Asymmetric synthesis of helical poly(quinoxaline-2,3-diyl)s by palladium-mediated polymerization of 1,2-diisocyanobenzenes: Effective control of the screw-sense by a binaphthyl group at the chain-end

Article abstract of DOI:10.1021/ja982500m

Aromatizing polymerization of 1,2-diisocyanobenzene derivatives was mediated by optically active organopalladium(II) complexes bearing 1,1'- binaphth-2-yl groups to give optically active poly(quinoxaline-2,3-diyl)s with varying screw-sense selectivities, which crucially depended upon the substituents on the binaphthyl groups. The most effective catalyst, which has 7'-methoxy-1,1'-binaphthyl group, induced the formation of a single screw- sense. Isolation and structural analyses (single-crystal X-ray diffraction and ¹H NMR spectroscopy) of intermediary [oligo(quinoxalinyl)]palladium complexes revealed that the screw-sense selection in the polymerization may be decisively governed by the diastereomeric ratios of the (terquinoxalinyl)palladium(II) complex intermediate.

Full text of DOI:10.1021/ja982500m

11880
J. Am. Chem. Soc. 1998, 120, 11880-11893
Asymmetric Synthesis of Helical Poly(quinoxaline-2,3-diyl)s by
Palladium-Mediated Polymerization of 1,2-Diisocyanobenzenes:
Effective Control of the Screw-Sense by a Binaphthyl Group at the
Chain-End
Yoshihiko Ito,* Toshiyuki Miyake, Seiji Hatano, Ryoto Shima, Takafumi Ohara, and
Michinori Suginome
Contribution from the Department of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto UniVersity, Kyoto 606-8501, Japan
ReceiVed July 15, 1998
Abstract: Aromatizing polymerization of 1,2-diisocyanobenzene derivatives was mediated by optically active
organopalladium(II) complexes bearing 1,1′-binaphth-2-yl groups to give optically active poly(quinoxaline-
2,3-diyl)s with varying screw-sense selectivities, which crucially depended upon the substituents on the
binaphthyl groups. The most effective catalyst, which has 7′-methoxy-1,1′-binaphthyl group, induced the
1
formation of a single screw-sense. Isolation and structural analyses (single-crystal X-ray diffraction and H
NMR spectroscopy) of intermediary [oligo(quinoxalinyl)]palladium complexes revealed that the screw-sense
selection in the polymerization may be decisively governed by the diastereomeric ratios of the (terquinoxalinyl)-
palladium(II) complex intermediate.
Introduction
polymer main-chains effectively, are highly desired for develop-
ment of new methodology for the synthesis of optically active
helical polymers.
Much interest has been focused on the synthesis of optically
active polymers directing toward development of new functional
materials.1 In addition to the asymmetric polymerization of
prochiral olefinic monomers,2,3 isocyanates and isocyanide,
which are devoid of prochirality, can also produce optically
active polymers with helical chirality of their backbones.1,4-6
Unlike the stereochemical control for the asymmetric polym-
erization of the prochiral monomers, the screw-sense generated
at the early stage of the polymerization was transmitted to the
propagating polymer main chains throughout the polymerization.
Thus, generation of helically well-ordered polymers with stable
screw-sense, which is able to be transmitted to newly formed
We reported an aromatizing polymerization of 1,2-diisocy-
anobenzenes promoted by methylpalladium(II) complexes,
producing poly(quinoxaline-2,3-diyl)s.7 The polymerization
proceeds with successive insertion of the two isocyano groups
of the diisocyanobenzene to the carbon-palladium bond of
organopalladium complex to give 2-quinoxalinylpalladium
complexes, whose carbon-palladium bond undergoes further
successive insertion of the diisocyanobenzenes to provide the
quinoxaline polymers. The poly(quinoxaline)s thus produced
feature their rigid helical structures, which arise from a sequence
of quinoxaline rings with regular dihedral angles between the
two adjacent rings.
(1) Okamoto, Y.; Nakano, T. Chem. ReV. 1994, 94, 349-372. Pu, L.
Acta Polym. 1997, 48, 116-141.
(2) For asymmetric cyclopolymerization of 1,5-hexadiene mediated by
optically active Zr complexes, see: Coates, G. W.; Waymouth, R. M. J.
Am. Chem. Soc. 1991, 113, 6270-6271. Coates, G. W.; Waymouth, R. M.
J. Am. Chem. Soc. 1993, 115, 91-98.
(3) For asymmetric synthesis of poly(olefin-alt-CO) mediated by optically
active palladium complexes, see: Brookhart, M.; Wagner, M. L. J. Am.
Chem. Soc. 1994, 116, 3641. Sen, A. Acc. Chem. Res. 1993, 26, 303. Nozaki,
K.; Sato, N.; Takaya, H. J. Am. Chem. Soc. 1995, 117, 9911. Jiang, Z.;
Sen, A. J. Am. Chem. Soc. 1995, 117, 4455.
(4) For screw-sense selective polymerization of isonitriles mediated by
optically active transition-metal catalysts, see: Kamer, P. C. J.; Nolte, R.
J. M.; Drenth, W. J. Am. Chem. Soc. 1988, 110, 6818-6825. Deming, T.
J.; Novak, B. M. J. Am. Chem. Soc. 1992, 114, 7926-7927. Deming, T. J.;
Novak, B. M. J. Am. Chem. Soc. 1993, 115, 9101-9111. Takei, F.; Yanai,
K.; Onitsuka, K.; Takahashi, S. Angew. Chem., Int. Ed. Engl. 1996, 35,
1554-1556.
(5) For optically active poly(isonitrile)s, see also: Nolte, R. J. M.; van
Beijnen, A. J. M.; Drenth, W. J. Am. Chem. Soc. 1974, 96, 5932-5933.
Deming, T. J.; Novak, B. M. J. Am. Chem. Soc. 1992, 114, 4400-4402.
(6) For optically active poly(isocyanate)s, see: Goodman, M.; Chen, S.-
C. Macromolecules 1970, 3, 398-402. Green, M. M.; Peterson, N. C.; Sato,
T.; Teramoto, A.; Cook, R.; Lifson, S. Science 1995, 268, 1860-1866.
Okamoto, Y.; Matsuda, M.; Nakano, T.; Yashima, E. Polym. J. 1993, 25,
391-396.
The first attempt for the synthesis of optically active, helical
poly(quinoxaline)s started with separation and isolation of two
diastereomerically pure bromo[oligo(quinoxalinyl)]palladium-
(II)-L* (L* ) di((S)-2-methylbutyl)phenylphosphine) com-
2
plexes, which were produced by the oligomerization of 3,6-di-
p-tolyl-1,2-diisocyanobenzene with optically active trans-
(bromo)methylpalladium(II)-L* .8 Right- and left-handed
2
bromo(quinquequinoxalinyl)palladium(II)-L*2 thus prepared were
subjected to ligand exchange reaction with a large excess of
(7) (a) Ito, Y.; Ihara, E.; Murakami, M.; Shiro, M. J. Am. Chem. Soc.
1990, 112, 6446-6447. (b) Ito, Y.; Ihara, E.; Uesaka, T.; Murakami, M.
Macromolecules 1992, 25, 6711-6713. (c) Ito, Y.; Ihara, E.; Murakami,
M. Polym. J. 1992, 24, 297.
(8) (a) Ito, Y.; Ihara, E.; Murakami, M. Angew. Chem., Int. Ed. Engl.
1992, 31, 1509-1510. (b) Ito, Y.; Ihara, E.; Murakami, M.; Sisido, M.
Macromolecules 1992, 25, 6810-6813. (c) Ito, Y.; Kojima, Y.; Murakami,
M. Tetrahedron Lett. 1993, 51, 8279-8282. (d) Ito, Y.; Kojima, Y.;
Murakami, M.; Suginome, M. Heterocycles 1996, 42, 597-615. (e) Ito,
Y.; Kojima, Y.; Murakami, M.; Suginome, M. Bull. Chem. Soc. Jpn. 1997,
70, 2801-2806.
10.1021/ja982500m CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/05/1998

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11881
Scheme 1a
a Reagents and conditions: (a) (i) ClCO2Me, Et3N, acetone, -15 °C; (ii) aq, NaN3 -15 °C; (iii) benzene 80 °C; (iv) aq KOH, 80 °C; (b) (i)
NaNO2, H2SO4, 0 °C; (ii) KI, H2SO4, 0 °C; (c) BBr3, CH2Cl2, -78 °C; (d) t-BuMe2SiCl, imidazole, DMF, rt.
achiral dimethylphenylphosphine. The enantiomerically pure
right- and left-handed bromo(quinquequinoxalinyl)palladium-
(II) bis(dimethylphenylphosphine) complexes isolated were used
as a catalyst for polymerization of 1,2-diisocyanobenzenes,
providing right- and left-handed helical poly(quinoxaline-2,3-
diyl)s after removal of the palladium moiety with methylmag-
nesium bromide, which exhibited symmetrical CD spectra and
the same optical rotations with opposite sign.8a
were conveniently prepared by the latter method, i.e., reaction
of binaphthyl halides with palladium(0)-phosphine complexes,
since the oxidative addition of the carbon-halogen bond onto
palladium was expected to proceed with retention of configu-
ration of the starting optically active binaphthyl halides.
Optically pure 2-iodo-1,1′-binaphthyls 1a-d were synthesized
according to the Miyano’s procedure, which involves stereo-
selective nucleophilic aromatic substitution reaction of (1R)-
menthyl 1-((1R)-menthoxy)naphthalene-2-carboxylate with the
corresponding 1-naphthyl Grignard reagents, giving binaphtha-
lenecarboxylic esters (Scheme 1).11 In contrast to the highly
diastereoselective coupling with 2-methoxy-1-naphthylmagne-
sium bromide, giving the corresponding binaphthylcarboxylic
acid with (S)-axial configuration, those with 1-naphthyl and
7-methoxy-1-naphthyl Grignard reagents gave 88:12 and 94:6
mixtures of the corresponding diastereomers, respectively, with
the (S)-axial chirality predominating. For the synthesis of 1b,
binaphthalenecarboxylic acid obtained by hydrolysis of the
diastereomeric mixture was purified by recrystallization of its
quinine salt to give the corresponding enantiomerically pure
acid. For the 7′-methoxy-1,1′-binaphthalene-2-carboxylate de-
rivative, recrystallization of the diastereomeric mixture of the
menthyl ester from ether-methanol gave diastereomerically pure
ester, which was used for the synthesis of (S)-1d. The
corresponding (R)-1d was similarly synthesized from the
enantioisomeric (1S)-menthyl 1-((1S)-menthoxy)naphthalene-
2-carboxylate. The TBDMS derivative (S)-1c was synthesized
from (S)-1a by demethylation with BBr3 followed by treatment
with TBDMSCl in the presence of base. Though it was difficult
to separate iodides 1a-d from the accompanying protiodeio-
dinated compounds, which were formed as byproducts in the
Sandmeyer reaction, the crude iodides were used for the
The screw-sense selective polymerization, however, involves
a tedious operation for the optical resolution, which is not
applicable for gram-scale synthesis of optically active poly-
(quinoxaline)s. Besides, the optically active, helical poly-
(quinoxaline)s derived from the (bromo)methylpalladium com-
plexes underwent slow racemization in solution. In this paper,
we describe the asymmetric polymerization of 1,2-diisocy-
anobenzenes promoted by optically active iodo(1,1′-binaphth-
2-yl)palladium(II) complexes as initiators.9,10 The axial chirality
of the binaphthyl group, which becomes far from the living
palladium terminus with propagation of the polymerization,
successfully induced high screw-sense selectivity to provide
optically pure, helical poly(quinoxaline-2,3-diyl)s. Moreover,
isolation and structural characterization of intermediary [oligo-
(quinoxalinyl)]palladium complexes shed light on mechanism
for induction of helical chirality of the poly(quinoxaline)s.
Result and Discussion
Synthesis of Optically Active Palladium(II) Initiators
Bearing 1,1′-Binaphth-2-yl Groups. General preparation of
alkyl- or arylpalladium(II) complexes involves transmetalation
of organometallic species with palladium(II) complexes, or
oxidative addition of organic halides with palladium(0) com-
plexes. The optically active binaphthylpalladium(II) complexes
(11) Hattori, T.; Hotta, H.; Suzuki, T.; Miyano, S. Bull. Chem. Soc. Jpn.
1993, 66, 613-622. They introduced p (plus) and m (minus) notation, which
indicates the direction of the twist of the two naphthalene rings, for
designation of the axial chirality of 1,1′-binaphthyl skeletons without
considering their substituents.
(9) Ito, Y.; Ohara, T.; Shima, R.; Suginome, M. J. Am. Chem. Soc. 1996,
118, 9188-9189.
(10) Ito, Y.; Miyake, T.; Ohara, T.; Suginome, M. Macromolecules 1998,
31, 1697-1699.

11882 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
synthesis of binaphthylpalladium initiators without further
purification.
The substituted binaphthyl iodides (S)-1a, (S)-1c, and (R)-
1d all have p-chirality, while (S)-1b and (S)-1d have m-chirality
(Chart 1).11
The binaphthyl iodides 1a-d were reacted with (PhMe2P)n-
Pd(0), generated in situ from (η5-cyclopentadienyl)(η3-allyl)-
palladium(II) and 3 equiv of PhMe2P at -78 °C,12 to give
bis(dimethylphenylphosphine)(1,1′-binaphth-2-yl)palladium-
(II) iodide derivatives 2a-d (eq 1). The complexes 2a-d were
then reacted with 3,6-di-p-tolyl-1,2-diisocyanobenzene (3) to
afford the corresponding [3-(binaphth-2-yl)quinoxalin-2-yl]-
palladium(II) complexes 4a-d, which are stable and easily
handled as initiators for the polymerization of 1,2-diisocy-
anobenzenes.
The complete retention of the enantiopurity of (S)-1d in the
transformation to (S)-4d was confirmed by a chiral HPLC
analysis of binaphthalenecarboxylic ester (S)-5d, which was
prepared by reaction of (S)-4d with carbon monoxide in the
presence of methanol (eq 2).13 In addition to 4a-d, a
Figure 1. ORTEP drawing of (P)-(S)-7 (30% probability, stereoview).
Chart 1. Binaphthyl Derivatives 1, 2, and 4
(S)-7 was separated and isolated in 31% yield as reddish crystals
by recrystallization from hexane-CH2Cl2 (eq 4). A 400 MHz
[(binaphthyl)quinoxalinyl]palladium(II) complex 4e was also
prepared from (S)-1b and the corresponding diisocyanide 6
according to the similar procedure (eq 3).
Synthesis of Enantiomerically Pure Right-Handed Helical
Polymers via Isolation of (Quinquequinoxalinyl)palladium-
(II) Complex. We were pleased to find that, in the attempted
oligomerization of 5 molar equiv of 3 with (S)-4a, diastereo-
merically pure (quinquequinoxalinyl)palladium(II) complex
1H NMR spectrum of the palladium complex exhibited the
distinct 10 methyl singlets of the tolyl groups and one methyl
singlet of the 2-methoxynaphthyl group. A single-crystal X-ray
analysis of (S)-7 revealed a right-handed helical structure (i.e.,
helical chirality of P), in which the two adjacent quinoxaline
rings Q(1)-Q(2), Q(2)-Q(3), and Q(3)-Q(4) are arranged at
the dihedral angles of approximately +150°, except for those
near the palladium terminus, Q(4)-Q(5), which is deviated to
nearly +170°, probably due to the intramolecular coordination
(12) Bennett, M. A.; Chiraratvatana, C.; Robertson, G. B.; Tooptakong,
U. Organometallics 1988, 7, 1403-1409 and references therein.
(13) The 1H NMR spectrum of (S)-5d at room temperature exhibited
two signals for each two methoxy groups, indicating slow rotation around
the C-C bond between quinoxaline and naphthalene rings. The measure-
ment at 100 °C in toluene-d8 allowed to observe coalesced signals for the
methoxy groups.

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11883
quinque- as well as sexi-quinoxalinylpalladium(II) complexes
isolated by optical resolution, the polymerization of 3 with (P)-
(S)-7 may proceed with retention of its preorganized screw-
sense to give highly pure, right-handed (P) helical poly-
(quinoxaline)s 8 after quenching, which can be regarded as a
standard for determination of the screw-sense selectivity.
Another standard polymer (P)-9, which was synthesized by
the reaction of 35 molar equiv of 6 with (P)-(S)-7 (eq 6), showed
Figure 2. Skeletal structure of (P)-(S)-7 determined by the X-ray
analysis. A side view (left; tolyl groups were omitted) and a top view
(right; binaphthyl, tolyl, phosphine, and iodo groups are omitted).
Selected bond distances (Å) and torsion angles (deg) are follows: Pd-
Cl ) 2.002(16), Pd-I ) 2.733(2), Pd-P ) 2.2214(5), Pd-N ) 2.144-
(11); Cl-C2-C3-C4 ) 147.3(21), C3-C4-C5-C6 ) 151.8(19),
C5-C6-C7-C8 ) 146.1(19), C7-C8-C9-C10 ) 145.2(19), C9-
C10-C11-C12 ) 168.5(21).
a similar CD spectrum characteristic of optically active (P)-
helical poly(quinoxaline)s but significantly different from that
of (P)-8, presumably due to the lack of phenyl chromophore
on each quinoxaline (Figure 4).
Screw-Sense Selective Polymerization of 1,2-Diisocyano-
3,6-di-p-tolylbenzene (3). With the standard CD spectra in
hand, [(substituted binaphthyl)quinoxalinyl]palladium(II) com-
plexes 4a-d were tested as the initiators for screw-sense
selective polymerization of 3 (40 equiv) in THF at room
temperature (Table 1). A catalyst (S)-4a, having a 2′-methoxy
substituent on the binaphthalene, promoted a polymerization of
of the nitrogen atom of Q(4) to the iodo(dimethylphenylphos-
phine)palladium terminus (Figures 1 and 2). The helical
structure once formed was stable with no change of CD
spectrum even on heating in benzene at 80 °C for 24 h.
The stable palladium(II) complex (P)-(S)-7 was still active
and induced the polymerization of 3 (35 equiv) at room
temperature, producing poly(quinoxaline) 8 after quenching the
living palladium terminus by NaBH4 (eq 5). The polymers
showed a remarkably strong CD spectrum between 250 and 370
nm (Figure 3). As previously demonstrated with optically active
Figure 3. CD spectra of (P)-8, (P)-10a-d, and (M)-10d.

11884 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
Figure 4. CD spectra of (P)-9, (P)-11a-d, and (M)-11d.
Table 1. Asymmetric Polymerization of 3 in the Presence of Optically Active 4a-d
3, giving poly(quinoxaline) 10a in 69% yield after quenching
with NaBH4. Though the polymer 10a exhibited a CD spectrum
characteristic of the right-handed optically active helical struc-
ture, the intensity of the CD spectrum indicated that the catalyst
(S)-4a induced screw-sense selectivity of only 20% based on
that of the standard polymer (P)-8 (entry 1; Figure 4). Of note
is that right-handed helical polymer 10b with 84% ee was
obtained in the polymerization of 3 catalyzed by (S)-4b at room
temperature (entry 2). Furthermore, catalyst (S)-4c, which has
a bulky (tert-butyldimethylsilyl)oxy group at the 2′-position,
induced right-handed screw-sense in 63% ee (entry 3). The
highest screw-sense selectivity was attained by using catalyst

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11885
Table 2. Polymerization of 6 in the Presence of Optically Active 4a-da
entry
catalyst (*Bin)
6/4
polymer (yield/%)
Mn/103
Mw/Mn
ee/% (config)
1
2
3
4
5
6
7
8
(S)-4a (2MeOBin)
(S)-4b (HBin)
(S)-4e (HBin)
(S)-4c (2SiOBin)
(S)-4d (7MeOBin)
(R)-4d (7MeOBin)
(S)-4d
40
40
40
40
40
40
60
100
11a (77)
11b (74)
11b′ (72)
11c (76)
11d (79)
11d (78)
11d60 (87)
11d100 (70)
7.3
8.3
10.0
20.0
11.1
8.8
1.48
1.30
1.25
2.43
1.39
1.15
1.33
1.21
<1
79 (P)
79 (P)
75 (P)
>95 (P)
>95 (M)
>95 (P)
>95 (P)
15.1
23.8
(S)-4d
a The group Q in the equation stands for the 5,8-di-p-tolylquinoxaline-2,3-diyl unit derived from 4. b Isolated by preparative GPC (no recycling).
c Determined by CD spectra in comparison with (P)-9 (cf. Figure 5.
(S)- and (R)-4d, which have a 7′-methoxy substituent on the
binaphthyl group (entry 4 and 5). Based on the CD spectrum,
nearly complete screw-sense selectivity for the right-handed
helical (P)-10d as well as for left-handed helical (M)-10d was
observed in the polymerization using (S)-4d and (R)-4d,
respectively (Figure 4). The coincidence of the shape of the
CD spectra for the polymers 10a-d with varying ee may
indicate that each polymer chain adopts pure P- or M-helix
without any other conformation, which may cause the significant
change of the CD shape. Optically active polymers thus
obtained were configurationally stable in solutions, resulting in
no CD spectral change even at 80 °C for at least several days.
It is remarkable that the (S)-catalysts always produce the right-
handed helical polymers (P)-10 regardless of the opposite axial
chirality of the binaphthyl skeletons between 2′-substituted ones
((S)-4a and 4c) and 2′-unsubstituted ones ((S)-4b and 4d). As
may be seen by shadowed circles of different size in Table 1
(small, medium, and large ones), the difference in steric
bulkiness at the both side of the chiral axes through the
binaphthyl groups may determine the screw-sense selectivity
of the polymerization. Thus, 7′-methoxy derivative 4d (entries
4 and 5), which has much different bulkiness in respect to the
axis, i.e., H (small) vs methoxyaryl moiety (large), gave nearly
complete selectivity, while the 2′-methoxy derivative 4a, in
which the bulkiness in respect to the axis is comparable, i.e.,
methoxy (medium) vs aryl moiety (medium), may result in low
selectivity (entry 1). According to this assumption, the moderate
selectivities with catalysts 4b and 4c may be attributed to the
moderate differences in the bulkiness in respect of the chiral
axes, i.e., H (small) vs aryl (medium) in 4b and aryl (medium)
vs tert-butyldimethylsiloxy (large) in 4c.14
Polymerization of 6 proceeded smoothly (18-36 h) at room
temperature in the presence of the optically active catalysts 4a-
d, providing poly(quinoxaline-2,3-diyl)s 11a-d, after quenching
with CH3MgBr/ZnCl2 (Table 2). As was observed in the
polymerization of 3, catalyst (S)-4b produced 11b of P-helix
with high selectivity (79% ee), while (S)-4a resulted in the
formation of racemate 11a (Table 2, entries 1 and 2). Catalyst
(S)-4c also produced 11c with P-helix of 75% ee in 76% yield
(entry 4).14 Furthermore, nearly complete screw-sense selection
was achieved by use of (S)- and (R)-4d having the 7′-methoxy
group to afford P- and M-helical polymers 11d, respectively
(entries 5 and 6). The tolyl groups of the catalysts 4a-d were
not essential to attain high screw-sense selectivity; catalyst (S)-
4e (eq 3) having two methyl groups instead of the two tolyl
groups on the quinoxaline ring promoted the polymerization of
6 with the selectivity identical to that using the corresponding
(S)-4b (entry 3).
Applicability of the present asymmetric polymerization for
the synthesis of higher molecular weight poly(quinoxaline)s was
successfully demonstrated by polymerization with 60 and 100
molar equiv of 6 in the presence of a catalyst (S)-4d at room
temperature (Table 2, entries 7 and 8). Notably, complete
screw-sense selectivity was attained even for the synthesis of
as high poly(quinoxaline)s as the quinoxaline 100mer, whose
CD spectrum is comparable with that of the standard poly-
(quinoxaline) (P)-9.
Optically active poly(quinoxaline-2,3-diyl)s 11 having a
binaphthyl group at the polymer end showed remarkable
stabilities of the helical structure in solutions, while the
corresponding polymers having methyl groups, which were
derived from methylpalladium(II) complex catalyst, underwent
racemization at room temperature.8e Helical polymers 11 were
not racemized even at 80 °C in benzene for 60 h. Presumably,
the binaphthyl group may serve as a “wedge” to prevent rotation
of the bond between the quinoxaline rings near the polymer
end.
Screw-Sense Selective Polymerization of 1,2-Diisocyano-
3,6-dimethylbenzenes Having Alkoxyalkyl Side-Chains at
4,5-Positions. Though the 3,6-di-p-tolyl groups of 3 effectively
stabilize the optically active helical structure of the polymers,
the bulky aromatic groups caused slow polymerization (5 days
for polymerization of 3 with 4d) and low solubility of the
polymers produced. The polymerization of 1,2-diisocyanoben-
zene 6, which has less sterically demanding methyl groups at
the 3,6-positions as well as two propoxymethyl groups at the
4,5-positions, was carried out.
With the chiral binaphthylpalladium(II) catalyst (S)-4b, screw-
sense selective polymerization of 1,2-diisocyanobenzenes 12 and
13, which have benzyloxymethyl and methoxyethoxymethyl
side-chains at the 4,5-positions, respectively, was carried out
(eq 7). The poly(quinoxaline-2,3-diyl)s 14b and 15b thus
obtained showed CD spectra identical to that for (P)-11b,
suggesting that the screw-sense selectivity as well as the helical
(14) The relatively large Mn as well as Mw/Mn value for the polymeri-
zation with 4c may be due to the sterically bulky 2-tert-butyldimethylsilyloxy
group on the binaphthyl initiator, which will probably cause slow initiation
in comparison with the following propagation steps.

11886 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
Table 3. Diastereomeric Ratios of
[Oligo(quinoxalinyl(palladium(II) Complexes 17-20
conformation of the polymers was not affected by the alkoxy-
side chains of the quinoxaline rings.
no. of quinoxaline diastereomeric
entry oligomer
*Bin
unit/n + 1
ratioa (de)
1
2
3
4
5
6
172
173
174
182
192
202
7MeOBin
7MeOBin
7MeOBin
2MeOBin
HBin
3
4
5
3
3
3
>99:1 (>98%)
>99:1 (>98%)
>99:1 (>98%)
52:48 (4%)
89:11 (79%)
84:16 (69%)
2SiOBin
1
a Determined by H NMR spectroscopy.
Chart 2
The Origin of the Screw-Sense Selection. Isolation and
Characterization of Intermediary [Oligo(quinoxalinyl)]pal-
ladium(II) Complexes. The present asymmetric polymerization
of 1,2-diisocyanobenzenes is particularly unique in that only
one chiral group at the polymer end, which departs from the
living palladium terminus on propagation of the polymerization,
is capable of controlling the whole helical structure of the
polymers. As already mentioned above, the preorganized right-
handed helix of the (quinquequinoxalinyl)palladium(II) (P)-(S)-7
having 2′-methoxybinaphthyl group at the initiating terminal
can induce helical structure with the same screw-sense in the
subsequent polymerization of 1,2-diisocyanobenzene, although
the corresponding [mono(quinoxalinyl)]palladium complex (S)-
4a having a 2′-methoxybinaphthyl group failed to give high
selectivity. The findings indicate that in the present screw-sense
selective polymerization, the screw-sense of the helix has been
already fixed at the pentamer stage but not yet determined at
the formation of [mono(quinoxalinyl)]palladium complex. How
and when was the screw-sense selectivity originated in the
asymmetric polymerization? To get insight into the asymmetric
induction, we carried out oligomerization of 16, which have
methoxy groups at the 4- and 5-positions instead of the propoxy
groups in 6, in the presence of catalysts 4a′ and 4d′, which
have trimethylphosphine ligands instead of dimethylphenylphos-
NMR.16 Not only the (terquinoxalinyl)palladium complexes
172, but also 171, catalyzed the polymerization of 6 to give
optically active, right-handed helical polymers corresponding
to (P)-11d as judged by CD spectra.
Unlike the 7′-methoxybinaphthylquinoxaline oligomers 17n,
oligo(quinoxaline)s 18n (n g 2), which were produced with (2′-
methoxybinaphthyl)palladium complex 4a′, were all existing as
mixtures of diastereomers (Chart 2). For example, (terquinox-
alinyl)palladium 182 obtained by preparative GPC in 31% yield
in the oligomerization of 16 catalyzed by 4a′ exhibited two sets
1
of signals corresponding to the two diastereomers (1:1) by H
NMR (Table 3, entry 4). The fact that (biquinoxalinyl)palladium
181 showed a 1H NMR spectrum assignable to a single species
on addition of PMe3 indicates that the diastereoisomerism may
occur with the formation of 182, suggesting that the ratios of
the diastereomers at the stage of 172 and 182 might govern the
screw-sense selectivities of the present asymmetric polymeri-
zation of 6.
1
phine ligands in 4a and 4d for clarity in H NMR analysis.15
Reaction of 2 equiv of 16 with 4d′ (7MeOBin) at room
temperature for 17 h afforded an oligomer mixture 171∼174
along with the recovered 4d′, which were isolated with
preparative GPC (eq 8). Noteworthy is that oligomers 172, 173,
Indeed, 1H NMR spectra revealed that (terquinoxalinyl)-
palladium complexes 192 (HBin) and 202 (2SiOBin), which were
derived by palladium initiators 4b′ and 4c′, respectively, were
existing as mixtures of two diastereomers in ratios of 89:11 and
84:16 (Chart 2; Table 3, entries 5 and 6). The diastereomeric
ratios were nearly consistent with the screw-sense selectivities
of the poly(quinoxaline)s derived from the polymerization of 6
with 4b and 4c (Table 2).
Conformational Analysis of the (Terquinoxalinyl)palla-
dium(II) Complexes in Solution by 1H NMR. The diastereo-
isomerism in the (terquinoxalinyl)palladium complexes, which
may arise from helical conformations of the three consecutive
quinoxalines and axial chirality of the binaphthyl groups, was
examined by conformational analysis of (terquinoxalinyl)-
and 174 thus isolated existed as a single species in solutions as
1
palladium complexes 172 in solution by means of H NMR
1
observed by H NMR spectroscopy (Table 3, entries 1-3).
Though (biquinoxalinyl)palladium complex 171 isolated by GPC
did not give the assignable 1H NMR spectrum, presumably due
to partial loss of the phosphine ligands, addition of Me3P to
the solution allowed observation of a single set of signals in 1H
spectroscopy.
Prior to the analysis, 1H NMR of 172 was assigned with help
of deuterated diisocyanobenzenes 16′ and 16′′ (Chart 3), each
of which has two CD3 groups either on the aromatic ring or on
the ether oxygen atoms instead of the respective CH3 groups in
(15) The difference in the phosphine ligands of 4, i.e., PMe2Ph or PMe3,
had essentially no effect on the polymerization reactions with respect to
the reaction rate, polymer yields, and the screw-sense selectivity.
(16) In contrast to this observation, addition of PMe3 to the solutions of
1
172-4 resulted in no change in their H NMR spectra.

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11887
steric repulsion between the 7′-methoxybinaphthyl moiety and
the methyl group of the second quinoxaline ring (Me3).
Helical conformations of other (terquinoxalinyl)palladium-
1
(II) complexes 182, 192, and 202 were also elucidated by H
NMR analyses of the corresponding labeled derivatives prepared
by the reactions of 4a′, 4b′, and 4c′ with 16′′, respectively. The
deuterium-labeled (terquinoxalinyl)palladium(II) complexes 182,
192, and 202 (CD35,6,9,10) exhibited diastereomeric pairs of signals
at 1.93 ( 0.01 ppm and 1.88 ( 0.01 ppm in varying ratios
(Table 3, entries 4-6), which were assignable to the Me2 groups.
It is reasonably assumed that one of each diastereomeric pair
exhibiting a signal at 1.93 ( 0.01 ppm has a helical conforma-
tion with the relative spatial arrangement of the terminal
naphthyl group as illustrated with 172-i (Figure 5a). Possible
helical conformations of 182, 192, and 202 are presented in Figure
6. It is now understood that both the (S)-HBin (Figure 6b) and
(S)-2SiOBin (Figure 6c) groups induce (P)-helices regardless of
the opposite axial chirality of the two binaphthyl groups. These
findings are in good agreement with the observed screw-sense
selectivities of the polymerization of 6 using palladium initiator
(S)-4b and (S)-4c, both of which provided the (P)- and (M)-
poly(quinoxaline)s in 90:10 and 88:12 ratios, respectively (Table
2).
Figure 5. Possible helical conformation of 172. (a) Right-handed helical
conformation. (b) Left-handed helical conformation (not existing). The
curved arrows indicate observed NOEs. The assignment of the Me
signals in 1H NMR was based on the synthesis of deuterated derivatives
172-i (Me3,4,7,8 ) CD3) 172-ii (Me5,6,9,10 ) CD3), 172-iii (Me7,8 ) CD3),
and 172-iv (Me9,10 ) CD3).
Chart 3
Thus, the screw-sense in the present polymerization of 1,2-
diisocyanobenzenes may be induced by sterically favorable
initiation with differentiation of the relative steric bulkiness on
the substituted naphthalene in respect to the axes of the
binaphthyl groups; i.e., the sterically bulkier group may
preferentially occupy the less congested space through the
propagation.
16 (Figure 5). Thus, 172-i, whose four aromatic methyl groups
(Me3,4,7,8) of the quinoxaline rings were labeled by deuterium,
was prepared and isolated by the reaction of two equiv of 16′
with 4d′. A similar reaction of 16′′ with 4d′ provided 172-ii,
in which the four methoxy groups (OMe5,6,9,10) of the quinoxa-
line rings were deuterated. Furthermore, 172-iii, deuterated at
the only two aromatic methyl groups (Me7,8) of the third
quinoxaline from the starting binaphthyl group, and 172-iv,
deuterated at the only two methoxy groups (OMe9,10) of the
third quinoxaline, were prepared by the reaction of 1 equiv of
16′ and 16′′ with 171, respectively.
Temperature-dependent 1H NMR measurements revealed that
the right-handed (P) and left-handed (M) helical 182-i were in
equilibrium; the signals at 1.88 and 1.93 ppm (∆ν ) 14.7 Hz)
coalesced at 312 K and those at 2.30 and 2.24 ppm (∆ν ) 17.4
Hz) coalesced at 318 K in C6D6. Thus, the activation energy
for the P-M interconversion is calculated to be 16.1-16.3 kcal/
mol (67.4-68.2 kJ/mol).
On the basis of the NMR structural analysis of oligo-
(quinoxaline)s, the screw-sense selective polymerization of 1,2-
diisocyanobenzene initiated by (S)-4d is schematically presented
in Scheme 2. The palladium initiator (S)-4d undergoes insertion
of the diisocyanobenzene to give (biquinoxalinyl)palladium(II)
species, which may be in rapid equilibrium between the two
conformers, each of which may lead either to right- or left-
handed helical poly(quinoxaline)s. However, subsequent inser-
tion of the diisocyanide may take place exclusively with the
formation of right-handed helical (P)-(terquinoxalinyl)palladium
species corresponding to 172. Even if the corresponding left-
handed (M)-(terquinoxalinyl)palladium(II) species might be
formed, the P-M equilibrium to the right-handed (P)-species
maintains the right-handed screw-sense for further polymeri-
zation. The equilibrium between (M)- and (P)-helical confor-
mations may be negligible for the higher [oligo(quinoxalinyl)]-
palladium, since no equilibrium was spectroscopically detected
for the pentameric (P)-(S)-7 having the terminal 2MeOBin group.
The 400 MHz 1H NMR of 172 showed eleven singlets
corresponding to the methyl groups between 1.9 and 3.6 ppm,
in addition to the aromatic signals between 6.6 and 8.7 ppm,
benzylic methylene protons between 4.2 and 4.7 ppm, and two
doublets assignable to the methyl groups of PMe3. The aromatic
proton signals were completely assigned by a COSY experiment.
Furthermore, comparison of the 1H NMR spectra of the
deuterated 172-i-iv led to assignment of the eleven methyl
singlets, though each pair of methyl groups on the same
quinoxaline ring were not distinguished at this stage.
On the basis of the assignment, ROESY measurement of 172
permitted us to assume favorable conformation in solution.
Remarkable NOE between the binaphthyl aromatic protons and
the aromatic methyl groups (a-c in Figure 5) as well as between
PMe3 and the aromatic methyl groups (d and e in Figure 5)
strongly suggests that the three consecutive quinoxalines in 172
adopt a right-handed helical structure in solution. In Figure
5a, a plausible helical conformation of 172 is depicted, being
in accordance with the NOEs as well as the X-ray structure of
(P)-(S)-7.17 The NMR experiments also enabled assignment
of the two methyl singlets of the tolyl group; the two signals at
1.93 and 2.29 ppm were assignable to Me2 and Me1, respec-
tively. For comparison, a possible left-handed helical confor-
mation is also given in Figure 5b. Obviously, if the two
structures are compared, the left-handed helix is disfavored by
Conclusion
Highly screw-sense selective polymerization of diisocy-
anobenzenes was promoted by optically active 1,1′-binaphth-
2-ylpalladium(II) complexes to give optically active poly-
(17) The dotted line between the palladium and the nitrogen of the second
quinoxaline shown in Figures 5 and 6 represents a weak coordinative bond,
the exsistence of which is presumed from the related X-ray structures of
ter- and quaterquinoxalinylpalladium complexes reported by us. See ref
7a.

11888 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
Experimental Section
General. All reactions using palladium complexes were carried out
under a dry nitrogen or argon atmosphere. Solvents were purified by
distillation in the presence of appropriate drying agents under argon.
The 1H, 13C, and 31P NMR spectra were recorded on a Varian Gemini
1
2000 equipped with a 7.0 T magnet (300 MHz for H NMR), unless
otherwise noted. The GPC analysis was carried out with TSK-GEL
G3000HHR column (CHCl3, polystyrene standard). Recycling prepara-
tive GPC was performed with JAI LC-908 equipped with JAIGEL-1H
and -2H columns in a series (CHCl3). For the FABMS measurements
(positive), 3-nitrobenzyl alcohol was used for the matrix. The CD
spectra were recorded on JASCO J-720. Mean residue ellipticity, θ,
per quinoxaline unit, was used for expression of intensity of the CD
spectrum of the polymer. On the estimation of the enantiomeric
excesses of the poly(quinoxaline)s by examination of the CD spectra,
the concentration of the polymers subjected to the CD measurements
were also confirmed by UV measurements.
1,2-Diisocyanobenzene Derivatives. The synthesis of 1,2-diiso-
cyanobenzenes is outlined in Scheme 3. All compounds are prepared
from 4,7-dibromo-5,6-di(bromomethyl)-2,1,3-benzothiadiazole (21).
The compounds 3, 6, 12, 13, and 16 were prepared according to the
reported procedure.7b The following is a representative procedure for
the synthesis of 16 (R1 ) R2 ) Me). Step a: To a solution of methanol
(5.1 mL, 120 mmol) in THF (125 mL) was added ethylmagnesium
bromide (1.7 M in THF, 38 mL, 62 mmol) dropwise at room
temperature over 0.5 h with external cooling by a water bath under a
nitrogen atmosphere; the mixture was stirred for additional 1 h at room
temperature. To the mixture were added hexamethylphosphoramide
(HMPA, 22 mL, 120 mmol) and 21 (6 g, 12 mmol) at room temperature;
then the mixture was stirred at 70 °C for 1 d. To the mixture cooled
to room temperature was added water (100 mL). Extraction with Et2O
(100 mL × 3) followed by column chromatography on silica gel
(eluent: hexane/ether ) 10:1, CH2Cl2 was used for dissolving the
compound) gave 4,7-dibromo-5,6-bis(methoxymethyl)-2,1,3-benzothia-
diazole (3.5 g, 73%). 1H NMR (CDCl3) δ 3.49 (s, 6H), 4.98 (s, 4H).
Step b: To a suspension of ZnCl2 (3.3 g, 24 mmol) in THF (18 mL)
was added methylmagnesium bromide (2.4 M in THF, 5.0 mL, 12
mmol) at 0 °C under a nitrogen atmosphere; the mixture was stirred
for additional 0.5 h at room temperature. To the mixture were added
4,7-dibromo-5,6-bis(methoxymethyl)-2,1,3-benzothiadiazole (1.2 g, 3.0
mmol) and PdCl2(dppf) (0.22 g, 0.30 mmol) at room temperature; the
mixture was stirred at 70 °C for 24 h. To the mixture cooled to room
temperature was slowly added water (eVolution of methane). Extraction
with ether followed by column chromatography on silica gel (hexane/
ether ) 3:1) afforded 5,6-bis(methoxymethyl)-4,7-dimethyl-2,1,3-
benzothiadiazole (0.57 g, 74%). 1H NMR (CDCl3) δ 2.78 (s, 6H),
3.47 (s, 6H), 4.69 (s, 4H). Step c: To a solution of sodium bis(2-
methoxyethoxy)aluminum hydride (Red-Al, 3.4 M in toluene, 24 mL,
89 mmol) in THF (56 mL) was added water (1.6 mL, 89 mmol)
dropwise over 20 min at 0 °C under a nitrogen atmosphere (eVolution
of hydrogen gas); the mixture was stirred for additional 0.5 h at 0 °C.
To the mixture was added 5,6-bis(methoxymethyl)-4,7-dimethyl-2,1,3-
benzothiadiazole (2.2 g, 8.9 mmol) in THF (28 mL) at 0 °C; the mixture
was stirred at 0 °C for 1 h and at room temperature for 10 h. To the
mixture were added water and ether (evolution of hydrogen gas); the
resultant suspension was filtered through a pad of Celite. Extraction
with ether followed by column chromatography on silica gel (eluent:
AcOEt/Et3N ) 50:1, CH2Cl2 was used for dissolving the compound)
afforded 4,5-bis(methoxymethyl)-3,6-dimethyl-1,2-phenylenediamine
(1.2 g, 60%). 1H NMR (CDCl3) δ 2.21 (s, 6H), 3.41 (s, 10H), 4.48 (s,
4H). Steps d and e: To a solution of 4,5-bis(methoxymethyl)-3,6-
dimethyl-1,2-phenylenediamine (1.2 g, 5.4 mmol) in CH2Cl2 was added
CH3CO2CHO (1.9 g, 21 mmol) dropwise at 0 °C under a nitrogen
atmosphere; the mixture was stirred at 0 °C-room temperature for 10
h. Precipitates formed were collected by filtration to afford the
corresponding diformamide (1.3 g, 88%). To a solution of the
diformamide (1.3 g, 4.7 mmol) in THF (45 mL) were added triethyl-
amine (6.7 mL, 47 mmol) and POCl3 (1.2 mL, 14 mmol) at 0 °C under
a nitrogen atmosphere; the mixture was stirred at 0 °C for 1 h. To the
Figure 6. Plausible right- and left-handed helical conformations of
(terquinoxalinyl)palladium complexes 182-202 having various (S)-
binaphthyl groups. (Assumed from the chemical shift of the Me2
groups.)
(quinoxaline-2,3-diyl)s of stable helical structures. The choice
of substituents on the binaphthyl groups was crucially important
to attain the high screw-sense selectivity; 7′-methoxybinaphth-
2-ylpalladium(II) complex produced helical poly(quinoxaline)s
of a single screw-sense. The highly effective control of the
helical sense by the 7′-methoxy-1,1′-binaphthyl group at the
initiation terminal of the polymer may arise from highly
diastereoselective formation of the (terquinoxalinyl)palladium-
(II) intermediate, whose screw-sense was completely maintained
for further propagation. The complete retention of the helical
structure in the polymerization was demonstrated by the
synthesis of optically pure polymers with varying molecular
weights up to 100mer.
The asymmetric polymerization has successfully been applied
for the screw-sense selective synthesis of poly(quinoxaline-2,3-
diyl)s having hydrophobic and/or hydrophilic side chains, by
which the surface of the polymer is modifiable for new
functional materials.

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11889
Scheme 2. The Chain-End Control Mechanism of the Screw)Sense Selective Polymerization of 1,2-Diisocyanobenzenes in the
Presence of (S)-4d (7MeOBin)
Scheme 3a
Deuterated Diisocyanobenzenes 16′ and 16′′. The CD3 groups of
16′ and 16′′ were introduced with CD3MgI (1 M in ether, Aldrich) at
step (b) and CD3OD (Aldrich) at step a (Scheme 3), respectively,
according to the procedure for the synthesis of 16.
1,2-Diisocyano-4,5-bis(methoxymethyl)-3,6-bis(trideuteriometh-
1
yl)benzene (16′): H NMR (CDCl3) δ 3.44 (s, 6H), 4.48 (s, 4H); 13C
NMR (CDCl3) δ 14.7 (pseudo septet (1:3:6:7:6:3:1), J ) 19.7 Hz),
58.7, 67.8, 123.9, 134.1, 138.0, 173.0; IR (KBr) 2125, 1098 cm-1
;
FABHRMS (pos) calcd for [C14H10D6N2O2 + H]+: m/z 251.1660.
Found: m/z 251.1665.
1,2-Diisocyano-4,5-bis[(trideuteriomethoxy)methyl]-3,6-dimeth-
ylbenzene (16′′): 1H NMR (CDCl3) δ 2.49 (s, 6H), 4.48 (s, 4H); 13C
NMR (CDCl3) δ 15.4, 57.8 (pseudo septet, J ) 22.0 Hz), 67.7, 123.9,
134.2, 138.0, 173.1; IR (KBr) 2126, 1122 cm-1; FABHRMS (pos) calcd
for [C14H10D6N2O2 + H]+: m/z 251.1660. Found: m/z 251.1673.
a Reagents and conditions: (a) R1OH (10 equiv), EtMgBr (5 equiv),
THF, HMPA (10 equiv), 80 °C, 24 h; (b) R2MgBr (4 equiv), ZnCl2 (8
equiv), PdCl2(dppf) (0.1 equiv), THF, reflux, 24 h; (c) Red-Al (10
equiv), H2O (10 equiv), THF, room temperature, 10 h; (d) CH3CO2CHO
(4 equiv), CH2Cl2 0 °C-room temperature, 10 h; (e) POCl3 (3 equiv),
Et3N (10 equiv), THF, 0 °C, 1 h.
Optically Pure Binaphthyl Iodides 1. The iodides were prepared
according to the procedure reported by Miyano et al. The following
is a representative procedure (four steps) for preparation of (S)-1d. (1R)-
Menthyl (S)-7′-Methoxy-1,1′-binaphthalene-2-carboxylate. To a
solution of 7-methoxy-1-naphthylmagnesium bromide (12 mmol) in
THF-benzene (1:1, 140 mL) was added (1R)-menthyl 1-((1R)-
menthoxy)naphthalene-2-carboxylate (4.9 g, 10.5 mmol) in benzene
(60 mL) at 0 °C; the mixture was stirred at 0 °C for 2 h and at room
temperature for 12 h. To the mixture was added saturated aq NH4Cl
(200 mL). The organic layer was washed with saturated aq NH4Cl,
water, and brine successively, and dried over magnesium sulfate.
Evaporation followed by column chromatography on silica gel (hexane:
ether ) 20:1) afforded (1R)-menthyl 7′-methoxy-1,1′-binaphthalene-
2-carboxylate (3.3 g, 68%) as a 94:6 mixture of the diastereomers.
Recrystallization from ether-methanol gave the diastereomerically pure
ester with (S)-axial chirality (2.2 g, 45%). 1H NMR (CDCl3) δ -0.2-
1.6 (m, 18H), 3.44 (s, 3H), 4.43 (dt, J ) 4.3, 10.9 Hz, 1H), 6.47 (d, J
) 2.5 Hz, 1H), 7.08 (dd, J ) 2.5, 9.0 Hz, 1H), 7.10-7.52 (m, 5H),
7.75-8.03 (m, 5H) (the corresponding ester with (R)-axial chirality
exhibited its methoxy signal at 3.46 ppm), 13C NMR (CDCl3) δ 15.7,
20.5, 21.8, 22.6, 25.6, 31.0, 33.9, 39.6, 46.1, 54.9, 74.5, 98.6, 105.1,
118.2, 123.0, 125.9, 126.6, 127.4, 127.5, 127.7, 127.9, 128.0, 128.8,
129.6, 129.9, 133.0, 134.6, 134.7, 136.3, 139.6, 157.6, 168.1, IR (KBr)
2964, 1704, 1274, 1134, 828, 772 cm-1. Anal. Calcd for C32H34O3:
mixture was added saturated aq NaHCO3 at 0 °C. Extraction with Et2O
followed by column chromatography on silica gel (hexane/ether ) 3:1
to 1:1) afforded 16 (0.49 g, 42%).
1,2-Diisocyano-4,5-bis(methoxymethyl)-3,6-dimethylbenzene (16):
1H NMR (CDCl3) δ 2.49 (s, 6H), 3.44 (s, 6H), 4.48 (s, 4H); 13C NMR
(CDCl3) δ 15.5, 58.8, 67.9, 124.1, 134.3, 138.0, 173.2; IR (KBr) 2124,
1102 cm-1. Anal. Calcd for C14H16N2O2: C, 68.83; H, 6.60; N, 11.47.
Found: C, 68.68; H, 6.57; N, 11.34.
The following diisocyanides were prepared by the procedures similar
to that used for 16. 1,2-Diisocyano-3,6-dimethyl-4,5-bis[(phenyl-
methoxy)methyl]benzene (12): 1H NMR (CDCl3) δ 2.44 (s, 6H), 4.44
(s, 4H), 4.47 (s, 4H), 7.30-7.42 (m, 10H); 13C NMR (CDCl3) δ 15.4,
65.2, 73.3, 124.0, 128.26, 128.32, 128.6, 134.3, 137.3, 138.1, 173.1;
IR (KBr) 2120, 1100 cm-1. Anal. Calcd for C26H24N2O2: C, 78.76;
H, 6.10; N, 7.07. Found: C, 78.67; H, 6.03; N, 7.07. 1,2-Diisocyano-
4,5-bis[(2-methoxyethoxy)methyl]-3,6-dimethylbenzene (13): 1H
NMR (CDCl3) δ 2.49 (s, 6H), 3.36 (s, 6H), 3.50-3.58 (m, 4H), 3.64-
3.70 (m, 4H), 4.62 (s, 4H); 13C NMR (CDCl3) δ 15.5, 59.0, 66.6, 70.1,
71.9, 124.0, 134.3, 138.1, 172.9; IR (KBr) 2124, 1100 cm-1. Anal.
Calcd for C18H24N2O4: C, 65.04; H, 7.28; N, 8.43. Found: C, 65.03;
H, 7.33; N, 8.28.

11890 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
C, 82.37; H, 7.34. Found: C, 82.33; H, 7.30. (S)-7′-Methoxy-1,1′-
binaphthalene-2-carboxylic Acid. A mixture of the ester (1.8 g, 3.9
mmol) and KOH (8.8 g, 156 mmol) in ethanol (80 mL) was heated
under reflux for 24 h. After evaporation of the solvent, water and ether
were added to the residue. The aqueous phase was washed with ether
several times and then acidified with hydrochloric acid. Extraction
with ether followed by evaporation afforded (S)-7′-methoxy-1,1′-
binaphthalene-2-carboxylic acid (1.3 g, 98%). 1H NMR (CDCl3) δ
3.47 (s, 3H), 6.43 (d, J ) 2.5 Hz, 1H), 7.13 (dd, J ) 2.5, 9.0 Hz, 1H),
7.25-7.30 (m, 2H), 7.42 (dd, J ) 7.3, 7.9 Hz, 1H), 7.50-7.59 (m,
1H), 7.80-8.10 (m, 6H). (S)-2-Amino-7′-methoxy-1,1′-binaphtha-
lene. To a solution of the acid (1.20 g, 3.7 mmol) in acetone (19 mL)
were added triethylamine (0.57 mL, 4.0 mmol) and then ethyl
chloroformate (0.66 mL, 4.4 mmol) in acetone (1.9 mL) at -15 °C.
The mixture was stirred at -15 °C for 30 min; then, sodium azide
(0.71 g, 11 mmol) in water (3.8 mL) was added to the solution at -15
°C. After 1 h at -15 °C, organic material was extracted with cold
benzene several times. The organic layer was washed with cold brine
and dried over sodium sulfate. After filtration, the benzene solution
was heated under reflux in the presence of MS4A for 2 h. To the
mixture was added KOH (10 g, 178 mmol) and water (20 mL) at room
temperature; the mixture was stirred for 12 h at room temperature.
Extraction with benzene followed by column chromatography on silica
gel (hexane:ether ) 4:1) afforded (S)-2-amino-7′-methoxy-1,1′-binaph-
thalene (0.87 g, 80%). 1H NMR (CDCl3) δ 3.16 (br s, 2H), 3.57 (s,
3H), 6.72 (d, J ) 2.6 Hz, 1H), 7.10-7.27 (m, 4H), 7.38-7.55 (m,
3H), 7.76-7.93 (m, 4H), 13C NMR (CDCl3) δ 56.9, 106.0, 120.0, 120.5,
124.0, 125.8, 126.4, 128.2, 129.7, 129.8, 129.9, 130.9, 131.5, 131.8,
135.2, 135.5, 136.1, 143.6, 160.0, IR (KBr) 3464, 3372, 1624, 838
[R]20 ) +87.9 (c 0.132, benzene); mp 158.0-158.5 °C. 1H NMR
D
(C6D6) δ 1.07 (m, 6H), 1.38 (d, J ) 6.3 Hz, 3H), 1.57 (d, J ) 6.7 Hz,
3H), 2.26 (s, 3H), 2.35 (s, 3H), 6.50-7.90 (m, 31H), 8.08 (d, J ) 8.4
Hz, 1H), 9.20 (d, J ) 8.8 Hz, 1H); 31P NMR (C6D6) δ -8.81 (d, J )
410 Hz), -14.41 (d, J ) 410 Hz). Anal. Calcd for C58H51N2P2PdI:
C, 65.03; H, 4.80; N, 2.61. Found: C, 65.02; H, 4.50; N, 2.47.
(S)-[3-[2′-(tert-Butyldimethylsilyl)oxy[1,1′-binaphthalene]-2-yl]-
5,8-bis(4-methylphenyl)-2-quinoxalinyl]bis(dimethylphenylphosphine)-
iodopalladium ((S)-4c). By a procedure similar to that used for the
synthesis of (S)-4a, (S)-4c was prepared in 15% yield from (S)-1c (87
mg, 0.17 mmol). (S)-4c was isolated by a column chromatography on
silica gel (hexane:ether ) 3/1, then hexane:CH2Cl2 ) 1/2). (S)-4c:
[R]20 ) +153.7 (c 0.89, benzene); mp 112.5-116.0 °C. 1H NMR
D
(C6D6) δ -0.50 (s, 3H), 0.20 (s, 3H), 0.57 (s, 9H), 1.10 (d, J ) 7.5
Hz, 3H), 1.42 (d, J ) 7.8 Hz, 6H), 1.58 (d, J ) 7.5 Hz, 3H), 2.32 (s,
3H), 2.46 (s, 3H), 6.3-6.6 (m, 3H), 6.67 (t, J ) 6.8 Hz, 2H), 6.77-
6.92 (m, 7H), 7.02-7.40 (m, 14H), 7.43 (d, J ) 7.8 Hz, 1H), 7.60 (d,
J ) 7.8 Hz, 2H), 7.71 (d, J ) 7.5 Hz, 1H), 8.19 (d, J ) 9.0 Hz, 1H),
10.17 (d, J ) 9.9 Hz, 1H); 31P NMR (C6D6) δ -13.2 (d, J ) 401 Hz),
-12.0 (d, J ) 401 Hz). Anal. Calcd for C64H65IN2OP2PdSi: C, 63.97;
H, 5.45; N, 2.33. Found: C, 64.20; H, 5.57; N, 1.96.
(S)-Bis(dimethylphenylphosphine)iodo[3-(7′-methoxy[1,1′-binaph-
thalen]-2-yl)-5,8-bis(4-methylphenyl)-2-quinoxalinyl]palladium ((S)-
4d). By a procedure similar to that used for the synthesis of (S)-4a,
(S)-4d was prepared in 82% yield from (S)-1d (70 mg, 0.17 mmol).
(S)-4d was isolated by a column chromatography on silica gel (hexane:
ether ) 3/1, then hexane:CH2Cl2 ) 1/2). (S)-4d: [R]20 ) +189 (c
D
0.31, benzene); mp 129.8-132.5 °C. 1H NMR (C6D6) δ 0.89 (t, J )
2.7 Hz, 3H), 1.39 (t, J ) 3.5 Hz, 3H), 1.47 (t, J ) 3.6 Hz, 3H), 1.53
(t, J ) 3.3 Hz, 3H), 2.27 (s, 3H), 2.35 (s, 3H), 2.96 (s, 3H), 6.5-7.0
(m, 14H), 7.15-7.3 (m, 12H), 7.47 (d, J ) 7.8 Hz, 1H), 7.72 (d, J )
6.0 Hz, 2H), 7.76 (d, J ) 8.7 Hz, 1H), 8.03 (d, J ) 8.7 Hz, 1H), 9.13
(d, J ) 8.4 Hz, 1H); 31P NMR (C6D6) δ -12.28 (s), -12.19 (s).
HRFABMS (pos) calcd for [C59H53IN2OP2Pd + H]+ m/z 1101.1791;
found m/z 1101.1709; calculated signals (intensity/% based on MH+):
m/z 1099 (25), 1100 (67), 1101 (100), 1102 (53), 1103 (75), 1104 (43).
Found: m/z 1100 (68), 1101 (100), 1102 (59). (R)-4d: [R]20D ) -179
(c 0.28, benzene).
cm-1
. Anal. Calcd for C21H17NO: C, 84.25; H, 5.72; N, 4.62.
Found: C, 84.23; H, 5.80; N, 4.68. The enantiomeric excess (>99.5%
ee) of the amine was confirmed by chiral HPLC analysis (Chiralcel-
AD; hexane: i-PrOH ) 98:2). (S)-2-Iodo-7′-methoxy-1,1′-binaph-
thalene (1d). To a mixture of the amine (0.15 g, 0.5 mmol) and sulfuric
acid (2.5 M, 12 mL) was added sodium nitrite (0.15 g, 2.2 mmol) in
water (1.5 mL) at -15 °C; the mixture was stirred for 30 min at -5
°C. To the mixture was added urea (0.38 g, 6.3 mmol) in sulfuric
acid (2.5 M, 2 mL). To the mixture was slowly added potassium iodide
(0.42 g, 2.5 mmol) in sulfuric acid (2.5 M, 3.6 mL) at -5 °C. CH2Cl2
was added to the solution, and the organic layer was separated. The
layer was washed with saturated aq Na2SO3, 1 N aq NaOH, 1 N HCl,
and water. Column chromatography on silica gel (hexane only to
hexane:ether ) 50:1) afforded (S)-1d (57 mg). The material contained
7′-methoxy-1,1′-binaphthalene (ca. 25 mol %), and the calculated yield
of (S)-1d was 22%. The iodide was used for the next step without
further purification. 1H NMR (CDCl3) δ 3.55 (s, 3H), 6.47 (d, J )
2.6 Hz, 1H), 7.11-7.18 (m, 1H), 7.19 (d, J ) 2.6 Hz, 1H), 7.23 (d, J
) 1.3 Hz, 1H), 7.29-7.34 (m, 1H), 7.40-7.53 (m, 2H), 7.67 (d, J )
8.8 Hz, 1H), 7.82-8.00 (m, 3H), 8.05 (d, J ) 8.8 Hz, 1H).
(S)-Bis(dimethylphenylphosphine)iodo[3-(2′-methoxy[1,1′-binaph-
thalen]-2-yl)-5,8-bis(4-methylphenyl)-2-quinoxalinyl]palladium ((S)-
4a). To a THF (5 mL) solution of (cyclopentadienyl)(π-allyl)palladium-
(II) (26 mg, 0.122 mmol) was added dimethylphenylphosphine (52 µL,
0.366 mmol) at -78 °C; the mixture was stirred at -78 °C for 15
min. Then, (S)-1a (50 mg, 0.122 mmol) was added to the mixture at
-78 °C. The mixture was allowed to warm to room temperature and
then heated to 50 °C. After 2 h at 50 °C, the mixture was cooled to
room temperature, and 3 (56 mg, 0.182 mmol) was added. The mixture
was stirred for 3 h at room temperature and then subjected to preparative
TLC to give (S)-4a (113 mg, 84%). (S)-4a: [R]20D ) -173 (c 0.164,
benzene); mp 208.0-208.5 °C. 1H NMR (C6D6) δ 1.18 (t, J ) 3.4
Hz, 3H), 1.19 (t, J ) 3.3 Hz, 3H), 1.45 (t, J ) 3.4 Hz, 3H), 1.55 (t, J
) 3.5 Hz, 3H), 2.27 (s, 3H), 2.36 (s, 3H), 2.71 (s, 3H), 6.53 (d, J )
9.1 Hz, 1H), 6.60-7.00 (m, 12H), 7.10-7.50 (m, 14H), 7.60-7.80
(m, 3H), 8.08 (d, J ) 8.7 Hz, 1H), 10.21 (d, J ) 8.8 Hz, 1H); 31P
NMR (C6D6) δ -12.55 (s). Anal. Calcd for C59H53N2OP2PdI•1/
2C6H6: C, 65.30; H, 4.94; N, 2.45. Found: C, 65.50; H, 4.88; N, 2.46.
(S)-Iodo[3-(7′-methoxy[1,1′-binaphthalen]-2-yl)-5,8-bis(4-meth-
ylphenyl)-2-quinoxalinyl]bis(trimethylphosphine)palladium ((S)-
4d′). To a THF (16 mL) solution of (cyclopentadienyl)(π-allyl)-
palladium(II) (114 mg, 0.54 mmol) was added trimethylphosphine (1
M in THF, 1.6 mL, 1.6 mmol); the mixture was stirred for 15 min at
-78 °C. Then, (S)-1d (198 mg, 0.48 mmol) in THF (1 mL) was added
to the mixture at -78 °C. The mixture was allowed to warm to room
temperature and then heated to 50 °C. After stirring for 2 h at 50 °C,
3 (223 mg, 0.72 mmol) was added to the mixture cooled to room
temperature. The mixture was stirred for 2 h at room temperature and
then subjected to column chromatography on silica gel (hexane:ether
) 3/1) to give (S)-4d′ (379 mg, 81%). (S)-4d′: 1H NMR (C6D6) δ
0.74 (dd, J ) 2.2, 4.2 Hz, 9H), 0.89 (dd, J ) 2.4, 3.3 Hz, 9H), 2.22 (s,
3H), 2.23 (s, 3H), 3.01 (s, 3H), 6.74 (d, J ) 2.1 Hz, 1H), 6.87 (t, J )
8.5 Hz, 1H), 6.90-7.10 (m, 4H), 7.10-7.25 (m, 3H), 7.33 (d, J ) 8.7
Hz, 1H), 7.36 (d, J ) 9.0 Hz, 1H), 7.40-7.60 (m, 6H), 7.65-7.73 (m,
3H), 7.95 (d, J ) 8.7 Hz, 1H), 9.00 (d, J ) 8.7 Hz, 1H); 31P NMR
(C6D6) δ -20.0 (s), -20.1 (s). Anal. Calcd for C49H49IN2OP2Pd: C,
60.23; H, 5.05; N, 2.87. Found: C,5.25; H, 60.05; N, 2.75.
(S)-[3-(1,1′-Binaphthalen-2-yl)-6,7-bis(1-propyloxymethyl)-5,8-
dimethyl-2-quinoxalinyl]bis(dimethylphenylphosphine)iodopalla-
dium ((S)-4e). By a procedure similar to that used for the synthesis
of (S)-4a, (S)-4e was prepared in 77% yield from (S)-1b (56 mg, 0.182
mmol). (S)-4e: mp 87-94 °C. 1H NMR (C6D6) δ 0.80-0.95 (m,
9H), 1.32 (d, J ) 7.2 Hz, 3H), 1.40-1.60 (m, 10H), 1.65 (d, J ) 7.5
Hz, 3H), 3.05 (s, 3H), 3.23 (t, J ) 6.6 Hz, 2H), 3.39 (t, J ) 6.6 Hz,
2H), 4.50 (d, J ) 10.5 Hz, 1H), 4.54 (d, J ) 11.1 Hz, 1H), 4.70 (d, J
) 11.1 Hz, 1H), 4.75 (d, J ) 10.5 Hz, 1H), 6.06 (d, J ) 7.5 Hz, 1H),
6.40 (t, J ) 7.5 Hz, 2H), 6.62 (t, J ) 7.5 Hz, 1H), 6.80-7.30 (m,
11H), 7.52 (d, J ) 8.7 Hz, 1H), 7.60-7.70 (m, 5H), 8.07 (d, J ) 8.4
Hz, 1H), 9.37 (d, J ) 8.7 Hz, 1H); 31P NMR (C6D6) δ -12.08 (d, J )
410 Hz), -14.24 (d, J ) 410 Hz). FABMS (pos) calcd signals
(intensity/% based on MH+) for [C54H59IN2OP2Pd + H]+: m/z 1061
(S)-[3-(1,1′-Binaphthalen-2-yl)-5,8-bis(4-methylphenyl)-2-quinox-
alinyl]bis(dimethylphenylphosphine)iodopalladium ((S)-4b). By a
procedure similar to that used for the synthesis of (S)-4a, (S)-4b was
prepared in 77% yield from (S)-1b (56 mg, 0.182 mmol). (S)-4b:

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11891
(26), 1062 (68), 1063 (100), 1064 (50), 1065 (75), 1066 (41), 1067
(39), 1068 (19). Found: m/z 1061 (48), 1062 (82), 1063 (100), 1064
(61), 1065 (79), 1066 (44), 1067 (37), 1068 (17).
General Procedure for the Synthesis of Poly[5,8-bis(4-meth-
ylphenyl)quinoxaline-2,3-diyl]s 10a-d. To a THF (1.4 mL) solution
of 4 (3-4 mg, 3.0 µmol) was added 3 (37.1 mg, 0.120 mmol) at room
temperature. The mixture was stirred for 5 days, and then THF (3
mL) and NaBH4 (4.1 mg, 0.108 mmol) were added. Extraction with
CH2Cl2 followed by purification by preparative GPC (no recycling)
gave poly(2,3-quinoxaline)s 10a-d in the yields shown in Table 1.
10: 1H NMR (CDCl3) δ 1.0-2.6 (br m, 6nH), 5.0-8.0 (br m, 10nH);
13C NMR (CDCl3) δ 20.1 (br s), 127-133 (br m), 134-140 (br m).
General Procedure for the Synthesis of Poly[5,8-dimethyl-6,7-
bis(propoxymethyl)quinoxaline-2,3-diyl]s 11a-d. To a solution of
4a-d (1.0 × 10-3 mmol) in THF (3 mL) was added 6 (12 mg, 4.0 ×
10-2 mmol) at room temperature. The mixture was stirred for 18-24
h, and then a solution of ZnCl2 (13.6 mg, 0.10 mmol) and MeMgBr
(5.0 × 10-2 mmol) in THF (1 mL) was added at room temperature.
After 0.5 h, water (0.5 mL) was added, and organic materials were
extracted with CHCl3, dried over sodium sulfate, and evaporated in
vacuo. The residue was subjected to preparative GPC (CHCl3) to give
polymers 11a-d in the yields indicated in Table 1. The binaphthyl
endo-groups were not detectable by the NMR measurements. 11: 1H
NMR (CDCl3) δ 0.90 (br t, J ) 6.9 Hz, 6nH), 1.4-1.7 (br m, 4nH),
2.34 (br s, 6nH), 3.47 (br s, 4nH), 4.58 (br s, 4nH); 13C NMR (CDCl3)
δ 10.7, 12.0, 22.9, 67.2, 72.7, 135.5, 136.4, 138.9, 152.2. Anal. Calcd
for 11d (n ) 39, C21H15O + C22H16N2 + (C18H24O2N2)39 + CH3): C,
72.71; H, 7.93; N, 9.09. Found: C, 72.23; H, 7.81; N, 8.33.
(S)-Methyl 3-(7′-methoxy[1,1′-binaphthalen]-2-yl)-5,8-bis(4-meth-
ylphenyl)-2-quinoxalinecarboxylate (5d). A mixture of (S)-4d (10
mg, 9.1 µmol), MeOH (5 mL), and CH2Cl2 (1 mL) was heated under
CO pressure of 30 atm at 90 °C for 14 h. Preparative TLC on silica
gel (hexane: ether ) 2:1) gave (S)-5d (5.7 mg, 97%). HPLC analysis
(Chiralcel AD, hexane:i-PrOH ) 96:4) showed no signal corresponding
to the (R)-isomer. 1H NMR (at 90 °C, CD3C6D5) δ 2.16 (s, 3H), 2.36
(s, 3H), 3.06 (br s, 3H), 3.22 (br s, 3H), 6.77 (br s, 1H), 6.85-7.05
(m, 8H), 7.19 (t, J ) 7.2 Hz, 1H), 7.25-7.55 (m, 9H), 7.65-7.75 (m,
3H); 13C NMR (CDCl3) δ 21.0, 51.6, 54.3, 105.0, 106.2, 119.5, 122.9,
126.6, 128.9, 129.0, 129.3, 129.8, 130.4, 131.3, 131.7, 133.3, 134.5,
135.6, 137.3, 137.5, 138.0, 158.2; IR (neat) 1734, 1140, 814 cm-1
.
HRFABMS (pos) calcd for [C45H34N2O3 + H]+: m/z 651.2647.
Found: m/z 651.2645.
(Dimethylphenylphosphine)iodo[3′′′′-(2′-methoxy[1,1′-binaphtha-
len]-2-yl-5,5′,5′′,5′′′,5′′′′,8,8′,8′′,8′′′,8′′′′-decakis(4-methylphenyl)[2,2′:
3′,2′′:3′<bold>′,2′′′:3′′′,2′′′′:3′′′′,2′′′′′-quinquequinoxalin]-3-yl]pal-
ladium ((P)-(S)-7). To a benzene (30 mL) solution of (S)-4a (107
mg, 0.097 mmol) was added 3 (30 mg, 0.097 mmol) in benzene (30
mL) at room temperature. The mixture was heated at 50 °C for 2 h
and then cooled to room temperature. The operation, i.e., addition of
3 (30 mg, 0.097 mmol) followed by heating at 50 °C, was repeated
four times more. Volatile material was evaporated in vacuo, and
residual solids were subjected to preparative GPC (CHCl3) to give crude
pentamer. The crude material was recrystallized in CH2Cl2/hexane to
give pure (P)-(S)-7 (65 mg, 31%). (P)-(S)-7: mp 255-260 °C (dec).
1H NMR (400 MHz, C6D6) δ 0.89 (s, 3H), 1.66 (s, 3H), 1.70 (d, J )
11.4 Hz, 3H), 1.83 (s, 3H), 1.88 (s, 3H), 1.92 (d, J ) 11.4 Hz, 3H),
1.96 (s, 3H), 2.00 (s, 3H), 2.04 (s, 3H), 2.16 (s, 3H), 2.34 (s, 3H), 2.41
(s, 3H), 3.52 (s, 3H), 5.91 (d, J ) 7.9 Hz, 2H), 6.24 (d, J ) 7.4 Hz,
2H), 6.31 (d, J ) 7.6 Hz, 2H), 6.45-7.86 (m, 57H), 7.88 (d, J ) 8.7
Hz, 2H), 8.23 (d, J ) 8.0 Hz, 2H). Anal. Calcd for C139H106IN10-
OPPd: C, 76.00; H, 4.86; N, 6.38. Found: C, 75.92; H, 4.91; N, 6.31.
Synthesis of (P)-Poly[5,8-dimethyl-6,7-bis(benzyloxymethyl)quin-
oxaline-2,3-diyl] (14b). To a solution of (S)-4b (5.1 mg, 4.7 × 10-3
mmol) in THF (14 mL) was added 12 (70 mg, 0.19 mmol) at room
temperature; the mixture was stirred for 16 h at room temperature. To
the mixture was added a solution of ZnCl2 (64 mg, 0.47 mmol) and
MeMgBr (0.24 mmol) in THF (1 mL) at room temperature. After 0.5
h, water (0.5 mL) was added, and organic materials were extracted
with CHCl3, dried over sodium sulfate, and evaporated in vacuo. The
residue was subjected to preparative GPC (CHCl3) to give polymer
14b (52 mg, 70%). 14b: Mn ) 9.04 × 103, Mw/Mn ) 1.15. The CD
spectrum was identical to that of (P)-11b. 14b: 1H NMR (CDCl3) δ
2.34 (br s, 6nH), 4.10-4.60 (br m, 8nH), 7.22 (br s, 10nH); 13C NMR
(CDCl3) δ 12.1, 66.6, 73.0, 127.7, 128.35, 128.41, 135.7, 136.3, 138.3,
139.0, 152.2.
X-ray Diffraction Study of (P)-(S)-7. A single crystal of (P)-(S)-7
mounted on a glass fiber was subjected to the data collection. Crystal
data for 7 (C139H106IN10OPPd): crystal size 0.30 × 0.20 × 0.50 mm;
monoclinic, space group P21 (no. 4), Z ) 2; a ) 12.853(4), b )
40.251(9), c ) 12.486(3) Å; â ) 117.36(2)°; V ) 5737(2) Å3, Fcalcd
)
Synthesis of (P)-Poly[5,8-dimethyl-6,7-di[(2-methoxyethoxy)meth-
yl]quinoxaline-2,3-diyl] (15b). By a procedure similar to that for 14b,
15b (11 mg, 42%) was synthesized from (S)-4b (1.9 mg, 1.8 × 10-3
mmol) and 13 (23.5 mg, 7.0 × 10-2 mmol). 15b: Mn ) 6.81 × 103,
Mw/Mn ) 2.32. The CD spectrum was identical to that of (P)-11b.
15b: 1H NMR (CDCl3) δ 2.34 (br s, 6nH), 3.32 (br s, 6nH), 3.53 (br
s, 4nH), 3.66 (br s, 4nH), 4.65 (br s, 2nH), 4.74 (br s, 2nH); 13C NMR
(CDCl3) δ 12.1, 58.9, 67.6, 69.7, 71.9, 135.6, 136.3, 138.9, 152.2.
1.27 g/cm3; µ ) 40.22 cm-1; max 2θ ) 125° (CuKR, λ ) 1.54178 Å,
graphite monochromator, ω/2θ-scan, T ) 293 K); 10431 reflections
measured, 9746 independent, 8803 included in the refinement, Lorent-
zian polarization; direct method, anisotropical refinement for non-
hydrogen atoms by full-matrix least-squares against |F| with program
package CrystanG (Mac Science), 1376 parameters; R ) 0.070, Rw
0.091. Hydrogen atoms were not included in the refinement.
)
Synthesis of Poly[5,8-di(4-methylphenyl)quinoxaline-2,3-diyl] (P)-
8. To a THF (0.5 mL) solution of (P)-(S)-7 (2.4 mg, 1.1 µmol) was
added 3 (12 mg, 0.038 mmol) at room temperature. The mixture was
stirred for 6 days, and then THF (1 mL) and NaBH4 (1.4 mg, 0.036
mmol) were added. Extraction with CH2Cl2 followed by purification
by preparative GPC (no recycling) gave poly(2,3-quinoxaline)s (P)-8
Synthesis of Iodobis(trimethylphosphine)[oligo(quinoxalinyl)]-
palladium(II) Complexes 171-174. To a solution of 4d′ (99 mg, 0.1
mmol) in THF (10 mL) was added 16 (50 mg, 0.2 mmol) at room
temperature. The mixture was stirred at room temperature for 20 h.
Evaporation of the solvent gave a crude mixture of [oligo(quinoxalinyl)]-
palladium(II) complexes, which was subjected to preparative GPC to
afford 171 (27 mg, 18%), 172 (72 mg, 39%), 173 (16 mg, 7%), and 174
(7 mg, 3%) together with recovered starting complex 4d′ (7 mg, 6%).
(7 mg, 48%). Mn ) 7.18 × 103, Mw/Mn ) 1.37. UV (CHCl3) λmax
)
271 nm (ꢀ 2.89 × 104). 1H NMR (CDCl3) δ 1.0-2.6 (br m, 6nH),
5.0-8.0 (br m, 10nH).
Iodo[3′-(7′-methoxy[1,1′-binaphthalene]-2-yl)-6,7-bis(methoxy-
methyl)-5,8-dimethyl-5′,8′-bis(4-methylphenyl)[2,2′-biquinoxalin]-
3-yl]bis(trimethylphosphine)palladium (171): 1H NMR (400 MHz,
C6D6) δ 0.57 (br s, 9H), 0.81 (s, br, 9H), 2.13 (s, 3H), 2.21 (s, 3H),
2.61 (br s, 3H), 2.90 (br s, 3H), 2.99 (s, 3H), 3.20 (s, 3H), 3.24 (s,
3H), 4.58-4.72 (m, 4H), 6.40-6.82 (br s, 1H), 6.82-7.10 (m, 5H),
7.10-7.34 (m, 6H), 7.37 (d, J ) 9.0 Hz, 1H), 7.45-7.55 (m, 7H),
7.58 (d, J ) 8.6 Hz, 1H), 8.0-8.4 (br s, 1H); 31P NMR (C6D6) δ -21.05
(br s). FABMS (pos) calcd signals (intensity/% based on MH+) for
[C63H65IN4O3P2Pd + H]+: m/z 1219 (25), 1220 (66), 1221 (100), 1222
(57), 1223 (76), 1224 (46), 1225 (41), 1226 (22), 1227 (7). Found:
m/z 1219 (55), 1220 (73), 1221 (100), 1222 (69), 1223 (87), 1224 (50),
1225 (49), 1226 (24), 1227 (4).
Synthesis of Poly[5,8-dimethyl-6,7-bis(propoxymethyl)quinoxa-
line-2,3-diyl] (P)-9. To a THF (2 mL) solution of (P)-(S)-7 (1.7 mg,
0.77 µmol) was added 3 (8.1 mg, 27 µmol) at room temperature. The
mixture was stirred for 12 h, and then a solution of ZnCl2 (375 mg,
2.7 mmol) and MeMgBr (1.35 mmol) in THF (1 mL) was added at
room temperature. After 0.5 h, water (0.5 mL) was added, and organic
materials were extracted with CHCl3, dried over sodium sulfate, and
evaporated in vacuo. The residue was subjected to preparative GPC
(CHCl3) to give polymers (P)-9 (8.1 mg, 85%). Mn ) 6.18 × 103,
Mw/Mn ) 1.65. UV (CHCl3) λmax ) 290 nm (ꢀ 8.0 × 105). 1H NMR
(CDCl3) δ 0.90 (br s, 6nH), 1.58 (br s, 4nH), 2.33 (br s, 6nH), 3.45 (br
s, 4nH), 4.57 (br s, 4nH); 13C NMR (CDCl3) δ 10.7, 12.0, 22.9, 67.1,
72.7, 135.6, 136.2, 138.9, 152.2.

11892 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Ito et al.
Iodo[3′′-(7′-methoxy[1,1′-binaphthalene]-2-yl)-6,6′,7,7′-tetrakis-
(methoxymethyl)-5,5′,8,8′-tetramethyl-5′′,8′′-bis(4-methylphenyl)-
[2,2′:3′,2′′-terquinoxalin]-3-yl]bis(trimethylphosphine)palladium
(172): 1H NMR (500 MHz, C6D6) δ 0.72 (d, J ) 7.1 Hz, 9H), 1.12 (d,
J ) 7.1 Hz, 9H), 1.93 (s, 3H), 2.02 (s, 3H), 2.29 (s, 3H), 2.34 (s, 3H),
2.91 (s, 3H), 2.95 (s, 3H), 2.98 (s, 3H), 3.13 (s, 3H), 3.14 (s, 3H), 3.15
(s, 3H), 3.54 (s, 3H), 4.25 (d, J ) 11.2 Hz, 2H), 4.34 (d, J ) 11.2 Hz,
1H), 4.38 (d, J ) 11.2 Hz, 1H), 4.49 (d, J ) 10.8 Hz, 1H), 4.54 (d, J
) 10.8 Hz, 1H), 4.56-4.62 (m, 2H), 6.61 (d, J ) 7.9 Hz, 2H), 6.70
(d, J ) 7.9 Hz, 2H), 6.87 (d, J ) 7.9 Hz, 2H), 6.93 (t, J ) 8.3 Hz,
1H), 7.00 (d, J ) 7.7 Hz, 1H), 7.01 (d, J ) 7.9 Hz, 2H), 7.03 (t, J )
8.3 Hz, 1H), 7.05 (d, J ) 2.2 Hz, 1H), 7.09 (t, J ) 7.1 Hz, 1H), 7.23
(d, J ) 7.7 Hz, 1H), 7.25 (d, J ) 8.8 Hz, 1H), 7.28 (dd, J ) 9.0, 2.2
Hz, 1H), 7.32 (d, J ) 8.3 Hz, 1H), 7.48 (d, J ) 7.1 Hz, 1H), 7.60 (d,
J ) 9.0 Hz, 1H), 7.66 (d, J ) 8.3 Hz, 1H), 8.46 (d, J ) 8.6 Hz, 1H),
8.67 (d, J ) 7.1 Hz, 1H); 31P NMR (C6D6) δ -23.65 (d, J ) 392 Hz),
-22.66 (d, J ) 392 Hz). Anal. Calcd for C77H81IN6O5P2Pd: C, 63.09;
H, 5.57; N, 5.73. Found: C, 63.12; H, 5.53; N, 5.67. FABMS (pos)
calcd signals (intensity/% based on MH+) for [C77H81IN6O5P2Pd + H]+:
m/z 1463 (22), 1464 (63), 1465 (100), 1466 (67), 1467 (78), 1468
(53), 1469 (45), 1470 (27), 1471 (11). Found: m/z 1463 (45), 1464
(75), 1465 (100), 1466 (75), 1467 (79), 1468 (53), 1469 (41), 1470
(18), 1471 (9). Deuterated derivatives 172-i-iv were prepared similarly
by reactions of 16′ or 16′′ and identified by 1H NMR and MS.
Compound 172-i: 1H NMR (C6D6) showed signals identical to that
for 172 except for disappearance of singlets at 2.02, 2.34, 3.15, and
3.54 ppm. FABMS (pos) m/z 1477 (MH+). Compound 172-ii: 1H
NMR (C6D6) showed signals identical to that for 172 except for
disappearance of singlets at 2.95, 2.98, 3.13, and 3.14 ppm. FABMS
(pos) m/z 1477 (MH+). Compound 172-iii: 1H NMR (C6D6) showed
signals identical to that for 172 except for disappearance of singlets at
2.02 and 3.15 ppm. FABMS (pos) m/z 1471 (MH+). Compound 172-
iv: 1H NMR (C6D6) showed signals identical to that for 172 except for
disappearance of singlets at 2.98 and 3.13 ppm. FABMS (pos) m/z
1471 (MH+).
Synthesis of 181 and 182. To a solution of 4a′ (99 mg, 0.1 mmol)
in THF (mL) was added 16 (50 mg, 0.2 mmol) at room temperature.
The mixture was stirred at room temperature for 10 h. Evaporation of
the solvent gave a crude mixture of [oligo(quinoxalinyl)]palladium(II)
complexes, which was subjected to preparative GPC to afford 181 (30
mg, 22%) and 182 (48 mg, 31%) together with higher oligomers (39
mg) and recovered starting complex 4d′ (8 mg, 8%).
Iodo[3′-(2′-methoxy[1,1′-binaphthalene]-2-yl)-6,7-bis(methoxy-
methyl)-5,8-dimethyl-5′,8′-bis(4-methylphenyl)[2,2′-biquinoxalin]-
3-yl]bis(trimethylphosphine)palladium (181): 181: 1H NMR (C6D6)
δ 0.55 (br s, 9H), 0.81 (br s, 9H), 2.20 (s, 3H), 2.23 (s, 3H), 2.30-
2.90 (br, 6H), 2.97 (br s, 3H), 3.24 (s, 3H), 3.26 (br s, 3H), 4.68 (br s,
3H), 4.72 (s, 3H), 6.50-7.68 (m, 20H), 7.96 (br s, 2H); 31P NMR (C6D6)
δ 22.5 (br). FABMS (pos) calcd signals (intensity/% based on MH+)
for [C63H65IN4O3P2Pd + H]+: m/z 1219 (25), 1220 (65), 1221 (100),
1222 (57), 1223 (76), 1224 (46), 1225 (41). Found: m/z 1219 (29),
1220 (80), 1221 (100), 1222 (79), 1223 (65), 1224 (43), 1225 (32).
Iodo[3′′-(2′-methoxy[1,1′-binaphthalene]-2-yl)-6,6′,7,7′-tetrakis-
(methoxymethyl)-5,5′,8,8′-tetramethyl-5′′,8′′-bis(4-methylphenyl)-
[2,2′:3′,2′′-terquinoxalin]-3-yl]bis(trimethylphosphine)palladium (182).
This compound was obtained as a mixture of two diastereomers ((P)-
(S)-isomer: (M)-(S)-isomer ) 52:48). 182: 1H NMR (500 MHz,
C6D6: (P)-(S)- and (M)-(S)-isomers are denoted by isomer A and B,
respectively, in the following description) δ 0.71 (d, J ) 6.1 Hz, 9H
for isomer A), 0.75 (s, 9H for isomer B), 1.10 (s, 9H for isomers A
and B), 1.89 (s, 3H for isomer A), 1.93 (s, 3H for isomer B), 2.20 (s,
3H for isomer B), 2.22 (s, 3H for isomer B), 2.24 (s, 3H for isomer
B), 2.30 (s, 3H for isomer A), 2.38 (s, 3H for isomer A), 2.53 (s, 3H
for isomer A), 2.92-3.22 (m, 18 H for isomers A and B), 3.64 (s, 3H
for isomers A and B), 4.20-4.58 (m, 6H for isomers A and B), 4.58-
4.72 (m, 2H for isomers A and B), 6.40-7.70 (m, 19 H for isomers A
and B), 7.78-8.00 (m, 1H for isomer A and 2H for isomer B), 8.34
(br s, 1H for isomer B), 8.44 (d, J ) 8.6 Hz, 1H for isomer A), 8.90
(d, J ) 7.7 Hz, 1H for isomer A); 31P NMR (C6D6) δ -23.8, -23.64,
-23.59, -23.4. FABMS (pos) calcd signals (intensity/% based on
MH+) for [C77H81IN6O5P2Pd + H]+: m/z 1463 (22), 1464 (63), 1465
(100), 1466 (67), 1467 (78), 1468 (53), 1469 (45), 1470 (27), 1471
(11). Found: m/z 1463 (58), 1464 (74), 1465 (100), 1466 (77), 1467
(74), 1468 (54), 1469 (47), 1470 (29), 1471 (25). 182-i: 1H NMR
(500 MHz, C6D6: (P)-(S)- and (M)-(S)-isomers are denoted by isomer
A and B, respectively, in the following description) δ 0.71 (d, J ) 6.1
Hz, 9H for isomer A), 0.75 (s, 9H for isomer B), 1.10 (s, 9H for isomers
A and B), 1.89 (s, 3H for isomer A), 1.93 (s, 3H for isomer B), 2.24
(s, 3H for isomer B), 2.30 (s, 3H for isomer A), 2.95-3.22 (m, 15 H
for isomers A and B), 4.20-4.58 (m, 6H for isomers A and B), 4.58-
4.72 (m, 2H for isomers A and B), 6.40-7.70 (m, 19 H for isomers A
and B), 7.78-8.00 (m, 1H for isomer A and 2H for isomer B), 8.34
(br s, 1H for isomer B), 8.44 (d, J ) 8.6 Hz, 1H for isomer A), 8.90
(d, J ) 7.7 Hz, 1H for isomer A). FABMS (pos) m/z 1477 [C77H69D12-
IN6O5P2Pd + H]+.
Synthesis of 192-i. To a solution of 4b′ (67 mg, 0.071 mmol) in
THF (mL) was added 16′ (36 mg, 0.142 mmol) at room temperature.
The mixture was stirred at room temperature for 10 h. Evaporation of
the solvent gave a crude mixture of [oligo(quinoxalinyl)]palladium(II)
complexes, which was subjected to preparative GPC to afford 192-i
(49 mg, 48%). 192-i: 1H NMR (500 MHz, C6D6) δ 0.71 (d, J ) 7.2
Hz, 9H), 1.13 (d, J ) 7.2 Hz, 9H), 1.93 (s, 3H), 2.22 (s, 3H), 2.93 (s,
3H), 2.95 (s, 3H), 3.14 (s, 3H), 3.15 (s, 3H), 4.25-4.40 (m, 4H), 4.49-
4.62 (m, 4H), 6.56 (d, J ) 7.4 Hz, 2H), 6.69 (d, J ) 7.9 Hz, 2H), 6.72
(d, J ) 7.5 Hz, 2H), 6.88 (t, J ) 7.9 Hz, 1H), 6.95-7.31 (m, 10H),
7.49-7.54 (m, 2H), 7.67-7.72 (m, 2H), 8.47 (d, J ) 8.6 Hz, 1H),
8.57 (d, J ) 6.6 Hz, 1H); 31P NMR (C6D6) δ -22.9, -23.3. FABMS
(pos) calcd signals (intensity/% based on MH+) for [C76H67D12IN6O4P2-
Pd + H]+: m/z 1445 (22), 1446 (63), 1447 (100), 1448 (66), 1449
(78), 1450 (53), 1451 (44), 1452 (26), 1453 (10). Found: m/z 1445
(47), 1446 (83), 1447 (100), 1448 (78), 1449 (76), 1450 (58), 1451
(42), 1452 (29), 1453 (12).
Iodo[3′′′-(7′-methoxy[1,1′-binaphthalene]-2-yl)-6,6′,6′′,7,7′,7′′-
hexakis(methoxymethyl)-5,5′,5′′,8,8′,8′′-hexamethyl-5′′′,8′′′-bis(4-
methylphenyl)[2,2′:3′,2′′:3′<bold>′,2′′′-quaterquinoxalin]-3-yl]bis-
(trimethylphosphine)palladium (173): 1H NMR (400 MHz, C6D6) δ
1.03 (d, J ) 7.3 Hz, 9H), 1.23 (d, J ) 7.3 Hz, 9H), 1.74 (s, 6H), 1.77
(s, 3H), 2.26 (s, 6H), 2.30 (s, 3H), 2.87 (s, 3H), 2.95 (s, 3H), 2.96 (s,
3H), 3.02 (s, 3H), 3.08 (s, 3H), 3.12 (s, 3H), 3.20 (s, 3H), 3.22 (s, 3H),
3.43 (s, 3H), 4.18 (d, J ) 11.2 Hz, 1H), 4.27-4.47 (m, 8H), 4.57 (d,
J ) 11.2 Hz, 1H), 4.65 (d, J ) 10.6 Hz, 1H), 4.69 (d, J ) 10.6 Hz,
1H), 6.65 (d, J ) 8.1 Hz, 2H), 6.79 (t, J ) 9.2 Hz, 1H), 6.9-7.0 (m,
4H), 7.1-7.2 (m, 6H), 7.24 (dd, J ) 2.4, 9.2 Hz, 1H), 7.31-7.36 (m,
3H), 7.41 (d, J ) 8.4 Hz, 1H), 7.53 (d, J ) 9.2 Hz, 1H), 7.70 (d, J )
8.4 Hz, 1H), 8.48-8.50 (m, 2H); 31P NMR (C6D6) δ -23.03, -23.76.
FABMS (pos) calcd signals (intensity/% based on MH+) for [C91H97-
IN8O7P2Pd + H]+: m/z 1707 (20), 1708 (60), 1709 (100), 1710 (76),
1711 (82), 1712 (61), 1713 (50), 1714 (32). Found: m/z 1707 (60),
1708 (76), 1709 (100), 1710 (71), 1711 (60), 1712 (53), 1713 (42),
1714 (37).
Iodo[3′′′′-(7′-methoxy[1,1′-binaphthalene]-2-yl)-6,6′,6′′,6′′′,7,7′,7′′,7′′′-
octakis(methoxymethyl)-5,5′,5′′,5′′′,8,8′,8′′,8′′′-octamethyl-5′′′′,8′′′′-
bis(4-methylphenyl)[2,2′:3′,2′′:3′<bold>′,2′′′:3′′′,2′′′′-quinquequin-
oxalin]-3-yl]bis(trimethylphosphine)palladium (174): 1H NMR (400
MHz, C6D6) δ 1.20 (dd, J ) 5.4, 1.6 Hz, 9H), 1.30 (dd, J ) 5.4, 1.6
Hz, 9H), 1.62 (s, 3H), 1.92 (s, 3H), 2.09 (s, 3H), 2.10 (s, 3H), 2.11 (s,
3H), 2.13 (s, 3H), 2.23 (s, 3H), 2.29 (s, 3H), 2.78 (s, 3H), 2.80 (s, 3H),
2.84 (s, 3H), 2.93 (s, 3H), 2.94 (s, 3H), 2.98 (s, 3H), 3.14 (s, 3H), 3.17
(s, 3H), 3.20 (s, 3H), 3.70 (s, 3H), 4.0-4.4 (m, 12H), 4.5-4.7 (m,
4H), 6.61 (d, J ) 8.1 Hz, 2H), 6.65 (d, J ) 8.1 Hz, 2H), 6.77 (d, J )
7.7 Hz, 2H), 6.90-7.03 (m, 4H), 7.1-7.2 (m, 3H), 7.25-7.35 (m, 2H),
7.4-7.5 (m, 2H), 7.55 (d, J ) 8.1 Hz, 1H), 7.65-7.70 (m, 2H), 8.69
(d, J ) 8.6 Hz, 1H), 8.76 (d, J ) 6.2 Hz, 1H); 31P NMR (C6D6) δ
-23.57, -23.68. FABMS (pos) calcd signals (intensity/% based on
MH+) for [C105H113IN10O9P2Pd + H]+: m/z 1951 (19), 1952 (57), 1953
(100), 1954 (85), 1955 (88), 1956 (69), 1957 (56), 1958 (37), 1959
(18). Found: m/z 1951 (56), 1952 (74), 1953 (100), 1954 (92), 1955
(80), 1956 (60), 1957 (43), 1958 (24), 1959 (17).
Synthesis of 202-i. To a solution of 4c′ (44 mg, 0.041 mmol) in
THF (1.5 mL) was added 16′ (21 mg, 0.082 mmol) at room temperature.

Synthesis of Helical Poly(quinoxaline-2,3-diyl)s
J. Am. Chem. Soc., Vol. 120, No. 46, 1998 11893
The mixture was stirred at room temperature for 10 h. Evaporation of
the solvent gave a crude mixture of [oligo(quinoxalinyl)]palladium(II)
complexes, which was subjected to preparative GPC to afford 202-i
(26 mg, 40%). 202-i: 1H NMR (500 MHz, C6D6) δ -0.06 (s, 6H),
0.46 (s, 9H), 0.69 (s, 9H), 1.12 (s, 9H), 1.89 (s, 3H), 2.43 (s, 3H), 3.02
(s, 3H), 3.11 (s, 3H), 3.13 (s, 3H), 3.21 (s, 3H), 4.35-4.51 (m, 4H),
4.56-4.67 (m, 4H), 6.66-7.31 (m, 17H), 7.39 (br s, 1H), 7.58 (d, J )
7.9 Hz, 1H), 7.72 (br s, 1H), 8.60 (br s, 1H), 8.75 (br s, 1H); 31P NMR
(C6D6) δ -23.7, -23.6. FABMS (pos) m/z 1578 [C82H81D12IN6O5P2-
PdSi + H]+.
Acknowledgment. This work was supported by Grant-in-
Aids from Ministry of Education, Science, Sports and Culture,
Japan.
Supporting Information Available: Tables of positional
and thermal parameters, and interatomic distances and angles
for 7 (9 pages, print/PDF). See any current masthead page for
ordering information and Web access instructions.
JA982500M