G. Della Sala et al. / Journal of Organometallic Chemistry 692 (2007) 1623–1627
1627
Table 4
Oxidation of carbene complexes 2 with TBHP (DCE, 70 °C)
Entry
2
R1
R2
R3
Reaction time (h)
Yield of 3 (%)
Yield of 4 (%)
1
2
3
4
5
6
7
8
b
d
e
k
l
Ph
Ph
Ph
Ph
Ph
Ph
Me3Si
H
Me
H
Me
Et
Allyl
g2-Allyl
Me
Me
Me
H
H
H
Allyl
Me
H
1.5
2
3
1.25
4
0.5
5
72
60
77
70
57
75
65
80
–
–
14
14
4
–
–
n.d.
j
i
m
Me
8
(d) H.I. Skulnick, H.W. Smith, R.J. Smith, W. Wierenga, U.S. Patent,
US4495349, 1986;
(e) K. Ley, G. Aichinger, H. Hagemann, E. Niemers, F. Hoffmeister,
Ger. Offen. DE2142317, 1973.
with 1,3-dialkyl and 1-alkyl uracil complexes while failed
with 3-alkyl analogs and g2-allyl derivatives. On the other
hand these uracil carbene complexes were satisfactorily oxi-
dated by t-butyl hydroperoxide. Noteworthy, the latter
reagent, employed for the first time in the oxidation of
Fischer-type carbene complexes, can be used in general as
a good alternative to the other already available methods.
New synthetic applications of Fischer carbene uracil com-
plexes, as the preparation of pyrimidine-2-ones, will be the
subject of future works.
[7] I.M. Lagoja, P. Herdewijn, Synthesis (2002) 301–314.
[8] P. Ramirez-Lopez, M. Gomez-Gallego, M.J. Mancheno, M.A. Sierra,
M. Bilurbina, S. Ricart, J. Org. Chem. 68 (2003) 3538–3545.
[9] A. Artillo, G. Della Sala, M. De Santis, A. Llordes, S. Ricart, A.
Spinella, J. Organomet. Chem. in press.
´
[10] A.M. Lluch, L. Jordi, F. Sanchez-Baeza, S. Ricart, F. Camps,
´
A. Messeguer, J.M. Moreto, Tetrahedron Lett. 33 (1992) 3021–
3022.
[11] D. Perdicchia, E. Licandro, S. Maiorana, B. Vandoni, C. Baldoli,
Org. Lett. 4 (2002) 827–830, and references cited therein.
[12] (a) J. Ezquerra, C. Pedregal, I. Merino, J. Florez, J. Barluenga, S.
Garcia-Granda, M.A. Llorca, J. Org. Chem. 64 (1999) 6554–6565;
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Acknowledgements
The authors acknowledge the financial support from
`
Universita di Salerno and the financial support from the
Spanish DGI (EMOCIONA Project CTQ2006-06333/
BQV).
[14] B.A. Anderson, W.D. Wulff, A. Rahm, J. Am. Chem. Soc. 115 (1993)
4602–4611.
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2 with
TBHP: In a screw capped ACE tube containing a solution of
metallocarbene 2 (0.1 mmol) in 1,2-dichloroethane, a solution of
TBHP (5.5 M in n-decane, 1 mmol) was added. The mixture was
warmed at 70 °C until completion of oxidation. Decoloration of
solution and formation of a white precipitate was indicative of
transformation. Sodium sulfite (10%) aqueous solution (6 ml) was
added and the resulting mixture was stirred for 3 h then
extracted with dichloromethane. The organic layers were dried
over magnesium sulfate, filtered and concentrated under reduced
pressure. Purification by flash chromatography using chloroform–
methanol mixtures as eluant afforded uracil 3.
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