2 T. Mori and H. Suzuki, Synlett, 1995, 383; H. Suzuki, T. Takeuchi
and T. Mori, J. Org. Chem., 1996, 61, 5944.
3 M. Freemantle, Chem. Eng. News, 1996, 7.
4 J. M. Bakke, I. Hegbom, E. Øvreeide and K. Aaby, Acta Chem.
Scand., 1994, 48, 1001; B. Arnestad, J. M. Bakke, I. Hegbom and
E. Ranes, Acta Chem. Scand., 1996, 50, 556.
5 cf. K. Smith, A. Musson and G. A. DeBoos, Chem. Commun., 1996,
469 and references cited therein.
6 F. J. Waller, A. G. M. Barrett, D. C. Braddock and D. Ramprasad,
Chem. Commun., 1997, 613; Tetrahedron Lett., 1998, 39, 1641 and
references cited therein.
2
3
–
Table 2 Nitration of aromatic compounds with equivalents of
VO(NO3)3
X
t/mina
ortho (%) meta (%) para (%)
Yield (%)
>99b
CH3
But
3
3
50
14
34
27
3
6
47
80
63
4
>99
97
98
I
20
4 d
CO2Me
67
a Minutes if not stated otherwise. b Trace amounts of 2,4- and 2,6-
disubstituted products were produced concurrently.
7 G. A. Olah, Aldrichimica Acta, 1979, 12, 43.
8 L. M. Stock and T. L. Wright, J. Org. Chem., 1979, 44, 3467; J. V.
Crivello, J. Org. Chem., 1981, 46, 3056.
tert-butylbenzene and phenol with VO(NO3)3 all indicated that
more than one of the nitro groups from the reagent was trans-
ferred during the reactions. Further investigations showed that
two equivalents of VO(NO3)3 are sufficient to achieve quantita-
tive nitration of three equivalents of the aromatic compound
(Table 2); as expected this stoichiometry led exclusively to the
mono-nitrated product.
We have demonstrated that VO(NO3)3 is an extremely power-
ful and efficient nitrating agent for aromatic compounds under
simple conditions. Evidence suggests that oxides of nitrogen are
liberated during the reaction cycles thereby leading to the pos-
sibility that the ‘reagent’ can be regenerated in the presence of
these oxides, and act as a highly active catalyst. These and other
developments of VO(NO3)3 in catalytic nitration processes are in
progress.
9 Vanadium() oxytrinitrate was produced from the reaction of
vanadium pentoxide with dinitrogen pentoxide using a modification
of the procedure described by Schmeisser: M. Schmeisser, Angew.
Chem., 1955, 67, 493. The dinitrogen pentoxide was most
conveniently prepared by the dehydration of white fuming nitric
acid with phosphorus pentoxide at 50 ЊC in the presence of a slow
stream of ozone, cf. N. S. Gruenhut, M. Goldfrank, M. L. Cushing
and G. V. Caesar, Inorg. Synth., 1950, 3, 78.
10 (a) The vanadium() oxytrinitrate, like all other nitrates, is moisture
sensitive and it was stored and handled in a dry nitrogen filled
glovebox containing 3 Å molecular sieves or in vacuo on a standard
vacuum manifold. The reagent can be stored at room temperature
in a glovebox for long periods of time. Slow decomposition occurs
at temperatures above 80 ЊC but beyond this we have no inform-
ation regarding the thermal stability of VO(NO3)3. We therefore
recommend CAUTION with respect to the use and storage of
vanadium oxytrinitrate; (b) although CH2Cl2 was used as solvent in all
the studies described, vanadium() oxytrinitrate is also soluble in
CCl4, CH3NO2, cyclohexane and CFCl3. With CH3CN it forms
a complex VO(NO3)3–CH3CN which has a low nitrating ability,
and other coordinating solvents like ethers, aromatics and amines
are not expected to be compatible with the reagent.
Acknowledgements
We thank the EPSRC for support of this work and Hicksons
Fine Chemicals for their interest.
References
Paper 8/01771I
Received 3rd March 1998
Accepted 27th March 1998
1 ‘Nitration: Methods and Mechanisms’, ed. G. A. Olah, R. Malhotra
and S. C. Narang, VCH, New York, 1989; ‘Electrophilic aromatic
substitution’, ed. R. Taylor, Wiley, Chichester, 1990.
1590
J. Chem. Soc., Perkin Trans. 1, 1998