Synthesis and catalytic application of chiral 1,1′-bi-2-naphthol-and biphenanthrol-based pincer complexes: Selective allylation of sulfonimines with allyl stannane and allyl trifluoroborate

Article abstract of DOI:10.1021/jo070288b

(Chemical Equation Presented) New easily accessible 1,1′-bi-2- naphthol- (BINOL-) and biphenanthrol-based chiral pincer complex catalysts were prepared for selective (up to 85% enantiomeric excess) allylation of sulfonimines. The chiral pincer complexes w

Full text of DOI:10.1021/jo070288b

Synthesis and Catalytic Application of Chiral 1,1′-Bi-2-naphthol-
and Biphenanthrol-Based Pincer Complexes: Selective Allylation of
Sulfonimines with Allyl Stannane and Allyl Trifluoroborate
Juhanes Aydin, K. Senthil Kumar, Mahmoud J. Sayah, Olov A. Wallner, and
Ka´lma´n J. Szabo´*
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm UniVersity,
SE-106 91, Stockholm, Sweden
kalman@organ.su.se
ReceiVed February 12, 2007
New easily accessible 1,1′-bi-2-naphthol- (BINOL-) and biphenanthrol-based chiral pincer complex
catalysts were prepared for selective (up to 85% enantiomeric excess) allylation of sulfonimines. The
chiral pincer complexes were prepared by a flexible modular approach allowing an efficient tuning of
the selectivity of the catalysts. By employment of the different enantiomeric forms of the catalysts, both
enantiomers of the homoallylic amines could be selectively obtained. Both allyl stannanes and allyl
trifluoroborates can be employed as allyl sources in the reactions. The biphenanthrol-based complexes
gave higher selectivity than the substituted BINOL-based analogues, probably because of the well-shaped
chiral pocket generated by employment of the biphenanthrol complexes. The enantioselective allylation
of sulfonimines presented in this study has important implications for the mechanism given for the pincer
complex-catalyzed allylation reactions, confirming that this process takes place without involvement of
palladium(0) species.
1. Introduction
philes is a very useful and well-established method,1,3,4 applica-
tion of electrophiles,5-11 including aldehydes8-10 and imines,5-7
has received considerable current attention. Development of new
methods for selective allylation of imines is particularly
important, as these substrates are more difficult to allylate than
aldehydes, and therefore relatively few efficient enantioselective
Development of catalytic asymmetric allylation reactions is
a challenging task in organic synthesis, as in these processes
the stereogenic carbon is created via enantioselective carbon-
carbon or carbon-heteroatom bond formation.1-3 Palladium
catalysis offers a versatile tool for enantioselective introduction
of the allylic moiety into nucleophilic1,3,4 and electrophilic5-7
substrates. Although asymmetric allylic alkylation of nucleo-
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10.1021/jo070288b CCC: $37.00 © 2007 American Chemical Society
Published on Web 05/25/2007
J. Org. Chem. 2007, 72, 4689-4697
4689

Aydin et al.
FIGURE 1. Chiral pincer complexes employed for allylation of sulfonimines.
processes are available.12-14 As asymmetric allylation of imines
leads to formation of chiral homoallyl amines, which are
important motifs in bioactive natural products and pharmaceu-
ticals,12 a large effort has been devoted recently to devise new
synthetically useful versions of these reactions.5-7,15-21 Con-
sidering the needs of versatile chiral homoallyl amines, full
control of the selectivity and possibilities for facile deprotection
of the amines are important requirements in method develop-
ment of the new catalytic processes.
There have been two major strategies for palladium-catalyzed
enantioselective allylation of imines. Yamamoto and co-
workers5,6 employed chiral allyl-palladium complexes for the
asymmetric induction. In these transformations the imine
substrates could be allylated with allyl stannanes via bis(allyl)-
palladium intermediates.22-25 Although this excellent method
found many applications for enantioselective synthesis of
homoallyl amines, the complex reactivity of bis(allyl)palladium
complexes imposes limitations on the synthetic scope of the
reaction.26-28 One problem is that allyl-allyl coupling may
occur prior to the allylation of the imine electrophile,26 which
leads to allylation of the chiral allylic ligand and accordingly
to loss of the chiral information. The allyl-allyl coupling is
particularly dominant in the presence of high phosphine
concentrations,26,29 and therefore use of chiral phosphines as
auxiliaries in allylation reactions via bis(allyl)palladium com-
plexes is strongly limited. A further problem arises from the
fact that bis(allyl)palladium complexes undergo facile isomer-
ization processes altering the hapticity of the allyl moi-
eties,23,24,27,28 and therefore either allyl group can be transferred
to the electrophile. For example, allylation of a chiral ligand
may lead to loss of the enantioselectivity of the catalyst.
We have shown that the above side reactions can be avoided
by the use of so-called “pincer complex”30-35 catalysts.36-38 By
use of pincer complex (such as 1) catalysis, the electrophilic
allylation reactions can be carried out without formation of bis-
(allyl)palladium intermediates. Furthermore, in pincer complex-
catalyzed reactions, phosphine-based ligands can be used for
chiral induction, which allows an efficient fine-tuning of the
selectivity of the catalyst. In consideration of these features,
the second strategy for palladium-catalyzed asymmetric allyl-
ation of imines is based on application of chiral pincer
complexes (such as 1) with allylstannanes (2) as reagents (cf.
eq 1).7 In a previous publication,7 we have shown that 1,1′-bi-
2-naphthol- (BINOL-) based chiral pincer complexes are
potentially useful catalysts for allylation of sulfonimines.
Unfortunately, the synthetically easily accessible pincer com-
plexes gave poor enantioselectivity (20% ee), while the synthesis
of more selective (up to 59% ee) catalysts could be only be
achieved with poor yield (18%). We have now found that the
enantioselectivity of the allylation can be considerably enhanced
by application of thioalkyl/aryl substituents (1a-d) in the
γ-position of the BINOL ligands or employment of biphenan-
throl-based complexes (1e,f). We were also able to prepare both
enantiomers of the thiomethyl- (1a,b) and biphenanthrol-based
complexes (1e,f) to study the possibilities for full control of
the enantioselectivity in the allylation processes (Figure 1).
(12) Ding, H.; Friestad, G. K. Synthesis 2005, 2815.
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2003, 42, 3927.
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(22) Nakamura, H.; Iwama, H.; Yamamoto, Y. J. Am. Chem. Soc. 1996,
118, 6641.
(23) Szabo´, K. J. Chem.sEur. J. 2000, 6, 4413.
(24) Wallner, O. A.; Szabo´, K. J. Chem.sEur. J. 2003, 9, 4025.
(25) Pichierri, F.; Yamamoto, Y. J. Org. Chem. 2007, 72, 861.
(26) Nakamura, H.; Bao, M.; Yamamoto, Y. Angew. Chem., Int. Ed.
2001, 40, 3208.
(27) Solin, N.; Narayan, S.; Szabo´, K. J. J. Org. Chem. 2001, 66, 1686.
(28) Solin, N.; Narayan, S.; Szabo´, K. J. Org. Lett. 2001, 3, 909.
(29) Me´ndez, M.; Cuerva, J. M.; Go´mez-Bengoa, E.; Ca´rdenas, D. J.;
Echavarren, A. M. Chem.sEur. J. 2002, 8, 3620.
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4690 J. Org. Chem., Vol. 72, No. 13, 2007

BINOL- and Biphenanthrol-Based Pincer Complexes
Furthermore, we employed allyl trifluoroborate (3) as an
alternative allyl source to allyl stannanes in the substitution
reactions. Our studies are focused on allylation of sulfonimines,
as these reactions afford homoallylic sulfonamines, which can
easily be deprotected, affording homoallyl amines. Exploration
of palladium-catalyzed asymmetric allylation of sulfonimines
is particularly important, as these species cannot be selectively
allylated via chiral bis(allyl)palladium complexes.6
requires that the palladation step be carried out by carbon-
hydrogen bond activation instead of the above-described oxida-
tive addition (8 f 1). As this carbon-hydrogen bond activation
applied by Bedford and co-workers39 requires harsh conditions
(150 °C/µν, 1 h, or 83 °C/6 days) in the final step of the
synthesis of the chiral pincer complexes, we employed our own
strategy allowing the synthesis of 1a-f under mild conditions.
2. Results and Discussion
Synthesis of Chiral Pincer Complexes 1a-f. Complexes
1a-f could be obtained by a flexible modular approach (eqs
3-6) starting from optically pure BINOL (6a-d) or biphenan-
throl derivatives (6e,f). In the first step 6a-f are converted to
the corresponding phosphochloridates 7a-f, which were coupled
with iodoresorcinol to obtain proligands 8a-f. These proligands
are usually very sensitive to hydrolysis, and therefore their
purification is difficult. For example, purification by column
chromatography leads to extensive loss of the proligands.
However, we have found that the crude product of 8 could be
metalated under mild conditions (20 °C, 4 h) with Pd2(dba)3
via facile oxidative addition of the carbon-iodine bond to
palladium(0). The obtained yields are usually high (60-76%)
except for the synthesis of ethyl sulfide 1c (27%). The mild
reaction conditions (20-35 °C/4 h) ensure that the BINOL
moieties do not undergo racemization in the applied pro-
cedure. In our experience, raising the reaction temperature
over 60 °C in any of the reaction steps leads to a certain
degree of racemization, decreasing the optical purity of pincer
complex 1.
As it appears from eqs 3-6, synthesis of the chiral pincer
complexes by the above sequence is flexible and highly modular.
Thus, starting from R-BINOL derivative40,41 6a (eq 3), chiral
pincer complex 1a was obtained ([R]D ) -544°), while its
enantiomer 1b ([R]D ) +542°) can be prepared from S-BINOL
derivative40 6b (eq 4). Similarly, both enantiomers 1e ([R]D )
-588°) and 1f ([R]D ) +586°) can be prepared from optically
pure biphenanthrol derivatives 6e (R-form) and 6f (S-form),
respectively (eqs 5 and 6) by slight modification of the reaction
conditions applied for preparation of 1a-d. Accordingly, by
use of the above procedure a great variety of chiral pincer
complexes can be prepared by choosing the appropriate BINOL
or biphenanthrol derivatives.
The above procedure is based on our previously published7
(web online August 2005) synthetic strategy devised for the
first preparation of BINOL-based chiral pincer complexes
(analogues of 1a-d). It should be mentioned that, independently
from us, Bedford and co-workers39 have developed a similar
synthetic scheme for synthesis of the parent BINOL-based
complex using resorcinol instead of iodoresorcinol for coupling
with the phosphochloridate component (such as 7). This strategy
(39) Baber, R. A.; Bedford, R. B.; Betham, M.; Blake, M. E.; Coles, S.
J.; Haddow, M. F.; Hurthouse, M. B.; Orpen, A. G.; Pilarski, L. T.; Pringle,
P. G.; Wingad, R. L. Chem. Commun. 2006, 3880.
J. Org. Chem, Vol. 72, No. 13, 2007 4691

Aydin et al.
The optically pure thioalkyl/aryl BINOL derivatives 6a-d
could be obtained by the procedure of Woodward and Snieckus
and their co-workers.40,41 Although there are literature proce-
dures available for resolvation of bisphenanthrol,42 in our hands
these procedures were not suitable for preparation of 6e and 6f
in sufficiently high optical purity and amounts required for
synthesis of 1e and 1f. Therefore, we devised a new method
for resolvation of bisphenanthrol. The racemic biphenanthrol
was obtained from 9 by a slightly modified procedure of
Hashimoto and co-workers (eq 7).43 The racemic mixture of 6e
and 6f was reacted with 1.7 equiv of (1S)-(+)-10-camphorsul-
fonyl chloride (10) in the presence of 1.1 equiv of NEt3 to give
diastereomeric monoesters 11a and 11b (eq 8). These mo-
noesters could easily be separated by silica chromato-
graphy in high yields (43% for each diastereomer). Optically
pure 6e and 6f were obtained from 11a and 11b by re-
duction with lithium aluminum hydride. Hydrolysis with
a strong base (such as NaOH) could not be used for deprotec-
tion of 11a,b because of substantial racemization of the
products. Diesters of 6e and 6f may also be obtained by
use of an excess of 10 and NEt3; however, these diesters
could not be efficiently separated by chromatography or
crystallization.
enantioselectivity in this reaction (entry 2) is slightly decreased
(71%). The reaction product (5a) was reduced with sodium in
ammonia, providing (1R)-1-phenyl-3-butenylamine44,45 (12) in
67% yield (without racemization), showing that the major
enantiomer, 5a, has the R configuration (eq 9). The allylation
reaction was also carried out with the S-BINOL analogue of 1a
(1b). The major product (74% ee) of this reaction was the
S-enantiomer 5b (entry 3). As the availability of R- and
S-BINOL precursors for preparation (see above) of 1a and 1b
are similar, the enantioselectivity of the presented reaction can
be fully controlled by the choice of the appropriate pincer
complex catalyst. The allylstannane reagent (2) could be
successfully replaced (eq 2) with potassium trifluoro(allyl)borate
(3),46 which reacted readily38,47 with 4a, providing homoallyl
amine 5a or 5b in good yield (eq 2), however, with somewhat
lower enantioselectivity than 2 (Table 1, entries 6 and 7).
Similarly to allylstannane (2), the reaction of 3 catalyzed with
R-BINOL derivative 1a gave predominantly R-product 5a,
while with S-BINOL derivative 1b the main product had
S-configuration (5b).
We have also studied the effects of the bulkiness of the R
substituent in 1 on the selectivity of the allylation process. It
was found that as one goes from methyl substituent (1a) to ethyl
substituent (1c) the enantioselectivity is slightly decreased (cf.
Table 1, entries 1 and 4), while thiophenyl derivative 1d proved
to be a relatively unselective catalyst (48% ee; entry 5). This
trend suggests that the enantioselectivity of 1a cannot be simply
increased by replacement of the thiomethyl functionality with
more bulky substituents. We have also attempted the enanti-
oselective allylation of a bulky sulfonimine 4b (entry 8);
however, this reaction proceeds much more slowly and with
lower selectivity (48% ee) than the corresponding process
with 4a.
Cinnamyl derivative 4c displayed high reactivity in the
allylation reaction, providing the corresponding allyl amine
derivative with 59% ee. The reactivity of the imine com-
ponent can also be increased by nitro substitution of the aro-
matic ring. Accordingly, 4d could be allylated with high
yield (85%) and only slightly lower selectivity (66% ee)
than 4a.
As indicated above, the enantioselectivity (71-74% ee)
obtained by 1a and 1b cannot be improved by simple increase
of the steric bulk of the thio alkyl substituent. On the basis of
our DFT modeling studies47 for pincer complex-catalyzed
allylation of sulfonimines, we reasoned that substitution of the
δ-position or simultaneous substitution of both the γ- and
δ-positions of the BINOL system would increase the selectivity
of the allylation reaction. In this respect, replacement of the
BINOL units with biphenanthrol moieties (such as in 1e,f)
appeared to be an attractive approach. Indeed, we have found
that the enantioselectivity of the allylation reaction can be
increased up to 85% ee by employment of biphenanthrol
Catalytic Allylation of Sulfonimines with Chiral Pincer
Complexes. The allylation reactions with allylstannane 2 and
benzenesulfonyl imine 4a could be carried out under mild
conditions (6-20 °C) in dry DMF or DMSO without additives
(eq 1, Table 1). Application of R-BINOL-based thiomethyl
catalyst (5 mol %) 1a in DMF provided encouraging levels of
enantioselectivity, affording homoallyl amine 5a with 73% ee
(Table 1, entry 1). The yield of this reaction (49%) could be
improved by use of DMSO as solvent (57%); however the
(40) Bo¨rner, C.; Dennis, M. R.; Sinn, E.; Woodward, S. Eur. J. Org.
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BINOL- and Biphenanthrol-Based Pincer Complexes
TABLE 1. Allylation of Sulfonimines in the Presence of Chiral Pincer Complexes 1a-fa
a In a typical reaction, 5 mol % catalyst 1 was employed. b Reaction temperature in degrees Celsius; time in hours. c Isolated yield. d 10 mol % catalyst
was employed. e A 1:1 mixture of DMF/THF was employed.
complexes 1e,f. Accordingly, nitro-substituted imine 4d reacted
(Table 1, entry 11) with 2 in the presence of 5 mol % 1e in
high yield (71%) and selectivity (85% ee). The yield could be
increased by using phenylsulfonyl derivative 4e, affording 5g
(78%) at the cost of a slight decrease in selectivity (82% ee).
The parent sulfonimine 4a also reacted with about as high
selectivity as 4d. Thus, the allylation reaction with 2 in the
presence of 1f provided 5b with 83% ee (entry 13). Similarly
to the thiomethyl complexes, the R-biphenanthrol-based complex
1e provides the homoallylamine products (5f,g) with R-
selectivity, while 1f, containing S-biphenanthrol moieties,
induces S-configuration at the stereogenic carbon of the product
5b. On the other hand, the higher selectivity of 1e,f is
accompanied by lower catalytic activity than BINOL derivatives
1a,b. This is reflected (cf. entries 3 and 13) by the relatively
low yield obtained for allylation of 4a with 1f (28%) compared
to 1b (53%). The yield can be improved either by increasing
the catalyst loading to 10 mol % (entry 14) or by employ-
ment of activated sulfonimines, such as 4d and 4e (entries 11
and 12).
3. Mechanistic Aspects
Model for Mechanism of Enantioselection. The above
experimental results (Table 1) clearly show that, by use of 2 or
3 as reagents, the R-BINOL-based catalyst (1a) provides mainly
R-homoallylamine 5a, while changing the configuration of the
BINOL ligand (1b) leads to reversal of the enantioselectivity,
resulting in S-homoallylamine 5b. Although the exact mecha-
nism of the enantioselection is not perfectly understood yet, on
the basis of previous DFT studies47 on the (achiral) pincer
complex-catalyzed allylation of sulfonimines, at least a qualita-
tive model can be constructed.
According to this model (Figure 2), the electrophilic carbon
of sulfonimine 4a interacts with the γ-position of the η1-allyl
moiety. Formation of the R-form 5a is supposed to proceed via
TS as shown in panel a, in which the sulfonimine functionality
points away from the R-BINOL-based complex. On the other
hand, in the TS structure for formation of the S-enantiomer 5b,
the sulfonimine group points in the opposite direction, experi-
encing repulsive steric interactions with the thiomethyl group
J. Org. Chem, Vol. 72, No. 13, 2007 4693

Aydin et al.
FIGURE 2. Supposed mechanism of the enantioselection in allylation of sulfonimine 4a with R-BINOL-based catalyst 1a and biphenanthrol
derivative 1e. (a) formation of 5a; (b) formation of 5b.
of the binaphthyl ligands. This interaction is thermodynamically
destabilizing, and therefore formation of the S-form 5b is
disfavored. Replacement of the BINOL moieties with biphenan-
throl units is expected to increase the selectivity of the catalyst
by increasing the destabilizing interactions with the sulfonimine
functionality in the type of TS structures shown in panel b.
Implications of This Study for the Mechanism of Pincer
Complex-Catalyzed Allylations. The present study further
confirms the mechanistic description given for the pincer
complex-catalyzed allylation reactions (eq 10).36,37,48 According
to this mechanism, the applied pincer complex (9) undergoes
transmetalation with the employed allylmetal reagent to give
η1-allyl palladium complex 10. Because of the η1-coordination
of the allyl moiety and the electron-supplying feature of the
pincer ligand, complex 10 is able to efficiently allylate elec-
trophiles (such as 5a and 5b) under catalytic conditions. We
have shown that complex 10 can be generated from pincer
complex 9 (R ) Ph49) and allyl stannane 237 or allyl boronate
3.47 According to this mechanistic picture, the palladium atom
does not undergo redox reactions under the catalytic transforma-
tion, and the enantioselectivity of the process is determined by
the reaction of the η1-allyl moiety of 10 with the electrophilic
substrate. Considering the enantioselectivity (up to 85%)
achieved in the above study, a possible palladium(0)-catalyzed
process can be ruled out. Recently, it was shown50,51 that
catalytically active palladium(0) can be generated from pincer
complexes; however, this process involves decomposition of
the pincer complex, which for the presented transformations
(eqs 1 and 2) would involve a complete loss of the enantiose-
lectivity of the catalyst. On the contrary, complexes 1a-f
displayed excellent stability under the allylation reactions, and
the unchanged catalyst could be detected in the final reaction
mixture of the process. This high stability suggests that highly
durable, easily recyclable catalysts may be obtained by im-
mobilization of 1a-f.
4. Conclusions
Easily accessible chiral BINOL- and biphenanthrol-based
pincer complexes readily catalyze the allylation of sulfonimines
up to 85% ee. So far, this is the highest enantioselectivity
achieved in pincer complex-catalyzed allylation reactions39,52,53
and also in palladium-catalyzed6 allylation of sulfonimines. Both
allyl stannanes and allyl trifluoroborates can be employed as
allyl sources in these processes. The enantioselectivity of the
transformation can be reversed by changing the configuration
of the BINOL or biphenanthrol ligands, and thus full control
(48) Johansson, R.; Wendt, O. F. Dalton Trans. 2007, 488.
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Chem. 2000, 24, 745.
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Sherrill, C. D.; Jones, C. W.; Weck, M. Organometallics 2005, 24, 4351.
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Nishiyama, H. Organometallics 2001, 20, 1580.
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BINOL- and Biphenanthrol-Based Pincer Complexes
127.4, 127.1, 126.9, 126.6, 125.7, 125.3, 124.8, 124.4, 123.9, 123,
122.96, 122.7, 122.65, 122.5, 111.5, 57.6, 50.1, 47.2, 42.9, 42.1,
26.5, 25.5, 18.6, 18.5. HRMS m/z 623.1862 (calcd [M + Na]+ for
C38H32NaSO5 323.1863). Spectral data for 11b: 1H NMR (400
MHz, CDCl3) δ 8.83 (q, J ) 8 Hz, 3H), 8.74 (d, J ) 8 Hz, 1H),
8.63 (d, J ) 8 Hz, 1H), 8.53 (d, J ) 8 Hz, 1H), 7.82 (m, 3H), 7.7
(t, J ) 7.5 Hz, 2H), 7.56 (m, 2H), 7.43 (m 3H), 7.31 (d, J ) 8.4
Hz, 1H), 5.71 (s, 1H), 2.93 (d, J ) 14.8 Hz, 1H), 2.05 (m, 2H),
1.79 (m, 4H), 1.46 (dddd, J ) 4.6 Hz, 1H), 1.24 (m, 1H), 0.35
(s, 3H), 0.09 (s, 3H). 13C NMR (100.5 MHz, CDCl3) δ 213, 148.1,
145.3, 132.1, 131.7, 131.4, 130.6, 129.9, 128.5, 128.1, 127.95,
127.9, 127.7, 127.5, 126.8, 126.4, 125.3, 124.9, 124.5, 123.9, 123.1,
122.9, 122.7, 122.63, 122.6, 111.6, 57.2, 49.1, 47.2, 42.5, 42.1,
26.6, 24.8, 18.4, 18.3. HRMS m/z 623.1863 (calcd [M + Na]+ for
C38H32NaO5S 323.1863).
of the enantioselectivity can be achieved. The enantioselection
is assumed to take place in the TS of the electrophilic attack of
the η1-allyl moiety coordinated to the chiral complex. The chiral
cavity of the biphenanthrol-based complex is better shaped than
that of the BINOL-based complexes, leading to higher selectivity
in the allylation process.
5. Experimental Section
All experiments were conducted under argon atmosphere em-
ploying standard manifold techniques. All solvents used in the
reactions were freshly distilled prior to use. NMR spectra were
1
recorded in CDCl3 on Varian or Bruker spectrometers with H at
300 or 400 MHz and 13C at 75.4 or 100.5 MHz with CDCl3 (δ[1H]
) 7.26, δ[13C] ) 77.0) as internal standard. 31P was recorded at
161.9 or 121.4 MHz with H3PO4 as external standard. HPLC
chromatograms were obtained by use of Acquity Ultra Performance
LC and Daicel Chiracel OD-H or AD-H columns with the
parameters given in each description. Optical rotations were
measured at 20 °C. Mass spectrometry data were obtained with a
Bruker MicrOTOF spectrometer (ESI) and a Bruker Biflex III
instrument (MALDI-TOF) with 2′,4′,6′-trihydroxyacetophenone
(THAP) as matrix. For column chromatography, Merck silica gel
60 (230-400 mesh) was used.
(+)-10-(10-Hydroxy-1,4-dihydro-9-phenanthrenyl)-5,8-dihy-
dro-9-phenanthrenol (6e). To lithium aluminum hydride (0.16 g,
4.2 mmol) in THF (2 mL) was added monoester 11a (0.51 g, 0.848
mmol) in THF (4 mL) dropwise at 0 °C in 30 min. Then this
reaction mixture was stirred for 19 h at 60 °C. Thereafter, water
(0.16 mL), 15% aqueous NaOH (0.16 mL), and once again water
(0.48 mL) were added in this order.54 Then ether (5 mL) was added,
and the precipitate was filtered and washed with ether (5 mL). To
the ether phase was added water (2 mL), and the pH of the mixture
was adjusted to about 6 by HCl (1 M) at 0 °C. Subsequently, the
ether phase was separated and the water phase was extracted with
ether (2 × 10 mL). The organic phases were collected, and after
evaporation the crude product was purified by chromatography
(pentane/EtOAc, 20:1) affording 90% yield with 99.5% ee. The
1H NMR and 13C NMR data are in accordance with the above-
described values obtained for racemic biphenanthrol (6e and 6f).
[R]D ) +68° (c ) 0.16, THF). HPLC (OD-H, hexane/i-PrOH 65:
35, flow rate 0.8 mL/min) minor enantiomer tR ) 12.24 min, major
enantiomer tR ) 15.60 min.
Synthesis of Racemic 10-(10-Hydroxy-1,4-dihydro-9-phenan-
threnyl)-5,8-dihydro-9-phenanthrenol (6e and 6f). A slightly
modified procedure by Hashimoto and co-workers43 was applied.
In an open beaker (300 mL), freshly purified 5,8-dihydro-9-
phenanthrenol 9 (0.32 g, 1.65 mmol) was dissolved in CH2Cl2 (11
mL). To this solution CuCl(OH)‚TMEDA (0.0038 g, 0.0165 mmol)
was added and this reaction mixture was stirred for 10 min.
Thereafter, another portion of CuCl(OH)‚TMEDA (0.0038 g, 0.0165
mmol) was added and the stirring was continued for a further 50
min. Then the reaction mixture was filtered through a thin pad of
silica, which was washed with CH2Cl2. The solvent was removed
and the crude product was purified by column chromatography with
pentane/EtOAc 10:1 as eluent to obtain a racemic mixture of 6e
(-)-10-(10-Hydroxy-1,4-dihydro-9-phenanthrenyl)-5,8-dihy-
dro-9-phenanthrenol (6f). The above procedure with monoester
1
11b afforded 6f in 90% yield with 99.5% ee. The H NMR and
13C NMR data are in accordance with the above-described values
obtained for racemic biphenanthrol (6e and 6f). [R]D ) -68° (c )
0.16, THF).42 HPLC (OD-H, hexane/i-PrOH 65:35, flow rate 0.8
mL/min) major enantiomer tR ) 12.24 min, minor enantiomer tR
) 15.60 min.
1
and 6f in 88% yield. H NMR (400 MHz, CDCl3) δ 8.82 (d, J )
8.5 Hz, 2H), 8.76 (d, J ) 8.5 Hz, 2H), 8.48 (d, J ) 8.5 Hz, 2H),
7.83 (t, J ) 7.6 Hz, 2H), 7.74 (t, J ) 7.6 Hz, 2H), 7.55 (t, J ) 7.6
Hz, 2H), 7.37 (t, J ) 7.6 Hz, 2H), 7.28 (d, J ) 8.5 Hz, 2H), 5.58
(s, 2H). 13C NMR (100.5 MHz, CDCl3) δ 149.4, 132, 131.7, 128.2,
127.7, 127.1, 126.9, 125.1, 124.9, 124.8, 123.5, 122.9, 122.7, 107.1.
HRMS m/z 387.1373 (calcd [M + H]+ for C28H19O2 387.1380).
General Procedure for Synthesis of BINOL-Based Complexes
1a-f. The corresponding BINOL derivative (6a-f) (0.528 mmol,
azeotropically dried with toluene) was stirred in freshly distilled
PCl3 (1.11 mL, 12.7 mmol) at 20 °C for 18 h. Then the excess
PCl3 was distilled under atmospheric pressure, and even traces of
PCl3 were removed by coevaporation with 2 × 3 mL toluene,
affording a yellow oil of 7a-f. The crude oil was dissolved in
toluene (5.0 mL), and then this solution was added to a mixture of
iodoresorcinol (0.062 g, 0.264 mmol) and DMAP (0.008 mg, 0.066
mmol) in toluene (1.0 mL). Subsequently, NEt3 (0.073 mL, 0.528
mmol) was added dropwise to this solution and the reaction mixture
was stirred for 22 h at 20 °C. Thereafter, the obtained suspension
was filtered through a thin pad of Celite, washed with toluene
(70 mL) and concentrated to give proligand 8a-f. Thereafter, 8a-f
was dissolved in toluene (5.0 mL) and this solution was added to
Pd2(dba)3 (0.088 g, 0.096 mmol) in toluene (1.0 mL). This reaction
mixture was stirred for 4 h at 20 °C. The crude reaction mixture
was thereafter subjected to silica gel chromatography with CH2-
Cl2/pentane 2:1 as eluent, affording the corresponding pincer
complex as a yellow solid.
Synthesis of Mono[(1S)-camphor-10-sulfonates] of 10-(10-
Hydroxy-1,4-dihydro-9-phenanthrenyl)-5,8-dihydro-9-phenan-
threnol (11a and 11b). Racemic biphenanthrol (6e and 6f) (0.145
g, 0.38 mmol), (1S)-(+)-10-camphorsulfonyl chloride 10 (0.116 g,
0.46 mmol), and DMAP (0.007 g, 0.057 mmol) were dissolved in
CH2Cl2 (6 mL). Then freshly distilled triethylamine (0.006 mL,
0.42 mmol) was added dropwise at 0 °C in 10 min. The
resultingsolution was stirred first at 0 °C for 1 h and then at rt for
14 h. Thereafter, another portion of (1S)-(+)-10-camphorsulfonyl
chloride (0.050 g, 0.2 mmol) in CH2Cl2 (1 mL) was added and the
stirring continued for an additional hour. Subsequently, water (2
mL) was added and the aqueous layer was extracted with CH2Cl2
(3 × 2 mL) and the collected organic layers were washed with
water (2 × 5 mL). The CH2Cl2 solution was dried and evaporated
and the residue was purified by column chromatography with pure
CH2Cl2 to separate the diastereomeric mixture, yielding 43% yield
of each diastereomer 11a and 11b. Spectral data for 11a: 1H NMR
(400 MHz, CDCl3) δ 8.82 (m, 3H), 8.73 (d, J ) 8 Hz, 1H), 8.6 (d,
J ) 8 Hz, 1H), 8.55 (d, J ) 8 Hz, 1H), 7.82 (m, 3H), 7.71 (m,
2H), 7.53 (m, 2H), 7.42 (t, J ) 8 Hz, 1H), 7.36 (t, J ) 8 Hz, 1H),
7.26 (d, J ) 8 Hz, 1H), 5.81 (s, 1H), 2.72 (d, J ) 14.9 Hz, 1H),
2.14 (m, 2H), 1.75 (m, 4H), 1.4 (m, 1H), 1.18 (m, 1H), 0.36
(s, 3H), 0.15 (s, 3H). 13C NMR (100.5 MHz, CDCl3) δ 212.8, 148.3,
145.4, 132.1, 131.6, 130.9, 129.9, 128.4, 128, 127.9, 127.8, 127.6,
Synthesis of Complexes 1a and 1b. These complexes were
prepared from 6a or 6b by the above general procedure, yield-
ing 0.169 g (76%) of 1a or 1b. Spectral data for 1a: 1H NMR
(400 MHz, CDCl3) δ 7.89 (d, J ) 8.0 Hz, 2H), 7.79 (d, J ) 8.0
Hz, 2H), 7.75 (s, 2H), 7.61 (s, 2H), 7.47 (t, J ) 7.6 Hz, 2H), 7.41
(54) Micovic, V. M.; Micovic, M. L. J. J. Org. Chem. 1953, 18, 1190.
J. Org. Chem, Vol. 72, No. 13, 2007 4695

Aydin et al.
(t, J ) 7.6 Hz, 2H), 7.15-7.34 (m, 9H), 6.83 (d, J ) 8.0 Hz, 2H),
2.62 (s, 6H), 2.50 (s, 6H). 13C NMR (100.5 MHz, CDCl3) δ 156.7,
156.5, 145.0, 144.97, 143.6, 133.1, 132.7, 132.3, 132.0, 131.7,
129.91, 129.85, 127.4, 127.22, 127.16, 126.9, 126.3, 126.2, 126.1,
125.6, 125.4, 125.1, 122.5, 122.4, 108.2, 108.1, 15.07, 14.99. 31P
NMR (121.4 MHz, CDCl3) δ 150.2. MALDI-TOF MS for 1a:
(M+ - I-) 1028.043, C50H35O6P2PdS4. Optical rotation data for
1a: [R]D ) -544° (c ) 0.67, CHCl3). Spectral data for 1b: 1H
NMR (400 MHz, CDCl3) δ 7.89 (d, J ) 8.0 Hz, 2H), 7.79 (d, J )
8.0 Hz, 2H), 7.76 (s, 2H), 7.60 (s, 2H), 7.48 (t, J ) 7.6 Hz, 2H),
7.42 (t, J ) 7.6 Hz, 2H), 7.17-7.34 (m, 9H), 6.82 (d, J ) 8.0 Hz,
2H), 2.63 (s, 6H), 2.50 (s, 6H). 13C NMR (100.5 MHz, CDCl3) δ
156.6, 156.5, 156.4, 145.0, 143.6, 133.1, 132.7, 132.3, 132.0, 131.7,
129.91, 129.85, 127.4, 127.22, 127.16, 126.9, 126.3, 126.2, 126.1,
125.6, 125.4, 125.1, 122.5, 122.4, 108.2, 108.1, 108.0, 15.07, 14.99.
31P NMR (161.9 MHz, CDCl3) δ 150.2. MALDI-TOF MS for 1b:
(M+ - I-) 1028.112, C50H35O6P2PdS4. Optical rotation data for
1b: [R]D ) +542° (c ) 0.59, CHCl3).
mmol) or potassium trifluoroallylborate 3 (0.0296 g, 0.20 mmol)
was added to a mixture of sulfonimine 4a-e (0.10 mmol) and the
corresponding catalyst 1a-f (0.005 mmol, 5.0 mol %) in 1.0 mL
of solvent. The reaction mixture was then stirred for the allotted
times and temperatures (Table 1). The crude product was purified
by silica gel chromatography (pentane/ethyl acetate 9:2) affording
the corresponding homoallylic amine 5a-g. The enantiomeric
excess was determined by chiral-phase HPLC (Daicel Chiracel
OD-H and AD-H columns).
N1-(1-Phenyl-3-butenyl)-1-benzenesulfonamide (5a). 1H NMR
(400 MHz, CDCl3) δ 7.66 (d, J ) 7.7 Hz, 2H), 7.45 (t, J ) 7.7
Hz, 1H), 7.33 (t, J ) 7.7 Hz, 2H), 7.15 (m, 3H), 7.06 (m, 2H) 5.52
(m, 1H), 5.06 (br d, J ) 12.9 Hz, 3H), 4.42 (q, J ) 6.9 Hz, 1H),
2.47 (br s, 2H). 13C NMR (100.5 MHz, CDCl3) δ 140.4, 140.1,
133.0, 132.3, 128.7, 128.4, 127.4, 127.1, 126.5, 119.3, 57.2, 41.9.
HRMS m/z 310.0875 (calcd [M + Na]+ for C16H17NaNO2S
310.0872). [R]D ) +47° (c ) 0.27, CHCl3) corresponding to 73%
ee. The enantiomeric excess of 5a was determined by chiral-phase
HPLC (Daicel Chiracel OD-H, hexane/iPrOH 95:5, flow rate 1.0
mL/min): major enantiomer tr ) 13.1 min, minor enantiomer tr )
18.0 min.
N1-(1-Phenyl-3-butenyl)-1-benzenesulfonamide (5b). The above
general procedure was employed except that 2 was added slowly
(in 24 h) to the reaction mixture, when 1f was employed as catalyst
(Table 1, entries 13 and 14). The NMR and HRMS data are identical
to those for 5a. [R]D ) -52° (c ) 0.21, CHCl3) corresponding to
83% ee. The enantiomeric excess of 5b was determined by chiral-
phase HPLC (Daicel Chiracel OD-H, hexane/iPrOH 95:5, flow rate
1.0 mL/min): minor enantiomer tr ) 13.1 min, major enantiomer
tr ) 18.0 min.
Synthesis of Complex 1c. This complex was prepared from 6c
1
by the above general procedure, yielding 63 mg (27%) of 1c. H
NMR (300 MHz, CDCl3) δ 7.84-7.93 (m, 4H), 7.79 (d, J ) 8.0
Hz, 2H), 7.72 (s, 2H), 7.37-7.54 (m, 4H), 7.14-7.36 (m, 9H),
6.81 (d, J ) 8.0 Hz, 2H), 2.93-3.24 (m, 8H), 1.42 (t, J ) 7.3 Hz,
6H), 1.34 (t, J ) 7.3 Hz, 6H). 13C NMR (75.4 MHz, CDCl3) δ
156.9 156.7, 145.7, 144.0, 132.3, 132.2, 131.9, 130.5, 130.3, 130.0,
129.9, 128.1, 127.8, 127.6, 127.3, 127.0, 126.3, 126.1, 125.9, 125.5,
122.9, 122.8, 108.0, 26.7, 26.5, 13.9, 13.5. 31P NMR (121.4 MHz,
CDCl3) δ 150.6. MALDI-TOF MS for 1c: (M+ - I-) 1084.059,
C54H43O6P2PdS4. Optical rotation data for 1c: [R]D ) -517° (c )
0.87, CHCl3).
Synthesis of Complex 1d. This complex was prepared from 6d
by the above general procedure, yielding 0.167 g (62%) of 1d. 1H
NMR (400 MHz, CDCl3) δ 7.69 (d, J ) 8.3 Hz, 4H), 7.58-7.64
(m, 8H), 7.52 (br d, J ) 7.0 Hz, 4H), 7.29-7.45 (m, 15H), 7.15-
7.25 (m, 10H), 6.76 (d, J ) 8.0 Hz, 2H). 13C NMR (100.5 MHz,
CDCl3) δ 156.6, 156.4, 156.3, 145.3, 144.3, 133.8, 133.6, 132.6,
132.22, 132.16, 131.9, 131.5, 131.1, 131.0, 130.7, 130.6, 130.1,
130.0, 129.6, 129.2, 128.4, 128.1, 127.9, 127.6, 127.2, 127.1, 126.2,
126.1, 123.1, 122.9, 108.2, 108.1, 108.0. 31P NMR (161.9 MHz,
CDCl3) δ 151.0. MALDI-TOF MS for 1d: (M+ - I-) 1276.042,
C70H43O6P2PdS4. Optical rotation data for 1d: [R]D ) -342° (c )
1.08, CHCl3).
N1-[1-(1,3-Benzodioxol-5-yl)-3-butenyl]-4-methyl-1-benzene-
sulfonamide (5c). 1H NMR (400 MHz, CDCl3) δ 7.56 (d, J ) 8.1
Hz, 2H), 7.16 (d, J ) 8.1 Hz, 2H), 6.56 (m, 3H), 5.87 (dd, J ) 1.3
and 9.5 Hz, 2H), 5.51 (m, 1H) 5.03 (m, 3H), 4.27 (q, J ) 6.7 Hz,
1H), 2.43 (m, 5H). 13C NMR (100.5 MHz, CDCl3) δ 147.6, 146.8,
143.0, 137.5, 134.3, 133.1, 129.2, 127.2, 120.2, 119.2, 107.9, 106.9,
101.0, 57.0, 41.8, 21.4. HRMS m/z 386.0928 (calcd [M + Na]+
for C18H19NaNO4S 368.0927). [R]D ) +29° (c ) 0.16, CHCl3)
corresponding to 48% ee. The enantiomeric excess of 5c was
determined by chiral-phase HPLC (Daicel Chiracel OD-H, hexane/
iPrOH 95:5, flow rate 1.0 mL/min): major enantiomer tr ) 24.1
min, minor enantiomer tr ) 31.7 min.
N1-1-[(E)-2-Phenyl-1-ethenyl]-3-butenyl-4-methyl-1-benzene-
sulfonamide (5d). 1H NMR (400 MHz, CDCl3) δ 7.73 (d, J ) 8.0
Hz, 2H), 7.24 (m, 5H), 7.14 (d, J ) 8.0 Hz, 2H), 6.3 (d, J ) 15.9
Hz, 1H), 5.81 (dd, J ) 7.0 Hz, 1H), 5.65 (m, 1H), 5.1 (m, 2H),
4.62 (d, J ) 7.2 Hz, 1H), 4.04 (m, 1H), 2.33 (br s, 5 H). 13C NMR
(100.5 MHz, CDCl3) δ 143.3, 138.0, 136.2, 132.7, 131.6, 129.5,
128.4, 128.3, 127.7, 127.3, 126.4, 119.5, 55.1, 40.2, 21.4. HRMS
m/z 350.1181 (calcd [M + Na]+ for C19H21NaNO2S 350.1185). [R]D
) -35° (c ) 0.26, CHCl3) corresponding to 59% ee. The
enantiomeric excess of 5d was determined by chiral-phase HPLC
(Daicel Chiracel OD-H, hexane/iPrOH 95:5, flow rate 1.0 mL/
min): major enantiomer tr ) 23.9 min, minor enantiomer tr ) 26.5
min.
N1-[1-(3-Nitrophenyl)-3-butenyl]-4-methyl-1-benzenesulfona-
mide (5e). 1H NMR (400 MHz, CDCl3) δ 8.01 (d, J ) 7.9 Hz, 1H),
7.84 (s, 1H), 7.52 (d, J ) 7.8 Hz, 3H), 7.39 (t, J ) 7.9 Hz, 1H),
7.13 (d, J ) 7.1 Hz, 2H), 5.5 (m, 1H), 5.1 (m, 3H), 4.49 (q, J )
6.3 Hz, 1H), 2.44 (t, J ) 7 Hz, 2H), 2.35 (s, 3H). 13C NMR (100.5
MHz, CDCl3) δ 148.1, 143.7, 142.6, 137.0, 133.0, 131.9, 129.5,
129.3, 127.1, 122.4, 121.7, 120.6, 56.3, 41.7, 21.4. HRMS m/z
369.0871 (calcd [M + Na]+ for C17H18NaN2O4S 369.0879). [R]D
) -67° (c ) 1.15, CHCl3) corresponding to 66% ee. The enantio-
meric excess of 5e was determined by chiral-phase HPLC (Daicel
Chiracel AD-H, hexane/iPrOH 95:5, flow rate 1.2 mL/min): minor
enantiomer tr ) 28.7 min, major enantiomer tr ) 33.5 min.
N1-[1-(3-Nitrophenyl)-3-butenyl]-4-methyl-1-benzenesulfona-
mide (5f). The above general procedure was employed except that
Synthesis of Complexes 1e and 1f. These complexes were
prepared from 6e or 6f by the above general procedure except that
the first (6e,f f 7e,f) and the second (7e,f f 8e,f) steps were run
for 24 and 48 h, respectively, at 35 °C, yielding 60% 1e or 1f.
These complexes were purified by using CH2Cl2/pentane (1:1) as
eluent. Spectral data for 1e: 1H NMR (300 MHz, CDCl3) δ 8.82
(m, 4H), 8.69 (m, 4H), 8.44 (m, 2H), 8.26 (d, J ) 8.2 Hz, 2H),
7.82 (t, J ) 7.5 Hz, 2H), 7.65 (m, 10H), 7.34 (m, 9H), 6.66 (d, J
) 7.9 Hz, 2H). 13C NMR (75.4 MHz, CDCl3) δ 156.4, 156.3, 156.1,
144.6, 144.3, 131.9, 131.7, 130.65, 130.5, 129.3, 129.1, 128.3,
127.5, 127.4, 126.8, 126.7, 126.5, 126.2, 124.1, 123.1, 123.04,
123.0, 122.7, 122.5, 120.8, 119.95, 108.4, 108.3, 108.2. 31P NMR
(121.4 MHz, CDCl3) δ 153.3. MALDI-TOF MS for 1e: (M+
-
I-) 1043.194, C62H35O6P2Pd. Optical rotation data for 1e: [R]D )
+586° (c ) 0.91, CHCl3). Spectral data for 1f: 1H NMR (400
MHz, CDCl3) δ 8.82 (m, 4H), 8.69 (m, 4H), 8.44 (m, 2H), 8.26
(d, J ) 8.2 Hz, 2H), 7.82 (t, J ) 7.5 Hz, 2H), 7.66 (m, 8H), 7.58
(t, J ) 7.5 Hz, 2H), 7.45 (d, J ) 8.2 Hz, 2H), 7.41 (d, J ) 8.2 Hz,
2H), 7.28 (m, 5H), 6.66 (d, J ) 7.9 Hz, 2H). 13C NMR (100.5
MHz, CDCl3) δ 156.4, 156.3, 156.2, 144.6, 144.3, 131.9, 131.7,
130.7, 130.5, 129.3, 129.1, 128.3, 127.5, 127.4, 126.8, 126.7, 126.5,
126.2, 124.1, 123.1, 123.04, 123.0, 122.7, 122.5, 120.8, 119.9,
108.4, 108.3, 108.2. 31P NMR (161.9 MHz, CDCl3) δ 153.4.
MALDI-TOF MS for 1f: (M+ - I-) 1043.333, C62H35O6P2Pd.
Optical rotation data for 1f: [R]D ) -588° (c ) 0.55, CHCl3).
General Procedure for Palladium Pincer Complex-Catalyzed
Allylation of Imines 4a-e. Tributylallylstannane 2 (0.062 mL, 0.20
4696 J. Org. Chem., Vol. 72, No. 13, 2007

BINOL- and Biphenanthrol-Based Pincer Complexes
2 was added slowly (in 24 h) to the reaction mixture, when 1e was
employed as catalyst (Table 1, entry 11). The NMR and HRMS
data are identical to those for 5e. [R]D ) +97° (c ) 0.67, CHCl3)
corresponding to 85% ee. The enantiomeric excess of 5f was
determined by chiral-phase HPLC (Daicel Chiracel AD-H, hexane/
iPrOH 95:5, flow rate 1.2 mL/min): major enantiomer tr ) 29.1
min, minor enantiomer tr ) 34.2 min.
Cl2 (3 × 10 mL) and the organic layer was dried over MgSO4 and
concentrated, followed by purification by silica-gel chromatography
(CH2Cl2/MeOH 4:2), affording 0.026 g (65%) of 12 with 66% ee.
The ee was determined by chiral-phase HPLC (Daicel Chiracel OD-
H, hexane/iPrOH 95:5 with 0.1% ethanolamine as additive in
iPrOH, flow rate 0.4 mL/min): R enantiomer tr ) 16.2 min, S
enantiomer tr ) 20.4 min. The absolute configuration of 12 was
assigned on the basis of literature data44,45 available for (1R)-1-
phenyl-3-butenylamine. [R]D ) +29° (c ) 0.99, CHCl3) corre-
N1-[1-(3-Nitrophenyl)-3-butenyl]-1-benzenesulfonamide (5g).
The above general procedure was employed except that 2 was added
slowly (in 24 h) to the reaction mixture, when 1e was employed as
1
sponding to 66% ee. H NMR (300 MHz, CDCl3) δ 7.3 (m, 5H),
1
catalyst (Table 1, entry 12). H NMR (400 MHz, CDCl3) δ 8.01
5.75 (m, 1H), 5.11 (m, 2H), 4.0 (m, 1H), 2.42 (m, 2H) 2.08 (br s,
2H). 13C NMR (75.4 MHz, CDCl3) δ 145.4, 135.2, 128.4, 127.0,
126.3, 117.7, 55.3, 43.9. HRMS m/z 148.1122 (calcd [M + H]+
for C10H14N 148.1121).
(d, J ) 8.1 Hz, 1H), 7.88 (s, 1H), 7.66 (d, J ) 8.1 Hz, 2H), 7.43
(m, 5H), 5.49 (m, 1H) 5.12 (m, 3H), 4.52 (q, J ) 6.7 Hz, 1H),
2.45 (t, J ) 6.7 Hz, 2H). 13C NMR (100.5 MHz, CDCl3) δ 148.1,
142.5, 140.0, 132.9, 132.7, 131.9, 129.4, 128.9, 127.0, 122.5, 121.6,
120.6, 56.4, 41.7. HRMS m/z 355.0721 (calcd [M + Na]+ for
C16H16NaN2O4S 355.0723). [R]D ) +88° (c ) 0.85, CHCl3)
corresponding to 82% ee. The enantiomeric excess of 5g was
determined by chiral-phase HPLC (Daicel Chiracel AD-H, hexane/
iPrOH 95:5, flow rate 1.2 mL/min): major enantiomer tr ) 32.3
min, minor enantiomer tr ) 35.8 min.
Acknowledgment. This work was mainly supported by the
Swedish Natural Science Research Council (VR). A postdoctoral
fellowship for K.S.K. by the Wennergren Foundations is greatly
acknowledged. We are indebted to the Alice and Knut Wal-
lenberg Foundation for funding a UPLC instrument.
(1R)-1-Phenyl-3-butenylamine (12). Ammonia (5 mL) was
condensed into a flask containing sodium (0.052 g, 2.28 mmol) at
-78 °C. Subsequently, 5a (0.077 g, 0.268 mmol, 67% ee) in THF
(1.3 mL) was added, and the reaction mixture was stirred for 75
min. Thereafter, water was added in small portions until the gas
evolution ceased. The crude mixture was then extracted with CH2-
Supporting Information Available: 1H/13C NMR spectra of
the prepared homoallyl amines as well as the NMR spectra (1H,
13C, and 31P) for chiral pincer complexes 1a-f. This material is
available free of charge via the Internet at http://pubs.acs.org.
JO070288B
J. Org. Chem, Vol. 72, No. 13, 2007 4697