PAPER
N-Alkylanilines by Reaction of (Z)-(tert-Butylsulfanyl)(aryl)diazenes with Alkyllithium Reagents
749
All the N-methylanilines listed in Table 2 were prepared according
to the procedure described above. In entries 35 and 37, the amount
of MeLi was doubled (18.75 mL, 30 mmol).
tained when the reaction was carried out under an atmosphere of
argon.
Yield 14: 0.79 g (36%).
Yield N-butylaniline: 0.72 g (48%).
Collateral Proofs
Proof A
A soln of MeLi in Et2O (1.6 M; 0.94 mL, 1.5 mmol) was cooled to
–78 °C and maintained under a nitrogen flow until evaporation of
the solvent. The white solid of MeLi so obtained was dissolved in
THF-d8 (2.5 mL) and the temperature was allowed to rise to 0 °C.
(Z)-(tert-Butylsulfanyl)(phenyl)diazene (3a) (0.19 g, 1 mmol) was
added, under stirring, and then the reaction mixture was allowed to
warm to r.t. A sample was drawn with a syringe and put into an
NMR-tube that was sealed, but not hermetically, and the progress of
the reaction was monitored by 1H NMR. The spectrum recorded af-
ter 10 min showed the absence of the peak at δ = 1.64, correspond-
ing to the starting diazosulfide 3a, and the presence of the
intermediate 10 (R = Me, Ar = Ph), as major product, and of a small
amount of the N-methylaniline [δ = 1.17 (s, t-Bu), 2.07 (s,
MeNN–), 2.73 (s, MeNH), 6.44–6.57, 6.63–6.91, 7.00–7.08 (3 m)].
Because of the rapid progress of the reaction, it was not possible to
quantify the peaks. Moreover, a white precipitate of lithium 2–me-
thylpropan-2-thiol (8) began to form. In time, the peaks at δ = 1.17,
2.07 and 6.63–6.91 decreased rapidly until disappearance after ca.
30 min, and simultaneously the peaks at δ = 2.73, 6.44–6.57 and
7.00–7.08 and the precipitate 8 increased. At this point the NMR
spectrum highlighted also a peak at δ = 1.39 (s), corresponding to
thiol (2) formed by partial hydrolysis of 8. This increased over time.
Acknowledgments
This work was supported by the Ministero dell’Università e della
Ricerca Scientifica e Tecnologica (MURST), National Project
‘Dry-state arenediazonium o-benzenedisulfonimides: synthesis, re-
activity and applications,’ by the National Research Council of Italy
(CNR), and by University of Torino.
References
(1) Barbero, M.; Degani, I.; Diulgheroff, N.; Dughera, S.; Fochi,
R.; Migliaccio, M. J. Org. Chem. 2000, 65, 5600.
(2) For some examples on the preparation, stability and
synthetic applications of (Z)-(tert-butylsulfanyl)(aryl)
diazenes, see: (a) van Zwet, H.; Kooyman, E. C. Recl. Trav.
Chim. Pays-Bas 1967, 86, 993. (b) van Beek, L. K. H.; van
Beek, G. C. Jr.; Boven, J.; Schoot, C. J. J. Org. Chem. 1971,
36, 2194. (c) Brokken-Zijp, J.; van de Bogaert, H.
Tetrahedron 1973, 29, 4169. (d) Brokken-Zijp, J.; van de
Bogaert, H. Tetrahedron Lett. 1974, 49. (e) Petrillo, G.;
Novi, M.; Dell’Erba, C.; Tavani, C.; Berta, G. Tetrahedron
1990, 46, 7977; and references therein. (f) Caposcialli, N.;
Dell’Erba, C.; Novi, M.; Petrillo, G.; Tavani, C. Tetrahedron
1998, 54, 3529; and references therein.
Proof B
According to the conditions reported in (1) for entry 2 of Table 2,
(Z)-(tert-butylsulfanyl)(phenyl)diazene (3a) (1.94 g, 10 mmol) was
treated with an excess of BuLi (1.6 M soln in hexane; 25.00 mL, 40
mmol) at –78 °C and then r.t. GC–MS analysis of the crude residue,
obtained after a work up identical to that described above, showed
the presence of two major products, i.e. N,N′-dibutyl-N-phenylhy-
drazine (14; R = Bu, Ar = Ph) [MS: m/z = 220 (M+)], and N-butyl-
aniline [MS: m/z = 149 (M+)], besides some unidentified by
products. The two major products were separated by flash chroma-
tography [PE–acetone (9.9:0.1)]. The first eluted product was 14,
which was further purified by a second flash chromatography [PE–
Et2O, (9.8:0.2)].
(3) For examples, see: (a) Gross, M. L.; Blank, D. H.; Welch,
W. M. J. Org. Chem. 1993, 58, 2104; and references therein.
(b) Lazny, R.; Poplawski, J.; Kobberling, J.; Enders, D.;
Brase, S. Synlett 1999, 1304; and references therein.
(c) Barbero, M.; Degani, I.; Diulgheroff, N.; Dughera, S.;
Fochi, R. Synthesis 2001, 2180; and references therein.
(4) Recent reviews on N-monoalkylation of anilines:
(a) Wurziger, H. Kontakte (Darmstadt) 1987, 3, 8; Chem.
Abstr. 1988, 109: 109906. (b) Xiaojian, Z.; Zuwang, W.
Huagong Jinzhan 1996, 5; Chem. Abstr. 1996, 124, 320046.
(5) Some recent examples on the N-monoalkylation of anilines:
(a) Wimmer, P.; Buysch, H. J.; Puppe, L.; Froehlich, C.
Bayer A.-G., Eur. Pat. 410243, 1991; Chem. Abstr. 1991,
115, 8274f. (b) Pappas, P. G.; Melville, J. B. Amoco Corp.
USA, US Pat. 5159115, 1992; Chem. Abstr. 1993, 118,
41193p. (c) Verardo, G.; Giumanini, A. G.; Strazzolini, P.;
Poiana, M. Synthesis 1993, 121. (d) Ivanov, E. I.;
Yield: 0.69 g (31%); bp 101–102 °C/0.5 torr.
1H NMR (CDCl3): δ = 0.96 (t, J = 7.1 Hz, 3 H), 0.98 (t, J = 7.3 Hz,
3 H), 1.25–1.68 (m, 8 H), 2.33 (dt, Jt = 7.4, Jd = 5.3 Hz, 2 H), 3.71
(t, J = 7.0 Hz, 2 H), 6.76–6.89 and 7.17–7.30 (2 m, 2:3, 5 H).
13C NMR (CDCl3, 400 MHz): δ = 147.71 (CN), 129.05 (CH),
119.35 (2 CH), 114.22 (2 CH), 45.23, 35.23, 29.78, 26.97, 20.93,
20.41 (CH2), 14.01, 13.88 (CH3).
Polishchuk, A. A. Zh. Obshch. Khim. 1993, 63, 403.
(e) Matsuo, K.; Shichida, Y.; Nishida, H.; Nakata, S.;
Okuba, M. J. Phys. Org. Chem. 1994, 7, 9. (f) Fache, F.;
Valot, F.; Milenkovic, A.; Lemaire, M. Tetrahedron 1996,
52, 9777; and references therein. (g) Sreekumar, K.; Jyothi,
T. M.; Talawar, M. B.; Kiran, B. P.; Rao, B. S.; Sugunan, S.
J. Mol. Catal. A: Chem. 2000, 152, 225; and references
therein. (h) Sreekumar, K.; Jyothi, T. M.; Govindankutty, R.
C.; Rao, B. S.; Sugunan, S. React. Kinet. Catal. Lett. 2000,
70, 161; and references therein. (i) Zhang, R.; Wu, Z.; Lin,
L.; Yang, H. SEPU 2000, 18, 532; Chem. Abstr. 2001, 134,
162664.
Anal. Calcd for C14H24N2: C, 76.31; H, 10.98; N, 12.71. Found: C,
76.45; H, 11.05; N, 12.66.
1
The second eluted product was the pure (TLC, GC, GC–MS, H
NMR) N-butylaniline.
Yield: 0.75 g (50%).
Yields remained unchanged when the reaction time at r.t. was pro-
longed to 16 h; yields comparable to those reported above were ob-
Synthesis 2003, No. 5, 742–750 ISSN 0039-7881 © Thieme Stuttgart · New York