ORGANIC
LETTERS
2002
Vol. 4, No. 5
827-830
New Methodologies for the Oxidation of
Fischer Carbene Complexes: Synthesis
of Hydrazides
,†
,†
Dario Perdicchia,* Emanuela Licandro,* Stefano Maiorana,†
Barbara Vandoni,† and Clara Baldoli‡
Dipartimento di Chimica Organica e Industriale, UniVersita` degli Studi di Milano,
Via C. Golgi, 19, I-20133 Milan, Italy, and C.N.R. Centro Studio Sintesi e
Stereochimica di Speciali Sistemi Organici, Via C. Golgi, 19, I-20133 Milan, Italy
Received January 2, 2002
ABSTRACT
We report new, high-yield methodologies for oxidizing Fischer carbenes, particularly hydrazinocarbene complexes. The reagents traditionally
used to oxidize Fischer carbenes have failed because of the stability of hydrazinocarbene complexes and the easy oxidation of formed
hydrazides in the reaction conditions. The three newly developed methodologies are very mild, fast, efficient, and complementary. Differently
functionalized hydrazinocarbene complexes can be oxidized to afford new hydrazides.
Many examples of synthetic applications of Fischer-type
carbene complexes have so far been reported.1 In general,
the synthetic strategy consists of functionalizing the com-
plexes (also in a stereoselective manner) and then converting
them into organic compounds. Among the reported proce-
dures for the recovery of the organic ligand as a stable
organic molecule, oxidation is the easiest and most efficient
and converts the metal-carbon into the OdC bond.
they are suitable substrates for metathesis reactions.4 In
connection with the last study, we became interested in the
recovery of the organic ligand as hydrazide by means of the
oxidation of hydrazinocarbene complexes.
Several methods have been reported to oxidize Fischer-
type alkoxy and amino carbene complexes, but there are
sometimes problems in terms of low yields (e.g., using
DMSO,5 oxone,5 ceric ammonium nitrate (CAN),5,6 PhIO,5
air7) or the formation of byproducts (e.g., using pyridine
N-oxide (PNO),8 silica and air,9 wet silica and air,10 CAN5,9).
We have recently developed two complementary synthetic
methodologies to obtain hydrazinocarbene complexes2 and
studied their reactivity.3 In particular, we have shown that
(3) Licandro, E.; Maiorana, S.; Perdicchia, D.; Baldoli, C.; Graiff, C.;
Tiripicchio, A. J. Organomet. Chem. 2001, 617-618, 399-411.
(4) Licandro, E.; Maiorana, S.; Vandoni, B.; Perdicchia, D.; Paravidino,
P.; Baldoli, C. Synlett 2001, 757-760.
(5) Ezquerra, J.; Pedregal, C.; Merino, I.; Florez, J.; Barluenga, J.; Garcia-
Granda, S.; Llorca, M. A. J. Org. Chem. 1999, 64, 6554-6565.
(6) Quayle, P.; Rahman, S.; Ward, E. Lucy M.; Herbert, J. Tetrahedron
Lett. 1994, 35, 3801-3804.
† University of Milan.
‡ C.N.R.
(1) For recent reviews, see: (a) Barluenga, J. Pure Appl. Chem. 1999,
71, 1385-1391. (b) De Meijere, A.; Schirmer, H.; Duetsch, M. Angew.
Chem., Int. Ed. 2000, 39, 3964-4002. (c) Sierra, M. A. Chem. ReV. 2000,
100, 3591-3637. (d) Barluenga, J.; Fananas, F. J. Tetrahedron 2000, 56,
4597-4628. (e) Herndon, J. W. Tetrahedron 2000, 56, 1257-1280. (f)
Barluenga, J.; Florez, J.; Fananas, F. J. J. Organomet. Chem. 2001, 624,
5-17.
(2) (a) Licandro, E.; Maiorana, S.; Manzotti, R.; Papagni, A.; Perdicchia,
D.; Pryce, M.; Tiripicchio, A.; Lanfranchi, M. Chem. Commun. 1998, 383-
384. (b) Licandro, E.; Maiorana, S.; Papagni, A.; Perdicchia, D.; Manzotti,
R.. Chem. Commun. 1999, 925-926.
(7) Licandro, E.; Maiorana, S.; Papagni, A.; Hellier, P.; Capella, L.;
Persoons, A.; Houbrechts, S. J. Organomet. Chem. 1999, 583, 111-119.
(8) Barluenga, J.; Aznar, F.; Barluenga, S.; Fernandez, M.; Martin, A.;
Garcia-Granda, S.; Pinera-Nicolas, A. Chem.-Eur. J. 1998, 4, 2280-2298.
(9) Neidlein, R.; Gurtler, S. Synthesis 1995, 325-329.
(10) Aumann, R.; Schroeder, J.; Heinen, H. Chem. Ber. 1990, 123, 1369-
1374.
10.1021/ol025504b CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/31/2002