Mendeleev Communications Electronic Version, Issue 5, 2001 1 Xenon difluoride–trimethylsilyl isocyanate–triflic acid as a new system for the amination of aromatic compounds Namig Sh. Pirkuliev,a,b Valery K. Brel,*a Novruz G. Akhmedov,b Nikolai S. Zefirova,b and Peter J. Stangc a Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, 142432 Moscow region, Russian Federation.Fax: +7 095 913 2113; e-mail: brel@ipac.ac.ru b Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation c Department of Chemistry, Unversity of Utah, Salt Lake City, UT 84112, USA 10.1070/MC2001v011n05ABEH001514 In the title system, OCNXeOSO2CF3 is formed, which readily oxidises iodobenzene to [PhI+–NCO –OTf]. The direct amination of aromatic substrates is possible with the use of XeF2–Me3SiNCO–CF3SO3H. Since the discovery of the first xenon compounds by Bartlett1 in 1962, a large number of xenon derivatives with Xe–F, Xe–Cl, Xe–O, Xe–N, Xe–C and Xe–N bonds were prepared.2 The methodology of Xe–element bond formation is based on the rupture of M–element bonds (where M = Bi, Sb or Si) with the aid of xenon fluorides.The Si–element fission bond is most promising and interesting for obtaining compounds with Xe–N bonds.2(a),3 Thus, D. D. DesMarteau3(c) used this approach for the preparation of the relatively stable compound FXe(NSO2F)2. Recently, theoretical computations and product analysis of the reaction of XeF2 with NaN3 and NaOCN indicated the intermediate formation of FXeN3 and FXeNCO.4 Previously, we found that the reaction of trimethylsilyl isocyanate with XeF2 or FXeOSO2CF3 in the presence of olefins proceeds through the formation of FXeNCO and OCNXeOSO2CF3 intermediates, which are easily added at the double bond of an olefin.In a continuation of this work, we studied the interaction of trimethylsilyl isocyanate with XeF2 or FXeOSO2CF3 in the presence of aromatic compounds.It is well known that, in this case, the reaction path strongly depends on the order in which the reactants were added. In particular, if finely dispersed XeF2 in CH2Cl2 was transformed into FXeOTf5 and the latter was treated with trimethylsilyl isocyanate and then with iodobenzene, mixed iodonium sulfonate 36 was obtained.† When trimethylsilyl isocyanate was added to a XeF2 solution in CH2Cl2 and the resulting mixture was subsequently treated with triflic acid and iodobenzene, phenyl(p-iodophenyl)iodonium triflate 4 and iodoanilines 5, 6 (as a mixture of ortho and para isomers) were isolated from the reaction mixture as a final products.‡ Note that in this case the formation of compound 3 was not detected.Consequently, the XeF2–Me3SiNCO–CF3SO3H system acts as an aminating reagent for aromatic compounds.7,8 Moreover, we found that with the use of other aromatic compounds such as benzene, toluene, chlorobenzene and o-xylene instead of iodobenzene the formation of amines 7 and 8 takes place (Table 1).† Typical procedure for the preparation of [PhI+NCO –OTf]. 5.52 mmol of Me3SiNCO was added to a stirred suspension of 4.72 mmol of CF3SO2OXeF5 in 20 ml of CH2Cl2 at –78 °C under argon.The mixture was allowed to warm up to –40 °C and stirred until the formation of a yellow homogeneous solution. The solution was cooled to –78 °C; then, 4.72 mmol of iodobenzene was added using a syringe. The mixture was allowed to warm to –5 °C and stirred for ~2 h. The precipitate was filtered off under argon, washed with cold diethyl ether and dried in vacuo to yield the material of >98% purity.The analytically pure compound can be obtained by recrystallization from CH2Cl2–Et2O. [Isocyanato(trifyloxy)-l3-iodo]benzene 3. 1HNMR (CD3CN) d: 8.3–7.5 (m). 13C NMR (CD3CN) d: 172.5 (CO), 136.6, 135.0, 132.9, 122.7 (Ph), 120.8. 19F NMR (CD3CN) d: –78.6 (CF3). IR (CCl4, n/cm–1): 2510, 1625 (NCO), 1258, 1178, 1023 (OTf).XeF2 + HOTf FXeOTf [Xe(OTf)(NCO)] TfO– PhI+–NCO CH2Cl2 Me3SiNCO – TMSF PhI – Xe 1 2 3 Scheme 1 ‡ Reaction of iodobenzene with XeF2–Me3SiNCO–HOTf. XeF2 (4.72 mmol) was dissolved in dry CH2Cl2 (15 ml)10 under argon; then, Me3SiNCO (5.1 mmol) was added. Triflic acid (10 mmol) was slowly added dropwise at –78 °C to the solution of FXeNCO in dry CH2Cl2 and then the mixture was stirred at –30 °C for ~1 h.Then, a large excess of PhI (12 mmol) was added to the suspension at –78 °C, and the mixture was stirred until no more gas (Xe) was evolved (see Table 1 for total reaction time). The solution was heated to room temperature and poured into a dilute solution of HCl with ice. An excess of iodobenzene and phenyl(p-iodophenyl)- iodonium triflate 4 were extracted with dichloromethane (3×15 ml).The volatile materials were then removed under reduced pressure to give an oily residue, which was dissolved in dry diethyl ether. The mixture was vigorously shaken for several minutes to precipitate slightly coloured crystals. Analytically pure samples were obtained by recrystallization from CH2Cl2–Et2O. The aqueous layer was neutralised with a 30% sodium hydroxide solution to pH ~13.The mixture of o- and p-iodoanilines 5, 6 was then extracted with dichloromethane and dried with MgSO4. Products were isolated after evaporating the solvent. Isomeric mixtures were analysed by 1H NMR. Phenyl(p-iodophenyl)iodonium triflate 4: yield 44%, mp 146–147 °C (lit.,11 144–148 °C). 1H NMR (CDCl3) d: 7.48 (m, 2H, Ph), 7.64 (m, 1H, Ph), 7.80 (m, 4H, C6H4), 8.10 (m, 2H, Ph). 19F NMR (CDCl3) d: –78.4 (CF3SO3). I I CF3SO2O I NH2 I H2N R NH2 R R' R' H2N 4 5 6 7a–d 8a–d i, Me3SiNCO ii, CF3SO2OH IC6H5 XeF2 a R = R' = H b R = Cl, R' = H c R = Me, R' = H d R = R' = Me Scheme 2 RR' C6H4 Table 1 Amination of aromatic compounds with XeF2–Me3SiNCO–CF3SO3H. Substrate Reaction time/h Yielda (%) aIsolated yields based on XeF2 used.orthoisomer paraisomer Yielda of 4 (%) C6H6 3 45 — MeC6H5 3 40 54 46 IC6H5 4 38 50 44 44 ClC6H5 6 35 45 48 o-Xylene 3 43 — —Mendeleev Communications Electronic Version, Issue 5, 2001 2 These results indicate that the XeF2–Me3SiNCO–CF3SO3H system makes it possible to perform conveniently electrophilic one-step amination of aromatic compounds with the formation of anilines in moderate yields.Highly deactivated aromatics slowly react under these conditions to form anilines in low yields. Thus, with nitrobenzene, the yields of nitroanilines were lower than 5%. In this case, the deactivation of a benzene ring probably occurs not only owing to the nitro group but also due to the further deactivation of the ring by the protonation of the nitro group in a triflic acid medium.9 It is believed that the amination of aromatic compounds§ involves the formation of the reactive triflate [H2N+=C=O –OTf] at the stage of the interaction of FXeNCO with triflic acid.This explanation was additionally supported by studies of the reactions with Me3SiOTf in place of HOTf. In this case, the [H2N+=C=O –OTf] species was not formed, apparently, due to the absence of hydrogen ions.Most likely, the formation of OCNXeOSO2CF3 occurs, and hence the reaction with iodobenzene leads to the formation of only iodonium sulfonate 3 (Scheme 1). Thus, we found that in the case of the XeF2–CF3SO3H– Me3SiNCO system the formation of OCNXeOSO2CF3 takes place, which readily oxidises iodobenzene to [PhI+–NCO –OTf].The direct amination of aromatic substrates with reasonable yields is possible with the use of XeF2–Me3SiNCO–CF3SO3H. We are grateful to NIH and FIRCA (2RO3TW000437) for financial support. References 1 N. Bartlett, Proc. Chem. Soc., 1962, 218. 2 (a) V. K. Brel, N. Sh. Pirkuliev and N. S. Zefirov, Usp. Khim., 2001, 70, 262 (Russ. Chem. Rev., 2001, 70, 231); (b) New Fluorinating Agents in Organic Synthesis, eds. L.German and S. Zemskov, Springer–Verlag, Berlin, 1989. 3 (a) D. D. DesMarteau, J. Am. Chem. Soc., 1978, 100, 6270; (b) D. D. DesMarteau, R. D. LeBlond, S. F. Hossain and D. Nothe, J. Am. Chem. Soc., 1981, 103, 7734; (c) J. F. Sawyer, G. J. Schrobilgen and S. J. Sutherland, J. Chem. Soc., Chem. Commun., 1982, 210; (d) A. A. A. Emara and G.J. Schrobilgen, Inorg. Chem., 1992, 31, 1323. 4 A. Schulz and T. M. Klapotke, Inorg. Chem., 1997, 36, 1929. 5 (a) T. M. Kasumov, N. Sh. Pirguliyev, V. K. Brel, Y. K. Grishin, N. S. Zefirov and P. J. Stang, Tetrahedron, 1997, 53, 13139; (b) M.Wechsberg, P. A. Bulliner, F. O. Sladky, R. Mews and N. Bartlett, Inorg. Chem., 1972, 11, 3063. 6 V. V. Zhdankin, C. M. Critell, P. J. Stang and N.S. Zefirov, Tetrahedron Lett., 1990, 31, 4821. 7 (a) R. Schroter and E. Muller, Houben–Weyl, Methoden der Organischen Chemie, Thieme Verlag, Stuttgart, 1957, vol. XI/1, pp. 341–488; (b) P. Kovacic, Friedel–Crafts and Related Reactions, Interscience Publishers, New York, 1964, vol. II/2, p. 1493; (c) T. Sheradsky, The Chemistry of Amino, Nitroso and Nitro Compounds and Their Derivatives, John Wiley, New York, 1982, part 1, pp. 395–416. 8 (a) C. Graebe, Ber. Dtsch. Chem. Ges., 1901, 34, 1778; (b) G. F. C. Jaubert and R. Hebd, Seances Acad. Sci., 1901, 132, 841; (c) P. Kovacic, R. L. Russel and R. B. Bennett, J. Am. Chem. Soc., 1964, 86, 1588; (d) P. Kovacic and R. B. Bennett, J. Am. Chem. Soc., 1961, 83, 221; (e) G. A. Olah and T. D. Ernst, J. Org. Chem., 1989, 54, 1203. 9 G. A. Olah, G. K. S. Prakash and J. Sommer, Superacids, John Wiley, New York, 1985. 10 D. D. Perrin, W. L. F. Armaredo and D. R. Perrin, Purification of Laboratory Chemicals (2nd edition), Pergamon Press, New York, 1980. 11 T. Kitamura, J.-I. Matsuyuki, K. Nagata, R. Furuki and H. Taniguchi, Synthesis, 1992, 945. § General procedure for the amination of aromatic compounds. The reactions with other aromatics were carried out as described above for the interaction of iodobenzene with XeF2–Me3SiNCO–HOTf system. Isomeric arylamines 7 and 8 were isolated in moderate yields (Table 1). Physico-chemical constants and spectral properties of 7 and 8 are in agreement with the published data. Received: 10th August 2001; Com. 01/1840