Tetrabutylammonium fluoride-assisted cross-coupling reaction between organic halides and tetraorganotin reagents catalyzed by palladium

Article abstract of DOI:10.1055/s-1999-2558

Palladium-catalyzed cross-coupling reaction between organostannanes and organic halides are much facilitated by an addition of tetrabutylammonium fluoride (TBAF). All four substituents on tin can take part in the carbon- carbon bond formation. A butyl moi

Full text of DOI:10.1055/s-1999-2558

LETTER
63
Tetrabutylammonium Fluoride-Assisted Cross-Coupling Reaction Between
Organic Halides and Tetraorganotin Reagents Catalyzed by Palladium
Keigo Fugami, a Shin-ya Ohnuma, a Masayuki Kameyama,b Takako Saotome,a and Masanori Kosugi*,a
a Department of Chemistry, Gunma University, Kiryu, Gunma 376-8515, Japan
b Oyama National College of Technology, Oyama, Tochigi 323-0806, Japan
Fax +81-277-30-1285; E-mail: kosugi@chem.gunma-u.ac.jp
Received 16 October 1998
Abstract: Palladium-catalyzed cross-coupling reaction between or-
ganostannanes and organic halides are much facilitated by an addi-
tion of tetrabutylammonium fluoride (TBAF). All four substituents
on tin can take part in the carbon-carbon bond formation. A butyl
moiety of tetrabutyltin could also take part in the reaction.
Key words: fluoride, palladium(II) catalyst, tetraorganotin, hyper-
coordination, cross-coupling
chromatography of the reaction mixture after the evapora-
tion of volatiles.
It is well established that the palladium-catalyzed cross-
coupling reaction between organic halides and organotins
is a useful synthetic reaction.1 The employment of highly
coordinated organotin reagents has widened the scope of
the reaction.2,3 Although organotin molecules can carry
four carbon functionalities on a tin atom, only one has
been utilized, probably due to the deactivating nature of
halogen in the haloorganotin reagents.1 Therefore, activa-
As shown in Table 1, the reaction produced the coupling
product in the presence of TBAF (runs 3-6), while it did
not in the absence of TBAF, at all (runs 1,2). The use of 2
mol equivs of TBAF to the tin reagent gave better results
(runs 5,6) than that of 1 mol equiv (runs 3,4). This could
be attributed to the consumption of the first equivalent in
substitution for chloride on tin. Thus the second equiva-
tion of the organotin reagent would be necessary in order lent would be necessary to obtain a sufficient reactivity.2a
to utilize the second or more carbon functionalities.4 Like
in the case of the organosilicon chemistry,5 generation of
a highly coordinated organotin species appears promising.
Recently, hyper-valent organotin species were suggested
as the active species in the palladium-catalyzed cross-cou-
pling reaction of organotin trichlorides with organic ha-
lides in aqueous base.6 Moreover, highly active organotin
reagents were developed by treatment of hetero-substitut-
ed organotin species with TBAF.2 But previous methods
require manipulation of labile reagents and/or synthesis of
a special reagent. We report here that commercially abun-
dant TBAF highly activates haloorganotin reagents and
made it possible to utilize more than one functionality of
tetraorganotin reagents for the palladium-catalyzed cross-
coupling reaction with aryl halides.
These results encouraged us to investigate the use of tet-
To assess the reactivity of the second functionality, the re- raorganotins as reagents that supply more than one func-
action of p-tolyldibutyltin chloride was first examined (eq tionality per one tin. For the reaction of dibutyldi(p-
1). A typical procedure is as follows: To a dioxane (5 mL) tolyl)tin, 2 mol equivs of a halide was used, and 4 mol
solution of bis(dibenzylideneacetone)palladium (0.01 equivs for a tetraorganotin. The results are summarized in
mmol) and triphenylphosphine (0.04 mmol) was added Table 2. A yield is given as the molar ratio between the
the halide (1.2 mmol), p-tolyldibutyltin chloride (0.6 product and the tin reagent. Both iodo- and bromoanisole
mmol), and TBAF (an amount indicated in Table 1), suc- reacted with aryltin reagents in the presence of TBAF,
cessively. The resulting yellow homogeneous solution though chloroanisole did not (run 11). The larger was the
was refluxed for 24 h. The reaction was cooled to rt and amount of TBAF added, the higher was the number of the
submitted to a VPC analysis to determine the yields of the functionalities that took part in the reaction (runs 3-10).
products after an addition of decane as an internal stan- The highest yields were obtained with 3 mol equivs of
dard. Isolated yields were obtained by silica-gel column TBAF to the tin reagent for the reaction with p-bromoani-
sole and with 4 mol equivs for that with p-iodoanisole.
Synlett 1999, No. 1, 63–64 ISSN 0936-5214 © Thieme Stuttgart · New Yorkrk

64
K. Fugami et al.
LETTER
crine disrupters, and required tin reagents being only a
quarter of the halide substrate.
Acknowledgement
Financial support by a Grant-in-Aid from the Ministry of Educati-
on, Science, Sports, and Culture of Japan (09750941 to K. F.) is gra-
tefully acknowledged.
References and Notes
(1) For reviews: Stille, J. K. Angew. Chem. 1986, 98, 483; Angew.
Chem., Int. Ed. Engl. 1986, 25, 508. Mitchell, T. N. Synthesis
1992, 803. Mitchell, T. N. In Metal-Catalyzed Cross-
Coupling Reactions; Diederich, F.; Stang, P. J., Eds.; Wiley-
VCH Verlag GmbH: Weinheim, 1998; p 167.
(2) a) Fouquet, E.; Pereyre, M.; Rodriguez, A. L. J. Org. Chem.
1997, 62, 5242, and references therein. b) Martinez, A. G.;
Barcina, J. O.; de Fresno Cerezo, A.; Subramanian, L. R. Syn-
lett 1994, 1047. c) We found after acceptance of this manus-
cript that in the ref. 2a) was introduced another attempt to
activate tetraorganotins by TBAF: Buffnoir, S.; Mestdagh, E.;
Rolando, C. Electron. Conf. Trends. Org. Chem. [CD-ROM],
Rzepa, H. S.; Leach, C.; Goodman, J. M., Eds.; Royal Chemi-
cal Society: Cambridge, 1996, Paper 42.
These results might suggest that bromide ion is more effi-
cacious than iodide in involving the haloorganotin into the
reaction, although not so much as fluoride ion is. Indeed,
for the reaction between di(p-tolyl)dibutyltin and p-bro-
moanisole, the use of three mol equivs of tetrabutylammo-
nium chloride and bromide in place of TBAF (185 %, run
7) resulted in the formations of the coupling product in
135 and 92 % yields, respectively. To our surprise, in this
condition, the reaction did not give the desired product in
the absence of TBAF, at all (runs 1 and 2). On the other
hand, it is now obvious that tetra(p-tolyl)tin can provide
all four p-tolyl groups under the coexistence of 6 mol
equivs of TBAF (run 13). The effect of TBAF would be
further emphasized with the result obtained with tetrabu-
tyltin of which otherwise inert butyl group could take part
in the reaction (run 14).
(3) Vedejs, E.; Haight, A. R.; Moss, W. O. J. Am. Chem. Soc.
1992, 114, 6556.
(4) Examples in which two or more carbon functionalities on a tin
atom were utilized in: a) a palladium-catalyzed reaction of
diphenyldibutyltin with p-nitrobenzoyl chloride, Labadie, J.
W.; Tueting, D.; Stille, J. K. J. Org. Chem. 1983, 48, 4634.
b) allylation of carbonyls with tetraallyltin, Kobayashi, S.;
Nagayama, S.; Busujima, T. Chem. Lett. 1997, 959.
c) Yasuda, M.; Kitahara, N.; Baba, A., 74th annual meeting of
the Chemical Society of Japan 4C330, Kyoto, 1998.
(5) Yoshida, J.; Tamao, K; Yamamoto, H.; Kakui, T.; Uchida, T.;
Kumada, M. Organometallics 1982, 1, 542. Hiyama, T. In
Metal-Catalyzed Cross-Coupling Reactions; Diederich, F.;
Stang, P. J., Eds.; Wiley-VCH Verlag GmbH: Weinheim,
1998; p 167, and references therein.
In comparison with the widely used organotributyltin re-
agents, the use of tetraorganotins would be advantageous,
giving less hazardous inorganic tin waste instead of tribu-
tyltin halides that are recently suspected as a kind of endo-
(6) Roshchin, A. I.; Bumagin, N. A.; Beletskaya, I. P. Tetrahe-
dron Lett. 1995, 36, 125. Rai, R.; Aubrecht, K. B.; Collum, D.
B. Tetrahedron Lett. 1995, 36, 3111.
Synlett 1999, No. 1, 63–64 ISSN 0936-5214 © Thieme Stuttgart · New York