Novel reaction of dimethylaniline with tetrabromomethane producing 4,4′-methylenebis(N,N-dimethylaniline)

Article abstract of DOI:10.1081/SCC-120020199

Reaction of N,N-dimethylaniline (1) with tetrahalomethanes such as tetrabromomethane and tetrachloromethane in acetonitrile was found to give 4,4′-methylenebis(N,N-dimethylaniline) (2) in considerable yield. The reaction is considered to be initiated by t

Full text of DOI:10.1081/SCC-120020199

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Novel Reaction of Dimethylaniline with
Tetrabromomethane Producing 4,4′-Methylenebis(N,N-
Dimethylaniline)
Yoshio Matsubara a , Takuya Matsuda a , Atsuhisa Kato a , Yoshikatsu Kakedai a & Yoshihiro
Yamaguchi a
a Faculty of Science and Engineering , Kinki University , Kowakae, Higashi-Osaka, Japan
Published online: 17 Aug 2006.
To cite this article: Yoshio Matsubara , Takuya Matsuda , Atsuhisa Kato , Yoshikatsu Kakedai & Yoshihiro Yamaguchi (2003)
Novel Reaction of Dimethylaniline with Tetrabromomethane Producing 4,4′-Methylenebis(N,N-Dimethylaniline), Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 33:11, 1885-1889, DOI:
10.1081/SCC-120020199
To link to this article: http://dx.doi.org/10.1081/SCC-120020199
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 11, pp. 1885–1889, 2003
Novel Reaction of Dimethylaniline with
Tetrabromomethane Producing
4,40-Methylenebis(N,N-Dimethylaniline)
*
Yoshio Matsubara, Takuya Matsuda, Atsuhisa Kato,
Yoshikatsu Kakedai, and Yoshihiro Yamaguchi
Faculty of Science and Engineering, Kinki University,
Kowakae, Higashi-Osaka, Japan
ABSTRACT
Reaction of N,N-dimethylaniline (1) with tetrahalomethanes such as
tetrabromomethane and tetrachloromethane in acetonitrile was
found to give 4,40-methylenebis(N,N-dimethylaniline) (2) in consider-
able yield. The reaction is considered to be initiated by the electron
transfer from N,N-dimethylaniline (p-donor) to tetrahalomethane
(s-acceptor).
*Correspondence: Yoshio Matsubara, Faculty of Science and Engineering,
Kinki University, 3-4-1 Kowakae, Higashi-Osaka, 577-8502, Japan.
1885
DOI: 10.1081/SCC-120020199
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
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1886
Matsubara et al.
The electron transfer (ET) is one of the most important elementary
process in the chemical and biochemical reactions.[1] Although many
reactions via CT complexes as the electron transfer process have been
reported,[2] to our knowledge, useful ones as the synthetic reactions are
very few. Very recently, we reported a versatile, single-step synthesis
of cyanocinnolines from aromatic hydrazones (p-donor) and TCNE
(p-acceptor) via radical ion pair dyad.[3] Selective radical bromination of
adamantane using OHꢀ (s-donor)/CBr4 (s-acceptor) is also reported.[4]
In this article, we wish to present a novel reaction producing
4,40-methylenebis(N,N-dimethylaniline) (2) using N,N-dimethylaniline
(1) (p-donor) and tetrabromomethane (s-acceptor) (Sch. 1).
Reaction of 1 with various halomethanes in several solvents is sum-
marized in Table 1. The reaction mixture (colorless) turned pale yellow,
violet, finally deep violet with time. When 1 (10 mmol) and tetrabromo-
methane (10 mmol) in acetonitrile (10 mL) was refluxed for 24 h, 2 (47%)
and 4,40,400-methylidynetris(N,N-dimethylaniline) (3) (11%) were obtained
along with trace amount of N-[4[bis[4-(dimethylamino)-phenyl]methy-
lene]-2,5-cyclohexadien-1-ylidene]-N-methylmethanaminum bromide (4),
respectively (Table 1, Entry 3).
Without solvent the reaction did not take place (Table 1, Entries 1
and 2). The crucial factor for 2 formation was the selection of solvents and
halomethanes. Acetonitrile among solvents used, and tetrabromomethane
among halomethanes used were the best choice (Table 1).
In addition we observed that (i) CHBr3 and PhNHCH3 form during
the reaction, (ii) 4-t-butyl-N,N-dimethylaniline ( p-substituted dimethyl-
aniline) or N,N-dimethylcyclohexylamine (nonaromatic dimethylamine)
Scheme 1. Reaction of dimethylaniline with tetrabromomethane in CH3CN.

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4,40-Methylenebis(N,N-Dimethylaniline)
Table 1. Reaction of 1 with halomethanes.a
1887
Substrate Halomethanes
(mmol)
Solvent
(mL)
Product 2 Product 3 Product 4
yield (%)
Entry
(mmol)
yield (%)
yield (%)
1
2
1 (10)
1 (10)
1 (10)
1 (1)
CBr4 (10)
CCl4 (10)
CBr4 (10)
CBr4 (2)
—
—
—
—
—
—
11 [17]
—
—
—
—
2
—
—
3
CH3CN (10)
CH3CN (5)
CH3CN (5)
Benzene (10)
CH2Cl2 (10)
CH3CN (10)
CH3CN (10)
CH3CN (10)
CH3CN (10)
47 [60]
[84]
[92]
1
Trace [–]
—
—
4
5
1 (1)
CBr4 (4)
6
1 (10)
1 (10)
1 (10)
1 (10)
1 (10)
1 (10)
CBr4 (10)
CBr4 (10)
CCl4 (10)
CHBr3 (10)
CHCl3 (10)
CHI3 (10)
—
—
7
—
8
8
15
Trace
Trace
Trace
Trace
9
3
10
11
3
2
6
2
aThe reaction was carried out at reflux in solvent under air atmosphere for 24 h.
Isolated product yield is shown. The value in parentheses shows HPLC yield.
do not afford the corresponding diphenylmethane (2) and any products,
(iii) light promotes, to some extent, the reaction, (iv) FeCl3 instead of CBr4
provides 2 in the absence of O2, and (v) the major product in the reaction
with TiCl4 in CH2Cl2 is not 2, but N,N,N0,N0-tetramethyl benzidine.
Based on these observations our reaction leading to 2 is considered to
proceed as shown in Sch. 2.
Formation of iminium ion intermediate (I) seems to be certain from
the chemical trapping of I generated in the dimethylaniline-Fe(III)
system.[5] Formation of 3 could be explained by the hydride (hydrogen
atom) abstraction from 2 followed by reaction with 1.
It should be noted that considerable amount of 4,40-methylenebis-
(N,N-dimethylaniline) is formed from dimethylaniline and CBr4 (week
acceptor) in acetonitrile.
EXPERIMENTAL SECTION
General Procedure for the Reaction of N,N-dimethylaniline
(1) with Various Halomethanes in Several Solvents
A typical procedure is described for the reaction of N,N-dimethyl-
aniline (1) with tetrabromomethane in acetonitrile. Tetrabromomethane
(10 mmol) was added dropwise to a acetonitrile solution (10 mL)

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1888
Matsubara et al.
Scheme 2. Proposed pathway for 2 formation.
of N,N-dimethylaniline (10 mmol). After the addition was completed, the
mixture was refluxed under air atmosphere for 24 h. As judged by TLC
analysis, the N,N-dimethylaniline was almost consumed, and then reaction
mixture was evaporated under reduced pressure. The residue was sepa-
rated by column chromatography (silica gel) with eluate (from benzene to
methanol) to give 4,40-methylenebis(N,N-dimethylaniline) (2) (1.99 mmol,
m.p. 89.0–91.0ꢁC), 4,40,400-methylidynetris(N,N-dimethylaniline) (3)
(0.28 mmol, 176.0–177.0ꢁC), and trace amount of N-[4[bis[4-(dimethyl-
amino)-phenyl]methylene]-2,5-cyclohexadien-1-ylidene]-N-methylmethan-
aminum bromide (4) (crystal violet analogue, ꢀmax 589 nm in MeOH),
respectively. The reaction products were identified using 1H NMR,
13C NMR, mass spectral analysis and HPLC, GLC chromatographic
examination revealed as compared with the authentic samples such as 2,
3, 4, N-methylaniline and bromoform. Calculation of HPLC yields were
run using calibration curves with anthracene as an internal standard and
yields of 2 and 3 are based on the 3 equivalents of 1 leading to 2 and 4
equivalents of 1 leading to 3.
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1889
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Received in Japan August23, 2002

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