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V. Theodorou et al. / Tetrahedron 63 (2007) 4284–4289
and the mixture was stirred at room temperature for 5 h.11
After that, the mixture was concentrated in vacuo to give
the corresponding chlorides as white solids, which were
used without further purification.
alumina, using the eluent dichloromethane/hexane (1:1),
the imines were isolated as yellow oils. Their 1H NMR spec-
tra were acquired and determined as a mixture of E and Z
geometric isomers.
4.2.3. Synthesis of p-monosubstituted tritylamines. To
a solution of the p-substituted tritylchloride (10 mmol) in
15 mL CH2Cl2, ammonium hydroxide (15 mL, 28% in wa-
ter) was added and the mixture was stirred vigorously for
about two days. After that, it was extracted with CH2Cl2
(2Â20 mL) and washed with water (2Â25 mL). The organic
layer was concentrated in vacuo and the resulting amine was
purified by column chromatography on silica using CH2Cl2
4.4.1. Benzophenone phenylimine (or benzophenone
anil) Ph2C]N–Ph. H NMR (250 MHz, CDCl3) d 6.72
(2H, dd, ArH), 6.92 (1H, dt, ArH), 7.10–7.27 (7H, m,
ArH), 7.37–7.48 (3H, m, ArH), 7.75 (2H, dd, ArH) (lit.2).
1
4.4.2. p-Bromobenzophenone phenylimine Br–C6H4–
PhC]N–Ph. H NMR (400 MHz, CDCl3) d 6.69 (2H, dd,
1
ArH), 6.89 (1H, m, ArH), 6.95 (2H, d, ArH), 7.05–7.24
(5H, m, ArH), 7.34–7.50 (3H, m, ArH), 7.59 (1H, m,
ArH), 7.69 (1H, m, ArH) (lit.3e,12a).
1
as eluent (yield: 70–80%). The H NMR spectra of the
respective compound confirmed its identity.3c
4.2.3.1. p-Bromophenyldiphenylmethylamine p–Br–
C6H4–Ph2C–NH2. 1H NMR (250 MHz, CDCl3) d 2.05
(2H, s, NH2), 7.19 (2H, d, ArH), 7.29 (10H, m, ArH), 7.44
(2H, d, ArH); white solid.
4.4.3. Benzophenone p-bromophenylimine Ph2C]N–
C6H4–Br. 1H NMR (400 MHz, CDCl3) d 6.60 (2H, dt,
ArH), 7.10 (2H, dd, ArH), 7.23–7.31 (5H, m, ArH), 7.38–
7.42 (2H, t, ArH), 7.46–7.51 (1H, m, ArH), 7.74 (2H, dd,
ArH) (lit.6).
4.2.3.2. Diphenyl-p-tolylmethylamine p-CH3–C6H4–
Ph2C–NH2. H NMR (250 MHz, CDCl3) d 2.17 (2H, s,
NH2), 2.33 (3H, s, CH3), 7.13 (4H, m, ArH), 7.26 (10H,
m, ArH); oil.
1
4.4.4. p-Methylbenzophenone phenylimine CH3–C6H4–
PhC]N–Ph. 1H NMR (250 MHz, CDCl3) d 2.29 and
2.39 (3H, s, CH3, as a mixture of E/Z isomers, w1:1),
6.72 (2H, dt, ArH), 6.88–7.26 (9H, m, ArH), 7.36–7.47
(1H, m, ArH), 7.64 (1H, d, ArH), 7.72–7.75 (1H, m, ArH)
(lit.9a).
4.2.3.3. p-Anisyldiphenylmethylamine p-CH3O–
C6H4–Ph2C–NH2. 1H NMR (250 MHz, CDCl3) d 2.19
(2H, s, NH2), 3.75 (3H, s, OCH3), 6.78 (2H, d, ArH), 7.13
(2H, d, ArH), 7.23 (10H, m, ArH); oil.
4.4.5. Benzophenone p-tolylimine Ph2C]N–C6H4–CH3.
1H NMR (250 MHz, CDCl3) d 2.23 (3H, s, CH3), 6.60
(2H, d, ArH), 6.91 (2H, d, ArH), 7.08–7.12 (2H, m, ArH),
7.22–7.26 (3H, m, ArH), 7.34–7.44 (3H, m, ArH), 7.69–
7.72 (2H, m, ArH) (lit.9b,c).
4.2.3.4.
Diphenyl-p-trifluoromethylphenylmethyl-
amine p-CF3–C6H4–Ph2C–NH2. 1H NMR (250 MHz,
CDCl3) d 2.16 (2H, s, NH2), 7.12 (2H, d, ArH), 7.24 (12H,
m, ArH); oil.
4.4.6. p-Methoxybenzophenone phenylimine CH3O–
C6H4–PhC]N–Ph. H NMR (250 MHz, CDCl3) d 3.75
1
4.3. Rearrangement of tritylamines
and 3.83 (3H, s, OCH3 as a mixture of E/Z isomers,
w1:1.7), 6.68–7.47 (12H, m, ArH), 7.69–7.75 (2H, m,
ArH) (lit.3c,9e,12b).
To a solution of 1 mmol of the respective tritylamine in
10 mL of THF, cooled to about À75 ꢀC, 1 mmol of a solution
of n-BuLi in hexane (1.6 M) was added under an argon at-
mosphere. A deep red-colored solution was obtained. The
solution was left at this temperature for about 1 h, then the
solvent was removed, CH2Cl2 was added (20 mL), and the
solution filtered and concentrated. The crude mixture8 was
directly absorbed on neutral preparative alumina plates
and eluted with a mixture of dichloromethane/hexane
(1:1). The obtained 1H NMR spectra confirmed the identity
of the products, in each case, by comparison with the pure
synthesized compounds.
4.4.7. Benzophenone p-anisylimine Ph2C]N–C6H4–
OCH3. 1H NMR (250 MHz, CDCl3) d 3.70 (3H, s, OCH3),
6.69 (4H, ws, ArH), 7.10–7.14 (2H, m, ArH), 7.26–7.29
(3H, m, ArH), 7.38–7.45 (3H, m, ArH), 7.72–7.76 (2H, dt,
ArH) (lit.9d).
References and notes
1. Theodorou, V.; Ragoussis, V.; Strongilos, A.; Zelepos, E.;
Eleftheriou, A.; Dimitriou, M. Tetrahedron Lett. 2005, 46,
1357 and references cited therein.
2. Theodorou, V.; Skobridis, K. Tetrahedron Lett. 2005, 46,
5021.
(Yield:w50–60% of imines, hydrolysis products of the im-
ines about 5% and other, not identified, minor byproducts
<2%, as well as unreacted tritylamines).
4.4. Synthesis of imines
3. (a) Stieglitz, J.; Leech, P. N. J. Am. Chem. Soc. 1914, 36, 272;
(b) Stieglitz, J.; Vosburgh, J. J. Am. Chem. Soc. 1916, 38,
2081; (c) Sisti, A. J.; Milstein, S. R. J. Org. Chem. 1974,
39, 3932; (d) Hofmann, R. V.; Poelker, D. J. J. Org. Chem.
1979, 44, 2364; (e) Stagner, B. A. J. Am. Chem. Soc. 1916,
38, 2069.
To a solution of the respective benzophenone (10 mmol) in
ether or toluene (10 mL), aniline (11 mmol) was added.
˚
The reaction mixture was refluxed upon 5 g of 4 A molecular
sieves for 12–24 h. After completion of the reaction, moni-
tored by TLC, the solution was filtered and concentrated
in vacuo. After purification by column chromatography on
4. Eisch, J. J.; Dua, S. K.; Kovacs, C. A. J. Org. Chem. 1987, 52,
4437.