bond interactions in assisting fluoride ion departure. The
hydrogen bond interactions are active on the free substrate in a
step prior to nucleophilic attack and not on the zwitterionic
intermediate; this is shown by the complexed substrate pathway
in Scheme 6.
OCH2), 2.38 (3H, s, CH3); δC(CDCl3) 150.391, 145.37, 141.50,
129.66, 140.02, 138.93, 129.52, 124.00, 80.17, 21.32.
2,4,6-Trinitrophenyl 3-chlorobenzyl ether
Mp 111–112 ЊC; δH(CDCl3) 8.80 (2H, s, NO2CCH), 7.48 (1H, s,
CH2CCHCl), 7.3–7.4 (3H, m, Ar), 5.30 (2H, s, OCH2);
δC(CDCl3) 150.18, 145.42, 141.99, 130.23, 135.15, 134.79,
129.83, 129.07, 127.07, 124.31, 79.24.
Experimental
Materials
Trinitrofluorobenzene was prepared by nitration of 2,4-dinitro-
fluorobenzene according to the literature.19 The crude product
was crystallized from cold ethanol; mp 122–123 ЊC. TNFB was
stored at Ϫ20 ЊC. Benzyl alcohol, 4-methylbenzyl alcohol,
methanol and isopropanol (Carlo Erba) were purified by distil-
lation.20 3-Methylbenzyl alcohol and 3-chlorobenzyl alcohol
were purified using a chromatographic column of silica gel
(eluant: light petroleum–diethyl ether 8:2) followed by distil-
lation. THF (Carlo Erba) was dried over sodium, distilled,
and then redistilled from LiAlH4, immediately before use, in
Acknowledgements
The authors thank the Ministero dellЈUniversità e della Ricerca
Scientifica
e Tecnologica, the Consiglio Nazionale delle
Ricerche (CNR, Roma) and the University of Bologna (funds
for selected research topics, A. A. 1997–1999).
References
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Nucleophilic Substitution Reactions, M. T. P. Int. Rev.; Org. Chem.,
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2 L. Forlani, J. Chem. Soc., Perkin Trans. 2, 1993, 1525.
3 L. Forlani, Gazz. Chim. Ital., 1982, 112, 205.
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a
nitrogen atmosphere.20 Tetrabutylammonium bromide
was recrystallized from anhydrous THF. δ-Valerolactame and
2-hydroxypyridine (Carlo Erba) were purified by the usual
procedures.6
5 N. S. Nudelman, in The Chemistry of Amino, Nitroso, Nitro and
Related Groups, ed. S. Patai, J. Wiley & Sons, London, 1996, ch. 26,
p. 1253.
6 F. Terrier, Nucleophilic Aromatic Displacement, VCH, New York,
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8 J. Murto, Acta Chem. Scand., 1966, 20, 310.
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10 R. Foster, Organic Charge Transfer Complexes, Academic Press,
London, 1970.
General
All products gave satisfactory elemental analyses. Mps are
uncorrected. UV/VIS spectra were recorded with Perkin-Elmer
Lambda 5 and Lambda 12 spectrophotometers. NMR data
were recorded on a Varian Gemini 300 MHz spectrometer;
J values are in Hz. Kinetic runs were performed by following
the appearance of the reaction product at λ = 320 nm in CCl4
and λ = 360 nm in THF. The reproducibility of kobs values was
4%.
11 L. Forlani and M. Bosi, J. Phys. Org. Chem., 1992, 5, 429.
12 E. M. Arnett, Prog. Phys. Org. Chem., 1963, 1, 223; D. D. Perrin
Dissociation Constant of Organic bases in Aqueous Solutions,
Butterworths, London, 1965; A. Albert, Ionization Constants of
Acid and Bases, Methuen, London, 1962.
13 C. F. Bernasconi and K. A. Howard, J. Am. Chem. Soc., 1983, 105,
4690; R. H. de Rossi and A. Veglia, J. Org. Chem., 1983, 48, 1879;
F. Terrier, L. Xiao, M. Hlaibi and J. C. Halle, J. Chem. Soc., Perkin
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15 L. Forlani, Gazz. Chim. Ital., 1991, 121, 475.
16 F. Pietra and A. Fava, Tetrahedron Lett., 1963, 1535; F. Pietra,
Tetrahedron Lett., 1965, 2405.
Reaction products
These were prepared by mixing appropriate solutions (in THF
or in CCl4) of TNFB (0.1 g, 0.4 mmol) in 1 mL of solvent and
alcohol (4 mmol) in 1 mL of solvent. The reaction was moni-
tored by TLC (silica gel, eluant: light petroleum–diethyl ether
8:2) The solid trinitrophenyl derivatives were separated on a
silica gel column (light petroleum–diethyl ether 7:3) and puri-
fied by crystallization from methanol. 2,4,6-Trinitrophenyl
methyl ether,21 2,4,6-trinitrophenyl isopropyl ether21 and 2,4,6-
trinitrophenyl benzyl ether22 were prepared following pro-
cedures reported in the literature.
17 C. K. Ingold, Structure and Mechanism in Organic Chemistry,
G. Bell, London, 1969, ch. 7.
2,4,6-Trinitrophenyl 3-methylbenzyl ether
18 J. Murto, Acta Chem. Scand., 1964, 18, 1043.
19 G. C. Shaw and D. L. Seaton, J. Am. Chem. Soc., 1961, 83, 5227.
20 J. A. Riddick and W. B. Bunger, Organic Solvents, ed. A.
Weissberger, Wiley-Interscience, New York, 1970.
21 G. E. Philbrook and D. J. Massey, J. Am. Chem. Soc., 1951, 73,
3454.
Mp 124–126 ЊC; δH(CDCl3) 8.90 (2H, s, NO2CCH), 7.2–7.4
(4H, m, Ar), 5.30 (2H, s, OCH2), 2.40 (3H, s, CH3); δC(CDCl3)
150.41, 145.43, 141.56, 130.57, 138.86, 132.90, 130.07, 128.86,
126.39, 124.09, 80.32, 21.31.
22 L. Horner, W. Kirmse and H. Fernekess, Chem. Ber., 1961, 94, 279.
2,4,6-Trinitrophenyl 4-methylbenzyl ether
Mp 108–110 ЊC; δH(CDCl3) 8.87 (2H, s, NO2CCH), 7.48 (2H d,
J 7.9, CHCCH2), 7.30 (2H, d, J 7.9, CHCCH3), 5.31 (2H, s,
Paper 9/00436J
1458
J. Chem. Soc., Perkin Trans. 2, 1999, 1455–1458