are versa-
tile building blocks for the synthesis of organic and
inorganic compounds. They find use for the synthesis of
aza-crown ethers,1 functionalized polymers,2 and, more
recently, for the synthesis of stable carbenes,3 stable
silylenes4 and related species5 (Scheme 1). Their complexes
with manganese,6a copper,6b and silver6c have been studied
as homogenous catalysts and their Pd(II) and Pt(II)
complexes have served as model compounds to study the
interaction of cis-platin and related anticancer drugs with
DNA.7
The reductive alkylation of ethylenediamines with acetone
has been used by Gelbhard for the synthesis of the
N-isopropyl derivatives.9c However, this approach only
allows the introduction of substituents of the general type
RR0CH– which excludes common substituents R such as
tBu or phenyl. Aldehydes form rather reduction resistant
cyclic imidazolidines and are not well suited for the
reductive alkylation of ethylenediamines. Acylation and
subsequent reduction of the N-acyl amines circumvents the
problem of polyalkylation but requires the use complex
hydrides in stoichiometric quantities.
A potentially general route for the synthesis of N,N0-di-
substituted ethylenediamines 1 that does not require
multiple steps, special equipment or expensive reagents is
the reaction of primary amines with 1,2-dibromoethane.
Scheme 1.
Despite earlier reports in the literature8,12 the synthetic
scope of the reaction has remained unclear. We have
previously obtained N,N 0-di-tert-butylethylenediamine and
N,N 0-diisopropyl ethylenediamine from the respective
primary amines and 1,2-dibromoethane in the context of
our research on stable carbenes,3 silylenes,4 and related
species5 and became interested to see if the developed
methodology could be extended to other primary amines as
well.
Despite their structural simplicity, the synthesis of N,N0-di-
substituted ethylenediamines 1 and indeed of substituted
ethylenediamines in general is not straightforward.8–11 The
Keywords: amines; polyethyleneimine; alkylation; chelate ligands;
ethylenediamine.
*
Corresponding author. Tel.: þ1-5198244120x53820; fax: þ1-
5197661499; e-mail: mdenk@uoguelph.ca
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)01149-9

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M. K. Denk et al. / Tetrahedron 59 (2003) 7565–7570
Scheme 2.
2. Results
nature, completion still required ,2 weeks at room
temperature which exceeded the reaction time required for
R¼tBu (3 days). This discrepancy may result from
solubility effects operating in the generally biphasic reaction
mixtures. While the lipophilic 1,2-dibromoethane will
reside predominantly in the organic phase, the amines will
reside in the aqueous phase for R¼Me, Et and iPr but in the
organic phase for R¼tBu.
The reactions of 1,2-dibromoethane with primary amines
RNH2 were carried out at room temperature with a set of
identical reaction conditions (see below) for R¼Me, Et, iPr
and tBu. Aniline, which was included as a representative of
aromatic amines, was found to be less reactive and required
heating.
GC-MS analysis of the crude amine mixtures showed the
formation of the desired substituted ethylenediamines 1 but
also demonstrated the formation of the piperazines 2 and
polyamines 3–5 as volatile side products (Scheme 2)18
which were isolated by fractional distillation and charac-
terized by spectroscopic methods (1H, 13C and GC-MS).
The use of water or the sequence of the addition of the
reagents did not significantly influence the product
distribution.
The less reactive aniline required heating which (contrast to
R¼alkyl) was also required to prevent a solidification of
the reactions mixture. With the exception of aniline, the
reactions were conveniently carried out in ordinary screw
cap storage bottles connected to a bubbler and inert gas line.
The best yields of 1 were obtained by reacting 1,2-
dibromoethane (1 equiv.) with an excess of the primary
amine (5 equiv.). Attempts to use the addition of auxiliary
bases like NaOH or Na2CO3 to reduce the amount of
primary amine to the theoretically required amount
(2 equiv.) led to lower yields. The yield of the diamines 1
increased in a regular fashion with the steric bulk of the
substituent from R¼Me to R¼tBu; no obvious correlation
existed for the yields of 2–5.
Fractional distillation over a 20 cm Vigreux column
separated the homologous amines 1, 3, 4, and 5 (GC
control) but gave mixtures of the ethylenediamines 1 and
piperazines 2 that required redistillation.14 Distillation
failed to separate 1a/2a (azeotrope) and 1e/2e (small boiling
point difference). Pure materials (GC) were obtained by
counter current extraction with hexane–water which leads
to enrichment of the more lipophilic piperazines 2 in the
organic phase. Complete separation was also achieved by
column filtration of the piperazine/ethylenediamine mix-
tures (ca. 1 g of mixture in 10 mL of hexanes) through a
30 cm column of neutral Al2O3. The piperazines have
significantly lower retention times and are thus readily
separated from the diamines which were obtained as second
fraction with the more polar CH2Cl2 as eluent. The former
method is better suited for large quantities while the column
filtration is better suited for small amounts.
The reactions did not require organic solvents but an
adequate amount of water greatly facilitated stirring by
keeping the voluminous amine hydrobromide salts which
form in the course of the reaction dissolved. Methylamine
and ethylamine were accordingly used in form of the readily
available aqueous solutions. Apart from facilitating stirring,
the presence of water also accelerates the reactions.13 This
effect was first noticed for tert-butyl amine which gave a
75–80% yield of ld after only 24 h at room temperature in
water as solvent whereas, the reaction in hexanes (no water)
required 4 days of boiling and the use of an efficient
overhead stirrer to give ld in 50% yield.
The generally very hygroscopic alkyl substituted ethylene-
diamines required extensive drying over solid NaOH and
subsequent distillation over sodium. Distillation over NaOH
or CaH2 was found to be insufficient.
Unlike tert-butylamine, the sterically less hindered amines
(R¼Me, Et, iPr) reacted in exothermic fashion and required
ice cooling and slow mixing of the components to prevent
losses of the volatile amine. Despite their initial exothermic
The multiplicities and relative intensities of the 1H and 13
C

M. K. Denk et al. / Tetrahedron 59 (2003) 7565–7570
7567
signals and the comparison of the shifts in 2–5 with those of
1 allowed the assignment of most signals, although the
assignment becomes more difficult with increasing chain
length. The terminal methylene protons RNHCH2 were
observed as broad singlets, triplets or with higher multi-
plicities (e.g. q). H,D-exchange experiments with D2O
reduced the signals to triplets and confirmed that the higher
multiplicities were caused by coupling with the NH protons.
filtered through a 30 cm column of neutral Al2O3 (10 g/1 g
of amine mixture). The filtrates were collected in 5 mL
fractions and the pure (by GC) fractions combined, to give,
after evaporation of the solvent in vacuo, the pure amines
1a, 2a, 1e and 2e. Recovery .90%.
3.1.1. N,N0-Dimethylethylenediamine (1a). CAS [110-70-
3]. Colorless oil, bp 121–1238C (azeotrope with 2a), bp 119–
1208C (pure), lit.11a 1208C. 1H (C6D6): 1.03 [s, br, 2H, NH],
2.33 [s, 6H, NCH3], 2.55 [s, 4H, NCH2]. 13C (C6D6): 36.7
[NCH3], 52.0 [NCH2]. GC-MS: tr¼3.25 min, m/z (rel. int.
%)¼101(20), 89(75), 75(5), 71(3), 58(100), 57(50), 56(25).
The EI-MS spectra of the ethylenediamines (1, 3–5)
showed [Mþ1] peaks15 which presumably result from
the formation of stable hydrates (and loss of [OH]z) in the
spectrometer. The less hygroscopic piperazines show the
usual [M]þz peaks.
3.1.2. 1,4-Dimethylpiperazine (2a). CAS [106-58-1]
Colorless oil, bp 127–1308C, lit.17 1308C. 1H (C6D6):
2.13 [s, 6H, NCH3], 2.33 [s, 8H, NCH2], 13C (C6D6): 46.2
[NCH3], 55.5 [NCH2]. GC-MS: tr¼4.98 min, m/z (rel. int.
%)¼144(100), 99(10), 85(15), 71(30), 70(35), 58(25),
57(20), 56(30).
3. Experimental
Melting points were recorded in sealed capillaries and are
uncorrected. GC-MS spectra were obtained with a Varian
CP-3800 GC/Saturn 2000 MS combination at an ionizing
voltage of 70 eV and a 30 m£0.25 mm Varian CP 5860
low bleed phenyl-dimethylsiloxane column (5% phenyl).
Temperature program: 4 min at 508C; 10 min constant
heating rate of 208C/min; 6 min at 2508C. NMR-spectra
(chemical shifts in d) were recorded with a Bruker 400 MHz
spectrometer at normal spectrometer temperature. The
NMR spectra are referenced versus TMS (1H and 13C,
internal) and were obtained with flame sealed samples. All
starting materials were obtained from Aldrich Inc. and used
as received. The products were handled in an atmosphere of
nitrogen or argon (purity 99.994 or better). Yields refer to
isolated products unless noted otherwise and are not
optimized. HR-MS data of the previously unknown amines
(4c, 5c) were obtained with a VG ZAB-R instrument at
the McMaster Regional Centre for Mass Spectrometry,
Hamilton, Ontario. All previously described compounds are
identified by their CAS numbers (in square brackets, see
below).
3.1.3. 1,4,7-Trimethyl-1,4,7-triazaheptane (3a). CAS
[105-84-0]. Colorless oil, bp 55–568C/0.1 Torr, lit.6a
1
608C/1 Torr. H (C6D6): 1.05 [s, 2H, NH], 2.10 [s, 3H,
3
4-CH3], 2.32 [s, 6H, 1,7-CH3], 2.36 [t, 4H, J(H,H)¼6 Hz,
HNCH2CH2], 2.53 [t, 4H, 3J(H,H)¼6 Hz, HNCH2CH2]. 13
C
(C6D6): 36.8 [HNCH3], 42.4 [C2NCH3], 50.1 [HNCH2],
57.8 [HNCH2CH2]. GC-MS: tr¼8.24 min, m/z (rel. int.
%)¼146(20), 114(5), 101(35), 89(5), 72(15), 58(100).
3.1.4. 1,4,7,10-Tetramethyl-1,4,7,10-tetraazadecane (4a).
CAS [105-78-2]. Colorless, viscous oil, bp 89–908C/
1
0.1 Torr, lit.6a 928C/1 Torr. H (C6D6): 1.24 [s, 2H, NH],
2.12 [s, 6H, C2NCH3], 2.13 [s, 6H, NHCH3], 2.39 [s, 5,6-
CH2], 2.40 [t, 4H, 3J(H,H)¼7 Hz, NHCH2CH2], 2.55 [q, 4H,
3J(H,H)¼7 Hz, NHCH2CH2]. 13C (C6D6) 36.8 [4,7-CH3],
42.8 [1,10-CH3], 50.2 [5,6-CH2], 56.4 [2,9-CH2], 57.8
[NHCH2CH2]. EI-MS (direct inlet): m/z (rel. int.
%)¼203(100) [Mþ1]þ, 129(5), 115(7), 72(12).
3.1.5. N,N0-Diethylethylenediamine (1b). CAS [111-74-0].
Colorless oil, bp 152–1538C, lit.11a 151–1528C. 1H (C6D6):
3.1. General procedure for the reaction of primary
amines with 1,2-dibromoethane
3
0.91 [s, 2H, NH], 1.01 [t, 6H, J(H,H)¼7 Hz, NCH2CH3],
2.53 [q, 4H, 3J(H,H)¼7 Hz, NCH2CH3], 2.60 [s, 4H,
NCH2CH2]. 13C (C6D6): 15.8 [NCH2CH3], 44.5
[NCH2CH3], 50.0 [NCH2CH2]. GC-MS: tr¼6.2 min, m/z
(rel. int. %)¼ 117(20) [Mþ1]þ, 72(20), 58(100).
The primary amine (5 mol), water (300 mL) and 1,2-di-
bromoethane (1 mol, 86 mL) were mixed in a bottle of
suitable size and magnetically stirred at room temperature
for 2 weeks. Initial ice cooling was required for the
sterically less hindered alkyl amines (R¼Me, Et and iPr).
Aniline was reacted by boiling for 24 h in a round bottom
flask equipped with a magnetic stirrer and reflux condenser.
The free amines are obtained by adding NaOH pellets in
20 g portions under ice cooling and constant stirring until
the NaOH remains undissolved (caution: gas evolution for
methylamine and ethylamine). The crude amine layer (top)
was separated, stirred with 50 g of NaOH pellets for 24 h
and decanted. The procedure was repeated until the NaOH
remained undissolved. The amines 1–5 were isolated by
fractional distillation of the crude, predried (NaOH) amine
mixture over 5 g of sodium with the help of a 30-cm
Vigreux column. For isolated yields, see Scheme 2.
3.1.6. N,N0-Diethylpiperazine (2b). CAS [102459-01-8].
Colorless oil, bp 171–1728C, lit.9c 169–1718C, lit.
1
3
17174–1768C. H (C6D6): 0.99 [t, 6H, J(H,H)¼7 Hz, N–
3
CH2CH3], 2.25 [q, 4H, J(H,H)¼7 Hz, NCH2CH3], 2.40
[s, 8H, NCH2CH2]. 13C (C6D6): 12.6 [CH3], 52.6
[NCH2CH3], 53.4 [NCH2CH2]. GC-MS: tr¼7.50 min, m/z
(rel. int. %)¼142(100), 127(30), 113(15), 99(30), 84(75),
70(75), 56(80).
3.1.7. 1,4,7-Triethyl-1,4,7-triazaheptane (3b). CAS [105-
93-1]. Colorless, viscous oil, bp 66–678C/0.1 Torr, lit.9c
102–1058C/11 Torr. 1H (C6D6): 0.93 [t, 3H, 3J(H,H)¼7 Hz,
3
C2NCH2CH3], 1.06 [t, 6H, J(H,H)¼7 Hz, HNCH2CH2],
1.20 [s, 2H, NH], 2.40 [q, 2H, 3J(H,H)¼7 Hz,
3
C2NCH2CH3], 2.57 [q, 4H, J(H,H)¼6 Hz, NHCH2CH3],
The incompletely separated fractions containing 1a/2a and
1e/2e were dissolved in a tenfold volume of hexanes and
2.47 [t, 4H, 3J(H,H)¼4 Hz, NHCH2CH2], 2.60 [t, 2H,

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M. K. Denk et al. / Tetrahedron 59 (2003) 7565–7570
3J(H,H)¼6 Hz, HNCH2CH2]. 13C (C6D6): 11.0 [4-
CH2CH3], 15.0 [1,7-CH2CH3], 43.3 [HNCH2CH2], 46.9
[HNCH2CH3], 47.2 [C2NCN2CH3], 52.9 [HNCH2CH2].
GC-MS: tr¼9.9 min, m/z (rel. int.%)¼188(10) [Mþ1]þ,
129(25), 86(75), 72(100), 58(40).
3.1.13. 1,4,7,10,13-Pentaisopropy1-1,4,7,10,13-pentaaza-
tridecane (5c). No CAS entry. Colorless, viscous oil, bp
1
3
184–1858C/0.1 Torr. H (C6D6): 0.96 [d, 12H, J(H,H)¼
7 Hz, 4,10-CH(CH3)2], 0.99 [d, 6H, 3J(H,H)¼6 Hz,
7-CH(CH3)2], 1.09 [d, 12H, 3J(H,H)¼6 Hz, 1,13-CH
(CH3)2], 1.48 [s, NH], 2.53 [s, 12H, 3,5,6,8,9,11-CH2],
3
3.1.8. 1,4,7,10-Tetraethyl-1,4,7.10-tetraazadecane (4b).
CAS [24426-33-3]. Colorless, viscous oil, bp 139–1408C/
0.1 Torr, lit.1g 85–868C/0.07 Torr, lit.9c 75–778C/0.2 Torr.
1H (C6D6): 0.97 [t, 6H, 3J(H,H)¼7 Hz, 4,7-CH2CH3],
1.09 [t, 6H, 3J(H,H)¼7 Hz, NHCH2CH3], 1.35 [s, 2H,
2.63 [mult. 4H, 2,12-CH2], 2.78 [sept, 2H, J(H,H)¼6 Hz,
1,13-CH(CH3)2], 2.87 [sept, 3H, 3J(H,H)¼7 Hz, 4,7,10-
CH(CH3)2]. 13C (C6D6): 18.3 [4,10-CH(CH3)2], 18.5
[7-CH(CH3)2], 23.4 [1,13-CH(CH3)2], 46.8, 49.2, 51.1,
51.2, 51.5, 52.0, 52.2 [NCH2þNCH(CH3)2]. GC-MS: tr¼
15.3 min, m/z (rel. int. %)¼400(10) [Mþ1]þ, 169(100),
100(55). EI HRMS m/z calcd. for C23H54N5 [MþH]þ:
400.4379. Found: 400.4379.
3
NH], 2.50 [s, 4H, 5,6-NCH2], 2.43 [q, 4H, J(H,H)¼7 Hz,
3
NHCH2CH3], 2.62 [q, 4H, J(H,H)¼7 Hz, 4,7-CH2CH3],
2.52 [t, 4H, 3J(H,H)¼6 Hz, HNCH2CH2], 2.63 [t, 4H,
3J(H,H)¼6 Hz, HNCH2CH2]. 13C (C6D6): 12.6 [4,7-
CH2CH3], 15.8 [1,10-CH2CH3], 44.7 [5,6-CH2], 48.3 [1,10-
CH2CH3], 48.8 [4,7-CH2CH3], 53.0, 54.5 [NCH2CH2].
GC-MS: tr¼11.5 min, m/z (rel. int. %)¼259(5) [Mþ1]þ,
144(30), 129(40), 86(100), 72(90), 58(45).
3.1.14. N,N0-Di-tert-butylethylenediamine (1d). CAS
[4062-60-6]. Colorless, oil, bp 196–1988C lit.11a 196–
1988C. 1H (C6D6): 0.75 [s, 2H, NH], 1.04 [s, 18H, C(CH3)3],
2.57 [s, 4H, NCH2]. 13C (C6D6): 29.4 [C(CH3)3], 43.6
[NCH2], 49.8 [C(CH3)3]. GC-MS: tr¼8.2 min, m/z (rel. int.
%)¼173(100) [Mþ1]þ, 157(10) [M2CH3]þ, 100(10).
3.1.9. N,N0-Diisopropylethylenediamine (1c). CAS [4013-
1
94-9]. Colorless oil, bp 169–1708C, lit.11a 169–1718C. H
3
(C6D6): 0.98 [d, 12H, J(H,H)¼6 Hz, NHCH(CH3)2], 0.88
3.1.15. 1,4-Di-tert-butylpiperazine (2d). [CAS 10125-77-
6]. Isolated as colorless solid by fractional distillation and
further purified by filtration of a hexane solution (,10%) over
[s, 2H, NH], 2.58 [s, 4H, NCH2], 2.66 [sept, 2H,
3J(H,H)¼6 Hz, CH(CH3)2]. 13C (C6D6): 23.4 [CH(CH3)2],
48.0 [CH(CH3)2], 50.7 [NCN2]. GC-MS: tr¼7.2 min, m/z
(rel. int. %)¼145(75) [Mþ1]þ, 86(25), 72(100), 58(25).
1
neutral Al2O3, bp 205–2068C, mp 83.5–84.58C H (C6D6):
1.02 [s, 18H, C(CH3)3], 2.53 [s, 8H, NCH2]. 13C (C6D6): 26.1
[C(CH3)3], 46.8 [NCH2], 53.1 [C(CH3)3]. GC-MS:
tr¼10.0 min, m/z (rel. int. %)¼198(15), 183(100), 157(5),
141(5), 127(55), 112(5), 98(10), 85(20), 70(15), 56(20).
3.1.10. 1,4-Diisopropylpiperazine (2c). [CAS 21943-18-
01]. Colorless, viscous oil, bp 178–1808C, lit.9c 93–
948C/13 Torr. 1H (C6D6): 0.90 [d, 12H, 3J(H,H)¼6 Hz,
NCH (CH3)2], 2.46 [s, 8H, NCH2], 2.73 [sept, 2H,
3.1.16. 1,4,7-Tri-tert-butyl-1,4,7-triazaheptane (3d). CAS
[24426-18-4]. Colorless, viscous oil, bp 94–958C/0.1 Torr,
3J(H,H)¼6 Hz,
NCH(CH3)2].
13C
(C6D6):
18.7
9c
1
[NCH(CH3)2], 49.0 [NCH2], 54.4 [NCH (CH3)2]. GC-MS:
tr¼9.16 min, m/z (rel. int. %)¼170(40), 155(100), 140(5),
127(15), 112(25), 98(60), 84(75), 70(30), 56(80).
lit.
148–1508C/17 Torr. H (C6D6): 0.75 [s, 2H, NH],
1.03 [s, 9H, 4-C(CH3)3], 1.11 [s, 18H, 1,7-C(CH3)3], 2.55–
2.65 [m, 8H, NCH2]. 13C (C6D6): 27.4 [4-C(CH3)3], 29.5
[1,7-C (CH3)3], 44.1 [NHCH2], 49.8 [NHC(CH3)3],
52.8 [CH2N(tBu)CH2], 54.6 [C2NC(CH3)3]. GC-MS: tr¼
11.5 min, m/z (rel. int. %)¼272(50) [Mþ1]þ, 256(5)
[M2CH3]þ, 185(60), 173(10), 157(10), 129(75), 113(10),
100(100), 73(80), 57(20).
3.1.11. 1,4,7-Triisopropy1-1,4,7-triazaheptane (3c). CAS
[10524-50-2]. Colorless, viscous oil, bp 79–808C/0.1 Torr,
lit.9c 123–1258C/14 Torr. 1H (C6D6): 0.89 [d, 6H, 3J(H,H)¼
3
7 Hz, 4-CH(CH3)2], 1.07 [d, 12H, J(H,H)¼7 Hz, 1,7-CH
(CH3)2], 1.30 [s, 2H, NH], 2.43 [t, 4H, 3J(H,H)¼6 Hz,
3,5-CH2], 2.57 [br, 4H, 3J(H,H)¼6 Hz, 2,6-CH2], 2.74
3.1.17. N,N0-Diphenylethylenediamine (1e). CAS [150-
61-8]. Colorless solid, mp 68.5–69.08C, lit 14 65–678C, bp
160–1628C/0.1 Torr. 1H (C6D6): 2.79 [s, 4H, CH2], 3.19 [s,
2H, NH], 6.40 [d, 4H, 3J(H,H)¼7 Hz, ortho-C6H5], 6.76 [t,
2H, 3J(H,H)¼7 Hz, para-C6H5], 7.15 [t, 4H, 3J(H,H)¼8 Hz,
meta-C6H5], 13C (C6D6): 43.0 [CH2], 113.2 [ortho-C6H5],
117.8 [para-C6H5], 129.5 [meta-C6H5], 148.5 [ipso-C6H5].
GC-MS: tr¼15.6 min, m/z (rel. int. %)¼212(25) [M]þz,
106(100), 77(35).
3
[sept, 2H, J(H,H)¼6 Hz, 1,7-CH(CH3)2], 2.80 [sept, 1H,
3J(H,H)¼6 Hz, 4-CH(CH3)2]. 13C (C6D6): 18.3 [4-CH
(CH3)2], 23.7 [1.7-CH (CH3)2], 46.8 [3,5-NCH2], 49.2
[1,7-CH (CH3)2], 50.3 [HNCH2], 50.5 [4-CH(CH3)2].
GC-MS: tr¼10.8 min, m/z (rel. int. %)¼230(80) [Mþ1]þ,
157(5), 100(100).
3.1.12. 1,4,7,10-Tetraisopropyl-1,4,7,10-tetraazadecane
(4c). No CAS entry. Colorless, viscous oil, bp 160–
1
3
1618C/0.1 Torr. H (C6D6): 0.96 [d, 12H, J(H,H)¼6 Hz,
4,7-CH(CH3)2], 1.09 [d, 12H, 3J(H,H)¼6 Hz, 1,10-
CH(CH3)2], 1.44 [s, 2H, NH], 2.47 [s, 4H, 5,6-CH2],
3.1.18. 1,4-Diphenylpiperazine (2e). CAS [613-39-8].
Colorless solid, mp 164–1658C, lit.16a 164–1658C, lit.16b
164.38C 1H (C6D6): 2.94 [s, 8H, NCH2], 6.40 [d, 4H,
3
3
2.52 [pseudo-q, 4H, J(H,H)¼7 Hz, 2-CH2], 2.62 [br, 4H,
3J(H,H)¼7 Hz, ortho-C6H5], 6.85 [t, 2H, J(H,H)¼7 Hz,
3
3
3-CH2], 2.76 [sept, 2H, J(H,H)¼7 Hz, CH(CH3)2], 2.85
para-C6H5], 7.22 [t, 4H, J(H,H)¼7 Hz, meta-C6H5]. 13C
3
[sept, J(H,H)¼7 Hz, CH(CH3)2]. 13C (C6D6): 18.4 [4,7-
(C6D6): 49.3 [CH2], 116.7 [ortho-C6H5], 120.1 [para-
C6H5]. 129.3 [meta-C6H5], 151.8 [ipso-C6H5]. GC-MS:
tr¼15.6 min, m/z (rel. int. %)¼238(100) [M]þ, 223(20),
196(15), 132(55), 105(60), 104(74), 77(50).
CH(CH3)2], 23.6 [1,10-CH(CH3)2], 46.8 [NCH2], 49.3
[NCH2], 51.1, 51.2, 51.5 [NCH2þNCH (CH3)2]. GC-MS:
tr¼13.1 min, m/z (rel. int. %)¼315(75) [Mþ1]þ, 169(25),
100(100). EI HRMS m/z calcd. for C18H4345 [MþH]þ:
315.3488. Found: 315.3479.
3.1.19. 1,4,7-Tripheny1-1,4,7-triazaheptane (3e). CAS

M. K. Denk et al. / Tetrahedron 59 (2003) 7565–7570
7569
36, 2607–2609. (h) Denk, M. K.; Thadani, A.; Hatano, K.;
Lough, A. J. Angew. Chem. 1997, 109, 2719–2721.
[68360-81-6]. Colorless solid, mp 118–1198C, bp 250–
1
3
2528C/0.1 Torr. H (C6D6): 2.90 [pseudo-q, 4H, J(H,H)¼
3
4. (a) Hitchcock, A. P.; Ennis, L. E.; Lehmann, J. F.; Denk, M. K.
J. Electron. Spectrosc. 2001, 114, 1037–1041. (b) Leites,
L. A.; Bukalov, S. S.; Denk, M. K.; West, R.; Haaf, M. J. Mol.
Struct.-THEOCHEM 2000, 550, 329–335. (c) Lehmann, J. F.;
Urquhart, S. G.; Ennis, L. E.; Hitchcock, A. P.; Hatano, K.;
Gupta, S.; Denk, M. K. Organometallics 1999, 18,
1862–1872. (d) Haaf, M.; Schmiedl, A.; Schmedake, T. A.;
Powell, R. A.; Millevolte, A. J.; Denk, M. K.; West, R. J. Am.
Chem. Soc. 1998, 120, 12714–12719. (e) Denk, M. K.;
Hatano, K.; Lough, A. J. Eur. J. Inorg. Chem. 1998,
1067–1070. (f) Urquhart, S.; Hitchcock, A. P.; Denk, M. K.
Organometallics 1998, 17, 2352–2360. (g) Metzler, N.; Denk,
M. K. Chem. Commun. 1996, 2657–2658. (h) Denk, M. K.;
Lennon, R.; Hayashi, R.; West, R.; Haaland, A.; Belyakov,
A. V.; Verne, H. P.; Wagner, M.; Metzler, N. J. Am. Chem.
Soc. 1994, 116, 2691–2692. (i) Denk, M.; Hayashi, R. K.;
West, R. J. Am. Chem. Soc. 1994, 116, 10813–10814. (j) Denk,
M.; Green, J. C.; Metzler, N.; Wagner, M. J. Chem. Soc.,
Dalton Trans. 1994, 2405–2410. (k) Denk, M.; Hayashi, R. K.;
West, R. J. Chem. Soc., Chem. Commun. 1994, 33–34.
5. (a) Denk, M. K.; Gupta, S.; Ramachandran, R. Tetrahedron
Lett. 1996, 9025–9028. (b) Denk, M. K.; Gupta, S.;
Ramachandran, R. Eur. J. Inorg. Chem. 1999, 41–49.
6. (a) Langenbeck, W.; Augustin, M.; Richter, F. H. Chem. Ber.
1961, 94, 831–832. (b) Pagenkopf, G.; Margerum, D. W.
J. Am. Chem. Soc. 1970, 92, 2683–2686. (c) Yperman, J.;
Mullens, J.; Franc¸ois, J. P.; Van Poucke, L. C. Inorg. Chem.
1983, 22, 1361–1365.
6 Hz, NHCH2], 3.05 [t, 4H, J(H,H)¼7 Hz, NHCH2CH2],
3.17 [s, 2H, NH], 6.36 [d, 4H, 3J(H,H)¼8 Hz, ortho-
3
C6H5NH], 6.61 [d, 2H, J(H,H)¼9 Hz, ortho-C6H5NC2],
3
6.74 [t, 2H, J(H,H)¼7 Hz, para-C6H5NH], 6.80 [t, 1H,
3J(H,H)¼7 Hz, para-C6H5NC2], 7.14 [t, 4H, 3J(H,H)¼
3
8 Hz, meta-C6H5NH], 7.22 [t, 2H, J(H,H)¼7 Hz, meta-
C6H5NC2]. 13C (C6D6): 41.3 [NHCH2], 50.9 [NHCH2CH2],
113.1 [ortho-C6H5NH], 113.3 [ortho-C6H5NC2], 117.5
[para-C6H5NC2], 117.8 [para-C6H5NH], 129.7 [meta-
C6H5NH], 129.9 [meta-C6H5NC2], 148.3 [ipso-C6H5NH],
148.4 [ipso-C6H5NC2]. EI-MS (direct inlet): m/z (rel. int.
%)¼332(74) [Mþ1]þ, 225(45), 212(50), 132(28), 120(100),
106(46), 91(26), 77(48), 65924).
Acknowledgements
This work has been supported by the Natural Sciences and
Engineering Research Council of Canada (NSERC) through
an operating grant and the Government of Ontario through a
Premiers Research Excellence Award (MKD, 2002–2007).
The comments of Professor Gordon Lange (University
of Guelph) on parts of the manuscript are gratefully
acknowledged.
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N,N0-diphenylethylenediamine (Aldrich D2, 700-4N, mp
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18. Quarternary ammonium salts were suggested as other possible
side products by one referee. While we have no evidence for
their formation under the reaction conditions employed, their
formation under more forcing conditions seems indeed likely.
¨
Previously reported melting points (a) Schonberg, A. Chem.