Photoreductive coupling of aldimines. Synthesis of C2 symmetrical diamines

Article abstract of DOI:10.1016/S0040-4020(00)00625-6

The photoreductive coupling of pyridine-, arene- and alkynecarboxaldimines is a very convenient procedure for the preparation of vicinal diamines in good to excellent yields. The usual trend gave an excess of meso diamine, which enhances the usefulness of

Full text of DOI:10.1016/S0040-4020(00)00625-6

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 7285–7289
Photoreductive Coupling of Aldimines.
Synthesis of C2 Symmetrical Diamines
*
´
´
Pedro J. Campos, Joaquın Arranz and Miguel A. Rodrıguez
´
´
´
Departamento de Quımica, Universidad de La Rioja, Grupo de Sıntesis Quımica de La Rioja, Unidad Asociada al C.S.I.C.,
Obispo Bustamante, 3, 26071 Logron˜o, Spain
Received 14 March 2000; revised 19 June 2000; accepted 6 July 2000
Abstract—The photoreductive coupling of pyridine-, arene- and alkynecarboxaldimines is a very convenient procedure for the preparation
of vicinal diamines in good to excellent yields. The usual trend gave an excess of meso diamine, which enhances the usefulness of this
method. The procedure tolerates bulky groups such as tert-butyl and diphenylmethyl on the nitrogen atom. ᭧ 2000 Elsevier Science Ltd. All
rights reserved.
Introduction
in the synthesis of different heterocyclic compounds.7,8 Our
experience in the photochemistry of imines and the growing
importance of 1,2-diamines, promted us to study the photo-
reduction of heterocyclic aldimines. Herein, we wish to
report our results in this field.
The 1,2-diamine functionality can be found in many natural
products, especially peptides, with valuable biological and
therapeutic properties.1 In recent years, several synthetic
diamine derivatives have also been employed as medicinal
agents, in particular in chemotherapy.1 Moreover, enantio-
merically pure vicinal diamines are also used increasingly in
stereoselective organic synthesis as chiral auxiliaries or as
metal ligands in catalytic asymmetric synthesis.1,2 Given the
significance of 1,2-diamines, a large number of methods for
the synthesis of these derivatives have been developed. In
principle, the reductive coupling of imines seems a simple
way to prepare symmetric vicinal diamines and, thus,
several procedures that make use of a metal or a metallic
complex have been reported.1–5 However, despite the high
versatility shown by the imines in the coupling reaction,
their photoreduction has not been extensively studied. In
fact, only one example of photoreductive coupling of aryl
N-alkylimines is described in the literature.6
Results and Discussion
First, we prepared the 3-pyridinecarboxaldehyde N-cyclo-
hexylimine 1a by a condensation of 3-pyridinecarboxalde-
hyde with cyclohexylamine. The absorption spectrum of 1a
in methanol showed bands at 202, 238 and 272 nm
(eϷ168,000, 155,000, and 55,000 MϪ1 cmϪ1, respectively).
Based on this spectrum, we carried out the irradiation of 1a
through quartz of a 2×10Ϫ2 M alcoholic solution of this
compound with a 450 W medium-pressure mercury lamp.
1
The reaction was monitored by H NMR spectroscopy.
Complete consumption of the starting material occurred
after 6 h. The reaction occurred with formation of a large
amount of polymeric material. After purification by column
chromatography, we noted the formation of the correspond-
ing d,l 2a and meso 3a 1,2-diamines (combined yield 45%),
In previous papers we have described the photochemical
behavior of several conjugated imines and their usefulness
Scheme 1.
Keywords: imines; photoreductive coupling; diamines.
* Corresponding author. Tel.: ϩ34-941-244811; fax: ϩ34-941-259431; e-mail: pedro.campos@dq.unirioja.es
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00625-6

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P. J. Campos et al. / Tetrahedron 56 (2000) 7285–7289
Table 1.
Entry
Imine 1
Ar
R
t (h)a
Yield (%)b
Ratio 2/3c
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
3-Pyridyl
3-Pyridyl
2-Pyridyl
2-Pyridyl
2-Pyridyl
2-Pyridyl
4-Pyridyl
Phenyl
c-Hex
t-Bu
n-Hex
c-Pr
c-Hex
Ph2CH
c-Hex
t-Bu
c-Hex
t-Bu
4
4
3
5
3
6
3
3
3
85
80
50
80
70
45
75
Ͼ95
75
65
52/48
38/62
43/57
37/63
48/52
50/50
44/56
45/55
58/42
49/51
5/95
9
10
11
Phenyl
2-Naphthyl
2-Naphthyl
1j
1k
10
10
c-Hex
21
a Irradiation time through Pyrex, for 1 mmol of imine 1.
b Isolated yield of isomer mixture after column chromatography.
c As determined by 300 MHz 1H NMR analysis of the crude products. Isomer structures were determined by analogy to other reported vicinal diamines.10
as elucidated by its spectroscopic data (1H and 13C NMR)
and mass spectrometry (Scheme 1).
described for the first time.5,9 The procedure tolerates bulky
groups such as tert-butyl and diphenylmethyl on the nitro-
gen atom (entries 2 and 6). In all cases, good to excellent
yields of the corresponding 1,2-diamines were obtained
(45–85%). In all the cases tested, some polymeric material
was obtained and the meso and d,l products needed to be
purified by column chromatography on silica gel.
We next investigated some mechanistic aspects of this
photoreduction reaction. We observed that the presence of
triplet quenchers (i.e. bubbling oxygen) inhibited the forma-
tion of the diamine. On the contrary, irradiation of the imine
in the presence of acetone (as triplet sensitizer) increased the
reaction rate. Both effects could indicate that the reaction
involves the formation of a triplet species. According to
these results, we irradiated 1a in the presence of acetone
through Pyrex glass (where imine absorption is almost null).
Under these experimental conditions, the polymer per-
centage was drastically reduced. Concerning the solvent,
those without hydrogen donor capability, such as tert-
butyl alcohol or n-hexane, were ineffective in the photo-
reduction coupling procedure, whereas the best results
were obtained in isopropyl alcohol. These results indicate
that hydrogen abstraction is essential for the development of
the reaction.
In order to explore the generality of the method, we under-
took the extension of this methodology to include the
irradiation of other aryl-, alkenyl- and alkynyl-based imines
with different N-substituents. We have verified the feasi-
bility of this reaction in the synthesis of 1,2-diamines
from phenyl and naphthyl aldimines (Table 1, entries
8–11). The irradiation of benzenecarboxaldimine 1h led
to the formation of symmetrical diamines in quantitative
yields (entry 8). Interestingly, the irradiation of naphthyl
derivative 1k gave the meso isomer 3k in high ratio (entry
11). The d,l diamine 2k could not be isolated.
The irradiation of alkenecarboxaldimines gave only poly-
meric material (the diamines could only be detected by
electrospray mass spectra). On the contrary, the photo-
reaction of alkynyl-based imines yielded the corresponding
diamines with meso-selectivity (Table 2, entries 1 and 2).
The d,l diamine 2m was obtained in very low yield and
could not be isolated.
The previous approach was extended to the irradiation of 2-
and 4-pyridinecarboxaldimines. The results are given in
Table 1. Some interesting points should be highlighted.
The usual trend gave a slight excess of meso diamine
(entries 2–5 and 7), in contrast to other methods reported
in the literature.1,3,4a This meso-selectivity has been recently
Table 2.
Entry
Imine 1
R1
R2
t (h)a
Yield (%)b
Ratio 2/3c
1
2
1l
1m
Ph-CuC
Ph-CuC
t-Bu
c-Hex
4
4
65
12
35/65
5/95
a Irradiation time through Pyrex, for 1 mmol of imine 1.
b Isolated yield of isomer mixture after column chromatography.
c As determined by 300 MHz 1H NMR analysis of the crude products. Isomer structures were determined by analogy to other reported vicinal diamines.10

P. J. Campos et al. / Tetrahedron 56 (2000) 7285–7289
7287
1
Conclusions
807 cmϪ1; H NMR (CDCl3) d 8.48 (dd, Jˆ4.8, 1.8 Hz,
2H), 8.35 (d, Jˆ1.8 Hz, 2H), 7.40 (d, Jˆ7.8 Hz, 2H), 7.19
(dd, Jˆ7.8, 4.8 Hz, 2H), 4.01 (s, 2H), 2.12 (m, 2H), 0.96–
1.99 (m, 22H); 13C NMR (CDCl3) d 149.8, 148.7, 136.3,
135.5, 123.1, 62.0, 53.1, 34.4, 32.5, 25.8, 24.8, 24.5; ESMS
m/z 379 (MHϩ). Anal. Calcd for C24H34N4: C: 76.13, H:
9.06, N: 14.81. Found: C: 76.03, H: 9.10, N: 14.87.
We have proven that the photoreductive coupling of
pyridine-, arene- and alkynecarboxaldimines is a very
convenient procedure for the preparation of vicinal
diamines in good to excellent yields. Moreover, the
anomalous meso-selectivity observed enhances the useful-
ness of this method. Further studies to elucidate the
mechanism and to extend the scope of this reaction are
planned.
(Rء,Rء)-N,N0-Di-tert-butyl-1,2-di(3-pyridyl)-1,2-ethylene-
diamine 2b. Yellow solid, mp 78–80ЊC; IR (CH2Cl2):
nˆ3653, 3287, 2969, 1690, 1577, 1476, 1425, 1390,
1
1365, 1214, 1089, 1025, 816 cmϪ1; H NMR (CDCl3) d
Experimental
8.36 (dd, Jˆ4.8, 1.8 Hz, 2H), 8.31 (d, Jˆ1.8 Hz, 2H),
7.55 (d, Jˆ7.8 Hz, 2H), 7.05 (dd, Jˆ7.8, 4.8 Hz, 2H),
3.68 (s, 2H), 1.70–2.00 (br, 2H), 0.89 (s, 18H); 13C NMR
(CDCl3) d 149.3, 148.0, 140.2, 135.0, 122.8, 61.8, 51.0,
30.0; ESMS m/z 327 (MHϩ). Anal. Calcd for C20H30N4:
C: 73.56, H: 9.27, N: 17.17. Found: C: 73.70, H: 9.21, N:
17.09.
1H and 13C NMR spectra were recorded on a Bruker ARX-
300 spectrometer in CDCl3 with TMS as internal standard.
Electrospray mass spectra were obtained on an HP 5989 B
apparatus with an HP 59987 A interface, in positive-ion
mode with methanol–water–acetic acid (60:35:5) as the
mobile phase. IR spectra were obtained on a Perkin–
Elmer 1000 spectrophotometer. Elemental analyses were
made using a CE Instrument Model 1110. All solvents
were purified by standard procedures and freshly distilled
prior to use. Reagents were of commercial grades (Aldrich).
Aldimines were prepared by condensation of the corre-
sponding aldehyde with the amine according to a literature
procedure.9
(Rء,Sء)-N,N0-Di-tert-butyl-1,2-di(3-pyridyl)-1,2-ethylene-
diamine 3b. Yellow solid, mp 72–74ЊC; IR (CH2Cl2):
nˆ3663, 3290, 3042, 2971, 1674, 1590, 1577, 1477,
1
1425, 1390, 1365, 1216, 1092, 1025, 630 cmϪ1; H NMR
(CDCl3) d 8.43 (dd, Jˆ4.8, 1.8 Hz, 2H), 8.42 (d, Jˆ1.8 Hz,
2H), 7.50 (d, Jˆ7.8 Hz, 2H), 7.15 (dd, Jˆ7.8, 4.8 Hz, 2H),
3.81 (s, 2H), 1.80–2.20 (br, 2H), 0.82 (s, 18H); 13C NMR
(CDCl3) d 149.7, 148.3, 139.6, 135.6, 122.8, 60.9, 51.0,
29.9; ESMS m/z 327 (MHϩ). Anal. Calcd for C20H30N4:
C: 73.56, H: 9.27, N: 17.17. Found: C: 73.40, H: 9.34, N:
17.26.
Typical procedure for the irradiation of aldimines
A solution of the corresponding aldimines (1 mmol) in a
mixture of isopropyl alcohol and acetone (100 mL, 70:30)
was bubbled with argon and irradiated through Pyrex, at
room temperature under an Ar atmosphere, using a
medium-pressure mercury lamp (450 W) until complete
consumption of the starting material had occurred (moni-
(Rء,Rء)-N,N0-Dihexyl-1,2-di(2-pyridyl)-1,2-ethylenedi-
amine 2c. Yellow oil; IR (CH2Cl2): nˆ3657, 3324, 2930,
2858, 1673, 1591, 1570, 1469, 1434, 1378, 1148, 1048, 996,
618 cmϪ1; 1H NMR (CDCl3) d 8.48 (d, Jˆ4.8 Hz, 2H), 7.34
(dd, Jˆ7.8, 7.5 Hz, 2H), 7.05 (dd, Jˆ7.5, 4.8 Hz, 2H), 6.89
(d, Jˆ7.8 Hz, 2H), 3.85 (s, 2H), 2.40–2.70 (br, 2H), 2.39 (t,
Jˆ6.0 Hz, 4H), 1.00–1.50 (m, 16H), 0.85 (t, Jˆ6.0 Hz, 6H);
13C NMR (CDCl3) d 161.2, 149.1, 135.4, 123.0, 121.7, 68.9,
47.8, 31.2, 29.9, 26.8, 22.3, 13.9; ESMS m/z 383 (MHϩ).
Anal. Calcd for C24H38N4: C: 75.33, H: 10.02, N: 14.65.
Found: C: 75.45, H: 9.97, N: 14.58.
1
tored by H NMR spectroscopy, see Table 1). The solvent
was evaporated under reduced pressure and the residue was
treated with NaHCO3 (25 mL, 10% aq solution) and
extracted with Et2O (3×25 mL). The organic layer was
dried (Na2SO4), filtered and the solvent removed under
reduced pressure. The resulting products were separated
and/or purified by column chromatography (silica gel,
MeOH/CH2Cl2). The yields (see Tables 1 and 2) described
refer to isomer mixture isolated products, relative to the
starting imine. The structures of 2h, 3h, 2i, and 3i were
determined by comparison of spectral data with those of
the authentic samples reported.
(Rء,Sء)-N,N0-Dihexyl-1,2-di(2-pyridyl)-1,2-ethylenedi-
amine 3c. Yellow oil; IR (CH2Cl2): nˆ3617, 3437, 2970,
2876, 1736, 1712, 1502, 1466, 1392, 1367, 1238, 1159,
1
1062, 909 cmϪ1; H NMR (CDCl3) d 8.49 (d, Jˆ4.8 Hz,
2H), 7.48 (dd, Jˆ7.8, 7.5 Hz, 2H), 7.07 (dd, Jˆ7.5,
4.8 Hz, 2H), 7.01 (d, Jˆ7.8 Hz, 2H), 4.10 (s, 2H), 2.40–
2.70 (br, 2H), 2.38 (t, Jˆ6.9 Hz, 4H), 1.00–1.50 (m, 16H),
0.85 (t, Jˆ6.9 Hz, 6H); 13C NMR (CDCl3) d 160.9, 149.0,
135.4, 123.0, 122.0, 67.4, 47.5, 31.5, 29.8, 26.7, 22.5, 13.9;
ESMS m/z 383 (MHϩ). Anal. Calcd for C24H38N4: C: 75.33,
H: 10.02, N: 14.65. Found: C: 75.20, H: 10.08, N: 14.72.
(Rء,Rء)-N,N0-Dicyclohexyl-1,2-di(3-pyridyl)-1,2-ethylene-
diamine 2a. Yellow oil; IR (CH2Cl2): nˆ3300, 2933, 2856,
1695, 1590, 1450, 1426, 1025, 808 cmϪ1; 1H NMR (CDCl3)
d 8.37 (dd, Jˆ4.8, 1.8 Hz, 2H), 8.21 (d, Jˆ1.8 Hz, 2H), 7.41
(d, Jˆ7.8 Hz, 2H), 7.11 (dd, Jˆ7.8, 4.8 Hz, 2H), 3.76 (s,
2H), 2.19 (m, 2H), 0.80–2.00 (m, 22H); 13C NMR (CDCl3)
d 149.4, 148.3, 137.2, 135.0, 122.9, 63.7, 53.6, 34.7, 32.4,
25.9, 24.8, 24.4; ESMS m/z 379 (MHϩ). Anal. Calcd for
C24H34N4: C: 76.13, H: 9.06, N: 14.81. Found: C: 76.25,
H: 9.01, N: 14.74.
(Rء,Rء)-N,N0-Dicyclopropyl-1,2-di(2-pyridyl)-1,2-ethylene-
diamine 2d. Yellow solid [obtained as a stereoisomeric
mixture (dl/mesoˆ37:63)]; IR (CH2Cl2): nˆ3625, 3422,
2945, 2836, 2024, 1627, 1592, 1571, 1472, 1435, 1338,
1018, 793, 606 cmϪ1 1H NMR (CDCl3) d 8.49 (d,
;
(Rء,Sء)-N,N0-Dicyclohexyl-1,2-di(3-pyridyl)-1,2-ethylene-
diamine 3a. Yellow solid, mp 123–125ЊC; IR (CH2Cl2):
nˆ2962, 2932, 2855, 1623, 1577, 1450, 1097, 1013, 864,
Jˆ4.8 Hz, 2H), 7.32 (dd, Jˆ7.8, 7.5 Hz, 2H), 6.95 (dd,
Jˆ7.5, 4.8 Hz, 2H), 6.84 (d, Jˆ7.8 Hz, 2H), 4.00 (s, 2H),

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P. J. Campos et al. / Tetrahedron 56 (2000) 7285–7289
3.01 (bs, 2H), 1.86 (m, 2H), 0.26 (m, 8H); 13C NMR
(CDCl3) d 161.4, 148.9, 135.5, 123.2, 121.6, 67.0, 28.3,
6.7, 6.2; ESMS m/z 295 (MHϩ). Anal. Calcd for
C18H22N4: C: 73.42, H: 7.54, N: 19.04. Found: C: 73.59,
H: 7.47, N: 18.94.
143.2, 135.6, 135.3, 128.5, 128.4, 128.4, 128.2, 128.1,
127.6, 127.5, 127.0, 126.9, 126.8, 126.8, 126.6, 124.7,
123.5, 122.4, 121.7, 66.9, 64.3; ESMS m/z 547 (MHϩ).
Anal. Calcd for C38H34N4: C: 83.47, H: 6.27, N: 10.25.
Found: C: 82.96, H: 6.37, N: 10.67.
(Rء,Sء)-N,N0-Dicyclopropyl-1,2-di(2-pyridyl)-1,2-ethylene-
diamine 3d. Yellow solid [obtained as a stereoisomeric
mixture (meso/dlˆ63:37)]; IR (CH2Cl2): nˆ3625, 3422,
2945, 2836, 2024, 1627, 1592, 1571, 1472, 1435, 1338,
(Rء,Rء)-N,N0-Dicyclohexyl-1,2-di(4-pyridyl)-1,2-ethylene-
diamine 2g. White solid, mp 131–133ЊC; IR (CH2Cl2):
nˆ3298, 3049, 2931, 2855, 1598, 1562, 1450, 1414,
1
1371, 1118, 994, 615 cmϪ1; H NMR (CDCl3) d 8.39 (d,
1018, 793, 606 cmϪ1
;
1H NMR (CDCl3) d 8.51 (d,
Jˆ4.5 Hz, 4H), 6.99 (d, Jˆ4.5 Hz, 4H), 3.68 (s, 2H), 2.30–
2.70 (br, 2H), 2.12–2.15 (m, 2H), 0.70–1.90 (m, 20H); 13C
NMR (CDCl3) d 151.2, 149.4, 122.9, 65.0, 53.9, 34.7, 32.4,
25.9, 24.8, 24.4; ESMS m/z 379 (MHϩ). Anal. Calcd for
C24H34N4: C: 76.13, H: 9.06, N: 14.81. Found: C: 76.31,
H: 8.99, N: 14.70.
Jˆ4.8 Hz, 2H), 7.45 (dd, Jˆ7.8, 7.5 Hz, 2H), 7.07 (dd,
Jˆ7.5, 4.8 Hz, 2H), 6.86 (d, Jˆ7.8 Hz, 2H), 4.26 (s, 2H),
3.00 (s, 2H), 1.93 (m, 2H), 0.28 (m, 8H); 13C NMR (CDCl3)
d 161.3, 149.1, 135.3, 123.8, 121.6, 68.7, 29.2, 6.9, 5.7;
ESMS m/z 295 (MHϩ). Anal. Calcd for C18H22N4: C:
73.42, H: 7.54, N: 19.04. Found: C: 73.59, H: 7.47, N:
18.94.
(Rء,Sء)-N,N0-Dicyclohexyl-1,2-di(4-pyridyl)-1,2-ethylene-
diamine 3g. Yellow solid, mp 139–141ЊC; IR (CH2Cl2):
nˆ3318, 3045, 2932, 2855, 1938, 1642, 1597, 1558,
(Rء,Rء)-N,N0-Dicyclohexyl-1,2-di(2-pyridyl)-1,2-ethylene-
diamine 2e. Yellow oil; IR (CH2Cl2): nˆ3287, 3045, 2969,
2869, 1682, 1589, 1577, 1476, 1450, 1424, 1390, 1365,
1
1450, 1414, 1124, 993, 613 cmϪ1; H NMR (CDCl3) d
8.47 (d, Jˆ4.5 Hz, 4H), 6.98 (d, Jˆ4.5 Hz, 4H), 3.97 (s,
2H), 2.30–2.70 (br, 2H), 2.13–2.15 (m, 2H), 0.75–1.90
(m, 20H); 13C NMR (CDCl3) d 150.0, 149.4, 123.2, 63.2,
53.3, 34.4, 32.5, 25.8, 24.8, 24.4; ESMS m/z 379 (MHϩ).
Anal. Calcd for C24H34N4: C: 76.13, H: 9.06, N: 14.81.
Found: C: 76.00, H: 9.11, N: 14.89.
1214, 1089, 1025, 957, 816, 629, 592 cmϪ1 1H NMR
;
(CDCl3) d 8.45 (d, Jˆ3.9 Hz, 2H), 7.38 (dd, Jˆ7.8,
7.5 Hz, 2H), 6.95–7.03 (m, 4H), 4.02 (s, 2H), 3.50–3.80
(br, 2H), 2.23 (m, 2H), 1.89 (m, 2H), 1.00–1.85 (m, 18H);
13C NMR (CDCl3) d 161.5, 148.9, 135.5, 123.2, 121.6, 66.2,
54.7, 34.3, 32.6, 25.9, 24.8, 24.6; ESMS m/z 379 (MHϩ).
Anal. Calcd for C24H34N4: C: 76.13, H: 9.06, N: 14.81.
Found: C: 76.28, H: 9.00, N: 14.72.
(Rء,Rء)-N,N0-Di-tert-butyl-1,2-di(2-naphtyl)-1,2-ethylene-
diamine 2j. White solid, mp 176–178ЊC; IR (CH2Cl2):
nˆ3686, 3166, 2778, 1602, 1496, 1391, 1363, 861,
(Rء,Sء)-N,N0-Dicyclohexyl-1,2-di(2-pyridyl)-1,2-ethylene-
diamine 3e. Yellow oil; IR (CH2Cl2): nˆ3654, 2936, 2858,
1697, 1598, 1451, 1377, 1097, 811 cmϪ1; 1H NMR (CDCl3)
d 8.47 (d, Jˆ4.2 Hz, 2H), 7.51 (dd, Jˆ7.8, 7.5 Hz, 2H),
7.04–7.10 (m, 4H), 4.22 (s, 2H), 2.40–2.80 (br, 2H), 2.23
(m, 2H), 0.90–1.78 (m, 20H); 13C NMR (CDCl3) d 162.1,
148.5, 135.5, 122.9, 121.5, 64.4, 54.0, 34.0, 32.6, 25.9, 24.7,
24.5; ESMS m/z 379 (MHϩ). Anal. Calcd for C24H34N4: C:
76.13, H: 9.06, N: 14.81. Found: C: 76.01, H: 9.12, N:
14.87.
826 cmϪ1; H NMR (CDCl3) d 7.82–7.85 (m, 8H), 7.67
1
(d, Jˆ8.4 Hz, 2H), 7.46–7.50 (m, 4H), 3.99 (s, 2H), 1.40–
1.60 (br, 2H), 0.65 (s, 18H); 13C NMR (CDCl3) d 142.3,
133.0, 132.9, 127.9, 127.7, 127.7, 127.6, 127.6, 126.3,
125.8, 125.4, 63.6, 50.9, 29.8; ESMS m/z 425 (MHϩ).
Anal. Calcd for C30H36N2: C: 84.85, H: 8.55, N: 6.60.
Found: C: 84.68, H: 8.65, N: 6.67.
(Rء,Sء)-N,N0-Di-tert-butyl-1,2-di(2-naphtyl)-1,2-ethylene-
diamine 3j. White solid, mp 178–180ЊC; IR (CH2Cl2):
nˆ3167, 2779, 1600, 1506, 1391, 1363, 861, 822 cmϪ1
;
(Rء,Rء)-N,N0-Di(diphenylmethyl)-1,2-di(2-pyridyl)-1,2-
ethylenediamine 2f. Yellow solid, mp 80–82ЊC; IR
(CH2Cl2): nˆ3433, 2930, 1715, 1657, 1591, 1570, 1493,
1H NMR (CDCl3) d 7.64–7.75 (m, 8H), 7.37–7.42 (m,
6H), 4.02 (s, 2H), 1.80–2.10 (br, 2H), 0.82 (s, 18H); 13C
NMR (CDCl3) d 143.0, 133.1, 132.4, 127.7, 127.4, 127.2,
126.3, 126.2, 125.5, 125.0, 63.8, 51.0, 29.8; ESMS m/z 425
(MHϩ). Anal. Calcd for C30H36N2: C: 84.85, H: 8.55, N:
6.60. Found: C: 84.75, H: 8.61, N: 6.64.
1
1471, 1453, 1434, 1158, 1027, 593, 552 cmϪ1; H NMR
(CDCl3) d 8.55 (d, Jˆ4.2 Hz, 2H), 7.60 (dd, Jˆ7.8,
7.5 Hz, 2H), 7.04–7.30 (m, 22H), 6.79 (m, 2H), 4.32 (s,
2H), 3.78 (s, 2H), 2.80–3.20 (br, 2H); 13C NMR (CDCl3)
d 161.9, 149.2, 149.2, 144.7, 143.1, 135.3, 128.6, 128.5,
128.4, 128.4, 128.3, 128.3, 128.1, 127.9, 127.7, 127.5,
127.4, 127.3, 127.2, 127.1, 127.0, 126.7, 126.6, 124.7,
121.7, 65.4, 64.3; ESMS m/z 547 (MHϩ). Anal. Calcd for
C38H34N4: C: 83.47, H: 6.27, N: 10.25. Found: C: 84.01, H:
6.10, N: 9.89.
(Rء,Sء)-N,N0-Dicyclohexyl-1,2-di(2-naphtyl)-1,2-ethylene-
diamine 3k. White solid, mp 203ЊC (decomposes); IR
1
(KBr): nˆ3454, 2927, 1651, 1455, 1118, 480 cmϪ1; H
NMR (CDCl3) d 7.78–7.85 (m, 8H), 7.50–7.55 (m, 6H),
4.17 (s, 2H), 2.07 (m, 2H), 1.80 (m, 2H), 0.63–1.42 (m,
20H); 13C NMR (CDCl3) d 139.4, 133.1, 133.0, 128.1,
127.8, 127.8, 127.6, 125.8, 125.8, 125.6, 65.0, 52.9, 34.6,
32.3, 25.9, 25.0, 24.6; ESMS m/z 477 (MHϩ). Anal. Calcd
for C34H40N2: C: 85.67, H: 8.46, N: 5.87. Found: C: 85.72,
H: 8.43, N: 5.85.
(Rء,Sء)-N,N0-Di(diphenylmethyl)-1,2-di(2-pyridyl)-1,2-
ethylenediamine 3f. Yellow oil; IR (CH2Cl2): nˆ3310,
3028, 2928, 1687, 1659, 1591, 1570, 1492, 1453, 1434,
1
1186, 1094, 1028, 552 cmϪ1; H NMR (CDCl3) d 8.45 (d,
Jˆ4.2 Hz, 2H), 7.46 (dd, Jˆ7.8, 7.5 Hz, 2H), 7.04–7.30 (m,
22H), 6.87 (m, 2H), 4.48 (s, 2H), 3.93 (s, 2H), 2.50–3.30
(br, 2H); 13C NMR (CDCl3) d 161.1, 148.8, 144.7, 143.7,
(Rء,Rء)-N,N0-Di-tert-butyl-1,2-di(phenylethynyl)-1,2-
ethylenediamine 2l. Brown oil; IR (CH2Cl2): nˆ3427,
2971, 1760, 1598, 1490, 1433, 1390, 1366, 1288, 1175,

P. J. Campos et al. / Tetrahedron 56 (2000) 7285–7289
7289
1
1093, 1029, 528 cmϪ1; H NMR (CDCl3) d 7.27–7.31 (m,
0589) and the Universidad de La Rioja (API-99/B05). One
10H), 3.71 (s, 2H) 1.40–1.60 (br, 2H) 1.20 (s, 18H); 13C
NMR (CDCl3) d 131.5, 131.4, 131.3, 128.1, 123.6, 91.8,
83.7, 53.7, 51.2, 51.0, 29.8; ESMS m/z 373 (MHϩ). Anal.
Calcd for C26H32N2: C: 83.82, H: 8.66, N: 7.52. Found: C:
83.90, H: 8.62, N: 7.48.
of us (J. A.) would like to thank the Ministerio de Educacion
´
y Cultura (Spain) for a fellowship.
References
(Rء,Sء)-N,N0-Di-tert-butyl-1,2-di(phenylethynyl)-1,2-
ethylenediamine 3l. Brown oil [obtained as a stereo-
isomeric mixture (meso/dlˆ67:33)]; IR (CH2Cl2):
nˆ3331, 2967, 2200, 1952, 1883, 1808, 1674, 1598,
1. Lucet, D.; Le Gall, T.; Mioskowski, C. Angew. Chem., Int. Ed.
Engl. 1998, 37, 2581–2627.
2. Bennani, Y. L.; Hanessian, S. Chem. Rev. 1997, 97, 3161–3195.
3. Dutta, M. P.; Boruah, A.; Prajapati, D.; Sandhu, J. S. Synlett
1998, 857–858.
4. (a) Alexakis, A.; Aujard, I.; Mangeney, P. Synlett 1998, 873–
874. (b) Alexakis, A.; Aujard, I.; Mangeney, P. Synlett 1998, 875–
876. (c) Mangeney, P.; Tejero, T.; Alexakis, A.; Grosjean, F.;
Normant, J. Synthesis 1998, 255–257.
5. Hirao, T.; Hatano, B.; Imamoto, Y.; Ogawa, A. J. Org. Chem.
1999, 64, 7665–7667.
1
1490, 1443, 1390, 1365, 1227, 1100, 1028, 528 cmϪ1; H
NMR (CDCl3) d 7.43–7.84 (m, 4H), 7.25–7.33 (m, 6H),
3.81 (s, 2H), 1.60–1.80 (br, 2H), 1.25 (s, 18H); 13C NMR
(CDCl3) d 131.5, 131.4, 128.1, 127.5, 126.0, 91.9, 83.6,
51.1, 50.9, 50.6, 29.9; ESMS m/z 373 (MHϩ). Anal. Calcd
for C26H32N2: C: 83.82, H: 8.66, N: 7.52. Found: C: 83.87,
H: 8.64, N: 7.49.
6. Padwa, A.; Bergmark, W.; Pashayan, D. J. Am. Chem. Soc.
1969, 91, 2653–2660.
(Rء,Sء)-N,N0-Dicyclohexyl-1,2-di(phenylethynyl)-1,2-
ethylenediamine 3m. Brown oil; IR (CH2Cl2): nˆ3420,
´
´
7. (a) Campos, P. J.; Tan, C.-Q.; Gonzalez, J. M.; Rodrıguez, M. A.
1
2932, 2856, 1686, 1598, 1490, 1451, 1116 cmϪ1; H NMR
Tetrahedron Lett. 1993, 34, 5321–5324. (b) Campos, P. J.; Tan,
´
´
C.-Q.; An˜on, E.; Rodrıguez, M. A. J. Org. Chem. 1996, 61, 7195–
(CDCl3) d 7.20–7.40 (m, 10H), 3.97 (s, 2H), 2.87 (m, 2H),
2.10–2.25 (br, 2H), 1.05–1.95 (m, 20H); 13C NMR (CDCl3)
d 131.8, 131.5, 128.2, 128.1, 128.0, 123.1, 88.3, 84.8, 52.1,
47.0, 34.3, 33.0, 32.4, 26.1, 25.3, 25.0, 24.7; ESMS m/z 425
(MHϩ). Anal. Calcd for C30H36N2: C: 84.85, H: 8.55, N:
6.60. Found: C: 85.06, H: 8.45, N: 6.49.
´
7197. (c) Campos, P. J.; An˜on, E.; Malo, M. C.; Tan, C.-Q.;
´
Rodrıguez, M. A. Tetrahedron 1998, 54, 6929–6938.
´
´
8. (a) Campos, P. J.; Tan, C.-Q.; Gonzalez, J. M.; Rodrıguez, M. A.
´
Synthesis 1994, 1155–1157. (b) Campos, P. J.; An˜on, E.; Malo,
´
M. C.; Rodrıguez, M. A. Tetrahedron 1998, 54, 14113–14122.
´
´
(c) Campos, P. J.; An˜on, E.; Malo, M. C.; Rodrıguez, M. A.
Tetrahedron 1999, 55, 14079–14088.
Acknowledgements
9. Hatano, B.; Ogawa, A.; Hirao, T. J. Org. Chem. 1998, 63,
9421–9424.
This work was supported by the Spanish DGICYT (PB97-
10. See Ref. 9 and references quoted therein.