Synthesis of unsymmetrical biaryls by palladium-catalyzed cross coupling reactions of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent

Article abstract of DOI:10.1021/jo990072c

Palladium-catalyzed cross coupling of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent, to give unsymmetrical biaryls is reported. The Pd(0)-catalyzed process proceeds in good yield with aryl iodides, most aryl trifiates, and electron-deficient aryl bromides.

Full text of DOI:10.1021/jo990072c

3266
J . Org. Chem. 1999, 64, 3266-3270
Syn th esis of Un sym m etr ica l Bia r yls by P a lla d iu m -Ca ta lyzed Cr oss
Cou p lin g Rea ction s of Ar en es w ith Tetr a bu tyla m m on iu m
Tr ip h en yld iflu or osilica te, a Hyp er va len t Silicon Rea gen t§
Molly E. Mowery and Philip DeShong*,†
Department of Chemistry and Biochemistry, The University of Maryland, College Park, Maryland 20742
Received J anuary 14, 1999
Palladium-catalyzed cross coupling of arenes with tetrabutylammonium triphenyldifluorosilicate,
a hypervalent silicon reagent, to give unsymmetrical biaryls is reported. The Pd(0)-catalyzed process
proceeds in good yield with aryl iodides, most aryl triflates, and electron-deficient aryl bromides.
In tr od u ction
Hypervalent silicon species have played an increased
role in Pd(0)-catalyzed cross coupling strategies.6-9 In
contrast to the tin reagents traditionally used in Stille-
type cross coupling reactions, silicon reagents are less
expensive and less toxic, and their byproducts are easier
to remove.2e,7 Previous studies by our group and others
have demonstrated that treatment of a tetravalent aryl-
siloxane, arylchlorosilane, or arylfluorosilane with an
anionic salt results in formation of a hypervalent silicon
species in situ, which, in turn, undergoes Pd(0)-catalyzed
couplings.6,7,9 A hypervalent silicon species has been
postulated to be the reactive intermediate in these
processes. Recently, we reported that tetrabutylammo-
nium triphenyldifluorosilicate (TBAT) can serve as a
phenylating agent in highly stereoselective Pd(0)-cata-
lyzed cross coupling reactions with allylic esters.7a In this
paper we report that TBAT can serve as an effective
transmetallation reagent in Pd(0)-catalyzed cross cou-
pling reactions with aryl iodides, some aryl triflates, and
electron-deficient aryl bromides.
Stoichiometric or catalytic palladium cross coupling
reactions have been used extensively in the formation of
C-C bonds.1 The Stille and Suzuki couplings are the two
methodologies most often utilized because of the high
yields obtained as well as the high degree of stereo-
selectivity that is observed.1-3 A major inadequacy of the
Stille coupling technology is a requirement of a large
excess of toxic tin reagents to achieve high yields. In
addition, the toxic tin byproducts are problematic to
remove.4 The Suzuki coupling has largely supplanted the
Stille method due to its generality, although it too has
limitations with regard to synthesis and stability of
reagents.5
† Phone: 301-405-1892. Fax: 301-314-9121. Email: pd10@umail.
umd.edu.
§ Dedicated to Duilio Argoni on the occasion of his 70th birthday.
(1) (a) Trost, B. M.; Verhoeven, T. R. In Comprehensive Organome-
tallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon: Oxford, 1982; Vol. 8, pp 799-938. (b) Tamao, K. Compre-
hensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon:
Oxford, 1991; Vol. 3, pp 435-480. (c) Knight, D. W., ref 1b pp 481-
578. (d) Tsuji, J . Palladium Reagents and Catalysts. Innovations in
Organic Synthesis; J ohn Wiley & Sons: New York, 1995; pp 1-985.
(2) For information about recent advances in elucidating the mech-
anism of the Stille reaction, see: (a) Casado, A. L.; Espinet, P. J . Am.
Chem. Soc. 1998, 120, 8978-8985. (b) Casado, A. L.; Espinet, P.
Organometallics 1998, 17, 954-959. For information concerning the
mechanism of the related Heck reaction, see: (c) Crisp, G. T. Chem.
Soc. Rev. 1998, 27, 427-436. For other articles about the Stille
reaction, see: (d) Stille, J . K.; Echavarren, A. M.; Williams, R. M.;
Hendrix, J . A. Org. Synth. 1992, 71, 97-106 and references therein.
(e) Del Valle, L.; Stille, J . K.; Hegedus, L. S. J . Org. Chem. 1990, 55,
3019-3023. (f) Echavarren, A. M.; Stille, J . K. J . Am. Chem. Soc. 1987,
109, 5478-5486. (g) Stille, J . K.; Groh, B. L. J . Am. Chem. Soc. 1987,
109, 813-817. (h) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25,
508-524. (i) Scott, W. J .; Stille, J . K. J . Am. Chem. Soc. 1986, 108,
3-3040. (j) Stille, J . K. Pure Appl. Chem. 1985, 57, 1771-1780. (k)
Farina, V.; Krishnaumurthy, V.; Scott, W. J . Org. React. 1997, 50,
1-652. (l) Farina, V. Pure Appl. Chem. 1996, 68, 73-78. (m) Farina,
V.; Roth, G. P. In Advances in Metal-Organic Chemistry; Liebeskind,
L. S., Ed.; J . A. I.: Greenwich, 1995; Vol. 5.
(5) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483.
(6) Mowery, M. E.; DeShong, P. J . Org. Chem. 1999, 64, 1684-1688.
(7) (a) Brescia, M.-R.; DeShong, P. J . Org. Chem. 1998, 63, 3156-
3157. TBAT is commercially available from Aldrich Chemical Co. and
Eburon Chemicals. For other papers relating to the application of
hypervalent silicates as reagents, see: (b) Pilcher, A. S.; DeShong, P.
J . Org. Chem. 1996, 61, 6901-6905. (c) Pilcher, A. S.; Ammon, H. L.;
DeShong, P. J . Am. Chem. Soc. 1995, 117, 5166-5167. (d) Pilcher, A.
S.; DeShong, P. J . Org. Chem. 1993, 58, 5130-5134. (e) Pilcher, A. S.;
Hill, D. K.; Waltermire, R. E.; Shimshock, S. J .; DeShong, P. J . Org.
Chem. 1992, 57, 2492-2495.
(8) For recent reviews on organosilicon compounds and cross
coupling reactions, see: (a) Hiyama, T. In Metal-catalyzed Cross-
coupling Reactions; Diederich, F., Stang, P. J ., Eds.; Wiley-VCH:
Weinhein, Germany, 1998; pp 421-452. (b) Horn, K. A. Chem. Rev.
1995, 95, 1317-1350. (c) Hiyama, T.; Hatanaka, Y. Pure Appl. Chem.
1994, 66, 1417-1478. (d) Chuit, C.; Corriu, R. J . P.; Reye, C.; Young,
J . C. Chem. Rev. 1993, 93, 1317-1448. (e) Hatanaka, Y.; Hiyama, T.
Synlett 1991, 845-853.
(9) For information about Pd-catalyzed, fluoride-promoted cross
coupling reactions of reactions of organohalosilanes with aryl and
alkenyl halides, see: (a) Gouda, K.; Hagiwara, E.; Hatanaka, Y.;
Hiyama, T. J . Org. Chem. 1996, 61, 7232-7233. (b) Hatanaka, Y.;
Goda, K.; Okahara, Y.; Hiyama, T. Tetrahedron 1994, 50, 8301-8316.
(c) Hatanaka, Y.; Fukushima, S.; Hiyama, T. Heterocycles 1990, 30,
303-306. (d) Hatanaka, Y.; Fukushima, S.; Hiyama, T. Chem. Lett.
1989, 1711-1714. For information about alkylation of aryl halides with
alkyltrifluorosilanes, see: (e) Matsuhashi, H.; Asai, S.; Hirabayashi,
K.; Hatanaka, Y.; Mori, A. Hiyama, T. Bull. Chem. Soc. J pn. 1997,
70, 437-444. (f) Matsuhashi, H.; Kuroboshi, M.; Hatanaka, Y.; Hiyama,
T. Tetrahedron Lett. 1994, 35, 6507-6510. For information about Pd-
catalyzed, NaOH-promoted reactions of organochlorosilanes with aryl
chlorides, see: (g) Hagiwara, E.; Gouda, K.; Hatanaka, Y.; Hiyama,
T. Tetrahedron Lett. 1997, 38, 439-442.
(3) For examples of natural product syntheses using Stille coupling,
see: (a) Kalivretenos, A.; Stille, J . K.; Hegedus, L. S. J . Org. Chem.
1991, 56, 2883-2894; and references therein. (b) Gyorkos, A. C.; Stille,
J . K.; Hegedus, L. S. J . Am. Chem. Soc. 1990, 112, 8465-8472. (c)
Discodermolide: Smith, A. B., III.; Qiu, Y.; J ones, D. R.; Kobayashi,
K. J . Am. Chem. Soc. 1995, 117, 12011-12012. (d) Rapamycin:
Nicolaou, K. C.; Chakraborty, T. K.; Piscopio, A. D.; Minowa, N.;
Bertinato, P. J . Am. Chem. Soc. 1993, 115, 4419-4420.
(4) For information regarding toxicology studies of tin reagents,
see: (a) Arakawa, Y. In Chemistry of Tin, 2nd ed.; Smith, P. J ., Ed.;
Blackie Academic & Professional: London, 1998; pp 388-428. (b)
Smith, P. J ., ref 4a, pp 429-441. (c) Aldridge, W. N. In Chemistry and
Technology of Silicon and Tin; Kumar Das, V. G., Weng, N. G., Gielen,
M., Eds.; Oxford University Press: New York, 1992; pp 78-92.
10.1021/jo990072c CCC: $18.00 © 1999 American Chemical Society
Published on Web 04/09/1999

Palladium-Catalyzed Cross Coupling of Arenes
J . Org. Chem., Vol. 64, No. 9, 1999 3267
Ta ble 1. Resu lts of Cr oss Cou p lin g Rea ction s Usin g TBATa
Sch em e 1
catalyst than bis(dibenzylideneacetone)palladium (Pd-
(dba)2), but APC is particularly air sensitive. Substituting
Pd(dba)2 for APC (entry 1 vs 2) did not have a significant
effect on either the yield or the product distribution. In
entry 5, where 2 equiv of TBAT and Pd(dba)2 are used,
there is more homocoupled product formed (4%) than
when APC is used (0%, entry 3), but the difference is
insignificant.
As was noted in the earlier study of allylic esters,7a the
presence of phosphines has no appreciable effect on the
yield of biaryls. When an equimolar amount of triphenyl-
phosphine to APC was included (entry 4), there was only
a 10% decrease in heterocoupled product formed and no
homocoupled product was observed. This indicates that
the reaction tolerates the presence of phosphine.2e,7a
Solvents were also evaluated to determine optimum
conditions. Dimethylformamide (DMF) was used initially
because it is the typical solvent employed in Stille
couplings.2e Switching to tetrahydrofuran (THF) resulted
in an increase in homocoupled product (entries 6a and
6b). However, changing both the catalyst from APC to
Pd(dba)2 and the solvent from DMF to THF gave the most
unsatisfactory results (entry 7). If Pd(dba)2 is used as the
catalyst, dioxane can be substituted for THF (entry 8)
and this lowers the amount of homocoupled product
formed. On the basis of these preliminary studies (entries
1-10), it was concluded that 2 equiv of TBAT, APC, or
Pd(dba)2 in DMF was the optimum reaction conditions
for the cross coupling reactions.
Resu lts a n d Discu ssion
The general reaction is shown in Scheme 1, and the
results are summarized in Table 1. Initial optimization
studies utilized 4′-iodoacetophenone as the aryl substrate.
Couplings performed with 5 equiv of TBAT and 20 mol
% allyl palladium chloride dimer (APC) in DMF gave 86%
of the heterocoupled product, 4-acetylbiphenyl, and 14%
of the homocoupled product, 4,4′-diacetylbiphenyl (Table
1, entry 1). Reducing the amount of TBAT to 2 equiv
(entry 3) gave a quantitative yield of heterocoupled
product. Further reducing the amount to 1.2 equiv also
gave exclusively the heterocoupled product, but the yield
was marginally lower (93% vs 100%, entry 10). Subse-
quent studies of the coupling reaction were performed
with 2 equiv of TBAT to obtain a maximum yield of the
heterocoupled product.
Under the optimized reaction conditions, 4-iodoanisole
(entry 11) gave almost a quantitative yield of hetero-
coupled product and no homocoupled product. Altering
catalysts and solvents reduced the yield of heterocoupled
Several palladium catalysts were also investigated.
Allylpalladium chloride dimer (APC) is a more reactive

3268 J . Org. Chem., Vol. 64, No. 9, 1999
Mowery and DeShong
Sch em e 2
Since aryl iodides are expensive and often difficult to
synthesize, aryl triflates were investigated as substrates
because of the ease of preparation from cheap, readily
available phenols.11 Using 4-tolyl trifluoromethane-
sulfonate (entry 26) or 4-phenyl trifluoromethane-
sulfonate (entry 27) gave only starting material. Again,
this problem was attributed to the lack of oxidative
addition to Pd(0). Strongly electron-deficient 4-nitro-
phenyl trifluoromethanesulfonate gave exclusively het-
erocoupled product 4-nitrobiphenyl (entry 28, 73%).
Results were also successful with 4-acetylphenyl (entry
29, 73%) and 4-carbomethoxyphenyl (entry 30, 90%)
triflate. It was also found that 1-naphthyl trifluoro-
methanesulfonate gave exclusively heterocoupled product
(entry 31) in a 71% yield.
Con clu sion
In summary, the hypervalent silicate complex TBAT
has been shown to be a highly effective transmetallation
reagent for the Pd(0)-catalyzed cross coupling of aryl
iodides and triflates and electron-deficient aryl bromides.
The reaction is tolerant to changes in the Pd catalyst as
well as the presence of an equimolar amount of phosphine
to catalyst. Changes in solvent used in the reaction can
also be tolerated at the expense of formation of slightly
more homocoupled product. Cross coupling reactions of
hypervalent silicon compounds expanded to transfer
substituted aryl groups in addition to phenyl will be
reported in due course.
adduct slightly (entry 12). Substrates such as 2-, 3-, and
4-iodotoluene gave the best results when APC and DMF
were used (entries 17, 15, and 13, respectively). This
demonstrated that the position of the substituent did not
affect the yield of homocoupled product.
Since the cross coupling worked well with aryl iodides,
extension to aryl bromides and chlorides was studied.
Using the electron-deficient 4-bromoacetophenone sur-
prisingly gave better results with Pd(dba)2 and THF
(entries 19 and 20). When 4-bromoanisole (entry 22) or
4-bromotoluene (entry 24) was employed, only starting
material was isolated. Attempts to couple aryl chlorides
were not successful either; 4-chloroacetophenone (entry
21), 4-chloroanisole (entry 23), or 4-chlorotoluene (entry
25) gave only starting material under standard condi-
tions. This has been a general trend seen in these cross
coupling reactions.5
The presumed mechanism in these reactions is de-
picted in Scheme 2.1d,2a-c The first step involves the
oxidative addition of the aryl halide to Pd(0) to form an
aryl palladium halide complex. Next, an R group is
transferred from the silicate reagent to Pd. The last step
is reductive elimination to generate the transmetallation
product and regeneration of the Pd(0) catalyst. In the
case of the aryl bromides and chlorides, it has been
proposed that the lack of reaction is the result of
ineffective oxidative addition to palladium since starting
material is recovered.1d,2a-c Recently, several solutions to
activation of chloro derivatives have been reported.10
Since TBAT appeared to be an effective phenylating
agent, an experiment was performed to determine if
TBAT could deliver all three phenyl groups when excess
TBAF was included. The experiment used 1 equiv of
4-iodoanisole, 1 equiv of TBAT, and 3 equiv of TBAF.
Three equivalents of TBAF are required to make the
silicon byproducts hypervalent again after each of the
phenyl transfers so that another phenyl group can be
transferred. The catalyst used was Pd(dba)2, and THF
was the solvent employed. Results indicated that 34% of
the starting material was isolated and 5% biphenyl (from
homocoupling of TBAT), 45% heterocoupled product, and
16% of the homocoupled product formed. These results
indicate that TBAT delivered approximately 1.25 phenyl
groups.
Exp er im en ta l Section
1
Gen er a l. All H and 13C NMR spectra were recorded on a
400 MHz instrument in CDCl3 unless otherwise indicated.
Chemical shifts are reported in parts per million (δ) downfield
from TMS. Coupling constants (J values are given in hertz
(Hz)) and spin multiplicities are indicated by the following
symbols: s (singlet), d (doublet), t (triplet), and m (multiplet).
IR absorbances are reported in reciprocal centimeters (cm-1).
Gas chromatography was performed on a Hewlett-Packard
5890 GC equipped with a flame ionization detector using a 25
m methyl silicone column.
Tetrahydrofuran (THF) and dioxane were distilled from
sodium/benzophenone ketyl. Dimethylformamide (DMF) was
distilled from molecular sieves. Glassware used in the reac-
tions was dried overnight in an oven at 120 °C. All reactions
were performed under an atmosphere of nitrogen unless noted
otherwise.
Allyl palladium chloride dimer, triflic anhydride, and all aryl
iodides, bromides, chlorides, and phenols were purchased from
Aldrich and used as received. Bis(dibenzylideneacetone)-
palladium (Pd(dba)2) was purchased from Acros. Triphenylphos-
phine (PPh3) was purchased from Aldrich and recrystallized
from pentane prior to use.
Tetrabutylammonium triphenyldifluorosilicate (TBAT) was
prepared according to the literature procedure7c and is com-
mercially available. All compounds were determined to be
1
>95% pure by GC and H NMR spectroscopy unless otherwise
noted.
Gen er a l P r oced u r e for th e Cr oss Cou p lin g Rea ction s
Utilizin g Ar yl Iod id es, Br om id es, a n d Ch lor id es (En tr ies
1-20). En tr y 1: 4-Acetylbip h en yl. To a solution of 0.101 g
(0.410 mmol) of 4′-iodoacetophenone and 1.113 g (2.062 mmol)
of TBAT in 10 mL of DMF was added 12 mg (0.033 mmol) of
allyl palladium chloride dimer. The reaction mixture was
degassed to remove oxygen via one freeze-pump-thaw cycle.
The red-brown mixture was heated at 95 °C for 5 h. The
resulting brown mixture was quenched by the addition of 50
(10) (a) Littke, A. F.; Fu, G. C. J . Org. Chem. 1999, 64, 10-11. (b)
Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. Engl. 1998, 37, 3387-
3388. (c) Old, D. W.; Wolfe, J . P.; Buchwald, S. L. J . Am. Chem. Soc.
1998, 120, 9722-9723.
(11) Ritter, K. Synthesis 1993, 735-762.

Palladium-Catalyzed Cross Coupling of Arenes
J . Org. Chem., Vol. 64, No. 9, 1999 3269
mL of H2O; the aqueous layer was then extracted with 4 × 50
mL of Et2O, and the combined organic layers were dried over
MgSO4 and concentrated in vacuo. Purification of the residue
by flash chromatography (25 mm, 17 cm, 0-10% EtOAc/
hexane) gave 70 mg (86%) of 4-acetylbiphenyl as a yellow solid
and 7 mg (14%) of 4,4′-diacetylbiphenyl, the homocoupled
product. Recrystallization from absolute EtOH yielded pale
yellow needles: TLC Rf ) 0.29 (10% EtOAc/hexane); mp 119-
119.5 °C (lit. mp 119-120 °C (EtOH));2f IR (CCl4) 3081 (w),
3038 (w), 3000 (w), 2931 (m), 2850 (w), 1691 (m), 1569 (s), 1538
mL of 10% HCl and 30 mL of saturated NaCl and then dried
over MgSO4 and concentrated in vacuo. This yielded 2.131 g
(96%) of a yellow oil that was 96% pure by GC. Purification of
the residue by column chromatography (15 mm, 19 cm, 25%
Et2O/pentane) gave 1.956 g (88%) of a colorless oil: TLC Rf )
0.75 (25% Et2O/pentane); IR (CCl4) 3050 (w), 2988 (w), 2938
1
(w), 2869 (w), 1600 (m), 1556 (m), 1506 (s); H NMR (CDCl3)
δ 2.36 (s, 3H), 7.14 (A of AB quartet, J AB ) 8.6, 2H), 7.22 (B of
AB quartet, J AB ) 8.6, 2H); 13C NMR (CDCl3) δ 20.7, 118.8 (q,
J C-F ) 320), 121.0, 130.7, 138.5, 147.6; LRMS 241 ((M + 1),
4), 240 ((M+), 43), 107 (100), 77 (46); HRMS (EI) calcd for
C8H7O3F3S (M+) 240.0068, found 240.0061. The IR and 1H
NMR are identical to the spectral data found in ref 16, and
the LRMS is identical to data found in ref 17. Elemental
analysis data can be found in ref 16.
1
(s); H NMR δ 2.63 (s, 3H), 7.38 (t, J ) 7.3, 1H), 7.46 (t, J )
7.4, 2H), 7.61 (d, J ) 7.2, 2H), 7.67 (A of AB quartet, J AB
)
8.4, 2H), 8.02 (B of AB quartet, J AB ) 8.4, 2H); 13C NMR δ
26.6, 127.2, 128.2, 128.9, 135.9, 139.9, 145.8, 197.7; LRMS (EI)
197 ((M + 1), 10), 196 ((M+), 59), 181 (100), 153 (35), 152 (41);
HRMS (EI) calcd for C14H12O 196.0888 (M+);, found 196.0883.
The IR and 1H NMR are identical to the spectral data found
in ref 2f.
P h en yl Tr iflu or om eth a n esu lfon a te: TLC Rf ) 0.53 (10%
EtOAc/hexane); IR (CCl4) 3066 (w), 1602, 1488 (m), 1427 (s),
1248 (m), 1225 (m), 1206 (m), 1173 (m), 1145 (s); 1H NMR
(CDCl3) δ 7.25-7.27 (m, 2H), 7.38-7.40 (m, 1H), 7.43-7.45
En tr y 11, 4-Meth oxybip h en yl: TLC Rf ) 0.46 (10%
EtOAc/hexane); mp 83.5-85.5 °C (lit. mp 90 °C (EtOH));12 IR
(CCl4) 3081 (w), 3047 (w), 3006 (w), 2931 (w), 2856 (w), 2838
1
(m, 2H). The IR and H NMR are identical to the spectral data
found in ref 18. Additional spectral information (13C, 19F, and
GC/MS data) can be found in ref 19.
1
(w), 1563 (s), 1512 (s); H NMR (CDCl3) δ 3.83 (s, 3H), 6.95-
6.97 (m, 2H), 7.40 (t, J ) 7.7, 2H), 7.50-7.54 (m, 5H); 13C NMR
(CDCl3) δ 55.4, 114.2, 126.6, 126.7, 128.2, 128.7, 135.2; LRMS
185 ((M + 1), 15), 184 ((M+), 100), 169 (39), 141 (35), 115 (21);
HRMS (EI) calcd for C13H12O 184.0888 (M+),; found 184.0885.
The 1H NMR, 13C NMR, and LRMS are identical to the spectral
data found in ref 13.
4-Nitr op h en yl Tr iflu or om eth a n esu lfon a te: TLC Rf )
0.37 (25% Et2O/hexane); mp 50.5-52 °C (lit. mp 53-54 °C);20
IR (CCl4) 3119 (w), 3087 (w), 3006 (w), 1717 (s), 1620 (m), 1488
(m), 1436 (s), 1348 (s); 1H NMR (CDCl3) δ 7.45-7.48 (m, 2H),
8.34-8.37 (m, 2H); 13C NMR (CDCl3) 118.6 (q, J C-F ) 321),
122.5, 126.0, 147.2, 153.1. The IR and 1H NMR are identical
to the spectral data found in ref 20. Reference 20 also contains
En tr y 13, 4-Meth ylbip h en yl: TLC Rf ) 0.47 (10% Et2O/
pentane); mp 44.5-46.5 °C (lit. mp 49 °C (EtOH));14 IR (CCl4)
3081 (w), 3063 (w), 3038 (w), 2925 (w), 2863 (w), 1556 (s), 1531
1
HRMS data. IR and H NMR data can also be found in ref 2f.
LRMS data can be found in ref 17.
1
(s); H NMR (CDCl3) δ 2.38 (s, 3H), 7.23 (m, 2H), 7.30 (t, J )
4-Acetylp h en yl Tr iflu or om eth a n esu lfon a te: TLC Rf )
0.38 (25% Et2O/hexane); IR (CCl4) 3107 (w), 3070 (w), 3009
7.6, 1H), 7.41 (t, J ) 7.6, 2H), 7.48 (d, J ) 8.1, 2H), 7.58 (d, J
) 7.3, 2H); 13C NMR (CDCl3) δ 21.1, 127.0, 128.7, 129.5, 137.0,
138.4, 141.2; LRMS 169 ((M + 1), 19), 168 ((M+), 100), 167
(63), 165 (24), 149 (52), 90 (21); HRMS (EI) calcd for C13H12
168.0939 (M+), found 168.0945. The IR and 1H NMR are
identical to the spectral data found in ref 14.
1
(w), 1649 (s), 1600 (m); H NMR (CDCl3) δ 2.61 (s, 3H), 7.36
(A of AB quartet, J AB ) 8.8, 2H), 8.04 (B of AB quartet, J AB
)
8.8, 2H); 13C NMR (CDCl3) δ 26.3, 118.6 (q, J C-F ) 321), 121.4,
130.4, 136.8, 152.3, 195.9. The IR and 1H NMR are identical
to spectral data found in ref 2f. Elemental analysis results are
available in ref 2f.
En tr y 15, 3-Meth ylbip h en yl: TLC Rf ) 0.47 (10% Et2O/
pentane); IR (CCl4) 3093 (w), 3069 (s), 3031 (s), 2969 (m), 2931
4-Ca r bom eth oxyp h en yl Tr iflu or om eth a n esu lfon a te:
TLC Rf ) 0.35 (10% EtOAc/hexane); IR (CCl4) 3000 (w), 2954
(m), 2845 (w), 1924 (w), 1732 (s), 1604 (m), 1499 (m), 1430 (s),
1412 (s), 1284 (s); 1H NMR (CDCl3) δ 3.92 (s, 3H), 7.33 (m,
1
(s), 2869 (w), 1600 (s), 1575 (s), 1531 (m); H NMR (CDCl3) δ
2.28 (s, 3H), 7.23-7.28 (m, 4H), 7.32-7.35 (m, 3H), 7.39-7.43
(m, 2H); 13C NMR (CDCl3) δ 20.8, 126.1, 127.1, 127.6, 128.4,
129.1, 129.5, 130.1, 130.6; LRMS 169 ((M + 1), 17), 168 ((M+),
100), 167 (54), 165 (23), 152 (21); HRMS (EI) calcd for C13H12
168.0939 (M+), found 168.0941. The IR and 1H NMR are
identical to the spectral data found in ref 14.
2H), 8.13 (m, 2H); 13C NMR (CDCl3) δ 52.4, 118.7 (q, J C-F
)
320), 121.4, 130.4, 131.8, 152.5, 165.4; LRMS 285 ((M + 1),
8), 284 ((M+), 76), 253 (100), 189 (89), 123 (28), 95 (33), 70
(32); HRMS (EI) calcd for C9H7O5F3S (M+) 283.9966, found
283.9965. The 1H NMR is identical to spectral data found in
ref 21.
En tr y 17, 2-Meth ylbip h en yl: TLC Rf ) 0.59 (10% Et2O/
pentane); IR (CCl4) 3063 (m), 3025 (m), 2963 (w), 2925 (m),
1
2869 (w), 1600 (s), 1550 (s); H NMR (CDCl3) δ 2.27 (s, 3H),
1-Na p h th yl Tr iflu or om eth a n esu lfon a te: TLC Rf ) 0.51
(10% EtOAc/hexane); IR (CCl4) 3062 (m); 1602 (m), 1508 (m),
1418 (s), 1388 (s), 1231 (m), 1201 (m), 1145 (s), 1071 (m), 1030
(m), 901 (s); 1H NMR (CDCl3) δ 7.44-7.50 (m, 2H), 7.57-7.65
(m, 2H), 7.85-7.92 (m, 2H), 8.07 (d, J ) 8.2, 1H). The IR and
1H NMR are identical to spectral data found in ref 2c.
Elemental analysis results can also be found in ref 2f. 13C
NMR, LRMS, and elemental analysis results can also be found
in ref 22.
7.22-7.44 (m, 9H); 13C NMR (CDCl3) δ 21.9, 124.6, 127.5,
128.3, 129.0, 138.7, 141.6; LRMS 169 ((M + 1), 20), 168 ((M+),
100), 167 (85), 165 (41), 153 (34), 152 (28); HRMS (EI) calcd
1
for C13H12 168.0939 (M+), found 168.0937. The IR, H NMR,
and HRMS are identical to the spectral data found in ref 15.
Gen er a l P r oced u r e for th e P r ep a r a tion of Tr ifla tes
To Be Used in Cr oss Cou p lin g Rea ction s (En tr ies 26-
31). The triflates were prepared using a modification of a
procedure in Synthesis.11
4-Tolyl Tr iflu or om eth a n esu lfon a te. To a 0 °C solution
of 1.002 g (9.27 mmol) of p-cresol in 5.3 mL of pyridine was
added 2.37 mL (14.09 mmol) of triflic anhydride. The reaction
turned brownish-yellow upon addition of the triflic anhydride.
The reaction was stirred at room temperature for 1.75 h. The
resulting mixture was quenched by the addition of 30 mL of
H2O; the aqueous layer was then extracted with 2 × 30 mL of
Et2O, and the combined organic layers were washed with 30
Cr oss Cou p lin g Rea ction s (En tr ies 28-31). En tr y 28,
4-Nitr obip h en yl: TLC Rf ) 0.56; mp 111.5-112 °C (lit. mp
113-115 °C (MeOH));23 IR (CCl4) 3067 (w), 3034 (w), 1604 (m),
(16) Cabri, N.; Candiani, A.; Bedeschi, A.; Penco, S.; Santi, R. J .
Org. Chem. 1992, 57, 1481-1486.
(17) Derocque, J .-L.; J ochem, M. Org. Mass. Spectrom. 1977, 12,
479-487.
(18) Anders, E.; Stankowiak, M. Synthesis 1984, 1039-1041.
(19) Olah, G. A.; Wu, A. Synthesis 1991, 204-206.
(20) Stille, J . K.; Echavarren, A. M.; Williams, R. M.; Hendrix, J .
A. Org. Synth. 1993, 71, 97-106.
(21) Percec, V.; Bae, J .-Y.; Zhao, M.; Hill, D. H. J . Org. Chem. 1995,
60, 176-185.
(22) Crisp, G. T.; Papadopoulos, S. Aust. J . Chem. 1988, 41, 1711-
1715.
(23) Wallow, T. I.; Novak, B. M. J . Org. Chem. 1994, 59, 5034-
5037.
(12) Neeman, M.; Caserio, M. C.; Roberts, J . D.; J ohnson, W. S.
Tetrahedron 1959, 6, 36-47.
(13) Lipshutz, B. H.; Siegmann, K.; Garcia, E.; Kayser, F. J . Am.
Chem. Soc. 1993, 115, 5, 9276-9282.
(14) Rao, M. S. C.; Rao, G. S. K. Synthesis 1987, 231-233.
(15) Rieke, R. D.; Schulte, L. D.; Dawson, B. T.; Yang, S. S. J . Am.
Chem. Soc. 1990, 112, 8388-8398.

3270 J . Org. Chem., Vol. 64, No. 9, 1999
Mowery and DeShong
1521 (w),1347 (s); 1H NMR (CDCl3) δ 7.47-7.49 (m, 3H), 7.61
(d, J ) 7.2, 2H), 7.72 (A of AB quartet, J AB ) 8.7, 2H), 8.29 (B
of AB quartet, J AB ) 8.7, 2H). The 1H NMR is identical to
spectral data found in ref 23. Additional spectral information
(13C NMR and MS data) can be found in ref 23.
(CDCl3) δ 7.21-7.25 (m, 2H), 7.33-7.35 (m, 4H), 7.43-7.46
(m, 6H); GC/MS 205 ((M+1), 13), 204 ((M+), 92), 203 (100),
202 (56), 101 (66). The IR and LRMS data are identical to
spectral data found in ref 26. Additional spectral information
(13C NMR, LRMS, and elemental analysis) can also be found
in ref 22.
En tr y 30, 4-Ca r bom eth oxybip h en yl: TLC Rf ) 0.37; mp
108-108.5 °C (lit. mp 116-117 (hexane/EtOAc));24 IR (CCl4)
3033 (w), 2952 (w), 1728 (m), 1560 (s), 1279 (s); 1H NMR
(CDCl3) δ 3.92 (s, 3H), 7.30-7.40 (m, 1H), 7.40-7.50 (m, 2H),
Ack n ow led gm en t. We thank Dr. Marc-Raleigh
Brescia for his contributions with preliminary experi-
ments. We thanks Dr. Yui-Fai Lam and Ms. Caroline
Ladd for their assistance in obtaining NMR and mass
spectral data. P.D. and M.M. thank the University of
Maryland for financial support. In addition, M.M.
thanks the Organic Division of the American Chemical
Society for a Graduate Fellowship (sponsored by Pfizer).
1
7.60-7.66 (m, 4H), 8.09 (d, J ) 8.3, 2H). The IR and H NMR
are identical to spectral data found in ref 24. LRMS data can
also be found in ref 24. 13C NMR data can be found in ref 25.
En tr y 31, 1-P h en yln aph th ylen e: TLC Rf ) 0.54; mp 191-
199 °C; IR (CCl4) 3071 (w), 3058 (w), 2986 (w), 1569 (s), 1533
(s), 1252 (s), 1217 (s), 1118 (s), 1006 (s), 834 (s); 1H NMR
J O990072C
(24) Barba, I.; Chinchilla, R.; Gomez, C. Tetrahedron 1990, 46,
7813-7822.
(25) Budesinsky, M.; Exner, O. Magn. Reson. Chem. 1989, 27, 585-
(26) Hofmann, J .; Zimmermann, G.; Guthier, K.; Hebgen, P.;
Homann, K.-H. Liebigs Ann. Chem. 1995, 631-636.
591.