Suzuki reactions with B-allyl-9-borabicyclo[3.3.1]nonane (B-allyl-9-BBN)

Article abstract of DOI:10.1055/s-1998-1590

The mixture of borate complexes formed on treatment of B-allyl-9-BBN with KOMe readily undergoes Suzuki reactions in the presence of catalytic amounts of Pd(0) complexes, thus transferring their allyl moiety to aryl bromides, -iodides or -triflates.

Full text of DOI:10.1055/s-1998-1590

February 1998
SYNLETT
161
Suzuki Reactions with B-Allyl-9-Borabicyclo[3.3.1]nonane (B-Allyl-9-BBN)
Alois Fürstner* and Günter Seidel
Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim/Ruhr, Germany
Fax: +49 - 208 - 306 - 2980; e-mail: fuerstner@mpi-muelheim.mpg.de
Received 20 October 1997
Abstract
: The mixture of borate complexes formed on treatment of B-
mixture, but some ligand scrambling leading to the formation of minor
allyl-9-BBN with KOMe readily undergoes Suzuki reactions in the
presence of catalytic amounts of Pd(0) complexes, thus transferring
their allyl moiety to aryl bromides, -iodides or -triflates.
amounts of K[(MeO) BBN] (δ = 4.5 ppm) and K[(allyl) BBN] (δ =
-15.6 ppm) cannot be avoided (Scheme 1).
2
2
The palladium catalyzed cross coupling of aryl halides, triflates or
diazonium salts with various organoboron derivatives in the presence of
a base became one of the most popular methods for C-C-bond
1,2
formations in recent years. Generally referred to as Suzuki reactions,
these transformations exhibit an unrivaled compatibility with functional
groups in both reaction partners and represent environmentally benign
processes with considerable appeal for the preparation of
pharmacologically active compounds and the production of fine
3
chemicals.
In order to widen the scope of Suzuki-type reactions, we have recently
described a complementary protocol employing 9-MeO-9-BBN as a
"shuttle" that allows to transfer i.a. methyl-, TMSCH - and alkynyl
2
4,5
groups which are beyond the scope of the traditional set-up. As a
further extension, we now report the first general procedure for the
transfer of allyl groups under Suzuki conditions.
Palladium-catalyzed cross coupling reactions of allylboron derivatives
are essentially unknown. In a close survey of the literature we found
only a brief mentioning of reactions of tricrotylboron in the presence of
6
aq. NaOH and Pd(PPh ) cat. and a preliminary report on the use of
3 4
7
allyl(dimethoxy)borane. The latter, however, is rather limited in scope
since only aryl iodides were found to be suitable substrates while
bromides afforded the cross coupling products in poor yield. Having in
mind our previous experiences that various types of organic residues
4
can be transferred from the 9-BBN template to an aryl-PdX species, we
investigated whether B-allyl-9-BBN may be useful in this context.
Scheme 1
B-Allyl-9-BBN can be prepared on a mole scale from allyl bromide and
8
B-methoxy-9-BBN in the presence of aluminum chips. Addition of 1
9
equiv. KOMe to a solution of this compound in THF leads to a mixture
Reaction of an aryl halide or triflate with this mixture of borate
complexes in the presence of 3 mol% of either PdCl (dppf) or
11
of borate complexes as can be deduced from the B NMR spectrum.
2
K[(MeO)(allyl)BBN] (δ = -1.5 ppm) is the major component of this
Pd(PPh ) in refluxing THF afforded the desired cross coupling
3 4

162
LETTERS
SYNLETT
products in good to excellent yields. The results are compiled in the
Table. As can be deduced from these experiments, electron rich and
electron poor substrates react with similar ease and several functional
groups turned out to be compatible. This includes ethers, esters,
aromatic ketones, thioketals and heterocyclic motives. Aldehydes,
however, are not tolerated as evident from Scheme 2.
(4) (a) Fürstner, A.; Seidel, G. Tetrahedron 1995, 51, 11165. (b) For a
similar concept see: Soderquist, J. E.; Matos, K.; Rane, A.;
Ramos, J. Tetrahedron Lett. 1995, 2401.
(5) For other applications of the Suzuki reaction from our laboratory
see: (a) Fürstner, A.; Seidel, G. J. Org. Chem. 1997, 62, 2332.
(b) Fürstner, A.; Konetzki, I. Tetrahedron 1996, 52, 15071.
(c) Fürstner, A.; Nikolakis, K. Liebigs Ann. 1996, 2107.
(d) Fürstner, A.; Seidel, G.; Gabor, B.; Kopiske, C.; Krüger, C.;
Mynott, R. Tetrahedron 1995, 51, 8875.
1
(6) Cited as unpublished results in ref. , p. 2476.
(7) Kalinin, V. N.; Denisov, F. S.; Bubnov, Y. N. Mendeleev
Commun. 1996, 206.
Scheme 2
(8) (a) Kramer, G. W.; Brown, H. C. J. Organomet. Chem. 1977, 132,
9. (b) For a review see: Yamamoto, Y. in Encyclopedia of
Reagents for Organic Synthesis (Paquette, L. A., Ed.), Wiley,
New York, 1995, 90.
Several practical aspects of this new allylation procedure are worth
mentioning. Although B-allyl-9-BBN is a very sensitive compound,
8
solutions of the borate complexes formed on addition of KOMe are
fairly easy to handle. They can be bottled and stored for extended
periods of time without loss of activity. The palladium catalyzed cross
coupling reactions usually proceed to completion in 30-60 min and only
a slight excess of the borate is required (≈ 1.2 equiv.). The conversion is
roughly indicated by the precipitation of the KX salts and can be
(9) It is important to use exactly 1.0 equiv. of KOMe per mole of B-
allyl-9-BBN; an excess of the base may cause allyl → 1-propenyl
isomerisations under the reaction conditions.
(10) (a) Echavarren, A. M.; Stille, J. K. J. Am. Chem. Soc. 1987, 109,
5478. (b) Farina, V.; Krishnan, B. J. Am. Chem. Soc. 1991, 113,
9585. (c) For a timely and comprehensive review see: Farina, V.;
Krishnamurthy, V.; Scott, W. J. Org. React. 1997, 50, 1.
11
quantitatively monitored by B NMR of aliquots of the crude mixtures.
Aryl bromides, iodides and triflates were found to react with
comparable ease. Since B-allyl-9-BBN can be easily prepared in
(11) For a leading reference on transition metal catalyzed reactions
using other allylmetal reagents see: Hayashi, T.; Konishi, M.;
Yokata, K-I.; Kumada, M. J. Organomet. Chem. 1985, 285, 359
and lit. cited.
8
multigram amounts, this new protocol is particularly suitable for large
scale preparations. As can be seen from entry 2, substituted allyl groups
can also be transferred in this way.
(12) Representative Procedure: To a solution of B-allyl-9-BBN (1.35
g, 8.3 mmol) in THF (120 mL) is added KOMe (582 mg, 8.3
mmol) and the mixture is stirred for 10 min until a clear solution is
This new Suzuki type allylation reaction favorably compares to the well
known Stille coupling employing allyltributyl (or trimethyl)
10,11
stannane.
Thus, compound 12 was prepared on a multigram scale in
12
formed. Triflate 11 (3.98 g, 6.9 mmol) and PdCl (dppf) (171 mg,
86% in only 0.5 h reaction time by means of this new method,
whereas the Stille coupling afforded the desired compound in
significantly lower yield only after extended periods of time
[allyltributylstannane (1.4 equiv.), Pd (dba) (3 mol%), tris(2-furyl)-
2
3 mol%) are introduced and the mixture is refluxed under Ar for
11
30 min. After that time the B NMR of an aliquot shows a single
peak at δ = 56.6 ppm (external standard: BF •Et O). For work-up
3
2
2
3
the volatiles are removed in vacuo, the residue is suspended in
phosphine (12 mol%), LiCl (3 equiv.), NMP, 40 °C, 48 h, 41%; 60 °C,
24 h, 60%]. Moreover, the purification of the product is easy in the
boron based protocol whereas the removal of the noxious tin residues
formed in the latter case may be tedious. These features make the new
Suzuki-type protocol for the transfer of allyl groups attractive for further
applications to organic synthesis.
CH Cl (120 mL) and the undissolved salts are filtered off over a
2
2
short pad of silica. Evaporation of the solvent and drying of the
-2
residue at 10 torr affords 12 (purity by NMR and GC ≥ 93%,
rest: cyclooctanone) as a colorless syrup (2.97g, 86%). An
analytically pure sample is obtained by flash chromatography
-1
using hexane/Et O (20/1) as the eluent. IR (cm ): 3077, 2940,
2
2840, 1719, 1689, 1639, 1605, 1456, 1423, 1379, 1327, 1271,
1208, 1160, 1096, 1047, 995, 912, 833, 734, 622.- H NMR (300
References and Notes
1
(1) Review: Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
MHz, CDCl ): δ = 6.33 (s, 2H), 5.92 (ddt, 1H, J = 16.4, 10.5, 6.4
3
(2) For some recent developments see: (a) Darses, S.; Genêt, J.-P.;
Brayer, J.-L.; Demoute, J.-P. Tetrahedron Lett. 1997, 4393.
(b) Giroux, A.; Han, Y.; Prasit, P. Tetrahedron Lett. 1997, 3841.
(c) Indolese, A. F. Tetrahedron Lett. 1997, 3513. (d) Sengupta, S.;
Bhattacharyya, S. J. Org. Chem. 1997, 62, 3405. (e) Andersen, N.
G.; Maddaford, S. P.; Keay, B. A. J. Org. Chem. 1996, 61, 9556.
(f) Hildebrand, J. P.; Marsden, S. P. Synlett 1996, 893. (g) Reetz,
M. T.; Breinbauer, R.; Wanninger, K. Tetrahedron Lett. 1996,
4499. (h) Saito, S.; Sakai, M.; Miyaura, N. Tetrahedron Lett.
1996, 2993. (i) Beller, M.; Fischer, H.; Herrmann, W. A.; Öfele,
K.; Broßmer, C. Angew. Chem. 1995, 107, 1992 and lit. cited.
Hz), 5.82 (ddt, 1H, J = 17.0, 10.4, 6.6 Hz), 5.18 (sext., 1H, J = 6.2
Hz), 5.07 (dq, 1H, J = 17.2, 1.6 Hz), 5.06 (dq, 1H, J = 10.1, 1.4
Hz), 5.04 (dq, 1H, J = 17.1, 1.6 Hz), 4.96 (dq, 1H, J = 10.2, 1.4
Hz), 3.80 (s, 3H), 3.79 (s, 3H), 3.37 (dd, 2H, J = 6.6, 1.3 Hz), 2.80
(m, 4H), 2.20 (m, 2H), 1.86-1.99 (m, 6H), 1.49-1.76 (m, 4H), 1.34
13
(d, 3H, J = 6.3 Hz).- C NMR (75 MHz, CDCl ): δ = 167.7,
3
161.3, 156.1, 139.8, 137.9, 136.3, 117.1, 116.4, 114.9, 105.8,
96.7, 71.5, 55.9, 55.3, 53.0, 38.4, 37.7, 37.5, 36.1, 28.6, 26.0,
+
25.4, 20.2, 20.1.- MS (EI, rel. intensity): 464 (14, [M ]), 243 (50),
223 (30), 207 (12), 206 (14), 205 (100), 204 (26), 187 (19), 177
(14), 173 (45), 168 (16), 167 (76), 145 (15), 135 (25), 125 (14),
(3) Applied Homogeneous Catalysis with Organometallic
Compounds (Cornils, B.; Herrmann, W. A., Eds.), VCH,
Weinheim, 1996, Vol. 2.
107 (14), 93 (13), 55 (11), 41 (12).- HR-MS (C H O S ): calcd.
25 36 4 2
464.20551; found 464.20384.