A Simple One-Pot Reaction to the Bis-dibenzo[b,f][1,5]diazocines: Useful Precursors of Novel Macrocycles

Article abstract of DOI:10.1055/s-2003-42448

The title compounds, namely 8,8′-bis-5,6,11,12-tetrahydrodibenzo[b,f] [1,5]diazocines, have been synthesized in 36-81% yields through a one-pot reaction by treatment of N,N,N′,N′-tetramethylbiphenyldiamine with the Vilsmeier's reagents derived from substituted N-methylformanilides and POCl₃. This was another application of 't-amino effect' in the synthesis of eight-membered ring systems. These products are designed as the precursors of novel macrocycles.

Full text of DOI:10.1055/s-2003-42448

PAPER
2839
A Simple One-Pot Reaction to the Bis-dibenzo[b,f][1,5]diazocines: Useful
Precursors of Novel Macrocycles
B
is-dibenzo[b,f][
1
i
,5]diaz
n
U
sef
g
C
vel
M
acrocyclesheng,*a Bo Wang,a Otto Meth-Cohnb
a
Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
E-mail: yingcheng1@263.net
b
Chemistry Department, Sunderland University, Sunderland, UK SR1 3SD, UK
Received 5 August 2003; revised 25 September 2003
tha[1,2-f][1,5]diazocines
6
or benzo[b]naphtha[2,1-
Abstract: The title compounds, namely 8,8 -bis-5,6,11,12-tetrahy-
drodibenzo[b,f][1,5]diazocines, have been synthesized in 36–81%
yields through a one-pot reaction by treatment of N,N,N ,N -tetram-
ethylbiphenyldiamine with the Vilsmeier’s reagents derived from
f][1,5]diazocines 7,5 and pentacyclic heterocycles, di-
benzo[b,b ]benzo[1,2-f:4,5-f ]bis[1,5]diazocines 86
(Figure 1). Herein we report our new synthetic approach
substituted N-methylformanilides and POCl3. This was another ap- to the novel heterocycles, bis-dibenzo[b,f][1,5]diazocines
plication of ‘t-amino effect’ in the synthesis of eight-membered ring
9, which could be the better candidates for macrocycles
systems. These products are designed as the precursors of novel
macrocycles.
due to their flexible ring system, as the intramolecular or
intermolecular coupling of compound 9 (X = Br) would
lead to the formations of bracelets such as 10 with differ-
ent sizes (Figure 2).
Key words: 8,8 -bis-5,6,11,12-tetrahydrodibenzo[b,f][1,5]diazo-
cines, N,N,N ,N -tetramethylbiphenyldiamine, N-methylformanil-
ides, Vilsmeier’s reagent, ‘t-amino effect’
H3C
N
CHO
H3C
Several years ago, we established a simple one-pot reac-
tion for the synthesis of 5,6,11,12-tetrahydrodiben-
N
X
N
CH3
zo[b,f][1,5]diazocines 4 by treatment of 4-substituted
X
N
6
N
N,N-dimethylanilines 3 with the Vilsmeier’s reagents that
were derived from the N-methylformanilides 1 with phos-
phorus oxychloride or oxalyl chloride1,2 (Scheme 1). This
methodology was then extended to the synthesis of ben-
zo[2,3]pyrido [6,7-b][1,5] diazocine 5.3 It was reported4
that the tetrahydrodibenzo[b,f][1,5]diazocines preferred a
boat conformation, and consequently we envisaged that
larger assemblies of linear fused analogues could be of in-
terest in the synthesis of novel macrocycles such as ‘mo-
lecular bracelets’. With this aim in mind, we have
synthesized the tetracyclic heterocycles, benzo[b]naph-
CH3
H3C
5
N
X
H3C
N
H3C
N
N
CH3
7
X
X
N
N
CH3
CH3
8
Figure 1
CH3
N
H3C
H
CH3
CH3
N
CH3
Y
N
N
Cl
CHO
POCl3
Y
X
H
N
CH3
X
3
C
X
1
H2
2
H3C
H3C
N
N
Y
Y
X
X
N
N
CH3
CH3
4
Scheme 1
SYNTHESIS 2003, No. 18, pp 2839–2843
x
x.
x
x
.
2
0
0
3
Advanced online publication: 23.10.2003
DOI: 10.1055/s-2003-42448; Art ID: F06603SS
© Georg Thieme Verlag Stuttgart · New York

2840
Y. Cheng et al.
PAPER
CH3
X
N
CH3
N
N
H3C
N
N
9
N
X
H3C
N
N
H3C
CH3
N
N
n
10
N
N
X
X
n = 1, 2
9'
CH3
H3C
Figure 2
One of the starting materials, N,N,N ,N -tetramethylbiphe- a large amount of starting materials. We then tried the re-
nyldiamine 11, was prepared from methylation of biphe- action using phosphorus oxychloride (POCl3) both as the
nyl diamine with trimethyl phosphate and followed by reactant and the solvent.
alkaline hydrolysis. The expected product precipitated in
high yield from the basic aqueous solution. However, an
attempted purification of crude products using silica gel
column chromatography resulted in a great loss of chem-
While heating in POCl3 at 75–80 °C, the N-methylforma-
nilides 1 were readily converted into the Vilsmeier’s re-
agents 2, which underwent a smooth reaction with the
N,N,N ,N -tetramethylbiphenyldiamine (11) in POCl3 at
ical yield, because the basic tetramethylbiphenyldiamine
80 °C for 15–16 hours to give the desired products 9 in
could not be totally eluted out from the column even via
36–81% isolated yields (Table 1). It should be noted that
using a huge amount of solvent. Fortunately, the TLC
the purification of the crude products with column chro-
analysis indicated that the crude products were of almost
matography proved inefficient, because the products pre-
identical composition. Therefore, tetramethylbiphenyl-
cipitated from the silica gel. The pure products (in powder
diamine was used in the next step reaction without further
form) were finally obtained by dissolving the precipitate
purification.
in CHCl3 and precipitating again with EtOH. The mecha-
To synthesize the bis-dibenzodiazocines 9, we initially nism of the formation of compounds 9 is similar to that of
prepared the Vilsmeier’s reagent by treatment of the me- 4. The biphenyldiamine 11 was double-formylated by the
thylformanilide 1 with oxalyl chloride, and then allowed Vilsmeier’s reagent to form a bis-iminium salt 12, which
it to react with diamine in CHCl3 solution. After refluxing transformed into the intermediate 13 through the hydride
for a period of time, the reaction mixture was basified and migration via the ‘t-amino effect’ rearrangement.7 The in-
worked-up. Under these reaction conditions, however, the tramolecular cyclization of 13 led to the formation of bis-
product 9 was obtained in only very low yield along with dibenzodiazocines 9 (Scheme 2).
CH3
CH3
N
N
Cl
CHO
(H3C)2N
N(CH3)2
POCl3
H
X
X
11
1
2
X = p - OMe, Me, OEt, Et, F, Cl, Br;
X = o - OMe, Me, Cl
H3C
CH3
+
N
CH3
X
N
H3C
H3C
+
X
N
N
N
N
CH3
+
CH3
+
N
N
X
H3C
X
X
CH3
CH3
12
CH3
13
N
H3C
CH3
10
CH3
11
12
9
7
N
N
N
N
8
1
H3C
N
N
X
2
6
X
N
CH3
H3C
X
5
9'
9
H3C
3
4
X = 2- OMe, Me, OEt, Et, F, Cl, Br;
X = 4- OMe, Me, Cl
Scheme 2
Synthesis 2003, No. 18, 2839–2843 © Thieme Stuttgart · New York

PAPER
Bis-dibenzo[b,f][1,5]diazocines: Useful Precursors of Novel Macrocycles
2841
Table 1 The Isolated Yields of Products 9
1
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
X
9
p-MeO
9a
p-Me
9b
p-EtO
9c
p-Et
9d
p-F
9e
p-Cl
9f
p-Br
9g
o-MeO
9h
o-Me
9i
o-Cl
9j
X
2-MeO
2-Me
42
2-EtO
39
2-Et
38
2-F
53
2-Cl
81
2-Br
79
4-MeO
36
4-Me
69
4-Cl
53
Yield (%) 65
8,8 -Bis-5,6,11,12-tetrahydrodibenzo[b,f][1,5]diazocines 9:
General Procedure
The structure of products 9 was assigned on the basis of
1
IR, H NMR, 13C NMR and MS spectroscopic data. A
Under a N2 atmosphere, the mixture of substituted N-methylforma-
nilide 1 (10 mmol) in POCl3 (10 mL) was heated at 75–80 °C for 30
min to form a red solution. The powder of N,N,N ,N -tetramethylbi-
phenyldiamine (11) was added portionwise to the red solution of the
Vilsmeier’s reagent in POCl3 after it cooled to r.t. The mixture was
then heated at 80 °C for about 16 h and then quenched to ice-cold
water (100 mL). The aq solution was basified to pH 9 with 10%
NaOH and extracted efficiently with a large amount of CHCl3 (5 ×
100 mL). After drying over MgSO4 and removal of the solvent, the
crude product was precipitated by refluxing the residue in EtOH.
The crude products were further purified by dissolving in CHCl3,
filtering off the insoluble materials and precipitating again with
EtOH.
characteristics of the compounds 9 in 1H NMR spectrum
is that the methylene protons of the diazocine ring ap-
peared as very broad peaks around 4.5 ppm at 25 °C,
which indicated a slow conformational flexion of the
eight-membered ring. These broad peaks sharpened to a
singlet while the probe temperature was increased to 40
°C. Some products, especially the compound 9e, did not
give all quaternary carbon signals in the 13C NMR spectra
due to their very low solubility in CHCl3. All of these
products 9 are insoluble in water and almost insoluble in
most organic solvents such as EtOAc, acetone, EtOH and
DMSO. They are only slightly soluble in CHCl3 and form
a yellow solution. The alkyl or alkoxy substituted prod-
ucts show the better solubility in CHCl3 as compared to
their halogen substituted analogs, and the 4-substituted
one is more soluble than its 2-substituted analogs. Since
the products were isolated through precipitation from
EtOH, their isolated yields not only depended on the elec-
tronic and steric effects of substitutents, but also on their
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-methoxydiben-
zo[b,f][1,5]diazocine (9a)
Yield: 65%; mp 241–242 °C.
IR (KBr): 1608, 1504 cm–1.
1H NMR (500 MHz, CDCl3): = 7.57 (d, J = 6.4 Hz, 1 H), 7.50 (s,
1 H), 7.10 (br s, 2 H), 6.94 (d, J = 7.1 Hz, 1 H), 6.90 (s, 1 H), 4.52
(s, 2 H), 4.46 (s, 2 H), 3.95 (s, 3 H), 3.07 (s, 3 H), 3.00 (s, 3 H).
solubility in EtOH. Although those powdery products 13C NMR (125 MHz, CDCl3): = 152.5, 149.8, 145.5, 131.3, 129.9,
129.4, 126.8, 126.2, 117.7, 117.6, 116.1, 113.2, 59.0, 58.7, 56.2,
40.0, 39.7.
MS (EI): m/z (%) = 162 (35), 503 (37), 534 (100) [M+], 535 (35).
have been purified by dissolving in CHCl3 and then pre-
cipitating with EtOH for several times, they still did not
give satisfactory elemental analysis. It should also be
pointed out that the compounds 9 always gave a middle to
strong absorption band around 3430 cm–1 in their IR spec-
tra. This absorption became weaker but did not disappear
totally, even after heating for long under vacuum indicat-
ing a strong complexation with water molecules. The
composition of compounds 9 was finally confirmed by
HRMS.
HRMS (FT–MS): m/z calcd for C34H38N4O2: 534.2989; found:
534.2992.
8,8 -Bis-5,6,11,12-tetrahydro-2,5,11-trimethyldibenzo[b,f]-
[1,5]diazocine (9b)
Yield: 42%; mp 264–265 °C.
IR (KBr): 1610, 1509 cm–1.
1H NMR (500 MHz, CDCl3): = 7.45 (dd, J = 8.3, 2.0 Hz, 1 H),
7.37 (s, 1 H), 7.05 (d, J = 7.9 Hz, 1 H), 6.98 (s, 1 H), 6.95 (d, J = 8.3
Hz, 1 H), 6.84 (d, J = 8.1 Hz, 1 H), 4.38 (s, 2 H), 4.34 (s, 2 H), 2.91
(s, 3 H), 2.87 (s, 3 H), 2.33 (s, 3 H).
13C NMR (125 MHz, CDCl3): = 149.8, 149.0, 132.4, 131.2, 129.9,
128.9, 127.9, 127.5, 126.2, 116.2, 116.1, 59.3, 59.0, 39.6, 39.5,
20.6.
In conclusion, we have provided a very simple and one-
pot reaction for the synthesis of novel heterocycles, 8,8 -
bis-5,6,11,12-tetrahydrodibenzo[b,f][1,5]diazocines, gen-
erally in good yields. We envisage that the intramolecular
or intermolecular coupling within one or two molecules of
these new heterocycles would lead to the construction of
novel supramolecular systems, and this study is under
progress.
MS (EI): m/z (%) = 146 (55), 471 (47), 502(100) [M+], 503 (45).
HRMS (FT–MS): m/z calcd for C34H38N4: 502.3091; found:
502.3092.
1
Melting points are uncorrected. H NMR and 13C NMR were ob-
tained on a Bruker Avance 500 spectrometer. IR spectra were re-
corded using an AVATAR 360 FT-IR spectrometer. Mass spectra
were recorded on a Trace MS instrument (EI-MS) or Bruker APEX-
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-ethoxydiben-
zo[b,f][1,5]diazocine (9c)
Yield: 39%; mp 257–259 °C.
2
(HRMS). The two starting materials, p-substituted N-
IR (KBr): 1608, 1504 cm–1.
1H NMR (500 MHz, CDCl3): = 7.44 (dd, J = 8.3, 1.8 Hz, 1 H),
7.36 (s, 1 H), 6.96 (d, J = 8.3 Hz, 1 H), 6.88 (d, J = 8.5 Hz, 1 H),
methylformanilide8 and N,N,N ,N -tetramethylbiphenyldiamine,9
were prepared according to the literature methods.
Synthesis 2003, No. 18, 2839–2843 © Thieme Stuttgart · New York

2842
Y. Cheng et al.
PAPER
6.81 (dd, J = 8.6, 2.6 Hz, 1 H), 6.78 (d, J = 2.4 Hz, 1 H), 4.36 (s, 2
H), 4.31 (s, 2 H), 4.05 (q, J = 7.0 Hz, 2 H), 2.92 (s, 3 H), 2.84 (s, 3
H), 1.43 (t, J = 7.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3): = 152.1, 149.9, 145.6, 131.5, 129.9,
129.5, 128.3, 126.1, 118.6, 117.8, 116.4, 114.2, 64.5, 59.5, 59.1,
40.1, 39.6, 15.4.
1H NMR (500 MHz, CDCl3): = 7.45 (dd, J = 8.2, 1.5 Hz, 1 H),
7.35 (s, 1 H), 7.27–7.32 (m, 2 H), 6.96 (d, J = 8.3 Hz, 1 H), 6.77 (d,
J = 8.6 Hz, 1 H), 4.38 (s, 2 H), 4.33 (s, 2 H), 2.90 (s, 3 H), 2.87 (s,
3 H).
13C NMR (125 MHz, CDCl3): = 149.9, 149.4, 134.2, 131.4, 129.9,
129.1, 127.1, 126.5, 117.3, 116.4, 110.1, 58.9, 58.5, 39.5, 39.4.
MS (EI): m/z (%) = 531 (45), 562 (100) [M+], 563 (40).
MS (EI): m/z (%) = 131 (40), 601 (35), 630 (55) [M+], 632 (100),
634 (50).
HRMS (FT–MS): m/z calcd for C36H42N4O2: 562.3302; found:
562.3271.
HRMS (FT–MS): m/z calcd for C32H33N4Br2: 631.1066; found:
631.1059.
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-ethyldibenzo-
[b,f][1,5]diazocine (9d)
Yield: 38%; mp 273–274 °C.
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-4-methoxydiben-
zo[b,f][1,5]diazocine (9h)
Yield: 36%; mp 262–264 °C.
IR (KBr): 1607, 1498 cm–1.
1H NMR (500 MHz, CDCl3): = 7.46 (d, J = 8.1 Hz, 1 H), 7.40 (s,
1 H), 6.93 (d, J = 7.6 Hz, 2 H), 6.88 (d, J = 7.8 Hz, 1 H), 6.84 (d, J
= 7.1 Hz, 1 H), 4.55 (s, 2 H), 4.27 (s, 2 H), 3.92 (s, 3 H), 2.92 (s, 3
H), 2.61 (s, 3 H).
IR (KBr): 1610, 1509 cm–1.
1H NMR (500 MHz, CDCl3): = 7.45 (dd, J = 8.3, 2.0 Hz, 1 H),
7.37 (d, J = 1.7 Hz, 1 H), 7.07 (d, J = 8.1 Hz, 1 H), 7.00 (s, 1 H),
6.95 (d, J = 8.3 Hz, 1 H), 6.86 (d, J = 8.1 Hz, 1 H), 4.39 (s, 2 H),
4.36 (s, 2 H), 2.91 (s, 3 H), 2.88 (s, 3 H), 2.63 (q, J = 7.6 Hz, 2 H),
1.28 (t, J = 7.6 Hz, 3 H).
13C NMR (125 MHz, CDCl3): = 149.7, 149.1, 137.0, 134.1, 131.2,
129.8, 127.8, 127.6, 127.4, 126.2, 116.1, 116.0, 59.3, 59.1, 39.5,
39.0, 28.2, 16.0.
13C NMR (125 MHz, CDCl3): = 154.5, 148.9, 140.7, 134.1, 131.7,
130.7, 126.9, 126.2, 123.5, 121.8, 115.0, 111.9, 58.9, 58.6, 56.2,
39.0, 38.7.
MS (EI): m/z (%) = 160 (25), 234 (26), 499 (35), 530 (100) [M+],
MS (EI): m/z (%) = 162 (35), 503 (30), 534 (100) [M+], 535 (35).
531 (35).
HRMS (FT–MS): m/z calcd for C34H38N4O2: 534.2989; found:
HRMS (FT-MS): m/z calcd for C36H42N4: 530.3404; found:
534.2990.
530.3398.
8,8 -Bis-5,6,11,12-tetrahydro-4,5,11-trimethyldibenzo[b,f]-
[1,5]diazocine (9i)
Yield: 69%; mp 220–222 °C.
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-fluorodibenzo-
[b,f][1,5]diazocine (9e)
Yield: 53%, mp 274–276 °C.
IR (KBr): 1608, 1505 cm–1.
1H NMR (500 MHz, CDCl3): = 7.57 (br s, 1 H), 7.49 (s, 1 H), 7.10
(d, J = 6.6 Hz, 1 H), 7.02–7.04 (m, 3 H), 4.50 (s, 2 H), 4.45 (s, 2 H),
3.05 (s, 3 H), 2.99 (s, 3 H).
IR (KBr): 1607, 1499, 1477 cm–1.
1H NMR (500 MHz, CDCl3): = 7.45 (dd, J = 8.3, 1.9 Hz, 1 H),
7.41 (s, 1 H), 7.16 (d, J = 7.3 Hz, 1 H), 7.05 (br s, 1 H), 6.92–6.97
(m, 2 H), 4.54 (s, 2 H), 4.26 (s, 2 H), 2.96 (s, 3 H), 2.54 (s, 3 H), 2.39
(s, 3 H).
13C NMR (125 MHz, CDCl3): = 131.3, 129.9, 127.6, 126.3, 118.1,
117.9, 116.8, 116.1, 114.6, 114.4, 59.2, 58.7, 39.9, 39.6.
MS (EI): m/z (%) = 150 (40), 479 (35), 510 (100) [M+], 511 (30).
13C NMR (125 MHz, CDCl3): = 150.6, 149.1, 134.5, 131.0, 130.5,
130.1, 129.0, 128.5, 126.1, 122.2, 114.9, 113.4, 58.9, 58.6, 39.2,
39.1, 19.5.
MS (EI): m/z (%) = 146 (37), 502(100) [M+], 503 (35).
HRMS (FT–MS): m/z calcd for C32H32N4F2: 510.2589; found:
510.2577.
HRMS (FT–MS): m/z calcd for C34H38N4: 502.3091; found:
502.3088.
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-chlorodibenzo-
[b,f][1,5]diazocine (9f)
Yield: 81%; mp 279–281 °C.
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-4-chlorodibenzo-
[b,f][1,5]diazocine (9j)
Yield: 53%; mp 199–201 °C.
IR (KBr): 1609, 1497 cm–1.
IR (KBr): 1608, 1500 cm–1.
1H NMR (500 MHz, CDCl3): = 7.57 (d, J = 7.9 Hz, 1 H), 7.48 (s,
1 H), 7.29 (d, J = 8.2 Hz, 1 H), 7.26 (s, 1 H), 7.10 (d, J = 8.0 Hz, 1
H), 6.96 (d, J = 8.4 Hz, 1 H), 4.51 (s, 2 H), 4.46 (s, 2 H), 3.03 (s, 3
H), 3.00 (s, 3 H).
13C NMR (125 MHz, CDCl3): = 149.4, 131.4, 131.3, 130.0, 128.5,
128.2, 128.2, 127.0, 126.4, 122.6, 116.6, 116.1, 58.9, 58.5, 39.6,
39.5.
1H NMR (500 MHz, CDCl3): = 7.47 (dd, J = 8.2, 2.0 Hz, 1 H),
7.42 (s, 1 H), 7.36 (d, J = 7.9 Hz, 1 H), 7.10 (d, J = 7.6 Hz, 1 H),
6.90–6.97 (m, 2 H), 4.53 (s, 2 H), 4.25 (s, 2 H), 2.93 (s, 3 H), 2.64
(s, 3 H).
13C NMR (125 MHz, CDCl3): = 148.5, 143.1, 135.9, 131.3, 130.3,
129.7, 126.3, 122.7, 120.3, 115.3, 112.2, 58.8, 58.3, 39.1, 39.0.
MS (EI): m/z (%) = 166 (40), 511(35), 542 (100) [M+], 544 (65), 546
MS (EI): m/z (%) = 166 (40), 542 (100) [M+], 544 (75), 546 (20).
(18).
HRMS (FT–MS): m/z calcd for C32H32N4Cl2: 542.1998; found:
HRMS (FT–MS): m/z calcd for C32H32N4Cl2: 542.1998; found:
542.1988.
542.1986.
Acknowledgement
8,8 -Bis-5,11-dimethyl-5,6,11,12-tetrahydro-2-bromodiben-
zo[b,f][1,5]diazocine (9g)
Yield: 79%; mp 286–288 °C.
IR (KBr): 1607, 1589, 1499 cm–1.
This work was supported by the National Natural Science Founda-
tion of China. We thank to the analytical center of Beijing Normal
University for their help with the spectroscopic analyses.
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Bis-dibenzo[b,f][1,5]diazocines: Useful Precursors of Novel Macrocycles
2843
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Synthesis 2003, No. 18, 2839–2843 © Thieme Stuttgart · New York