Direct Palladium-Catalyzed Phosphinylation of Aryl Triflates with Secondary Phosphines. Its Scope and Limitations: The Synthesis of Optically Active Carboxylated 2-(Diphenylphosphino)-1,1'-binaphthalenes

Full text of DOI:10.1021/jo971428s

J . Org. Chem. 1998, 63, 3463-3467
3463
Dir ect P a lla d iu m -Ca ta lyzed
P h osp h in yla tion of Ar yl Tr ifla tes w ith
Secon d a r y P h osp h in es. Its Scop e a n d
Lim ita tion s: Th e Syn th esis of Op tica lly
Active Ca r boxyla ted
2-(Dip h en ylp h osp h in o)-1,1′-bin a p h th a len es
F igu r e 1.
Gabriel Martorell, Xavier Garc´ıas, Marcus J anura, and
J ose´ M. Saa´*
and secondary phosphines also added to this decision, as
well as the fact that closely related palladium-catalyzed
aminations of aromatic halides have been recently
achieved using aminostannanes, aminoboranes, or, even
simpler, NH compounds in the presence of a strong base.8
A survey of the literature on transition metal-catalyzed
formation of carbon-phosphorus bonds revealed that
palladium-catalyzed coupling of aryl halides with stan-
nyl- and silylphosphines had already been recognized as
a useful entry to tertiary phosphines back in 1987,9 but
the method has remained largely unexplored since then.
Imamoto’s phosphine-borane complexes, on the other
hand, have been shown to undergo coupling with aryl
iodides, but failure has been reported with other aryl
halides,10 as well as with aryl triflates.11 Special mention,
in this regard, merits the recently published BINAP
synthesis through nickel(0)-catalyzed C-P(III) formation
carried out on the corresponding triflate, where the
palladium(0)-catalyzed reaction had previously failed.12
Formation of C-P(V) bonds mediated by palladium-
catalyzed reactions appears to be less problematic as
judged by the abundant number of inter- or intramolecu-
lar couplings of P(V)-H nucleophiles such as phosphinic
esters,13 secondary phosphine oxides,14 or phosphonate
esters15 with halides or even triflates16 in the presence
of weak bases. Nevertheless, as demonstrated by Mor-
gans et al., this reaction could not be applied to the
Departament de Quı´mica, Universitat de les Illes Balears,
07071 Palma de Mallorca, Spain
Received August 1, 1997
In tr od u ction
A major objective of modern organic synthesis is
improving the efficiency of chemical reactions (“atom
economy” as put for by B. M. Trost1) and phase-separa-
tion as well.2 The advantages of using water-soluble3
and/or “fluorous-phase”-soluble reagents or catalysts to
this end have been highlighted in the recent literature.
We have recently embarked on a program to explore
catalytic, enantioselective organometallic chemistry in
nonconventional solvents for which we required a flexible,
rapid access to a variety of water-soluble (or otherwise)
chiral ligands for use as auxiliaries in the synthesis of
enantiomerically pure compounds. Herein we report on
a simple and reliable methodology for the preparation of
carboxylated phosphines and phosphine oxides which
bears a close relationship with the recently discovered
palladium-catalyzed amination of aromatic halides.4 We
also report on its scope and limitations when applied to
the synthesis of chiral, optically active monophosphine
1 (Figure 1), a carboxylated analogue of Hayashi’s
MOPs.5 Chiral 2-(diphenylphosphino)-2′-alkoxy-1,1′-bi-
naphthyls (MOPs) have been employed as chiral mono-
dentate ligands in catalytic, enantioselective hydrosyli-
lation6 and reduction of allylic esters.7
(8) Paul, F.; Patt, J .; Hartwig, J . F. J . Am. Chem. Soc. 1994, 116,
5969. Guram, A. S.; Buchwald, S. L. J . Am. Chem. Soc. 1994, 116,
7901. Paul, F.; Patt, J .; Hartwig, J . F. Organometallics 1995, 14, 3030.
Hartwig, J . F.; Paul, F. J . Am. Chem. Soc. 1995, 117, 5373. Driver, M.
S.; Hartwig, J . F. J . Am. Chem. Soc. 1995, 117, 4708. Louie, J .;
Hartwig, J . F. Tetrahedron Lett. 1995, 36, 3609. Guram, A. S.; Rennels,
R. A.; Buschwald, S. L. Angew. Chem., Int. Ed. Engl. 1995, 34, 1348.
Wolfe, J . P.; Buchwald, S. L. J . Org. Chem. 1997, 62, 1264. Louie, J .;
Driver, M. S.; Hamann, B. C.; Hartwig, J . F. J . Org. Chem. 1997, 62,
1268. For a recent mechanistic study, see: Driver, S.; Hartwig, J . F.
J . Am. Chem. Soc. 1997, 119, 8232.
(9) Tunney, S. E.; Stille, J . K. J . Org. Chem. 1987, 52, 748.
(10) Imamoto, T.; Oshiki, T.; Onozawa, T.; Kusumoto, T.; Sato, K.
J . Am. Chem. Soc. 1990, 112, 5244. Oshiki, T.; Imamoto, T. J . Am.
Chem. Soc. 1992, 114, 3975. Imamoto, T. Pure Appl. Chem. 1993, 65,
655.
The condensation of an aromatic electrophile and a
primary or secondary phosphine is arguably the most
direct, general route toward carboxylated phosphines.
Given the well-known regiochemical limitations of aro-
matic nucleophillic substitutions we decided to explore
the palladium-catalyzed direct phosphination of aromatic
triflates as an attractive, presumably general, alternative
toward that end. The availability of the required triflates
(1) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 259.
(2) Studer, A.; Hadida, S.; Ferrito, R.; Sun-Young, K.; J eger, P.; Wipf,
P.; Curran, D. Science 1997, 275, 823.
(3) Herrmann, W. A.; Kohlpaintner, C. Angew. Chem., Int. Ed. Engl.
1993, 32, 1524.
(4) The first publications on the subject are due to the following:
Kosugi, M.; Kameyama, M.; Migita, T. Chem. Lett. 1983, 927. Kosugi,
M.; Kameyama, M.; Sano, H.; Migita, T. Nippon Kagaku Kaishi 1985,
3, 547. See ref 8 for more recent work.
(5) Uozumi, Y.; Tanahashi, A.; Lee, S.-Y.; Hayashi, T. J . Org. Chem.
1993, 58, 1945.
(6) Uozumi, Y.; Hayashi, T. J . Am. Chem. Soc. 1991, 113, 9887.
Uozumi, Y.; Lee, S.-Y.; Hayashi, T. Tetrahedron Lett. 1992, 33, 7185.
Hatanaka, Y.; Goda, K.; Yamashita, F.; Hiyama, T. Tetrahedron Lett.
1994, 35, 7981.
(11) Horiuchi, T.; Ohta, T.; Stephan, M.; Takaya, H. Tetrahedron:
Asymmetry 1994, 5, 325.
(12) Cai, D.; Payack, J . F.; Bender, D. R.; Hughes, D. L.; Verhoeven,
T. R.; Reider, P. J . J . Org. Chem. 1994, 59, 7180.
(13) Xu, Y.; Li, Z.; Xia, J .; Guo, H.; Huang, Y. Synthesis 1983, 377.
Xu, Y.; Li, Z. Synthesis 1986, 240. Xu, Y.; Zhang, J . Synthesis 1984,
778. Lei, H.; Stoakes, M. S.; Schwabacher, A. W. Synthesis 1992, 1255.
(14) Xu, Y; Xia, J .; Guo, H. Synthesis 1986, 691. Xu, Y.; Li, Z.; Xia,
J .; Guo, H.; Huang, Y. Synthesis 1984, 781.
(15) Hirao, T.; Masunaga, T.; Yamada, N.; Ohshiro, Y.; Agawa, T.
Bull. Chem. Soc. J pn. 1982, 55, 909. Hirao, T.; Masunaga, T.; Ohshiro,
Y.; Agawa, T. Tetrahedron Lett. 1980, 21, 3595. Hirao, T.; Masunaga,
T.; Ohshiro, Y.; Agawa, T. Synthesis 1981, 56. Casalnuovo, A. L.;
Calabrese, J . C. J . Am. Chem. Soc. 1990, 112, 4324.
(7) Hayashi, T.; Iwamura, H.; Naito, M.; Matsumoto, Y.; Uozumi,
Y.; Miki, M.; Yanagi, K. J . Am. Chem. Soc. 1994, 116, 775. Hayashi,
T.; Iwamura, H.; Uozumi, Y.; Matsumoto, Y.; Ozawa, F. Synthesis 1994,
526.
(16) Petrakis, K. S.; Nagabushan, T. L. J . Am. Chem. Soc. 1987,
109, 2831.
S0022-3263(97)01428-X CCC: $15.00 © 1998 American Chemical Society
Published on Web 04/30/1998

3464 J . Org. Chem., Vol. 63, No. 10, 1998
Notes
Ta ble 1
Sch em e 1
report of Amatore and J utand et al.,18 we found that the
presence of a chelating phosphine is also a stringent
requirement for the reaction to occur (triflate 7a re-
mained almost unaltered after heating with diphe-
nylphosphine, PdCl2(PPh3)2, and diisopropylethylamine,
for several hours at 100 °C, as shown by 19F NMR
monitoring). After some experimentation it was found
that acceptable-to-good yields of the final phosphine oxide
products were obtained when employing a catalytic
amount (5-10% mol, per each -OTf rest) of PdCl2(PPh3)2
as catalyst precursor (both Pd(OAc)2 and NiCl2(PPh3)2
gave somewhat lower yields in most cases), diisopropy-
lethylamine as base (other bases assayed were sodium
carbonate, DABCO or sodium tert-butoxide, yielding
much poorer results in the former two cases and complete
destruction in the latter case), and 1,3-bis(diphenylphos-
phino)propane (nonchelating phosphines or arsines such
as PPh3 or PAs3 did not work, whereas dppb, dppe, or
dppf19 gave substantially lower yields) in refluxing DMF
as solvent (THF and other low-boiling temperature
solvents gave recovered starting material) (Scheme 1).
Either secondary alkyl or aryl phosphines can be em-
ployed as reactants though yields with the former are
significantly lower (Table 1, entry 3).
synthesis of BINAPO as only one triflate moiety was
found to undergo coupling.17
Resu lts a n d Discu ssion
Although aside from our original objective, a number
of experiments have been carried out to shed some light
into the mechanism of the reaction20 and in particular,
in an attempt to establish the nature of the phosphorus
actual reagent (either a P-H or a P-(O)H species)
involved in the coupling step. Extensive 31P NMR
monitoring of the phosphinylation reaction under differ-
ent conditions (both the DMF-d6 and DMSO-d6 employed
as solvents contained some residual water and were not
degassed) has led us to the following observations: (1)
in the absence of palladium no significant Ph2PH to
Ph2P(O)H oxidation was observed even after heating Ph2-
PH or a mixture of 7a + Ph2PH + R3N for several hours;
(2) when oxygen (air) is introduced on purpose, Ph2PH
is consumed completely even in the absence (slow reac-
tion) of palladium; significantly, in the presence of a
palladium(0) species such as (Ph3P)4Pd, residual oxigen
in the medium promotes the instantaneous oxidation of
Ph2PH into Ph2P(O)H; (3) fast oxidation also occurs when
the mixture 7a + Ph2PH is heated in the presence of the
catalytic Pd(II) species being used [PdCl2(PPh)3 or Pd-
(OAc)2], either with (faster) or without (slower) added
amine; the red-orange (with added amine) or yellowish
solutions (without amine) so produced contain both Ph2-
PH (rapidly exchanging, broad signal) and Ph2P(O)H
(sharp); these later observations agree well with the
occurrence of the well-established redox processes Pd(II)
In light of the successful amination of aryl halides
promoted by palladium(0),4,8 the analogous coupling of
secondary phosphines with simple aryl triflates in the
presence of base appeared to us as the solution of choice
for a rapid access to nonsymmetric tertiary phosphines.
We were conscious though that complications may appear
as a result of competition of the different phosphines for
the palladium species present in the catalytic cycle.
Accordingly, for our planned access to carboxylated
monophosphine 1 we choose to optimize first the reaction
with the carboxyl-substituted aryl triflates 2, 3, 4, 5, and
6 in the presence of an appropriate base (Table 1). For
the sake of completeness this methodology was also
extended to some extra examples of simple aryl triflates
(7 and 8) whose results are also included in Table 1.
Initial assays immediately showed that only phosphine
oxides were obtained instead of the desired tertiary
phosphines. Nevertheless, as only one single example
of this R2PH to R2ArPO transformation had been re-
ported in the literature,17 we have further pursued the
optimization (carried out with triflates 6 and 7) of such
reaction variables as the source of catalyst, the bidentate
phosphine ligand added, and base, solvent, and temper-
ature. It is worth remarking at this point that the
reaction did not occur if carried out in the absence of the
palladium catalyst (triflate 7a remained unaltered after
heating with diphenylphosphine and triethylamine or
diisopropylethylamine, for 15 h at 100 °C, as shown by
19F NMR monitoring). In agreement with the recent
(18) Amatore, C.; Broeker, G.; J utand, A.; Khalil F. J . Am. Chem.
Soc. 1997, 119, 5176.
(19) Acronyms dppb, dppe, dppf, and dppp stand for 1,4-bis-
(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)ethane, 1, 1′-
bis(diphenylphosphino)ferrocene, and 1,3-bis(diphenylphosphino)-
propane, respectively.
(17) Kurtz, L.; Lee, G.; Morgans, D., J r.; Waldyke, M. J .; Ward, T.
Tetrahedron Lett. 1990, 31, 6321. See also: Doucet, H.; Brown, J . M.
Tetrahedron: Asymmetry 1997, 8, 3775.
(20) Detailed mechanistic studies are in progress.

Notes
J . Org. Chem., Vol. 63, No. 10, 1998 3465
f Pd(0)//Ph2PH f Ph2PPPh2,9 followed by palladium(0)-
catalyzed oxidation (see below). In summary, this quali-
tative study revealed that in our reaction mixtures an
excess of rapidly equilibrating Ph2PH (31P, broad) coexists
with a limited amount of free Ph2P(O)H (31P, narrow) at
the outset of the reaction, i.e., prior to the addition of
triflates.
carboxylated phosphines by recourse to the usual trichlo-
rosilane/triethylamine reduction procedure.24 Phosphine
2 (R ) P(Ph)2) was obtained uneventfully by reduction
of 2b. However, direct reduction of phenol 1b (R1 ) H,
R ) P(O)PPh2) was unsuccessful, due to the ease of
oxidation of the corresponding phenolic phosphine. Re-
duction took place as expected on the easily available
benzyl derivative 1b (R1 ) Bz, R ) P(O)PPh2), the
corresponding phosphine 1 (R1 ) Bz) being thus obtained
without difficulty.
Sizable amounts of optically active (R) phosphine 1 (R1
) Bz) were obtained in this manner, starting with triflate
1a (R1 ) H), itself obtained from the corresponding
optically active phenol, available by resolution of racemic
3-(m et h oxyca r bon yl-2,2′-dih ydr oxy-1,1′-bin a ph t h a -
lene.25
In principle, the following crude working hypothesis
for the formation of the final Ph2P(O)Ar products can be
considered: (i) Ph2PH is completely oxidized to Ph2P(O)H
during the initial stages of the reaction by Pd(0)21-
catalyzed oxidation promoted by oxygen which enters the
reaction vessel; the key phosphinylation reagent will thus
be Ph2P(O)H; (j) the key coupling step involves Ph2PH/
R3N attack on the species resulting from oxidative
+
addition [ArPd(L)2 TfO-],22 followed by oxidation23 of
ArPd(L)2PPh2 to ArPd(L)2P(O)Ph2 and, eventually, by
reductive elimination; (k) coupling as in (j) leads to
phosphines Ph2PAr which are then oxidized to the final
Ph2P(O)Ar products. The failure to isolate tertiary
phosphines Ph2PAr from the reaction mixtures would
suggest that either (i) or (j), or a combination or both, is
the actual mechanistic scheme operating in our reactions.
Even though we are prone to consider (j) as a less
plausible alternative, it is clear that careful mechanistic
work is needed to clarify this point.20
In summary, the palladium-catalyzed coupling of sec-
ondary phosphines with aryl triflates is a convenient
method for making C-P bonds. Phosphine oxides are
obtained instead of the expected phosphines. Even
though a wide range of aryl triflates can be used as
substrates, the method failed for some naphthalene
derivatives, for which Morgans’ phosphinylation proce-
dure which uses pure, commercial Ph2P(O)H worked well.
We have also uncovered that Ph2PH can act as a strong
inhibitor of Morgans’ phosphinylation, though only for
naphthalene derivatives. In light of the much wider
availability of secondary phosphines and their being
much cheaper (10 times) than the corresponding phos-
phine oxides, we suggest the use of our method for
accessing aryl phosphine oxides. Carboxylated phos-
phines 1 and related analogues can now be assayed in
two-phase organometallic chemistry.
An unexpected limitation was found for the case of
naphthyl triflates. Thus, in striking contrast with our
results using common aryl triflates, the application of our
optimized palladium-catalyzed methodology (method A)
to the preparation of monophosphine oxide 1b from 1a
(R1 ) H) failed, monotriflate 1a (R1 ) H) being recovered
unchanged. On the other hand, application of Cai’s
nickel(0) protocol to 1a (R1 ) H) led to a very complex
mixture in which we could not find evidence of the
desired phosphine. Eventually, the desired 1a to 1b (R1
) H) conversion could be achieved by using a slightly
modified Morgans’ phospinylation procedure which em-
ploys pure, commercial Ph2P(O)H as reactant (method
B). The unexpected failure of 1a (2-methyl-1-naphthyl
and 2-naphthyl triflate behaved analogously as according
to NMR analysis) to undergo coupling with Ph2PH
(method A) was initially taken as a disclaim of mecha-
nism (i) above. However, things turned out to be also
complicated for Morgans’ phosphinylation reaction as we
discovered (31P and 19F NMR monitoring) that Ph2PH can
act as a strong inhibitor for this reaction as applied for
naphthyl triflates. In fact, we found that whereas
common aryl triflates such as 7a undergo phosphinyla-
tion reaction with either (a) pure Ph2P(O)H or (b) pure
Ph2PH and (c) a 1:1 mixture of Ph2PH and Ph2P(O)H,
the corresponding reaction carried out with 1a worked
well only with (a) pure Ph2P(O)H but failed to occur with
(b) Ph2PH or (c) a 1:1 mixture of Ph2PH and Ph2P(O)H;
identical results were found for 2-methyl-1-naphthyl or
2-naphthyl triflate as revealed by NMR. Again, a clear
explanation must await a full mechanistic study.
Exp er im en ta l Section
Gen er a l. Melting points were taken on a capillary melting
point apparatus and are uncorrected. NMR spectra (1H, 13C,
31P) were obtained on a Bruker AMX-300 spectrometer in CDCl3
or DMSO-d6. Low- and high-resolution electron impact mass
spectra were recorded at 70 eV ionizing energy. Elemental
analyses were obtained at the Servicio de Microanalisis de la
U. de Zaragoza. Column chromatographies were performed on
Merck silica gel (Kieselgel 40). Commercial anhydrous DMF,
NiCl2(PPh3)2, PdCl2(PPh3)2, Pd(OAc)2, HPPh2, and 1,4-
diazabicyclo[2.2.2]octane (DABCO) were used as received. Ra-
cemic 3-(methoxycarbonyl)-2,2′-dihydroxy-1,1′-binaphthalene was
obtained by copper-mediated heterocoupling involving 2-naph-
thol and 2-hydroxy-3-naphthoic acid as described by Hovorka
et al. and eventually resolved into its enantiomers.26 Phenol
triflates 1a -8a and naphthyl triflates were prepared as previ-
ously reported from the corresponding phenols.27 The purity of
all compounds for which no elemental analysis is provided was
judged to be higher than 95% by 13C and 1H NMR (see
Supporting Information). The NMR samples employed for the
mechanistic analysis were prepared using Schlenk tecniques
under argon, and eventually the tubes were sealed.
(24) Naumann, K.; Zon, G.; Mislow, K. J . Am. Chem. Soc. 1969, 91,
7012. Vineyard, B. D.; Knowles, W. S.; Sabacky, S. J .; Bachman, G.
L.; Weinkauff, D. J . J . Am. Chem. Soc. 1977, 99, 5946.
(25) Hovorka, M.; Scigel, P.; Gunterova, J .; Tichy, M.; Za´vada, J .
Tetrahedron 1992, 48, 9503.
For the sake of completeness we have proceeded to
convert a couple of phosphine oxides to the corresponding
(26) To be reported in due course. Partially enriched material has
been obtained by enantioselective oxidative coupling in the presence
of a chiral amine. See: Smrcina, M.; Pola´kova´, J .; Vyskocil, S.;
Kocovsky, P. J . Org. Chem. 1993, 58, 4534.
(27) (a) Saa´, J . M.; Martorell, G.; Garc´ıa-Raso, A. J . Org. Chem.
1992, 57, 678. (b) Martorell, G.; Garc´ıa-Raso, A.; Saa´, J . M. Tetrahedron
Lett. 1990, 31, 2357. (c) Saa´, J . M.; Dopico, M.; Martorell, G.; Garc´ıa-
Raso, A. J . Org. Chem. 1990, 55, 991. (d) Saa´, J . M.; Martorell, G. J .
Org. Chem. 1993, 58, 1963.
(21) Palladium and platinum(0) possess catalytic activity in the
oxidation of phosphines. See: Takahashi, S.; Sonogashira, K.; Hagi-
hara, N. J . Chem. Soc. J pn. 1966, 87, 610. Kashiwagi, T.; Yasuoka,
N.; Kasai, N.; Kakudo, M. J . Chem. Soc., Chem. Commun. 1969, 743.
(22) J utand, A.; Mosleh, A. Organometallics 1995, 14, 1810.
(23) For a related Re-PPh2 to Re-P(O)Ph2 oxidation, see: Buhro,
W. E.; Georgiou, S.; Hutchinson, J . P.; Gladysz, J . A. J . Am. Chem.
Soc. 1985, 107, 3346.

3466 J . Org. Chem., Vol. 63, No. 10, 1998
Notes
Gen er a l P r oced u r e for th e P a lla d iu m -Ca ta lyzed Cou -
p lin g of Secon d a r y P h osp h in es w it h Ar yl Tr ifla t es.
Meth od A. A three-necked round-bottom flask charged with a
mixture of 0.2 mmol of triflate, 0.3 mmol of diphenylphosphine
(or diethylphosphine), dppp (0.015 mmol), and PdCl2(PPh3)2 (0.01
mmol) and diisopropylethylamine (1 mmol) in 2.5 mL of DMF
was heated overnight to reflux, under argon. Water and ether
(25 mL) were added, and the organic phase was washed with
1.5 N HCl (6 × 20 mL), brine, and water and finally dried over
anhydrous sodium sulfate. Evaporation to dryness yielded crude
material which was purified by column chromatography (n-
hexanes-ethyl acetate). Final crystallization or bulb-to-bulb
distillation furnished pure products.
132.78, 132.64, 132.51, 132.39, 132.35, 129.08, 128.92 124.78,
123.32, 114.73, 114.56, 55.90 ppm. EIMS: m/e (%) 292 (M+, 21),
262 (100), 183 (85), 152 (11), 108 (30), 107 (18), 75 (4), 51 (7).
HRMS calcd for C19H17O2P: 308.09661. Found: 308.09517.
[2-(Met h oxym et h yl)-6-m et h oxyp h en yl]d ip h en ylp h os-
p h in e Oxid e (8b). Solid, mp 107-108 °C. IR (film) ν: 3060,
2970, 1590, 1570, 1465, 1440, 1270, 1185, 1120, 1070, 755, 725,
700, cm-1 1H NMR δ: 7.69-7.37 (m, 12H), 6.75 (dd, 1H, J ) 8
.
and 4.9 Hz), 5.13 (s, 2H), 3.38 (s, 3H), 3.20 (s, 3H) ppm. 31P
NMR δ: 29.74 ppm. 13C NMR δ: 160.99, 160.93, 148.49, 148.41,
136.41, 134.98, 134.19, 134.16, 132.69, 132.56, 132.48, 132.45,
131.85, 131.71, 131.60, 131.56, 129.11, 128.95, 128.59, 128.43,
121.66, 121.53, 118.37, 117.03, 111.24, 111.16, 72.71, 72.67,
58.99, 55.41 ppm. EIMS: m/e (%) 352 (0.4), 351 (2), 278 (22),
277 (52), 201 (12), 199 (12), 183 (11), 149 (82), 86 (64), 84 (100),
77 (15). Anal. Calcd for C21H21O3P: C, 71.59; H, 5.96. Found:
C, 71.68; H, 5.95.
(3-Meth oxyca r bon ylp h en yl)d ip h en ylp h osp h in e Oxid e
(2b). Colorless oil, bp 135-140 °C/0.02 mmHg. IR (film) ν:
3060, 2950, 1725, 1440, 1295, 1270, 1195, 1130, 1120, 750, 730,
700 cm-1 1H NMR δ: 8.32 (d, 1H, J ) 12.1 Hz), 8.18 (dd, 1H,
.
J ) 7.8 and 1.2 Hz), 7.87 (dd, 1H, J ) 7.8, and 11.7 Hz), 7.67-
7.43 (m, 11H), 3.85 (s, 3H) ppm. 31P NMR δ: 26.40 ppm. 13C
NMR δ: 166.68, 136.84, 136.71 134.69, 133.60, 133.48, 133.46,
133.33, 133.16, 132.78, 132.75, 132.64, 132.51, 131.77, 131.19,
131.03,129.38, 129.29, 129.22, 129.13, 52.90 ppm. EIMS: m/e
(%) 336 (M+, 50), 335 (100), 277 (30), 259 (10), 201 (20), 183 (23),
152 (33), 77 (28). HRMS calcd for C20H17O3P: 336.09153.
Found: 336.09049.
[3-Meth oxycar bon ylph en yl]dieth ylph osph in e Oxide (2c).
Obtained as a yellow oil, bp 210-215 °C (0.001 mmHg). IR (film)
ν: 2980, 1720, 1295, 1270, 1160, 1140, 750 cm-1
.
1H NMR δ:
8.26 (ddd, 1H, J ) 10.9, 1.4 and 1.1 Hz), 8.17 (ddd, 1H, J ) 7.8,
1.5 and 1.1 Hz), 7.96 (tm, 1H, J ) 7.6 Hz), 7.58 (tm, 1H, 5.5
Hz), 3.92 (s, 3H), 1.95 (m, 4H), 1.09 (m 6H) ppm. 31P NMR δ:
41.77 ppm. 13C NMR δ: 166.94, 136.06, 135.96, 133.81, 133.26,
133.22, 132.61, 131.86, 131.73, 131.16, 129.65, 129.51, 53.06,
23.37, 22.45, 6.17, 6.10 ppm. EIMS: m/e (%) 240 (M+, 7), 212
(100), 211 (99), 183 (34), 151 (9), 123 (9), 105 (9), 77 (10). HRMS
calcd for C12H17O3P: 240.09153. Found: 240.09169.
(4-Meth oxyca r bon ylp h en yl)d ip h en ylp h osp h in e Oxid e
(3b). White solid, mp 104-105 °C. IR (film) ν: 3060, 2960,
1730, 1440, 1290, 1280, 1200, 1125, 1110, 740, 730, 710 cm-1
.
1H NMR δ: 8.10 (dd, 2H, J ) 8.4 and 2.4 Hz), 7.75 (dd, 2H, J )
11.5 and 8.4 Hz), 7.68-7.45 (m, 10H), 3.93 (s, 3H) ppm. 31P
NMR δ: 26.65 ppm. 13C NMR δ: 166.04, 138.15, 136.81, 132.98,
132.37, 132.01, 131.95, 131.90, 131.82, 131.77, 130.98, 129.28,
129.12, 128.53, 128.36, 52.27 ppm. EIMS: m/e (%) 336 (M+, 40),
335 (100), 278 (6), 277 (18), 201 (11), 199 (8), 152 (10), 77 (15).
HRMS calcd for
335.08415.
[3,5-B i s (m e t h o x y c a r b o n y l)p h e n y l]d i p h e n y lp h o s -
p h in e Oxid e (4b). Solid, mp 224-225 °C. IR (film) ν: 3060,
2950, 1730, 1440, 1320, 1250, 1200, 1150, 1120, 1000, 750, 725,
(R ,S )-3-Me t h o x y c a r b o n y l-2-h y d r o x y -2′-[[(t r iflu o r o -
m eth yl)su lfon yl]oxy]-1,1′-bin a p h th a len e. Pale yellow solid,
mp 156-160 °C. 1H NMR: δ 10.81 (s, 1H, OH), 8.73 (s, 1H,
ArH), 7.91-8.09 (m, 3H, ArH), 7.53-7.60 (m, 2H, ArH), 7.33-
7.42 (m, 4H, ArH), 7.04-7.26 (m, 1H, ArH), 4.07 (s, 3H, OCH3)
ppm. 13C NMR: δ 171.9, 155.25, 146.54, 137.67, 134.79, 134.08,
133.45, 131.51, 130.54 (2C), 129.19, 128.40, 127.77, 127.67,
127.36, 126.93, 125.45, 124.97, 120.34, 119.04 (q, J ) 320 Hz,
CF3), 115.12, 114.72, 53.56 ppm. EIMS: m/z (%) 476 (M+, 100),
444 (44), 295 (69), 283 (86). HRMS calcd for C23H15O6SF3:
476.0530. Found: 476.0541.
C
20H16O3P (M+ - 1): 335.08370. Found:
700 cm-1
.
1H NMR δ: 8.83 (d, 1H, J ) 1.2 Hz), 8.54 (dd, 2H, J
P a lla d iu m -Ca ta lyzed Cou p lin g of Secon d a r y P h osp h in e
Oxid es w ith Ar yl Tr ifla tes. Meth od B. A three-necked
round-bottom flask charged with a mixture of 0.2 mmol of
triflate, 0.4 mmol of diphenylphosphine oxide, dppp (0.015
mmol), and Pd(AcO)2 (0.01 mmol) and diisopropylethylamine (1
mmol) in 2.5 mL of DMSO was heated overnight to reflux, under
argon. The solvent was removed under reduced pressure. To
the residue were added water and ether (25 mL), and the organic
phase was washed with 1.5 N HCl (6 × 20 mL), brine, and water
and finally dried over anhydrous sodium sulfate. Evaporation
to dryness yielded a crude material which was purified by
column chromatography (n-hexanes-ethyl acetate). Final crys-
tallization or bulb-to-bulb distillation furnished pure products.
(R ,S )-3-M e t h o x y c a r b o n y l-2-h y d r o x y -2′-(d i p h e n y l-
p h osp h in yl)-1,1′-bin a p h th a len e (1b) (R1 ) H). The title
compound was obtained by treating (R,S)-3-(methoxycarbonyl)-
2-hydroxy-2′-[[(trifluoromethyl)sulfonyl]oxy]-1,1′-binaphtha-
lene as shown above. It was obtained as a yellow solid, mp 178-
179 °C. IR (film) ν: 3060, 2980, 1740, 1685, 1440, 1350, 1330,
) 11.6 and 1.2 Hz), 7.69-7.46 (m, 10H), 3.92 (s, 3H) ppm. 31P
NMR δ: 25.53 ppm. 13C NMR δ: 166.06, 137.59, 137.45, 134.90,
134.50, 133.16, 133.12, 132.79, 132.66, 131.92, 131.77, 131.47,
129.58, 129.42, 53.32 ppm. EIMS: m/e (%) 394 (M+, 55), 393
(100), 379 (32), 363 (15), 335 (18), 201 (24), 199 (7), 183 (12),
152 (8), 77 (20). HRMS calcd for C22H18O5P (M+ - 1): 393.08918.
Found: 393.08931.
[2-M e t h o x y c a r b o n y l-6-m e t h o x y p h e n y l]d i p h e n y l-
p h osp h in e Oxid e (5b). Solid, mp 123-126 °C. IR (film) ν:
3060, 2950, 1730, 1570, 1460, 1440, 1300, 1185, 1120, 1150,
1120, 1060, 760, 730, 700 cm-1 1H NMR δ: 7.71-7.38 (m, 11H),
.
7.22 (dd, 1H, J ) 8.2 and 2.4 Hz), 6.95 (dd, 1H, J ) 8.2 and 3.6
Hz), 3.79 (s, 3H), 3.34 (s, 3H) ppm. 31P NMR δ: 24.90, ppm.
13C NMR δ: 170.14, 170.08, 160.77, 160.72, 141.65, 141.59,
135.10, 134.36, 134.34, 133.65, 132.69, 132.56, 132.50, 132.46,
132.07, 131.94, 131.88, 131.84, 129.12, 128.96, 128.62, 128.45,
122.02, 121.90, 120.58, 119.26, 114.09, 114.01, 55.88, 53.20 ppm.
EIMS: m/e (%) 365 (0.4), 352 (11), 351 (50), 289 (9), 199 (11),
152 (15), 91 (100), 77 (56). Anal. Calcd for C21H19O4P: C, 68.85;
H, 5.19. Found: C, 69.04; H, 5.20.
1300, 1215, 1125, 920, 755, 730, 719, 705 cm-1
.
1H NMR δ:
10.38 (s, 1H), 8.30 (s, 1H), 7.93 (m, 3H), 7.67 (m, 3H), 7.55 (td,
1H, J ) 6.6 and 1.1 Hz), 7.41 (td, 1H, J ) 7.2 and 1.5 Hz), 7.27
(m, 8H), 7.11 (td, 1H, J ) 7.2 and 1.5 Hz), 6.95 (m, 3H), 3.99 (s,
3H) ppm. 31P NMR δ: 25.84 ppm. 13C NMR δ: 170.72, 154.19,
140.03, 140.10, 138.19, 135.50, 135.47, 134.69, 133.98, 133.45,
133.32, 133.29, 132.71, 132.51, 131.84, 131.81, 131.76, 131.71,
131.58, 131.15, 131.11, 130.39, 129.71, 129.62, 129.54, 128.81,
128.73, 128.66, 128.56, 128.50, 127.83, 127.66, 127.19, 127.14,
126.17, 124.49, 119.50, 119.43, 113.72, 53.15 ppm. EIMS: m/e
(%) 528 (M+, 61), 468 (22), 326 (100), 295 (15), 277 (29), 267 (24),
239 (14), 214 (10), 201 (98), 155 (5), 77 (12). HRMS calcd for
C34H25O4P: 528.14904. Found: 528.15063.
(5-Me t h o x y c a r b o n y lp h e n y l)-1,3-b is d ip h e n y lp h o s -
p h in e Oxid e (6b). Obtained as a solid, mp 224-225 °C. 1H
NMR δ: 8.58 (dd, 2H, J ) 11.1 and 1.4 Hz), 7.93 (t, 1H, J ) 1.4
Hz), 7.59-7.39 (m, 20H), 3.86 (s, 3H) ppm. 31P NMR δ: 25.60
ppm. 13C NMR δ: 165.79, 139.67, 139.53, 139.38, 136.82, 136.78,
136.67, 136.63, 135.95, 135.81, 134.62, 134.48, 132.98, 132.96,
132.94, 132.53, 132.46, 132.39, 131.82, 131.67, 131.52, 131.01,
129.39, 129.13, 46.16 ppm. EIMS: m/e (%) 536 (M+, 42), 535
(43), 459 (18), 335 (100), 334 (59), 257 (19), 201 (86), 199 (32),
152 (28), 77 (71). HRMS calcd for C32H26O4P2: 536.13063.
Found: 536.12903.
(4-Meth oxyp h en yl)d ip h en ylp h osp h in e Oxid e (7b). Ob-
tained as a yellow oil, bp 223-225 °C (0.04 mm of Hg). IR (film)
ν: 3060, 2950, 1600, 1505, 1440, 1290, 1255, 1190, 1180, 1120,
(R ,S )-3-Me t h o x y c a r b o n y l-2-(b e n zy lo x y )-2′-(d ip h e n -
ylp h osp h in yl)-1,1′-bin a p h th a len e (1b) (R1 ) Bz). To a
stirred solution of 528 mg (1 mmol) of 1b (R1 ) H) and 276 mg
of potassium carbonate (2 mmol) in dry DMF (5 mL) was added
257 mg (180 µL, 1.5 mmol) of benzyl bromide via syringe. The
mixture was heated at 60-70 °C for 1-2 h, until the yellow color
1030, 730, 710, 700 cm-1 1H NMR δ: 7.67-7.42 (m, 12H), 6.94
.
(dd, 2H, J ) 8.8 and 2.2 Hz), 3.81 (s, 3H) ppm. 31P NMR δ:
27.12 ppm. 13C NMR δ: 163.07, 163.03, 134.58, 134.43, 134.16,

Notes
J . Org. Chem., Vol. 63, No. 10, 1998 3467
completely vanished. The solution was cooled to room temper-
ature and was partitioned into ether and 2 N hydrochloric acid.
The organic layer was washed with hydrochloric acid and brine,
dried over anhydrous sodium sulfate, and evaporated to dryness.
The solid residue was purified by column chromatography on
silica gel (a 4:1 mixture of ethyl acetate-methylene choride was
used as eluant) to yield 575 mg (93% yield) of 1b (R1 ) Bz) as a
white solid. Recrystallization in hexanes-ethyl acetate afforded
white needles, mp 122-4 °C. 1H NMR: δ 8.24 (s, 1H, ArH),
7.85-8.01 (m, 3H, ArH), 7.72 (d, J ) 8 Hz, 1H, ArH, 7.42-7.56
(m, 3H, ArH), 7.02-7.36 (m, 14 H, ArH), 6.92 (d, J ) 8 Hz, 1H,
ArH), 6.68-6.82 (m, 2H, ArH), 6.65 (m, 1H, ArH), 5.01 (d, J )
10 Hz, 1H, OCH2), 4.33 (d, J ) 10 Hz, 1H, OCH2), 3.91 (s, 3H,
OCH3) ppm. 13C NMR: δ 167.18, 153.33, 139.57, 139.46, 137.81,
136.36, 135.27, 135.25, 134.94, 134.38, 133.97, 133.82, 133.68,
133.00, 132.84, 132.76, 132.70, 132.50, 132.29, 132.13, 132.07,
132.00, 131.83, 131.80, 131.39, 131.35, 131.15, 130.02, 129.87,
129.85, 129.28, 129.25, 129.19, 129.00, 128.89, 128.77, 128.73,
128.67, 128.63, 128.57, 128.50, 128.40, 128.12, 127.80, 127.78,
127.73, 127.61, 126.75, 126.03, 124.89, 76.00, 52.90 ppm. 31P
NMR: δ 27.94 (s, 1P) ppm. EIMS: m/z (%) 618 (M+, 19), 527
(45), 416 (20), 201 (100). HRMS calcd for C41H31O4P: 618.1960.
Found: 618.1951.
Gen er a l P r oced u r e for t h e R ed u ct ion of P h osp h in e
Oxid es. At 0 °C, trichlorosilane (1 mmol) was carefully added
to a mixture of phosphine oxide (0.2 mmol) and triethylamine
(4.8 mmol) in xylene (5 mL) in a three-necked round-bottom
flask, under argon. The mixture was then heated to reflux
overnight. To the cooled mixture were added ether and sodium
bicarbonate. Solids were removed by filtration, and the solvent
was removed under reduced pressure. The crude phosphine was
purified by column chromatography on silica gel using hexane/
ethyl acetate as eluant.
(R ,S )-3-Me t h o x y c a r b o n y l-2-(b e n zy lo x y )-2′-(d ip h e n -
ylp h osp h in o)-1,1′-bin a p h th a len e (1) (R1 ) Bz). Obtained
by reduction of 1b (R1 ) Bz) according to the general method
above in 73% yield as a colorless solid, mp 184-6 °C. 1H NMR:
δ 8.65 (s, 1H, ArH), 7.93-7.97 (m, 3H, ArH), 7.49-7.56 (m, 2H,
ArH), 7.33-7.40 (m, 3H, ArH), 7.01-7.24 (m, 14H, ArH), 6.83
(d, J ) 8.5 Hz, 1H, ArH), 6.68 (m, 2H, ArH), 5.01 (d, J ) 9.9 Hz,
1H, OCH2), 4.47 (d, J ) 9.9 Hz, 1H, OCH2), 3.95 (s, 3H, OCH3)
ppm. 13C NMR: δ 167.67, 153.12, 153.10, 141.93, 141.47, 138.79,
138.62, 137.96, 137.89, 137.71, 137.45, 137.29, 136.58, 136.55,
134.68, 134.40, 134.27, 134.07, 133.92, 133.82, 133.77, 133.53,
131.57, 131.45, 131.25, 131.22, 130.10, 129.51, 128.94, 128.75,
128.72, 128.67, 128.52, 128.49, 128.38, 127.94, 127.47, 127.42,
127.37, 126.78, 126.02, 125.86, 75.90, 52.95 ppm. 31P NMR: δ
-15.26 ppm. EIMS: m/z (%) 602 (M+, 1), 571 (3), 495 (100).
HRMS calcd for C41H31O3P: 602.2011. Found: 602.2008.
Chiral, optically active (R)-1 ([R]20 ) -49.8 °, c ) 1, THF)
D
was obtained analogously.
Ack n ow led gm en t. Financial support by the DGI-
CYT (PB93-0424) is gratefully acknowledged. X. Gar-
cias and B. Martorell thank the Ministry of Education
and Culture for a fellowship.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra of 1, 1b (R1 ) H), 1b (R1 ) Bz), 2b, 2c, 3b, 4b, 5b, 6b,
7b, and 8b (26 pages). This material is contained in libraries
on microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
J O971428S