INVESTIGADORES
MARTIN Sandra Elizabeth
congresos y reuniones científicas
Título:
Reactivity of Aryl Triflates in Palladium Catalyzed Cross-Coupling Reaction with Organoheteroatom Stannanes
Autor/es:
MARIANA BONATERRA; SANDRA E. MARTÍN; ROBERTO A. ROSSI
Lugar:
Los Cocos, Córdoba, Argentina
Reunión:
Conferencia; 9th Latin American Conference on Physical Organic Chemistry (CLAFQO9); 2007
Resumen:
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REACTIVITY OF ARYL
TRIFLATES IN PALLADIUM CATALYZED CROSS-COUPLING REACTION WITH ORGANOHETEROATOM
STANNANES
Mariana Bonaterra, Sandra E. Martín and Roberto A. Rossi
Instituto de Investigaciones en Físico Química de Córdoba
(INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas,
Universidad Nacional de Córdoba.
Ciudad Universitaria. 5000
Córdoba-Argentina. E-mail:marianab@mail.fcq.unc.edu.ar
The palladium catalyzed cross-coupling reaction of
organic electrophiles with organostannanes is a powerful methodology for C-C1 and C-Heteroatom2
bond formation. A variety of substrates undergo the coupling reaction, the aryl
halides being the most thoroughly studied.1 As organic triflates are
readily available from the corresponding phenol or enolate, they have become
important coupling partners in synthesis for the construction of complexes
molecules.
Recently, we have developed a versatile
methodology that allows C-heteroatom bond formation through a cross-coupling
Pd-catalyzed reaction of different electrophiles with organoheteroatom
stannanes R3SnZPhn (Z = P, As, Sb, Se).2a,b,d
To extend the applications of this methodology, we have studied more
extensively the Pd-catalyzed cross-coupling of these stannanes with aryl
triflates (eq 1). In the present work, we
report on the scope and limitations of the
coupling reaction of aryl triflates with heteroatom containing stannanes.
The
experiments have been performed in order to understand the effect of
different additives (LiCl and CuI), ancillary ligand (Ph3P, Ph3As),
solvent and catalyst, in order to establish the optimal reaction conditions, and
to
explain the mechanism of this cross-coupling reaction with
triflates.
One of the most striking aspects of this reaction is the effect of the
addition of LiCl. Another remarkable characteristic is the polarity of the
solvent employed. We observed that the cross-coupling reaction with stannane 1b proceeded more efficiently in the
presence of LiCl and in DMF as solvent. A dramatic improvement in the yield of the
arsane 4 was observed when the
cross-coupling reaction was conducted with Ph3P as ancillary ligand.
In the presence of CuI as co-catalyst, the Pd-catalyzed reaction also became
more efficient. Some important features of the mechanisms and particularly the
effects of each additive on it will
be discussed.
Similarly, we have studied the reactivity of
other organohetereatom stannanes containing phosphorus (1a), antimony (1c)
and selenium (2) as transferable groups in cross-coupling reactions with
triflates.
1.Farina, V.;
Krishnamurthy, V.; Scott, W. J. The Stille Reaction; Paquette, L. A.,
Ed.; Organic Reactions; John Wiley & Sons: New York, 1997; Vol. 50.
2. For some examples in C-P
bond formation see: (a) Martín, S. E.; Bonaterra, M.; Rossi, R. A. J.
Organomet. Chem. 2002, 664, 223. For C-As and C-Sb
see: (b) Bonaterra, M.; Martín, S. E.; Rossi, R. A. Org. Lett. 2003,
15, 2731. For C-S, C-Si and C-Sn see: (c) Rossi, R.
A.; Martín, S. E. Coord. Chem. Rev. 2006, 250, 575. For
C-Se see: (d) Bonaterra, M.; Martín, S. E.; Rossi, R. A. Tetrahedron
Lett. 2006, 47, 3511.