P. Zardi et al. / Journal of Organometallic Chemistry 716 (2012) 269e274
273
The lack of formation of 2,3-dihydro-N-(4-nitrophenyl)-1H-
inden-1-amine (18) confirmed that cobalt porphyrins are not
competent catalysts for the direct CeH amination of a-substituted
longer observable, and then by IR spectroscopy, which measured
the characteristic N3 absorbance in the range 2095e2130 cmꢁ1. The
reaction was considered to be finished when the absorbance of the
azide measured was below 0.03 (by using a 0.5 mm thick cell). The
solution was then evaporated to dryness and the residue purified
cyclic styrenes. Thus, when a hydrogen atom abstraction is
impossible the uncatalysed reaction is the only achievable process
[34]. It should be noted that the ruthenium porphyrin mediated
CeH amination of indene yielded 18 in moderate yields [12].
In our belief, the dissimilar catalytic performance of ruthenium
and cobalt complexes in the amination of 1-phenyl-1,2-
dihydronapthalene (Scheme 8) and indene (Scheme 9) strongly
agrees with different mechanisms for the two catalytic reactions.
by flash chromatography using
hexane ¼ 1:50 as the eluent.
a
mixture ethyl acetate/n-
6: 1H NMR (400 MHz, CDCl3, 298 K)
d
, ppm: 7.46 (d, 2H,
J ¼ 8.7 Hz), 7.33 (d, 1H, J ¼ 7.6 Hz), 7.27e7.17 (m, 3H), 6.66 (d, 2H,
J ¼ 8.7 Hz), 4.73e4.68 (m, 1H), 4.66 (d, 1H, J ¼ 6.4 Hz, NH),
2.93e2.77 (m, 2H), 2.07e1.96 (m, 2H), 1.94e1.85 (m, 2H). 13C NMR
(100 MHz, CDCl3, 298 K) d, ppm: 150.4 (CN), 137.7 (C), 136.6 (C),
3. Conclusions
133.9 (2 CH), 129.3 (CH), 129.0 (CH), 127.7 (CH), 126.3 (CH), 120.4
(C), 112.3 (2 CH), 98.6 (C), 50.7 (CH), 29.1 (CH2), 28.6 (CH2), 19.4
(CH2). Anal. Calcd for C17H16N2 C, 82.22; H, 6.49; N, 11.28. Found C,
82.30; H, 6.54; N, 10.97.
In summary, data reported herein indicate that the mechanism
of amination reactions catalysed by cobalt (II) porphyrins should be
determined well through the substrate behaviour. The high reac-
tivity of an endocyclic CeC double bond coupled with the good
hydrogen donor capability of dihydronaphthalene establishes
a mechanism in which hydrogen atom abstractions are the key-
steps in CeH amination.
7: 1H NMR (300 MHz, CDCl3, 298 K)
d, ppm: 8.28 (d, 1H,
J ¼ 7.6 Hz), 7.64 (d, 2H, J ¼ 8.6 Hz), 7.45e7.40 (m, 1H), 7.34 (d, 1H,
J ¼ 7.6 Hz), 7.26e7.23 (m, 1H), 6.88 (d, 2H, J ¼ 8.6 Hz), 2.94 (pst, 2H,
J ¼ 6.1 Hz), 2.49 (pst, 2H, J ¼ 6.1 Hz), 2.01e1.93 (m, 2H). 13C NMR
(75 MHz, CDCl3, 298 K) d, ppm: 166.7 (C), 156.4 (CN), 142.1 (C), 133.7
(2 CH), 133.4 (C), 131.7 (CH), 129.3 (CH), 127.0 (CH), 126.9 (CH), 120.5
(2 CH), 119.8 (C), 106.6 (C), 30.7 (CH2), 30.2 (CH2), 23.6 (CH2). Anal.
Calcd for C17H14N2 C, 82.90; H, 5.73; N, 11.37. Found C, 83.15; H,
5.85; N, 10.95.
4. Experimental
4.1. Materials and methods
8: 1H NMR (400 MHz, CDCl3, 298 K)
d, ppm: 7.47 (d, 1H,
Unless otherwise specified all reactions were carried out in
nitrogen atmosphere employing standard Schlenk techniques and
magnetic stirring. Benzene was dried by M. Braun SPS-800 solvent
purificationsystem.1,2-Dichloroethanewasdistilled overanhydrous
calcium chloride and kept under nitrogen. All the other starting
materials were commercial products used as received. Aryl azides
[1,16,44], tetraphenylporphyrin [45,46] and Co(TPP) [47] were syn-
thesised by methods as reported in the literature or with minor
modifications. The purity of olefins and aryl azides employed was
confirmed by GCeMS or 1H NMR spectroscopy. NMR spectra were
recorded at room temperature on a Bruker AC-300, operating at
300 MHz for 1H, at 75 MHz for 13C and at 282 MHz for 19F or on
a Bruker Avance 400-DRX spectrometers, operating at 400 MHz for
1H and at 100 MHz for 13C. Chemical shifts (ppm) are reported
relative to TMS. The 1H NMR signals of the compounds described in
the following have been attributed by COSY and NOESY techniques.
Assignments of the resonance in 13C NMR were made using the APT
pulse sequence and HSQC and HMBC techniques. GCeMS analyses
were performed on Shimadzu QP5050A instrument. Infrared spectra
were recorded on a Varian Scimitar FTS 1000 spectrophotometer.
Elemental analyses were recorded in the analytical laboratories of
Milan University. All the reagents employed for the preparation of
the ligands and their complexes were of the highest grade available
and used without further purification. Unless otherwise stated, all
catalytic tests were carried out under an atmosphere of purified
dinitrogen using modified Schlenk techniques.
J ¼ 6.8 Hz), 7.30 (d, 2H, J ¼ 8.7 Hz), 7.25e7.22 (m, 2H), 7.20e7.18 (m,
1H), 6.70 (d, 2H, J ¼ 8.7 Hz), 4.67 (m, 1H), 3.85 (bs, 1H, NH),
t
2.94e2.78 (m, 2H), 2.05-1.82 (m, 4H), 1.37 (s, 9H, Bu). 13C NMR
(100 MHz, CDCl3, 298 K) d, ppm: 145.1 (C), 139.9 (C), 138.4 (C), 137.7
(C), 129.4 (CH), 129.0 (CH), 127.1 (CH), 126.2 (2 CH), 126.1 (CH), 112.5
(2 CH), 51.2 (CH), 31.6 (CH3), 29.4 (CH2), 28.8 (CH2), 19.4 (CH2). Anal.
Calcd for C20H25N C, 85.97; H, 9.02; N, 5.01. Found C, 86.21; H, 9.17;
N, 5.31.
11: 1H NMR (400 MHz, CDCl3, 298 K)
d, ppm: 8.29 (d, 1H,
J ¼ 7.9 Hz), 7.60 (s, 1H), 7.46e7.42 (m, 1H), 7.36e7.32 (m, 1H),
7.26e7.25 (m, 3H), 2.96 (pst, 2H, J ¼ 6.1 Hz), 2.52 (pst, 2H,
J ¼ 6.1 Hz), 2.03e1.96 (m, 2H). 13C NMR (100 MHz, CDCl3, 298 K)
d,
ppm: 167.8 (C), 152.9 (C), 141.8 (C), 132.9 (C), 132.4 (q, J ¼ 131 Hz, 2
CCF3), 131.5 (CH), 128.9 (CH), 126.7 (CH), 126.6 (CH), 123.5
(J ¼ 270 Hz, q, 2 CF3), 119.9 (2 CH), 116.5 (CH), 30.3 (CH2), 29.8 (CH2),
22.8 (CH2). 19F NMR (282 MHz, CDCl3, 298 K)
Calcd for C18H13F6N C, 60.51; H, 3.67; N, 3.92. Found C, 60.87; H,
3.91; N, 3.78.
d
, ppm: ꢁ63.2. Anal.
13: 1H NMR (300 MHz, CDCl3, 298 K)
d, ppm: 8.42 (d, 2H,
J ¼ 8.9 Hz), 8.26 (d, 2H, J ¼ 8.9 Hz), 8.04 (d, 1H, J ¼ 7.3 Hz), 7.51 (pst,
1H, J ¼ 7.3 Hz), 7.28-7.24 (m, 2H), 3.46 (pst, 2H, J ¼ 6.1 Hz), 2.95 (pst,
2H, J ¼ 6.1 Hz), 2.19-2.06 (m, 2H). 13C NMR (75 MHz, CDCl3, 298 K)
d,
ppm: 134.8 (CH), 129.6 (CH), 128.6 (2 CH), 128.1 (CH), 127.3 (CH),
124.5 (2 CH), 34.1 (CH2), 29.7 (CH2), 22.8 (CH2), (quaternary carbons
were not detected). Anal. Calcd for C16H14N2O4S C, 58.17; H, 4.27; N,
8.48. Found C, 58.44; H, 4.42; N, 8.22.
Analytic data for compounds 1 [13], 2 [48], 4 [49], 5 [50], 10 [13],
12 [23], 14 [23], 15 [51], 17 [43] and 18 [13] are in agreement with
those reported in the literature. Compound 3 was spectroscopically
identical with an authentic sample. All reaction yields are reported
in Table 2.
16: 1H NMR (300 MHz, C6D6, 298 K)
d, ppm: 7.88 (d, 2H,
J ¼ 9.0 Hz), 7.16-7.00 (m, 9H), 5.83 (d, 2H, J ¼ 9.0 Hz), 4.56 (s,1H, NH),
2.70-2.64 (m, 2H), 2.03e1.97 (m, 2H), 1.47-1.34 (m, 2H). 13C NMR
(75 MHz, C6D6, 298 K) d, ppm: 150.7 (C),146.9 (C),139.1 (C),139.0 (C),
137.9 (C), 63.3 (C), 129.8 (CH), 129.5 (CH), 129.1 (CH), 128.9 (CH),
128.1 (CH), 127.7 (CH), 127.1 (CH), 126.9 (CH), 126.8 (CH), 125.7 (2
CH), 114.4 (2 CH), 42.1 (CH2), 30.3 (CH2), 20.0 (CH2). Anal. Calcd for
C22H20N2O2 C, 76.72; H, 5.85; N, 8.13. Found C, 76.98; H, 6.03; N, 7.94.
4.2. General procedure for catalytic reactions
In a typical run, the azide (1.34 ꢀ 10ꢁ4 mol) was added to
a solution of catalyst (1.07 ꢀ 10ꢁ5 mol) and dihydronaphthalene
(2.5 ml) in 1,2-dichloroethane (2.5 mL). The resulting solution was
heated at 75 ꢂC using a preheated oil bath. The consumption of the
aryl azide was monitored by TLC up to the point that its spot was no
Acknowledgements
We thank MiUR (PRIN projects) for the financial support and
prof. F. Ragaini for fruitful scientific discussions.