Chelating retardation effect in nickel assisted phosphinatioa: Syntheses of atropisomeric P,N ligands

Article abstract of DOI:10.1016/S0040-4020(00)00816-4

Ni(PPh₃)₂Cl₂ was found to be an effective reagent in nickel assisted phosphination of biaryl O,N triflates with chlorodiphenylphosphine to yield atropisomeric P,N ligands. The chelating effect of the substrates in the reaction played an important role. Only the monodentate PPh₃ rather than bidentate dppe (1,2-bis(diphenylphosphino)ethane) nickel complex was found to be an effective reagent. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00816-4

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 8893±8899
Chelating Retardation Effect in Nickel Assisted Phosphination:
Syntheses of Atropisomeric P,N Ligands
Fuk Yee Kwong,a Albert S. C. Chanb and Kin Shing Chana,
*
aDepartment of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
bDepartment of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Received 22 May 2000; revised 23 August 2000; accepted 7 September 2000
AbstractÐNi(PPh3)2Cl2 was found to be an effective reagent in nickel assisted phosphination of biaryl O,N tri¯ates with chlorodiphenyl-
phosphine to yield atropisomeric P,N ligands. The chelating effect of the substrates in the reaction played an important role. Only the
monodentate PPh3 rather than bidentate dppe (1,2-bis(diphenylphosphino)ethane) nickel complex was found to be an effective reagent.
q 2000 Elsevier Science Ltd. All rights reserved.
Introduction
amination,11 and transfer hydrogenation reactions.12 Herein,
we report the synthesis of new atropisomeric P,N ligands by
nickel assisted phosphination and the chelation effect in the
reaction cycle.
Atropisomeric phosphine ligands have played a crucial role
in the development of asymmetric catalysis. The most
successful phosphine is the well known 2,20-bis(diphenyl-
phosphino)-1,10-binaphthyl (BINAP)1 4 ligand which was
®rstly reported in 1980 and applied to many asymmetric
catalysis.2 This discovery of the BINAP ligand initiated
the development of other mixed donor atropisomeric
ligands based on the binaphthyl or other biaryl backbones
such as QUINAP3 5 and MAP 64 (Fig. 1).
Results and Discussion
Initial attempts to convert the aromatic hydroxyl group of
pyridylphenol 8a to pyridylphenyl bromide 7 by the reaction
with triphenylphosphine dibromide did not yield any bro-
mide 7. The starting material 8a decomposed likely due to
the extreme high reaction temperature (3208C).13
This class of hemilabile ligands possesses a combination of
hard and soft donor atoms, and have different features asso-
ciated with each donor atom that provide unique reactivity
to their metal complexes.5 One important property of these
potential ligands is that they can stabilize metal ions in a
variety of oxidation states and geometries. Moreover, the
hard ends weakly coordinate to soft metal centers and easily
dissociate in solution to afford a vacant site whenever
demanded. On the other hand, their chelating effect confers
stability to the catalyst in the absence of substrates. In
addition, P,N ligands can display quite different coordination
modes compared with P,P and N,N ligands.6,7 The p-accep-
tor character of the phosphorus ligand can stabilize a metal
center in a low oxidation state, while the nitrogen s-donor
ability makes the metal more susceptible to oxidative addi-
tion reactions. Recently, the attention has been focused on
P,N ligands that they have been used very successfully in
asymmetric catalytic reactions such as allylic substitution,8
hydrosilylation,9 hydroboration±oxdation,10 hydroboration±
Alternatively, pyridylphenol 8a was transformed into the
corresponding pyridylphenyl tri¯ate 8b by using tri¯uoro-
methanesulfonic anhydride (tri¯ic anhydride) in the
presence of excess 4-(N,N-dimethyl)aminopyridine14
(DMAP) or pyridine15,16 in dry dichloromethane in 95%
yield (Scheme 1). Similarly, biaryl pyridylphenols17,3a 8a±
12a were also transformed into the corresponding O,N
tri¯ates 8b±12b respectively in good yield (Scheme 1).
In the nickel catalyzed phosphination of aryl tri¯ates,
Hiemstra and co-workers reported the failed transformation
Keywords: bis(triphenylphosphine) nickel(II) dichloride; P,N ligand; phos-
phination.
* Corresponding author. Tel.: 1852-2609-6376; fax: 1852-2603-5057;
e-mail: ksc@cuhk.edu.hk
Figure 1. Atropisomeric ligands.
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00816-4

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F. Y. Kwong et al. / Tetrahedron 56 (2000) 8893±8899
Scheme 2. Literature methods in phosphination.20,21
ligand was probably due to the coordinating pyridyl group
of the substrate apart from possible steric hindrance. The
inactivity of the nickel catalyst may be due to the hard
pyridyl group, which chelates the hard nickel center and
renders the complex coordinatively saturated.24 A similar
chelating inhibition effect was also observed in the Rh
catalyzed hydrogenation with pyridylphosphines.25
When the catalyst was changed from the bidentate
Ni(dppe)Cl2 into monodentate Ni(PPh3)2Cl2, the corre-
sponding BINAP was obtained even in the presence of
added pyridine in the phosphination of BINOL ditri¯ate 3
(Table 1, entries 3 and 4). Presumably, the monodentate
triphenylphosphine dissociated more easily in the course
of the reaction and provided a vacant coordination site for
the nickel center. The monodenate Ni(PPh3)2Cl2 was then
applied to the O,N tri¯ate 8b for the successful synthesis of
P,N ligand 8c (Table 2, entry 1 and 2).
Scheme 1. Tri¯uoromethanesulfonation of quinolyl and pyridylphenols.
(conditions: 1.1 equiv. Tf2O, 3 equiv. pyridine, dry CH2Cl2, room tempera-
ture)
of BIFOL ditri¯ates 13 into BIFAP 14 even with prolonged
reaction time at elevated temperature and the use of
stoichiometric amount of Ni(dppe)Cl2 catalyst (Fig. 2).18
However, the sterically less hindered benzofuranyl tri¯ate
15 was reactive enough and gave the monophosphine
product 16 in moderate yield (Fig. 2).18 Therefore, the steric
hindrance in nickel catalyzed phosphination imposes the
limitation on the size of ortho-substitutent in aryl tri¯ate
substates.19
In order to optimize the reaction conditions, other polar
aprotic solvents were screened. N,N-Dimethylpyrolidinone
(NMP) was found to be suitable for this reaction but the
ratio of phosphine to reduction product was lower than in
DMF solvent (Table 2, entries 2 and 3). However, the less
polar solvent THF proved to be inferior (Table 2, entry 4).
When the reaction temperature was lowered, a higher ratio
of phosphine to reduction product was obtained but longer
reaction time was required and an extremely low yield of 8c
was obtained (Table 2, entry 5). Moreover, the monodentate
Ni(PPh3)2Br2 complex was also found to be effective for the
phosphination (Table 2, entry 6).
Apart from the steric hindrance, we found that the chelating
substrate inhibited the nickel assisted phosphination.
Attempted phosphination of pyridylphenyl tri¯ate 8b by
using nickel catalyzed phosphination with diphenyl-
phosphine20 or chlorodiphenylphosphine21 did not yield
any of the desired P,Nproduct 8c (Scheme 2).22,23
The problem of failed phosphination of this substrate may
be due to the steric or chelation inhibition. In order to inves-
tigate the possibility of chelation inhibition, a control
experiment with coordinating additive was designed for
the phosphination of BINOL ditri¯ates 3 to BINAP 4. The
addition of two equivalents of pyridine to the nickel cata-
lyzed phosphination of BINOL ditri¯ates 3 showed that
only a trace amount of BINAP was detected even with
extended reaction time with most of the starting material
recovered (Table 1, entries 1 and 2). In the absence of
pyridine, same as with literature report, BINAP was
obtained in moderate yield.21 The failed conversion of
BINOL ditri¯ates 3 to BINAP 4 in the presence of added
pyridine suggested that the unsuccessful synthesis of P,N
The optimized Ni(PPh3)2Cl2 assisted phosphination was
found to be applicable for the synthesis of other atropiso-
meric P,N ligands 8c±11c and QUINAP3a 12c from their
corresponding O,N tri¯ates (Table 3). The relatively
Table 1. Pyridine inhibitory effect in nickel assisted phosphination
Entry
Catalysts
Solvent
DMF
DMF, 2eq. Py
DMF
DMF, 2eq. py
Time/d
Yielda (%)
1
2
3
4
Ni(dppe)Cl2
Ni(dppe)Cl2
Ni(PPh3)2Cl2
Ni(PPh3)2Cl2
1.5
3
1.5
2
35
Traceb
30
29
a Isolated yield.
b Starting material was recovered.
Figure 2. Steric effect in phosphination of BIFOL ditri¯ate.

F. Y. Kwong et al. / Tetrahedron 56 (2000) 8893±8899
Table 2. Nickel assisted phosphination of O,N tri¯ates with chlorodiphenylphosphine
8895
Entry
Catalyst
Solvent
Temp (8C)
Time/d
H:PPh2 ratioa
Yield (%)b
1
2
3
4
5
6
Ni(dppe)Cl2
Ni(PPh3)2Cl2
Ni(PPh3)2Cl2
Ni(PPh3)2Cl2
Ni(PPh3)2Cl2
Ni(PPh3)2Br2
DMF
DMF
NMP
THF
DMF
DMF
110
110
110
110
50
5
1.5
4
5
11
1.5
/
0
41
15
0
2
20
2:3
3:2
/
1:7
2:3
110
a Estimated by 1H NMR integration.
b Isolated yield of phosphine product.
stronger pyridine coordinating substrates required longer
reaction time (Table 3, entry 1±3). The less coordinating
isoquinolyl substrates reacted a little faster (Table 3, entry 4
and 5). Presumably the stronger coordinating group showed
a stronger chelating retardation effect in the nickel assisted
phosphination.
The synthesized atropisomeric P,N ligand pyphos was
Table 3. Syntheses of atropisomeric P,N ligands
a
1
Estimated by H NMR integration.
b Isolated yield of phosphine products.

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F. Y. Kwong et al. / Tetrahedron 56 (2000) 8893±8899
chromatography was performed on silica gel 60 F254 plates.
Silica gel (70±230 and 230±400 mesh) was used for column
chromatography.
1H NMR spectra were recorded at 300 MHz and the chemi-
cal shifts were referenced internally to the residual proton
resonance in CDCl3 (d 7.26 ppm), or with tetramethylsilane
(TMS) (d 0.00 ppm) as the internal standard. 13C NMR
spectra were obtained at 75 MHz and referenced to the resi-
dual CHCl3 (d 77.0 ppm) in CDCl3. 31P NMR spectra were
obtained at 162 MHz and chemical shifts were referenced to
85% H3PO4 (d 0.00 ppm) externally. Mass spectra were
recorded either in electron ionization (EI) or fast atom
bombardment (FAB) mode using m-nitrobenzyl alcohol
(NBA) as the matrix. X-Ray data has been deposited in
Cambridge Crystallographic Center.
Scheme 3. Metallation of pyphos.
General procedure for tri¯uoromethanesulfonation of
pyridylphenols
3,5-Di-tert-butyl-2-(30-methyl-20-pyridyl)phenyl tri¯uoro-
methanesulfonate (8b). 3,5-Di-tert-butyl-2-(30-methyl-20-
pyridyl)phenol17 (8a) (297 mg, 1.0 mmol) was dissolved
in dry dichloromethane (5 mL) under nitrogen at room
temperature in a three-necked round bottom ¯ask. Pyridine
(0.26 mL, 3.0 mmol) was added under nitrogen. Tri¯uoro-
methanesulfonic anhydride (tri¯ic anhydride) (0.18 mL,
1.1 mmol) in dry dichloromethane (3 mL) was then added
dropwise to the reaction mixture. White fumes evolved and
the color of the solution changed from yellow to orange. The
reaction mixture was stirred at room temperature for 2 h.
Water (5 mL) was added and the aqueous phase was
extracted by dichloromethane (20 mL£3). The combined
organic extract was washed with water, brine, and dried
over MgSO4. The solvent was removed by rotary-evapora-
tion to give the brown residue which was puri®ed by column
chromatography on silica gel using a solvent mixture
(hexane/ethyl acetate ˆ5:1) as the eluent to afford 3,5-di-
tert-butyl-2-(30-methyl-20-pyridyl)phenyl tri¯uoromethane-
sulfonate (8b) (408 mg, 95%) as a white solid. Rfˆ0.6
(hexane/ethyl acetateˆ4:1); mp 96±988C; 1H NMR
(300 MHz, CDCl3) d 1.16 (s, 9H), 1.36 (s, 9H), 2.12 (s,
3H), 7.20 (s, 1H), 7.23 (dd, 1H, Jˆ7.8 Hz, 4.8 Hz), 7.57
(d, 1H, Jˆ8.0 Hz), 7.63 (d, 1H, Jˆ0.8 Hz), 8.53 (d, 1H,
Jˆ4.0 Hz); 13C NMR (75 MHz, CDCl3) d 19.1, 29.7,
31.1, 35.1, 37.5, 115.4, 118.2 (q, JCFˆ317.6 Hz), 124.4,
132.7, 133.1, 138.3, 146.4, 148.2, 150.5, 152.1, 152.5; MS
(EI): m/z (relative intensity) 430 (M111, 74), 414 (52), 296
(19), 281 (100), 266 (22); HRMS (ESIMS) calcd for
C21H26F3NO3SH1 430.1658, found 430.1647.
Figure 3. X-Ray crystal structure of Pd±pyphos complex.
metallated with bis-acetonitrilepalladium(II) dichloride in
acetonitrile at room temperature to form the Pd±pyphos
complex 8d in 80% yield (Scheme 3). The crystal structure
of Pd±pyphos showed that both the phosphine group and
pyridine group coordinate to the palladium center (Fig. 3).
Therefore pyphos behaves as a bidentate ligand. The biaryl
P,N ligand possesses a dihedral angle of 738 between the
phenyl and pyridyl rings.
Conclusion
In conclusion, the chelation inhibition of nickel assisted
phosphination with Ph2PCl was observed. Modi®ed con-
ditions using Ni(PPh3)2Cl2/Zn/Ph2PCl were found for the
successful preparation of P,N ligands from pyridylphenols
via pyridylphenyl tri¯ates.
General procedure for nickel assisted phosphination of
O,N tri¯ates
Experimental
Unless otherwise noted, all materials were obtained from
commercial suppliers and used without further puri®cation.
THF was distilled from sodium benzophenone ketyl imme-
diately prior to use. DMF and NMP were distilled from
magnesium sulfate under nitrogen.26 Zinc was activated
by washing with dilute hydrochloric acid followed by
water, ethanol and dry ether.26 Ni(PPh3)2Cl2 and
Ni(PPh3)2Br2 were prepared from NiCl2 and NiBr2 hydrate
respectively according to the literature method.27 Thin layer
2-(20-Diphenylphosphino-40,60-di-tert-butyl-10-phenyl)-
3-methylpyridine (pyphos) (8c). To a solution of 3,5-di-
tert-butyl-2-(30-methyl-20-pyridyl)phenyl tri¯uoromethane-
sulfonate (8b) (107 mg, 0.25 mmol) and bis(triphenyl-
phosphine) nickel(II) chloride (82 mg, 0.13 mmol) in dry
DMF (1 mL) under nitrogen in a Te¯on stopcock ¯ask.
Chlorodiphenylphosphine (45 mL, 0.25 mmol) was added
counter¯ow with nitrogen and Zn (11 mg£3, 0.5 mmol)
was then added in three portions. The color of the solution

F. Y. Kwong et al. / Tetrahedron 56 (2000) 8893±8899
8897
was gradually changed from blue to dark red. The solution
was heated to 1108C under nitrogen for 1.5 days. The
reaction mixture was then cooled down and the solvent
was removed by vacuum evaporation. The residue was
redissolved in dichloromethane and puri®ed by short
column chromatography on silica gel using a solvent
mixture of (hexane/ethyl acetateˆ6:1, Rfˆ0.6) as eluent to
obtain the crude product. This crude product was then
puri®ed by column chromatography on silica gel with eluent
(toluene/ethyl acetateˆ20:1) to afford the 2-(20-diphenyl-
phosphino-40,60-di-tert-butyl-10-phenyl)-3-methylpyridine
(pyphos) (8b) (47 mg, 41%) as a light yellow solid. Rfˆ0.6
butyl-2-(30,50-dimethyl-20-pyridyl)phenol (9a) (311 mg,
1.0 mmol), tri¯uoromethanesulfonic anhydride (0.18 mL,
1.1 mmol), pyridine (0.26 mL, 3.0 mmol), dichloromethane
(8 mL) were used to obtain 3,5-di-tert-butyl-2-(30,50-
dimethyl-20-pyridyl)phenyl tri¯uoromethanesulfonate (9b)
(407 mg, 92%) as a white solid. Rfˆ0.6 (hexane/ethyl
acetateˆ5:1); mp 106±1088C; 1H NMR (300 MHz,
CDCl3) d 1.15 (s, 9H), 1.35 (s, 9H), 2.07 (s, 3H), 2.37 (s,
3H), 7.18 (d, 1H, Jˆ1.5 Hz), 7.37 (d, 1H, Jˆ0.6 Hz), 7.60
(d, 1H, Jˆ1.8 Hz), 8.35 (d, 1H, Jˆ1.2 Hz); 13C NMR
(75 MHz, CDCl3) d 18.1, 19.1, 31.1, 31.8, 35.1, 37.5,
115.4, 118.2 (q, JCFˆ317.9) Hz, 124.3, 129.6, 132.6,
133.0, 138.0, 146.6, 148.2, 150.5, 152.3, 152.4; MS (EI):
m/z (relative intensity) 444 (M111, 43), 428 (9), 310 (15),
295 (100); HRMS (ESIMS) calcd for C22H28F3NO3SH1
444.1815, found 444.1804.
1
(toluene/ethyl acetateˆ15:1); mp 135±1378C; H NMR
(300 MHz, CDCl3) d 1.13 (s, 9H), 1.17 (s, 9H), 1.94 (s,
3H), 7.04±7.30 (m, 13H), 7.60 (d, 1H, Jˆ2.0 Hz), 8.34 (d,
1H, Jˆ4.3 Hz); 13C NMR (75 MHz, CDCl3) d 19.9, 31.1,
32.4, 34.8, 37.2, 125.8, 127.9, 128 (d, JCPˆ8.0 Hz), 128.2
(d, JCPˆ4.6 Hz), 130.1, 131.2 (d, JCPˆ7.6 Hz), 131.1 (d,
JCPˆ7.5 Hz), 133.4 (d, JC Pˆ19.3 Hz), 134.0 (d,
JCPˆ20.0 Hz), 137.1 (d, JCPˆ8.7), 138.0 (d, JCPˆ9.3 Hz),
138.2, 145.1, 147.1 (d, JCPˆ5.6 Hz), 149.7; 31P NMR
(162 MHz, CDCl3) d 211.60; MS (EI): m/z (relative
intensity) 465 (M1, 80), 450 (88), 408 (100), 388 (82),
374 (22), 358 (35), 342 (23); HRMS (ESIMS) calcd for
C32H36NPH1 466.2658, found 466.2622.
2-(20-Diphenylphosphino-40,60-di-tert-butyl-10-phenyl)-
3,5-dimethylpyridine (9c). The general procedure of nickel
catalyzed phosphination for 8c was used. 3,5-Di-tert-butyl-
2-(30,50-dimethyl-20-pyridyl)phenyl tri¯uoromethanesulfo-
nate (9b) (111 mg, 0.25 mmol), bis(triphenylphosphine)
nickel(II) chloride (82 mg, 0.13 mmol), chlorodiphenyl-
phosphine (45 mL, 0.25 mmol), Zn (11 mg£3, 0.5 mmol),
DMF (1 mL) were used to obtain 2-(20-diphenyl-
phosphino-40,60-di-tert-butyl-10-phenyl)-3,5-dimethylpyri-
dine (9c) (48 mg, 40%) as a light yellow solid. Rfˆ0.6
[2-(20-Diphenylphosphino-40,60-di-tert-butyl-10-phenyl)-
1
3-methylpyridine]palladium(II)
dichloride
(8d).
(toluene/ethyl acetateˆ15:1); mp 111±1148C; H NMR
Pd(CH3CN)2Cl2 (5.6 mg, 0.022 mmol) was dissolved in
degassed acetonitrile (1 mL) at room temperature under
(300 MHz, CDCl3) d 1.13 (s, 9H), 1.17 (s, 9H), 1.89 (s,
3H), 2.35 (s, 3H), 7.05±7.29 (m, 12H), 7.59 (d, 1H,
Jˆ2.0 Hz), 8.18 (s, 1H); 13C NMR (75 MHz, CDCl3) d
18.2, 19.9, 31.1, 32.4, 34.8, 37.2, 125.8, 127.9, 128.0 (d,
JCPˆ8.0 Hz), 128.2 (d, JCPˆ4.6 Hz), 130.1, 131.2 (d, JCPˆ
7.6 Hz), 132.1 (d, JCPˆ7.5 Hz), 133.4 (d, JCPˆ19.3 Hz),
134.0 (d, JCPˆ20.0 Hz), 137.1 (d, JCPˆ8.7 Hz), 138.0 (d,
JCPˆ9.3 Hz), 138.1, 145.1, 147.1 (d, JCPˆ5.6 Hz), 149.6;
31P NMR (162 MHz, CDCl3) d 211.78; MS (EI): m/z (rela-
tive intensity) 479 (M1, 5), 464 (5), 444 (17), 428 (54), 310
(13), 295 (76), 280 (100); HRMS (ESIMS) calcd for
C33H38NPH1 480.2814, found 480.2807.
nitrogen.
2-(20-diphenylphosphino-40,60-di-tert-butyl-10-
phenyl)-3-methylpyridine (pyphos) (8c) (10 mg, 0.022
mmol) was then added and the color of the solution was
changed from pale yellow to yellow. The reaction mixture
was stirred for 5 min at room temperature and the solvent
was removed under reduced pressure. The yellow solid was
recrystallized in dichloromethane/ether to obtain [2-(20-
diphenylphosphino-40,60-di-tert-butyl-10-phenyl)-3-methyl-
pyridine]palladium(II) dichloride (8d) (11 mg, 80%) as
orange crystals. mp 3208C (decomposed); 1H NMR
(300 MHz, CDCl3) d 9.29 (d, 1H, Jˆ3.7 Hz), 7.75 (s,
1H), 7.52±7.55 (m, 2H), 7.27±7.44 (m, 7H), 7.04±7.11
(m, 3H), 6.94±6.99 (m, 2H), 2.20 (s, 3H), 1.24 (s, 9H),
1.09 (s, 9H); 31P NMR (162 MHz, CDCl3) d 34.15; MS
(FAB): m/z (relative intensity) 642 (M111, 25); HRMS
(ESIMS) calcd for C32H36NPCl2PdH1 642.1073, found
642.1063. X-Ray crystal was grown under the solvent
mixture of dichloromethane/diethyl ether and the X-ray
data has been deposited in Cambridge Crystallographic
Center (CCDC 147228). Formula: C33H38Cl4NPPd, molecu-
3,4,5-Trimethyl-2-(30-methyl-20-pyridyl)phenyl tri¯uoro-
methanesulfonate (10b). The general procedure of tri¯uoro-
methanesulfonation for 8b was used. 3,4,5-Trimethyl-2-(30-
dimethyl-20-pyridyl)phenol17 (10a) (250 mg, 1.10 mmol),
tri¯uoromethanesulfonic anhydride (0.20 mL, 1.21 mmol),
pyridine (0.27 mL, 3.3 mmol), dichloromethane (6 mL)
were used to obtain 3,4,5-trimethyl-2-(30-methyl-20-
pyridyl)phenyl tri¯uoromethanesulfonate (10b) (355 mg,
90%) as a white solid. Rfˆ0.5 (hexane/ethyl acetateˆ4:1);
1
Ê
lar weight, 727.81, lˆ.71073 A 294(2) K, Crystal: Tri-
mp 64±668C; H NMR (300 MHz, CDCl3) d 1.99 (s, 3H),
Ê
Ê
clinic, P1; aˆ10.326 (1) A, bˆ10.354 (1) A, cˆ16.468
2.10 (s, 3H), 2.23 (s, 3H), 2.37 (s, 3H), 7.05 (s, 1H), 7.26
(dd, 1H, Jˆ8.2, 3.9 Hz), 7.63 (d, 1H, Jˆ7.7 Hz), 8.56
(d, 1H, Jˆ4.4 Hz); 13C NMR (75 MHz, CDCl3) d 17.1,
18.4, 20.9, 29.7, 116.0, 118.2 (q, JCFˆ 317.8 Hz), 124.5,
130.8, 133.1, 136.1, 137.1, 137.9, 138.3, 144.6, 147.0,
153.9; MS (EI): m/z (relative intensity) 359 (M1, 42), 344
(66), 226 (79), 211 (100), 196 (16), 182 (19); HRMS
(ESIMS) calcd for C16H16F3NO3SH1 360.876, found
360.878.
Ê
(2) A; aˆ95.753 (7)8, bˆ91.135 (6)8, gˆ106.230 (7)8,
Ê 3
3
Vˆ1679.9 (4) A , Zˆ2, density(calculated)ˆ1.439 Mg/m ,
Crystal Sizeˆ0.30£0.25£0.20 mm, re¯ections collectedˆ
5396, independent re¯ectionsˆ5396 (Rintˆ0.0000), data/
restraints/parametersˆ5396/0/362, R Indices (all data):
R1ˆ0.0483, vR2ˆ0.1382 [I.2s(I)]; R1ˆ0.0518, vR2ˆ
0.1439 (all data); GOFˆ1.063.
3,5-Di-tert-butyl-2-(30,50-dimethyl-20-pyridyl)phenyl tri-
¯uoromethanesulfonate (9b). The general procedure of
tri¯uoromethanesulfonation for 8b was used. 3,5-Di-tert-
2-(20-Diphenylphosphino-40,50,60-trimethyl-10-phenyl)-
3-methylpyridine (10c). The general procedure of nickel

8898
F. Y. Kwong et al. / Tetrahedron 56 (2000) 8893±8899
catalyzed phosphination for 8c was used. 3,4,5-Trimethyl-
2-(30-methyl-20-pyridyl)phenyl tri¯uoromethanesulfonate
(10b) (90 mg, 0.25 mmol), bis(triphenylphosphine) nickel
(II) chloride (82 mg, 0.13 mmol), chlorodiphenylphosphine
(45 mL, 0.25 mmol), Zn (11 mg£3, 0.5 mmol), DMF
(1 mL) were used to obtain 2-(20-diphenylphosphino-
40,50,60-trimethyl-10-phenyl)-3-methylpyridine (10c) (38 mg,
38%) as a white solid. Rfˆ0.4 (toluene/ethyl acetateˆ15:1);
mp 100±1028C; 1H NMR (300 MHz, CDCl3) d 1.90 (s, 3H),
1.97 (s, 3H), 2.20 (s, 3H), 2.21 (s, 3H), 6.79 (d, 1H,
Jˆ4.0 Hz), 7.12±7.28 (m, 11H), 7.51 (d, 1H, Jˆ7.6 Hz),
8.32 (d, 1H, Jˆ4.1 Hz); 13C NMR (75 MHz, CDCl3) d
15.9, 16.9, 19.0, 20.9, 122.2, 128.0 (d, JCPˆ7.1 Hz), 128.2
(d, JCPˆ7.2 Hz), 132.2 (d, JCPˆ9.3 Hz), 132.7 (d, JCPˆ
13.4 Hz), 132.8, 133.4 (d, JCPˆ19.1 Hz), 133.8 (d,
JCPˆ20.0 Hz), 136.2, 136.9, 137.2 (d, JCPˆ10.8 Hz),
137.4, 137.7 (d, JCPˆ11.6 Hz), 146.1, 159.6 (d, JCPˆ
5.6 Hz); 31P NMR (162 MHz, CDCl3) d 211.53; MS (EI):
m/z (relative intensity) 395 (M1, 100), 379 (25), 334 (9),
318 (66); HRMS (ESIMS) calcd for C27H26NPH1 396.1876,
found 396.1886.
(23), 392 (21), 375 (10); HRMS (ESIMS) calcd for
C35H37NPH1 502.2658, found 502.2646.
1-(20-Isoquinolyl)naphthyl
tri¯uoromethanesulfonate
(12b). The general procedure of tri¯uoromethanesulfo-
nation for 8b was used. 1-(20-Hydroxy-10-naphthyl)iso-
quinoline3a (12a) (250 mg, 0.92 mmol), tri¯uoro-
methanesulfonic anhydride (0.17 mL, 1.01 mmol), pyridine
(0.22 mL, 2.77 mmol), dichloromethane (6 mL) were used
to obtain 1-(20-isoquinolyl)naphthyl tri¯uoromethanesulfo-
nate (12b) (334 mg, 90%) as a light yellow solid. Rfˆ0.6
(hexane/ethyl acetateˆ4:1); 1H NMR (300 MHz, CDCl3) d
7.29 (d, 1H, Jˆ8.5 Hz), 7.40 (t, 1H, Jˆ7.7 Hz), 7.49±7.43
(m, 2H), 7.57 (t, 1H, Jˆ7.6 Hz), 7.62 (d, 1H, Jˆ9.1 Hz),
7.72 (m, 1H), 7.85 (d, 1H, Jˆ5.7 Hz), 7.97 (d, 1H,
Jˆ8.3 Hz), 8.00 (d, 1H, Jˆ8.3 Hz), 8.11 (d, 1H,
Jˆ9.1 Hz), 8.79 (d, 1H, Jˆ5.7 Hz); MS (EI): m/z (relative
intensity) 403 (M1, 80), 254 (100), 128 (12), 126 (21).
Acknowledgements
3,5-Di-tert-butyl-2-(20-isoquinolyl)phenyl
tri¯uoro-
We thank Professor T. C. W. Mak for X-ray crystallo-
graphic analysis and the Research Grants Council of Hong
Kong for ®nancial support (MF/rgcgrant/rgccav/564/98-
ERB003).
methanesulfonate (11b). The general procedure of
tri¯uoromethanesulfonation for 8b was used. 3,5-Di-tert-
butyl-2-(20-isoquinolyl)phenol17 (11a) (50 mg, 0.15
mmol), tri¯uoromethanesulfonic anhydride (28 mL, 0.17
mmol), pyridine (36 mL, 0.45 mmol), dichloromethane
(2 mL) were used to obtain 3,5-di-tert-butyl-2-(20-isoquino-
lyl)phenyl tri¯uoromethanesulfonate (11b) (62 mg, 89%) as
a white solid. Rfˆ0.5 (hexane/ethyl acetateˆ5:1); mp 78±
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