1
010
M. Al-Masum et al. / Tetrahedron Letters 52 (2011) 1008–1010
O
Pd(0)
Ar
O
Ar
Cl
O
O
Pd
Ar
Ar
Pd Cl
Inorganic
byproducts
O
K CO3
2
BF K
3
Ar
Pd CO
KCl
3
Scheme 2.
with acylating agents such as, phenyl acetyl chloride and acetic
anhydride were attempted but no significant progress was
obtained.
So far, it appears that utilizing 1,4-dioxane as the solvent system
resulted in successful cross-coupling product formation. Although
References and notes
1.
(a) Al-Masum, M.; Alam, S. Tetrahedron Lett. 2009, 50, 5201; (b) Darses, S.; Genet,
J.-P. Chem. Rev. 2008, 108, 288; (c) Molander, G. A.; Jean-Gerard, L. J. Org. Chem.
2007, 72, 8422; (d) Molander, G. A.; Figueroa, R. Aldrichchimica Acta 2005, 38, 49;
(e) Molander, G. A.; Felix, L. A. J. Org. Chem. 2005, 70, 3950; (f) Tremblay-Morin,
J.-P.; Raeppel, S.; Gaudette, F. Tetrahedron Lett. 2004, 45, 3471; (g) Molander, G.
A.; Ribagorda, M. J. Am. Chem. Soc. 2003, 125, 11148; (h) Quach, T. D.; Batey, R. A.
Org. Lett. 2003, 5, 1381; (i) Molander, G. A.; Bernardi, C. R. J. Org. Chem. 2002, 67,
8424; (j) Molander, G. A.; Katona, B. W.; Machrouhi, F. J. Org. Chem. 2002, 67,
8416; (k) Pucheault, M.; Darses, S.; Genet, J.-P. Eur. J. Org. Chem. 2002, 3552; (l)
Molander, G. A.; Rivero, M. R. Org. Lett. 2002, 4, 107; (m) Batey, R. A.; Thadani, A.
N.; Smil, D. V.; Lough, A. Synthesis 2000, 990; (n) Darses, S.; Michauld, G.; Genet,
J.-P. Eur. J. Org. Chem. 1999, 1875; (o) Kabalka, G. W.; Al-Masum, M. Org. Lett.
2006, 8, 11; (p) Kabalka, G. W.; Dadush, E.; Al-Masum, M. Tetrahedron Lett. 2006,
1
,4-dioxane is a non-polar solvent not typically used for microwave
reactions, thepolarizabilityofthe twooxygenand therelativelyhigh
boiling point provided favorable conditions for cross-coupling to oc-
cur. Changing molar ratios of the reagents, changing the palladium
complex, ligand, increasing amount of Pd-catalyst, and changing
the amount of potassium carbonate base had no effect in an isopro-
panol/H
2
O or 100% isopropanol solvent system.5
4
7, 7459; (q) Kabalka, G. W.; Al-Masum, M.; Mereddy, A. R.; Dadush, E.
A mechanism for the direct cross-coupling reaction of potas-
sium styryltrifluoroborates and benzoyl chlorides is proposed in
Scheme 2. The catalytic cycle involves the palladium inserted
nucleophilic species of benzoyl chloride by oxidative addition fol-
lowed by ligand exchange with the base, K CO . The transmetalla-
2 3
tion of the organoboron species to the organopalladium species
subsequently occurs, followed by the formation of the desired
Tetrahedron Lett. 2006, 47, 1133; (r) Arvela, R. K.; Leadbeater, N. E.; Mack, T. L.;
Kormos, C. M. Tetrahedron Lett. 2006, 47, 217; (s) Kabalka, G. W.; Al-Masum, M.
Tetrahedron Lett. 2005, 46, 6329.
2
.
.
(a) Labadie, J. W.; Stille, J. K. J. Am. Chem. Soc. 1983, 105, 6129; (b) Milstein, D.;
Stille, J. K. J. Am. Chem. Soc. 1978, 100, 3636.
(a) Urawa, Y.; Ogura, K. Tetrahedron Lett. 2003, 44, 271; (b) Haddach, M.;
McCarthy, J. R. Tetrahedron Lett. 1999, 40, 3109; (c) Bumagin, N.; Korolev, D. N.
Tetrahedron Lett. 1999, 40, 3057; (d) Xin, B.; Zhang, Y.; Cheng, K. Synthesis 2007,
3
1
970; (e) Eddarir, S.; Cotelle, N.; Bakkour, Y.; Ronaldo, C. Tetrahedron Lett. 2003,
4, 5339.
4. Spectral data of new compounds: Compound 3a: LRMS: Calculated for
a,b-unsaturated ketone by reductive elimination and the re-gener-
4
ation of palladium catalyst.
+
1
C
17
H
16
O
2
M
252. Found: 252. H NMR (CDCl
Aromatic), 3.79 (s, 3H, OCH ), 2.30 (s, 3H, CH
88.7, 144.0, 140.7, 131.1, 129.6, 128.3, 120.7, 113.7, 55.4, 21.4. Compound 3c:
LRMS: Calculated for C17H13F3O M 290. Found: 292 (M+2). H NMR (CDCl3,
300 MHz) d 8.06–7.31(m, 8H, aromatic), 7.79 (d, J = 15.6 Hz, 1H), 7.61 (d,
3
, 300 MHz) d 7.96–6.88 (m, 10H,
); C NMR (CDCl , 75.5 MHz) d
3 3
In conclusion, we were able to report the development of a new
palladium catalyst system allowing the successful cross-coupling
reactions of potassium styryltrifluoroborates and benzoyl chlo-
13
3
1
+
1
rides, furnishing
a,b-unsaturated aromatic ketones or chalcones
1
3
J = 15.6 Hz, 1H), 2.47 (s, 3H, CH
3
); C NMR (CDCl
3
, 75.5 MHz) d 189.4, 162.5,
in a single step process under microwave heating. The procedure
possesses several advantages over similar reactions such as the fact
that potassium styryltrifluoroborates are easy to prepare, non-
toxic, and easily removable. Further use of these developments in
synthetic organic chemistry is in progress.
19
145.5, 135.1, 130.6, 128.6, 125.9, 124.1, 21.8; F NMR (CDCl , 282.3 MHz) d
3
+
1
À63.2. Compound 3e: LRMS: Calculated for C16
9 3 2
H F Cl O M 244. Found: 246. H
NMR (CDCl
3
, 300 MHz) d 8.09–7.47 (m, 6H, aromatic), 7.76 (d, J = 21.0 Hz, 1H),
1
3
7.71 (d, J = 15.9 Hz, 1H); C NMR (CDCl
3
, 75.5 MHz) d 187.4, 164.6, 143.8, 137.3,
19
133.3, 131.3, 130.4, 128.8, 127.4, 122.8; F NMR (CDCl
3
, 282.3 MHz) d À63.2
1
+
(
CF
3
). Compound 3g: LRMS: Calculated for C15
H
10FClO M 260. Found: 262.
H
1
3
NMR (CDCl
3
, 300 MHz) d 7.83–6.84 (m, 10H, Aromatic); C NMR (CDCl
3
,
,
1
9
7
2
5.5 MHz) d 188.3, 143.4, 131.3, 131.0, 129.2, 121.7, 115.8; F NMR (CDCl
82.3 MHz) À102.4 (F). Compound 3h: LRMS: Calculated for C16
3
Acknowledgments
H
11
F
3
O M+ 276.
1
Found: 276. H NMR (CDCl
3
, 300 MHz) d 8.11–7.43 (m, 10H, Aromatic), 7.74 (d,
J = 15.9 Hz, 1H); 1 C NMR (CDCl
, 75.5 MHz) d 199.9, 158.9, 142.7, 134.4, 130.4,
28.7, 125.7, 31.5; 19F NMR (CDCl
, 282.3 MHz) d À63.2 (CF ).
. No cross-coupling product was obtained in iso-propanol or iso-propanol/water.
3
Financial support from US department of education Title III
Grant, Tennessee State University is thankfully acknowledged.
3
1
3
3
5
Supplementary data