77Se NMR chemical shifts of 9-(arylselanyl)triprycenes: New standard for planar structures of ArSeR and applications to determine the structures in solutions

Article abstract of DOI:10.1021/jo801786j

(Chemical Equation Presented) A set of new δ(Se) parameters is proposed as a standard for the planar (pl) orientational effect of p-YC ₆H₄ (Ar) in ArSeR, employing 9-(arylselanyl)triptycenes (1: p-YC₆H₄SeTpc). The Se-C_R bond in ArSeR is placed on the Ar plane in pl and it is perpendicular to the plane in pd. Large upfield shifts are observed for Y = NMe₂, OMe, and Me (-22 to -6 ppm) and large downfield shifts for Y = COOEt, CN, and NO₂ (19-37 ppm), relative to Y = H, with small upfield and moderate downfield shifts by Y of halogens (-1 ppm for Y = F and 4 ppm for Y = Cl and Br). This must be the result of the p(Se)-π(C₆H₄)-p(Y) conjugation in 1 (pl). While the character of δ(Se) in 1 (pl) is very similar to that in 9-(arylselanyl)anthracenes (2 (pl)), it is very different from that of 1-(arylselanyl)anthraquinones (3 (pd)). Sets of δ(Se) of 1 and 2 must serve as the standard for pl and that of 3 does for pd in solutions. Structures of various ArSeR in solutions are determined from the viewpoint of the orientational effect based on the standard δ(Se) of 1-3. While the structure of 2-methyl-1-(arylselanyl)naphthalenes is concluded to be all pl in solutions, those of 8-chloro- and 8-bromo-1-(arylselanyl)naphthalenes are all pd, except for Y = COOEt, CN, and NO₂: The equilibrium between pd and pl contributes to those with Y = COOEt, CN, and NO₂. The structure of 1-(arylselanyl)naphthalenes changes depending on Y. The structures of ArSeMe and ArSeCOPh are shown to be pl and pd, respectively, in solutions. Those of ArSePh and ArSeAr seem to change depending on Y. δ(Se) of 1-3 are demonstrated to serve as the standard to determine the structures in solutions. The rules of thumb derived from the characters in δ(Se) for 1-3 are very useful to determine the structures of ArSeR in solutions, in addition to the analysis based on the plots.

Full text of DOI:10.1021/jo801786j

77Se NMR Chemical Shifts of 9-(Arylselanyl)triptycenes: New Standard for
Planar Structures of ArSeR and Applications to Determine the Structures
in Solutions
Takashi Nakamoto, Satoko Hayashi, and Waro Nakanishi*
Department of Material Science and Chemistry, Faculty of Systems Engineering, Wakayama UniVersity,
930 Sakaedani, Wakayama 640-8510, Japan
nakanisi@sys.wakayama-u.ac.jp
ReceiVed August 9, 2008
A set of new δ(Se) parameters is proposed as a standard for the planar (pl) orientational effect of p-YC6H4
(Ar) in ArSeR, employing 9-(arylselanyl)triptycenes (1: p-YC6H4SeTpc). The Se-CR bond in ArSeR is
placed on the Ar plane in pl and it is perpendicular to the plane in pd. Large upfield shifts are observed
for Y ) NMe2, OMe, and Me (-22 to -6 ppm) and large downfield shifts for Y ) COOEt, CN, and
NO2 (19-37 ppm), relative to Y ) H, with small upfield and moderate downfield shifts by Y of halogens
(-1 ppm for Y ) F and 4 ppm for Y ) Cl and Br). This must be the result of the p(Se)-π(C6H4)-p(Y)
conjugation in 1 (pl). While the character of δ(Se) in 1 (pl) is very similar to that in 9-(arylselanyl)an-
thracenes (2 (pl)), it is very different from that of 1-(arylselanyl)anthraquinones (3 (pd)). Sets of δ(Se)
of 1 and 2 must serve as the standard for pl and that of 3 does for pd in solutions. Structures of various
ArSeR in solutions are determined from the viewpoint of the orientational effect based on the standard
δ(Se) of 1-3. While the structure of 2-methyl-1-(arylselanyl)naphthalenes is concluded to be all pl in
solutions, those of 8-chloro- and 8-bromo-1-(arylselanyl)naphthalenes are all pd, except for Y ) COOEt,
CN, and NO2: The equilibrium between pd and pl contributes to those with Y ) COOEt, CN, and NO2.
The structure of 1-(arylselanyl)naphthalenes changes depending on Y. The structures of ArSeMe and
ArSeCOPh are shown to be pl and pd, respectively, in solutions. Those of ArSePh and ArSeAr seem to
change depending on Y. δ(Se) of 1-3 are demonstrated to serve as the standard to determine the structures
in solutions. The rules of thumb derived from the characters in δ(Se) for 1-3 are very useful to determine
the structures of ArSeR in solutions, in addition to the analysis based on the plots.
Introduction
in solutions, even if the structures are determined in crystals.
Plain rules are necessary to determine geometric and electronic
structures based on δ(Se) in solutions, which must be founded
on theoretical background and familiar to experimental chemists.
NMR spectroscopy has been established as an extremely
powerful tool to study physical, chemical, and biological
sciences.1,2 NMR chemical shifts (δ) are widely applied to
determine structures2-5 and follow reactions routinely.1,2 77Se
NMR chemical shifts (δ(Se)) are widely applied to determine
the structures, since they are very sensitive to structural changes
of selenium compounds.2-5 We often worry about the structures
of compounds in solutions, when investigations are carried out
(1) (a) Organic Selenium Compounds: Their Chemistry and Biology; Klay-
man, D. L., Gu¨nther, W., Eds.; Wiley: New York, 1973. (b) The Chemistry of
Organic Selenium and Tellurium Compounds; Patai, S., Rappoport, Z., Eds.;
John-Wiley and Sons: New York, 1986; Vols. 1 and 2. (c) Organic Selenium
Chemistry; Liotta, D., Ed.; Wiley-Interscience: New York, 1987. (d) Organose-
lenium Chemistry, A practical Approach; Back, T. G., Ed.; Oxford University
Press: Oxford, UK, 1999. (e) Organoselenium Chemistry Modern DeVelopments
in Organic Synthesis; Topics in Current Chemistry Series; Wirth, T., Ed.;
Springer: New York, 2000.
* To whom correspondence should be addressed. Phone: +81 73 457 8252.
Fax: +81 73 457 8253.
10.1021/jo801786j CCC: $40.75
Published on Web 11/06/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 9259–9269 9259

Nakamoto et al.
SCHEME 1. The pd, pl, and np Notation in the Benzene
CHART 1
System and Types A-C in the Naphthalene System
Charge-transfer mechanism has been proposed to explain the
downfield shifts by the neighboring oxygen6 and the mechanism
is demonstrated to play an important role in weak interactions.4
Other mechanisms must also be important when the structures
are discussed based on the observed δ(Se) values. We pointed
out the importance of the orientational effect, for better
understanding the structures of p-YC6H4SeR (ArSeR) in solu-
tions based on δ(Se).5
SCHEME 2. 1 (A: pl), 2 (A: pl), and 3 (B: pd), Together
with Plausible Structures of 4-19
Odom tried to explain δ(Se) of p-YC6H4SeCOPh based on
those of related compounds such as p-YC6H4SeMe.3b However,
the effort was not successful. We wondered if the orientational
effect must be responsible for the results: The electronic effect
on δ(Se) of p-YC6H4SeCOPh must be very different from that
on δ(Se) of p-YC6H4SeMe due to the different orientational
effects for the two. Such effect was seldom discussed in the
substituent effect.7
Typical conformers in relation to the orientational effect of
ArSeR are planar (pl) and perpendicular (pd) conformers, where
the Se-CR bond in ArSeR is on the Ar plane in pl and it is
perpendicular to the plane in pd.8,9 Scheme 1 shows pl and pd
notation, together with np (nonplanar and nonperpendicular
conformer), employing ArSeX. Scheme 1 also shows the type
A (A), B, and C notation3e,4,5 exemplified by the naphthalene
system, 8-G-1-(XSe)C10H6: The Se-X bond is placed almost
perpendicular to the naphthyl plane in A, the bond is located
on the plane in B, and the C structure is the intermediate
between A and B.
To clarify the relationship between the structures and δ(Se),
it is necessary to fix the conformers of all aryl groups in ArSeR
examined.7 9-(Arylselanyl)triptycenes (1: p-YC6H4SeTpc) must
be an excellent candidate for pl where Y ) H (a), NMe2 (b),
OMe (c), Me (d), F (e), Cl (f), Br (g), COOEt (h), CN (i), and
NO2 (j) at the ground state (Chart 1). Recently, we proposed
sets of δ(Se) for pl and pd employing 9-(arylselanyl)anthracenes
(2: p-YC6H4SeAtc) and 1-(arylselanyl)anthraquinones (3:
p-YC6H4SeAtq), respectively, where Y ) H (a), NMe2 (b), OMe
(c), Me (d), F (e), Cl (f), Br (g), COOEt (h), CN (i), and NO2
(j) (Chart 1).10 The orientational effect on δ(Se) should be firmly
established for 1 in addition to 2 and 3.
The A, B, and C notation is applied to the conformers of the
9-anthryl and 1-anthraquinonyl groups in 2 and 3, respec-
tively.3e,4,5,8-10 The structure of 2 is A for the 9-anthryl group
and pl for the substituted phenyl group, which is denoted by 2
(A: pl). That of 3 is B for the 1-anthraquinonyl group and pd
for the substituted phenyl group (3 (B: pd)). We call the ground
state of 1 (A: pl) (1 (A: pl)), after the notation of 2
(A: pl) and 3 (B: pd): The Se-CAr bond in 1 (A: pl) is on the
bisected plane of two phenyl groups in the triptycyl group (see
Chart 1). The set of δ(Se) of 1 (δ(Se: 1)) must be typical for
pl. Scheme 2 shows some plausible structures of the triptycene,
anthracene, anthraquinone, naphthalene, and benzene systems,
which will be discussed in this work (see also Chart 2).
The mechanisms of the orientational effect in 2 and 3 are
elucidated thoroughly by employing the calculated absolute
(2) (a) MacFarlane, W.; Wood, R. J. J. Chem. Soc., Dalton Trans. 1972, 13,
1397–1401. (b) Iwamura, H.; Nakanishi, W. J. Synth. Org. Chem. Jpn. 1981,
39, 795–804. (c) The Chemistry of Organic Selenium and Tellurium Compounds;
Patai, S., Rappoport, Z., Eds.; John-Wiley and Sons: New York, 1986; Vol.
1, Chapter. 6. (d) Compilation of Reported 77Se NMR Chemical Shifts; Klapotke,
T. M., Broschag, M., Eds.; Wiley: New York, 1996. (e) Duddeck, H. Prog.
Nucl. Magn. Reson. Spectrosc. 1995, 27, 1-323.
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3943.
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Soc. 1998, 120, 3635–3640. (d) Nakanishi, W.; Hayashi, S. J. Org. Chem. 2002,
67, 38–48.
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Chem. Soc. 1993, 115, 5056–5059.
(7) The importance of relative conformations between substituents and probe
sites in the substituent effects is pointed out. See for example: Bordwen, K.;
Grubbs, E. J. Angular Dependence of Dipolar Substituent Effects. In Progress
in Physical Organic Chemistry; Taft, R. W., Ed.; John Wiley & Sons: New
York, 1993; Vol. 19, pp 183-224. See also references cited therein.
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9912.
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71, 5574–5585.
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9260 J. Org. Chem. Vol. 73, No. 23, 2008

77Se Chemical Shifts NMR of 9-(Arylselanyl)triptycenes
SCHEME 3. Interconversion between Conformers in 1
TABLE 1. Results of QC Calculations on 1a
CHART 2
E(A: pl)
∆E(A: pl)a
∆E(A: pd)a
∆E(B: pd)a
level
(au)
(kJ mol-1
)
(kJ mol-1
)
(kJ mol-1
)
B3LYPb
-3403.3506
-3396.0128
as 0.0
as 0.0
17.9
19.4
24.2
30.3
MP2c
a Relative to (A: pl). b The 6-311+G(d) basis sets being employed for
Se and the 6-311G(d) basis sets for C and H. c The 6-311+G(d) basis
sets being employed for Se and the 4-31G(d) basis sets for C and H.
stereochemistry in 1. The process from 1 (A: pl) to 1 (B: pd)
is called the gear rotation (GR) whereas that from 1 (A: pl) to
1 (A: pd) corresponds to the isolated rotation (IR). While the
IR process changes the sites in the p-YC6H4 group, GR changes
those in both p-YC6H4 and triptycyl groups. The (A: pl) structure
is confirmed for 1a, 1b, 1c, 1f, and 1j by the X-ray analysis,
although not shown.13 The IR process is detected to be
energetically more favored than the GR process by the dynamic
1H NMR measurements for 1,13 together with the quantum
chemical (QC) calculations.
QC calculations are performed on 1a (Y ) H), using the
Gaussian 03 program14 at DFT (B3LYP)15,16 and MP217 levels.
Table 1 shows the results of QC calculations. 1a (A: pl) is
optimized as the global minimum and 1a (A: pd) and 1a
(B: pd) are predicted to be the transition states at both B3LYP
and MP2 levels. The expectations are supported by the calcula-
tions. Consequently, δ(Se: 1) should serve as the standard for
(A: pl) in the ground state. 1a (A: pd) is predicted to be more
stable than 1a (B: pd). δ(Se) of 1 (A: pl) are determined and
the efficiency as the standard for pl is examined next.
paramagnetic shielding tensors (σp(Se)).11 The proposed
δ(Se: 2) and δ(Se: 3) values should act as the standards for the
orientational effect to determine the structures of ArSeR in
solutions. However, the temperature dependence in δ(Se: 2) is
larger than that in δ(Se: 3), which shows that the structure of 2
(A: pl) is less rigid relative to that of 3 (B: pd). It is worthwhile
to examine the new set of δ(Se) in 1 (A: pl) before applying
δ(Se: 2) and δ(Se: 3) to determine the structures of various
ArSeR in solutions, if the temperature dependence in δ(Se: 1)
is substantially smaller than that in δ(Se: 2). The p-YC6H4Se
group in 1 is attached directly to the sp3 carbon whereas that in
2 to the sp2 carbon: The effect of R in p-YC6H4SeR on δ(Se)
is also of interest, which is another reason to examine δ(Se: 1)
of (A: pl).
77Se NMR Chemical Shifts and Behavior of 1. The
δ(Se: 1) values were measured in chloroform-d solutions (0.040
M) at the temperatures of 213, 297, and 333 K, similarly to the
case of 2 and 3 (0.050 M). Table 2 shows δ(Se) for 1a-3a
from MeSeMe and δ(Se)SCS for 1-3 from 1a-3a, the parent
selenium compounds with Y ) H, respectively. Characteristic
points of 1 (A: pl) are summarized as follows: Large upfield
shifts are observed for Y ) NMe2, OMe, and Me (-22 to -6
ppm) and large downfield shifts for Y ) COOEt, CN, and NO2
(19-37 ppm) relative to Y ) H, with small upfield and
moderate downfield shifts by Y of halogens (-1 ppm for Y )
Here we propose a new set of δ(Se) for pl employing 1. After
confirmation of the availability of δ(Se: 1) as the standard for
pl, the structures in solutions are analyzed for various ArSeR
(4-19) shown in Chart 2, in view of the orientational effect.8,12
Results and Discussion
Survey of Structure and Stereochemistry of 1. Scheme 3
shows the (A: pl), (A: pd), and (B: pd) structures and some
(13) The dynamic 1H NMR spectroscopy was applied on 1. The ground state
nature of 1 (A: pl) is established. These results are in accordance with those
obtained based on δ(Se). Details of the dynamic stereochemistry based on the
temperature-dependent 1H NMR spectroscopy for 1, together with the structures,
will be reported elsewhere.
(14) Frisch, M. J. et al. Gaussian 03, revision D.02; Gaussian, Inc.:
Wallingford, CT, 2004.
(15) (a) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785–789. (b)
Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200–
206.
(16) (a) Becke, A. D. Phys. ReV. A 1988, 38, 3098–3100. (b) Becke, A. D.
J. Chem. Phys. 1993, 98, 5648–5652.
(17) (a) Møller, C.; Plesset, M. S. Phys. ReV. 1934, 46, 618–622. (b) Gauss,
J. J. Chem. Phys. 1993, 99, 3629–3643. (c) Gauss, J. Ber. Bunsenges., Phys.
Chem. 1995, 99, 1001–1008.
(11) (a) Encyclopedia of Nuclear Magnetic Resonance; Grant, D. M., Harris,
R. K., Eds.; John Wiley & Sons: New York, 1996. (b) Nuclear Magnetic
Shieldings and Molecular Structure; Tossell, J. A., Ed.; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1993. (c) Calculation of NMR and EPR
Parameters. Theory and Applications; Kaupp, M., Bu¨hl, M., Malkin, V. G., Eds.;
Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2004. (d) Spins
in Chemistry; McWeeny, R., Ed.; Academic Press: New York, 1970. (e) Markin,
V. G.; Malkina, O. L.; Eriksson, L. A. A Tool for Chemistry. In Modern Density
Functional Theory; Seminario, J. M., Politzer, P., Eds.; Elsever: Amsterdam,
The Netherlands, 1994. (f) Density-functional Methods in Chemistry and Material
Science; Springborg, M., Ed.; John Wiley & Sons: New York, 1977.
(12) Hayashi, S.; Yamane, K.; Nakanishi, W. J. Org. Chem. 2007, 72, 7587–
7596.
J. Org. Chem. Vol. 73, No. 23, 2008 9261

Nakamoto et al.
TABLE 2. Observed δ(Se)SCS of 1-3a
compd
T (K)
NMe2 (b)
OMe (c)
Me (d)
H (a)
F (e)
Cl (f)
Br (g)
CO2Et (h)
CN (i)
NO2 (j)
1
1
1
213
297
333
213
297
333
213
297
333
-21.63
-20.45
-20.03
-22.7
-21.0
-21.3
-20.6
-19.6
-19.5
-11.61
-11.24
-11.06
-12.7
-12.2
-12.7
-15.5
-15.0
-15.0
-5.93
-5.95
-5.98
-6.3
-6.6
-6.8
-9.2
-9.0
-9.1
0.00 (257.13)
0.00 (258.97)
0.00 (259.63)
0.0 (245.3)
0.0 (249.0)
0.0 (250.6)
0.0 (511.4)
0.0 (512.3)
0.0 (512.5)
-0.71
-0.66
-0.76
-3.3
3.74
3.68
3.55
1.9
1.5
1.0
-7.1
-7.1
-7.2
4.16
4.14
3.97
2.4
1.6
1.2
-6.4
-6.4
-6.7
18.69
17.20
16.47
17.4
16.2
15.2
0.1
29.90
28.62
27.93
27.7
26.2
24.8
8.5
36.56
33.67
32.41
32.7
30.4
29.0
2.7
2b
2b
2b
3b
3b
3b
-3.6
-3.9
-10.5
-10.2
-10.3
0.0
-0.3
8.2
7.9
2.5
2. 2
a δ(Se)SCS are given for 1-3 and δ(Se) for 1a-3a in parentheses, measured in chloroform-d (0.040 M for 1 and 0.050 M for 2 and 3).
b Reference 10.
TABLE 3. Correlations in δ(Se)SCS of 1-3a
F and 4 ppm for Y ) Cl and Br). This must be the result of the
entries
1
correlation
a
b
r2
n
typical p-π conjugation of the p(Se)-π(C6H4)-p(Y) type in
1 (A: pl). The characters of 1 (A: pl) are very similar to those
of 2 (A: pl) whereas they are very different from those of 3
(B: pd). However, there are some differences between δ(Se) in
1 (A: pl) and those in 2 (A: pl): Y of halogens in 2 (A: pl)
cause moderate upfield shifts by Y ) F (-4 ppm) and small
downfield shifts by Y ) Cl and Br (1-2 ppm). The differences
would be ascribed to the sp3 versus sp2 carbon atoms attached
directly to the p-YC6H4Se groups in 1 and 2, respectively.
The higher temperature dependence of δ(Se) in 2 (A: pl)
relative to 3 (B: pd) has been pointed out.10 The results strongly
suggest that the global minima of 3 (B: pd) are thermally very
stable and the (B: pd) structure is exclusive for all Y examined
in 3; however, 2 (A: pl) would fluctuate around the global
minima. 2 (A: pl) could equilibrate slightly with 2 (B: pd) for
Y of strong donors such as NMe2. The p-π conjugation of the
p(Se)-π(C6H4)-p(Y) type affects the stability of the conform-
ers. Therefore, Y of acceptors stabilize (A: pd) through the
favorable p-π conjugation, whereas Y of donors will destabilize
(A: pd) through unfavorable interactions between electron-rich
p(Se) and p(Y), which would facilitate the equilibrium between
(A: pd) and (B: pd). The δ(Se) values and the temperature
dependence must be carefully examined especially for Y of
strong donors such as Y ) NMe2 and/or OMe.
δ(Se: 1)SCS:297 vs
δ(Se: 1)SCS:213
0.9394
-0.09
0.9996
10
2
3
4
5
6
δ(Se: 1)SCS:333 vs
δ(Se: 1)SCS:213
δ(Se: 2)SCS:333 vs
δ(Se: 2)SCS:213
δ(Se: 3)SCS:333 vs
δ(Se: 3)SCS:213
δ(Se: 2)SCS:213 vs
δ(Se: 1)SCS:213
0.9128
0.9155
0.9463
0.960
-0.20
-0.75
-0.31
-1.4
0.9992
0.9996
0.9994
0.998
10
10
10
10
8b
δ(Se: 3)SCS:213 vs
δ(Se: 1)SCS:213
0.541
-8.7
0.989
a The constants (a, b, r2) are defined by eq 1 in the text. b Neglecting
the data for Y ) H and NO2.
the temperature changes from213 to 333 K (relative to 1a).
Similarly, δ(Se)SCS for 2b (Y ) NMe2) and 2j (Y ) NO2) shift
downfield and upfield by 1.4 and 3.7 ppm, respectively, when
the temperature changes from 213 to 333 K (relative to 2a).
The substituent effect on the temperature dependence in 1 and
2 is almost equal. Consequently, the temperature dependence
can be discussed based on δ(Se: 1a) and δ(Se: 2a), which is
discussed above. These results strongly support that the (A: pl)
structure in 1 is stable enough to employ δ(Se: 1) as the standard
of pl.13
What are the δ(Se) values and the temperature dependence
in 1 (A: pl)? δ(Se) of 1a (Y ) H) at 213 K is 257.13 relative
to MeSeMe: The value shifts downfield by 2.50 ppm when the
temperature goes up to 333 K under the measurement conditions
(relative to MeSeMe).18 The value of 2.50 ppm for 1a is 0.47
times larger than that in 2a (5.3 ppm)19 for the temperature range
of 213-333 K. The smaller temperature dependence of
δ(Se: 1a) relative to δ(Se: 2a) must show that the 1 (A: pl)
structure is more rigid than the case of 2, under the measurement
conditions containing the temperature change. δ(Se) of 1b (Y
) NMe2) are 235.50 (257.13 - 21.63) and 239.60 at 213 and
333 K, respectively, and those of 1j (Y ) NO2) are 293.69 and
292.04, respectively. Consequently, δ(Se) of 1b (Y ) NMe2)
and 1j (Y ) NO2) move downfield and upfield by 4.10 and
1.65 ppm, respectively, when the temperature goes up from 213
to 333 K. Similarly, δ(Se) of 2b (Y ) NMe2) and 2j (Y )
NO2) move downfield and upfield by 6.7 (229.3 - 222.6) and
1.6 ppm,19 respectively, when the temperature goes up from
213 to 333 K. The temperature dependence in δ(Se: 1b) (4.10
ppm) is substantially smaller than that of δ(Se: 2b) (6.7 ppm),
which shows that the (A: pl) structure is more stable in 1 than
the case of 2, under the measurement conditions.
To examine the temperature dependence of 1 further, δ(Se:
1) at 297 and 333 K are plotted versus those at 213 K. Plots
are analyzed according to eq 1. Table 3 collects the a, b, and r2
values for the correlations (entries 1 and 2). The correlations
are excellent (r2 > 0.999). The results suggest that the
temperature dependence of δ(Se: 1) is governed by a simple
mechanism. As mentioned above, the temperature depend-
ence of δ(Se) in 1 (A: pl) was smaller than that in 2 (A: pl)
(about 0.47 times), which must be the reflection of the more
stable global minima of 1 (A: pl), relative to 2 (A: pl).
y ) ax + b (r2: square of the correlation coefficient) (1)
We supposed that the temperature dependence of 1 would
be the reflection of the extended population to larger torsional
(18) The temperature dependence of δ(Se) of MeSeMe is reported to be ca.
2.5 ppm over the temperature range of 222-323 K with a 60% chloroform
solution. See: Luthra, N. P.; Dunlap, R. B.; Odom, J. D. J. Magn. Reson. 1983,
52, 318–322. In our case, δ(Se) of MeSeMe shifts downfield by 5.6 ppm for a
10% chloroform solution, relative to the frequency of the spectrometer, when
the temperature changes from 213 to 333 K. The results show that the temperature
dependence of 1a is about 1.5 times of that of MeSeMe. The temperature
dependence of δ(Se) of 1j is comparable to that of MeSeMe.
(19) (Se) of 2b (Y ) NMe2) and 2j (Y ) NO2) move downfield by 6.7 and
1.6 ppm, respectively, relative to MeSeMe, when the temperature changes from
213 to 333 K.
δ(Se)SCS for 1b (Y ) NMe2) and 1j (Y ) NO2) shift
downfield and upfield by 1.60 and 4.15 ppm, respectively, when
9262 J. Org. Chem. Vol. 73, No. 23, 2008

77Se Chemical Shifts NMR of 9-(Arylselanyl)triptycenes
TABLE 4. Observed δ(Se)SCS of 4-9a
compd
NMe2 (b)
OMe (c)
Me (d)
H (a)
F
(e)
Cl (f)
Br (g)
CO2Et (h)
CN (i)
NO2 (j)
4b
5c
6d
7d
8e
-11.5
-6.8
-14.9
-14.0
-9.8
-2.3
-12.8
-6.2
-4.8
-9.1
-8.6
-6.6
-0.9
-7.0
0.0 (274.6)
0.0 (361.0)
0.0 (460.1)
0.0 (451.0)
0.0 (434.3)
0.0 (235.4)
0.0 (429.0)
1.1
-1.6
-6.3
-6.4
-2.7
-0.7
0.1
1.4
-1.7
-5.7
-5.9
-1.9
-0.2
0.6
15.0
7.0
3.9
2.7
8.1
29.2
18.6
15.4
13.4
19.6
4.7
-17.2
-5.0
13.8
13.2
3.8
13.5
9e
27.1
a δ(Se)SCS are given for 4-9, together with δ(Se) for 4a-9a in parentheses, measured in chloroform-d. b Reference 12. c References 10 and 12.
d Reference 4d. e Reference 4a.
angles around the energy minima due to the relatively shallow
energy surface. The temperature dependence in solvation must
also affect the dependence of δ(Se).
Basic behaviors of δ(Se) for 2 (A: pl) and 3 (B: pd) are
discussed in the preceding paper.10 The plots of δ(Se: 2)SCS:333
versus δ(Se: 2)SCS:213 and δ(Se: 3)SCS:333 versus δ(Se: 3)SCS:213
gave excellent correlations, which are also shown in Table 3
for convenience of comparison (entries 3 and 4, respectively:
r2 > 0.999). δ(Se)SCS of 2 (A: pl) and 3 (B: pd) are plotted
versus those of 1 (A: pl). Panels a and b of Figure 1 show
the plots of δ(Se: 2)SCS:213 versus δ(Se: 1)SCS:213 and
δ(Se: 3)SCS:213 versus δ(Se: 1)SCS:213, respectively. The former
gave a very good correlation (r2 ) 0.998: Figure 1a): The
difference between δ(Se: 1)SCS and δ(Se: 2)SCS for Y of halogens
must be responsible for r2 slightly smaller than 1.000. A good
correlation was also obtained for the latter (Figure 1b), although
data corresponding to Y ) H and NO2 deviated from the
correlation. Table 3 collects the correlations (entries 5 and 6,
respectively).
Compilation of these results, the rules of thumb, which are
useful to examine the structures of ArSeR in solutions in view
of the orientational effect based on δ(Se: 1)SCS, δ(Se: 2)SCS
,
and δ(Se: 1)SCS as the standards, are summarized as follows:
(1) For 1 (A: pl), δ(Se: 1e: Y ) F) is very close to
δ(Se: 1a: Y ) H) with δ(Se: 1f: Y ) Cl) and δ(Se: 1g: Y )
Br) also close to δ(Se: 1a). (2) δ(Se: 2f: Y ) Cl) and δ(Se: 2g: Y
) Br) are very close to δ(Se: 1a) for 2 (A: pl). (3) In the case of
3 (B: pd), δ(Se: 3h: Y ) COOEt) is very similar to δ(Se: 3a) and
δ(Se: 3i: Y ) CN) is more downfield of δ(Se: 1j: Y ) NO2). (4)
Indeed, δ(Se) of 3 (B: pd) correlates well with δ(Se) of 1 (A: pl)
(and 2 (A: pl)), except for Y ) H and NO2, but the magnitude of
the y-intercept (b in eq 1) is evaluated to be large (around 9 ppm)
even if data corresponding to Y ) H and NO2 are neglected. (5)
The points corresponding to Y ) H, Me, and OMe seem to align
linearly in the plot of δ(Se: 3) (pd) versus δ(Se: 1 or 2) (pl) (see
Figure 1b). The rules of thumb are applied to examine the structure
of p-YC6H4SeR in solutions, in addition to the plot for each
compound in question.
How can the structures of the naphthalene system be
determined based on δ(Se)SCS in solutions from the view of the
orientational effect? δ(Se)SCS values of 4-9 are analyzed based
on those of 1-3, first.
Structures of the Naphthalene System in Solutions
Analyzed Based on δ(Se)scs. Table 4 collects δ(Se)SCS of the
naphthalene system, 4-9. To organize the process for the
analysis, δ(Se: 9)SCS are plotted versus δ(Se: 4)SCS and
δ(Se: 7)SCS are versus δ(Se: 6)SCS. The correlations are given
in Table 5 (entries 1 and 2, respectively). The correlations are
excellent (r2 g 0.999). The results show that the structure of
each member in 9 is very close to that of 4 and the structure of
7 to that of 6, in solutions. Therefore, the structures of 4 (or 9),
FIGURE 1. Plots of δ(Se: 2)SCS:213 versus δ(Se: 1)SCS:213 (a) and
δ(Se: 3)SCS:213 versus δ(Se: 1)SCS:213 (b).
5, 6 (or 7), and 8 should be analyzed from the viewpoint of the
orientational effect. δ(Se: 1)SCS:213, δ(Se: 2)SCS:213, and
δ(Se: 3)SCS:213 are employed for the analysis. The correlations
are shown in Table 5. The plots versus δ(Se: 1)SCS:213 and
δ(Se: 3)SCS:213 are employed for the analysis in the text.
δ(Se: 4)SCS are plotted versus δ(Se: 1pl)SCS:213 and
δ(Se: 2pl)SCS:213. The correlations are excellent (entries 3 and
4, respectively, in Table 5: r2 ) 0.997 and 1.000, respectively).
J. Org. Chem. Vol. 73, No. 23, 2008 9263

Nakamoto et al.
TABLE 5. Correlations between δ(Se)SCS in 2-9, together with 1a
entries
1
correlation
a
b
r2
n (Y)
δ(Se: 9)SCS-Ar vs
δ(Se: 4)SCS
δ(Se: 7)SCS vs
δ(Se: 6)SCS
0.969
-0.9
0.999
7
2
0.904
0.842
0.898
0.906
0.618
0.777
0.634
0.735
0.674
0.846
0.714
0.771
2.096
0.638
-0.5
-1.3
-0.4
-0.1
-4.3
0.4
0.999
0.997
1.000
0.999
0.999
0.972
0.995
0.963
0.999
0.966
0.999
0.960
0.941
0.992
7
3
δ(Se: 4)SCS vs
δ(Se: 1)SCS:213
δ(Se: 4)SCS vs
δ(Se: 2)SCS:213
δ(Se: 7)SCS vs
δ(Se: 3)SCS:213
δ(Se: 5)SCS vs
δ(Se: 1)SCS:213
δ(Se: 5)SCS vs
δ(Se: 1)SCS:213
δ(Se: 5)SCS vs
δ(Se: 2)SCS:213
δ(Se: 5)SCS vs
δ(Se: 2)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 1)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 1)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 2)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 2)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 3)SCS:213
δ(Se: 8)SCS-Ar vs
δ(Se: 3)SCS:213
7
4
7
5
5b
6c
4d
6c
4d
4e
3f
4e
3f
4e
3f
6
7
8
-3.1
0.5
9
10
11
12
13
14
15
-4.9
-0.5
-3.9
-0.6
11.4
-0.2
FIGURE 3. Plot of δ(Se: 7)SCS versus δ(Se: 3pd)SCS:213
.
those for Y ) CN and NO2 do substantially. δ(Se: 7h: Y )
COOR) is fairly close to δ(Se: 7a). The results demonstrate
that the structure of 7 is all pd, except for Y ) COOEt, CN,
and NO2; while pd in 7 is slightly equilibrated with pl for Y )
COOEt, pd and pl are substantially equilibrated for Y ) CN
and NO2. The conclusion obtained for 7 must also be effective
for 6 in solutions.
Why do 6 and 7 equilibrate between pd and pl in solutions
for Y ) CN and NO2? The driving force for the (B: pd)
structures of 6 and 7 is the energy lowering effect through the
hypervalent 3c-4e interaction of the np(X)---σ*(Se-C) type
(X ) Cl and Br). Similarly, that of 3 (B: pd) is the hypervalent
3c-4e interaction of the np(O)---σ*(Se-C) type. The p-π
conjugation of the p(Se)-π(Atc)-π(CdO) type assists strongly
to stabilize 3 (B: pd) in addition to the hypervalent 3c-4e
interaction in 3 (B: pd). Namely, the driving force to stabilize
3 (B: pd) is very strong whereas that in 6 and 7 would not be
so strong. Consequently, 6 and 7 cannot exist exclusively as
(B: pd) for Y ) CN and NO2 (and Y ) COOEt). They
equilibrate between (B: pd) and (A: pl) in solutions. Scheme 4
explains the interactions.
a The constants (a, b, r2) are defined by eq 1 in the text. b Y ) OMe,
Me, H, Cl, and Br. c Y ) F, Cl, Br, COOEt, CN, and NO2. d Y )
NMe2, OMe, Me, and H. e Y ) Cl, Br, COOEt, and NO2. f Y ) OMe,
Me, and H.
δ(Se: 5)SCS are plotted versus δ(Se: 1pl)SCS:213, δ(Se: 2pl)SCS:
213, and δ(Se: 3pd)SCS:213 next. Panels a and b in Figure 4 show
the plots versus δ(Se: 1pl)SCS:213 and δ(Se: 3pd)SCS:213, respec-
tively. The plot in Figure 4a is analyzed by two groups: Data
with Y ) NMe2, OMe, Me, and H make up one group and
those with Y ) NO2, CN, COOEt, Br, Cl, and F belong to
another. The correlations are given in Table 5 (entries 6-9).
Correlations seem poor in the plot versus δ(Se: 3pd)SCS (Figure
4b). One might conclude that the structure of 5 is (A, pl) for Y
) NO2, CN, COOEt, Br, Cl, and F in solutions at first glance.
However, the correlation must be carefully examined, since the
b values are -3.1 to -4.3, which are not close to 0.0 (see entries
6 and 8 in Table 5). The structure of 5 should be exclusively
(A: pl) for Y ) NO2 and CN; however, the equilibrium between
(A: pl) and (B: pd) contribute gradually in solutions as the
acceptor ability of Y becomes weaker, although the plot gives
an excellent correlation for Y ) NO2, CN, COOEt, Br, Cl, and
F. Finally (B: pd) would be predominant for Y ) NMe2 (and
Y ) OMe) in solutions. The equilibrium would substantially
contribute to the structure of 5 with Y ) H, Me, and halogens.
FIGURE 2. Plot of δ(Se: 4)SCS versus δ(Se: 1pl)SCS:213
.
Figure 2 shows the plot of δ(Se: 4)SCS versus δ(Se: 1pl)SCS:213
The structures are concluded to be pl for all members in 4 and
9 in solutions.
δ(Se: 7)SCS are plotted versus δ(Se: 3pd)SCS:213 next. Figure
3 shows the results. An excellent correlation is obtained for Y
) OMe, Me, H, Cl, and Br (r2 g 0.999): The correlation with
Y ) OMe, Me, H, Cl, and Br is shown in Table 5 (entry 5).
Data for Y ) COOEt deviate slightly from the correlation and
.
9264 J. Org. Chem. Vol. 73, No. 23, 2008

77Se Chemical Shifts NMR of 9-(Arylselanyl)triptycenes
SCHEME 4. Driving Force for the Formation of (B: pd) in 3, 6, and 7
Three conformers should be in equilibrium for 8 in solutions,
as shown in eq 2. Conformer 8 (AB-1) will be stabilized by Y of
strong donors such as Y ) OMe, 8 (AB-2) by acceptors such as
Y ) NO2, and 8 (CC) by Y of electronically neutral groups
correlations. An excellent correlation is obtained for Y ) NO2,
COOEt, Br, and Cl in the plot of δ(Se: 8)SCS versus δ(Se: 1pl)SCS:
213 (r2 g 0.999), together with a good correlation for Y ) OMe,
Me, and H (r2 ) 0.96-0.97) with small b values (-0.5 to -0.6)
(Figure 5a). Figure 5a is very similar to Figure 4a, although data
for 8i (Y ) CN) are missing. A good correlation is obtained in
the plot of δ(Se: 8)SCS versus δ(Se: 3pd)SCS:213 (r2 g 0.992) with a
very small b value (-0.2) for Y ) OMe, Me, and H (Figure 5b).
The results strongly support that the structure of 8 is AB-2 for Y
) NO2, COOEt, Br, and Cl in solutions whereas it is mainly AB-2
for Y ) OMe, Me, and H, although some equilibrium may
contribute to that for 8 for Y of electronically neutral groups.
such as H. δ(Se: 8)SCS are plotted versus δ(Se: 1pl)SCS:213
,
δ(Se: 2pl)SCS:213, and δ(Se: 3pd)SCS:213. Panels a and b of Figure 5
show the plots of δ(Se: 8)SCS versus δ(Se: 1pl)SCS:213 and
δ(Se: 3pd)SCS:213, respectively. The plots are analyzed as two
8a (Y ) H), 8c (Y ) OMe), and 8f (Y ) Cl) are observed
as 8 (CC), 8 (AB-1), and 8 (AB-2), respectively, in crystals.8
Namely, 8 (AB-1) is stabilized by the np(Se)---σ*(Se-C)
interactions for Y of donors and (AB-2) by those with Y of
acceptors. The structure of 8 must be in equilibrium between
the three conformers in solutions for Y of electronically neutral
groups. The consideration is in accordance with the predicted
structures in solutions.
Correlations are better with δ(Se: 2) than δ(Se: 1) as the
standard in some cases. This is ascribed to the sp3 versus sp2
carbon atom attached directly to the p-YC6H4Se group in 1
versus 2, respectively. This must be of interest as the R effect
on δ(Se) of p-YC6H4SeR, although the observed differences
seem small.
After clarification of the structures in solutions for the
naphthalene system, the next extension is to clarify the structures
of the benzene system in solutions.
Structures of the Benzene System in Solutions Ana-
lyzed Based on δ(Se)scs. Table 6 collects the δ(Se)SCS values
of the benzene system (10-19).5 The δ(Se)SCS values of 10-19
are plotted versus those of 1-3. Table 7 summarizes the results.
The correlations versus δ(Se: 2)SCS:213 seem slightly better than
those versus δ(Se: 1)SCS:213 if all data of each compound are
plotted as shown in Table 7. However, the correlations versus
δ(Se: 1)SCS:213 are better than those versus δ(Se: 2)SCS:213 in
some cases when data of each compound are plotted separately
by two groups. The plots of δ(Se: 10-19)SCS versus δ(Se: 1)-
SCS:213 separately by the two groups, together with the correla-
tions, are shown in Figures 6-9: The correlations versus δ(Se:
2)SCS:213 are given in Table S1 of the Supporting Information
FIGURE 4. Plots of δ(Se: 5)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
J. Org. Chem. Vol. 73, No. 23, 2008 9265

Nakamoto et al.
solvent
TABLE 6. Observed δ(Se)SCS of 10-19a b
,
compd
OMe (c)
Me (d)
H (a)
F (e)
-4.0
Cl (f)
Br (g)
CO2Et (h)
NO2 (j)
10
11
11′
12
13
14
15
16
17
18
19
-23.0
-10.4
-12.5
-15.5
-28.0
-12.0
-12.6
18.7
-17.0
-7.2
-5.9
-8.6
-16.2
-7.8
-7.1
7.9
0.0 (145)
-3.0
2.5
1.6
-1.7
-3.7
0.2
neat
CDCl3
neat
CDCl3
CDCl3
CDCl3
CDCl3
CDCl3
e
0.0 (207.8)
0.0 (202.0)
0.0 (423.6)
0.0 (423.6)
0.0 (320.8)
0.0 (641.5)
0.0 (869.0)
0.0 (395.5)
0.0 (368.6)
0.0 (370.2)
2.8
20.1c
16.1d
9.7
13.1
8.6
33.4
31.4
22.7
23.8
18.0
4.2
-2.0
-1.3
-7.1
0.9
-10.7
-2.5
-7.1
-4.5
-4.1
0.8
-46.0
-8.8
-4.6
-4.0
-7.3
-0.1
-2.3
0.3
0.5
-2.1
1.3
9.4
8.4
-6.8
e
e
-13.4
26.6
a δ(Se)SCS are given for 10-19, together with δ(Se) for 10a-19a in parentheses. b Given or summarized in reference 5. c COOH. d COOME. e Not
specified.
should be pl in solutions for each member examined, although
a slight equiliburium with pd might contribute to the structures
especially for Y of strong donors.
A unique equilibrium may contribute to p-YC6H4SeC6H4Y′-
p′ (13′) in solutions. Equation 3 shows the equilibrium.
Conformer 13′ (C2) is observed for Y ) Y′ in crystals,20 13′
(pl) will be stabilized when the accepting ability of Y is stronger
than that of Y′ and 13′ (pd) will be more stable than 13′ (pl) if
Y is a stronger donor than Y′. The structures of 12 and 13 in
solutions will be analyzed considering the equilibrium shown
by eq 3.
ArSePh (12) corresponds to 13′ with Y′ ) H. Panels a
and b of Figure 6 show the plot of δ(Se: 12)SCS versus
δ(Se: 1)SCS:213 and δ(Se: 3)SCS:213, respectively. Whereas the
r2 values are not so good if analyzed for all Y, the values
become larger than 0.997 if data are analyzed separately by
Y ) OMe, Me, and H (Group 1) and Y ) NO2, COOEt, Br,
and Cl (Group 2), except for δ(Se: 12)SCS versus δ(Se: 3)SCS:
213 for Group 2. The results show that the structure of 12 is
pl for Group 2. However, the negative b value of -4.4 ppm
for Group 2 in the plot of δ(Se: 12)SCS versus δ(Se: 1)SCS:213
must be the reflection of the substantial equilibrium for Y of
electronically neutral groups. The structure of 12 for Group
1 is expected to be pd. However, the structure is more
plausible in equilibrium between pl and pd for Group 1,
although pd would be predominant for Y ) OMe.
Panels a and b of Figure 7 show the plot of δ(Se: 13)SCS
versus δ(Se: 1)SCS:213 and δ(Se: 3)SCS:213, respectively. Figure
7a,b is close to Figure 6a,b, respectively, although some
deviations are observed in Figure 7a. δ(Se: 13)SCS are all
negative for Y ) F, Cl, and Br and δ(Se: 13j: Y ) NO2)SCS is
relatively close to δ(Se: 13h: Y ) COOEt)SCS, which must be
the reflection of the substantial contribution from pd. This must
be intrinsically observed, since if the structure of 13 is pl for Y
it should be pd for Y′, where Y ) Y′ in 13. Large magnitudes
of the b values in the plots for Group 2 support the consideration.
The structure must also be in equilibrium with that of the C2
symmetry, especially for Y of electronically neutral groups.
FIGURE 5. Plots of δ(Se: 8)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
(SI). δ(Se: 1)SCS:213 and δ(Se: 3)SCS:213 are employed to analyze
the structures of the benzene system in the text.
δ(Se: 10)SCS will not be discussed, since some data needed
for discussion are missing. The plots of δ(Se)SCS in 11 versus
δ(Se: 1)SCS:213 and δ(Se: 2)SCS:213 gave very good correlations
(cf. 11′, measured neat). The r2 values are larger than 0.99. The
plots are shown in Figure S1 in the SI. The structure of 11
(20) (a) Blackmore, W. R.; Abrahams, S. C. Acta Crystallogr. 1955, 8, 323–
328. (b) Klapo¨tke, T. M.; Krumm, B.; Polborn, K. Eur. J. Inorg. Chem. 1999,
1359–1366.
9266 J. Org. Chem. Vol. 73, No. 23, 2008

77Se Chemical Shifts NMR of 9-(Arylselanyl)triptycenes
TABLE 7. Correlations of δ(Se)SCS for 10-19 versus Those of 1-3a
δ(Se: 1)SCS:213
δ(Se: 2)SCS:213
δ(Se: 3)SCS:213
compd
a
b
r2
a
b
r2
a
b
r2
n
δ(Se: 10)SCS
δ(Se: 11)SCS
δ(Se: 11′)SCS
δ(Se: 12)SCS
δ(Se: 13)SCS
δ(Se: 14)SCS
δ(Se: 15)SCS
δ(Se: 16)SCS
δ(Se: 17)SCS
δ(Se: 18)SCS
δ(Se: 19)SCS
1.567
0.951
0.900
0.752
1.016
0.599
0.305
-1.309
0.346
0.298
0.807
-4.9
-0.3
-1.1
-4.1
-9.3
-2.7
-5.5
1.4
0.871
0.992
0.998
0.973
0.908
0.969
0.762
0.997
0.919
0.936
0.990
1.625
1.014
0.952
0.804
1.086
0.634
0.330
-1.410
0.375
0.324
0.871
-2.8
0.8
0.1
0.871
0.994
0.999
0.983
0.929
0.972
0.799
0.999
0.933
0.955
0.996
1.399
2.013
1.874
1.754
2.468
1.321
0.852
-2.810
0.845
0.723
1.783
2.4
16.1
14.7
9.6
10.6
8.3
1.1
-20.3
4.4
3.1
11.8
0.623
0.683
0.716
0.814
0.886
0.778
0.984
0.685
0.823
0.829
0.727
5
7
7
7
8
8
8
4
6
6
6
-3.3
-8.0
-1.9
-5.1
0.0
-1.7
-2.1
-1.4
-2.2
-2.5
-2.4
a The constants (a, b, r2) are defined by eq 1 in the text.
FIGURE 7. Plots of δ(Se: 13)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
FIGURE 6. Plots of δ(Se: 12)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
Although δ(Se)SCS shift largely to upfield by Y ) OMe and
Me in both pl and pd, the downfield shifts by Y ) COOEt and
NO2 are large only in pl whereas the shift values are very small in
pd (see Table 2). The behavior seems to have an affect on the a
J. Org. Chem. Vol. 73, No. 23, 2008 9267

Nakamoto et al.
FIGURE 9. Plots of δ(Se: 15)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
FIGURE 8. Plots of δ(Se: 14)SCS versus δ(Se: 1pl)SCS:213 (a) and those
versus δ(Se: 3pd)SCS:213 (b).
correlation line in Figure 8a must correspond to the equilibrium
with pd for Y ) Me and OMe.
values in the plots of δ(Se: 11-13)SCS versus δ(Se: 1)SCS:213. While
the a values are 0.951 (11), 1.336 (12), and 2.414 (13) for Group
1 (Y ) OMe, Me, and H), they are 0.951 (11), 0.743 (12), and
0.946 (13) for Group 2 (Y ) NO2, COOEt, Br, and Cl). The ratios
in a (13)/a (11) are 0.254 and 0.995 for Group 1 and Group 2,
respectively.
Panels a and b of Figure 8 show the plot of δ(Se: 14)SCS
versus δ(Se: 1)SCS:213 and δ(Se: 3)SCS:213, respectively. The
δ(Se: 14)SCS values for Y ) H, Cl, and Br are very close to
each other and that for Y ) F is also close to them. The
δ(Se: 14)SCS value for Y ) NO2 is very different from that for
Y ) COOEt. The observations show the pl character of
δ(Se: 14)SCS. Consequently, the structure is concluded to be pl
for all members of 14, although some equilibrium between pl
and pd may contribute as the donor ability of Y becomes larger.
The deviation of the data for Y ) Me and OMe from the
δ(Se: 15)SCS are reported not to correlate well with those of
3b
usual ArSeR such as δ(Se: 11)SCS
.
Panels a and b of Figure
9 show the plot of δ(Se: 15)SCS versus δ(Se: 1)SCS and
δ(Se: 3)SCS, respectively. The correlation in Figure 9b is good
(r2 ) 0.984). Therefore, the structure of 15 is concluded to be
pd for all members in solutions, although a slight equilibrium
with pl would contribute in solutions. The rules of thumb
support this conclusion.
The plot of δ(Se: 16)SCS versus δ(Se: 1pl)SCS is of great
interest, since the correlation constant is negative (a ) -1.3).
Further investigations are necessary to clarify the reason for
the negative correlation, since the data for the plot are limited.
δ(Se: 18)SCS seem to correlate well with δ(Se: 1pl)SCS and
δ(Se: 17)SCS are also expected to with δ(Se: 1pl)SCS. However,
data for the plots are not enough to consider the structures in
9268 J. Org. Chem. Vol. 73, No. 23, 2008

77Se Chemical Shifts NMR of 9-(Arylselanyl)triptycenes
271.0-272.5 °C; 1H NMR (300 MHz, CDCl3/TMS) δ 5.44 (s, 1H),
6.92 (dt, J ) 1.4, 7.6 Hz, 3H), 7.01 (dt, J ) 1.3, 7.4 Hz, 3H),
7.07-7.11 (m, 3H), 7.16-7.20 (m, 2H), 7.40 (dd, J ) 1.2, 7.2 Hz,
3H), 7.54 (d, J ) 7.4 Hz, 3H); 13C NMR (75.5 MHz, CDCl3/TMS)
δ 54.2, 61.0, 123.3 (3C), 124.9 (3J(Se,C) ) 12.1 Hz, 3C), 125.0
(3C), 125.4, 125.8 (3C), 128.7 (m-Ph, 2C,), 129.9 (2J(Se,C) ) 15.6
Hz, 2C), 130.7, 144.0 (2J(Se,C) ) 6.2 Hz, 3C), 145.3 (3C); 77Se
(57.3 MHz, CDCl3/Me2Se) δ 259.0. Anal. Calcd for C26H18Se: C,
76.28; H, 4.43. Found: C, 76.42; H, 4.33.
solutions. δ(Se: 19)SCS correlate well with δ(Se: 1 pl)SCS, which
may show that 19 exists predominantly in pl in solutions,
although data for the plot are not enough to conclude the
structures, either.
The sp2 and sp3 carbon atoms are attached directly to the
p-YC6H4Se group in 1 and 2, respectively. Therefore, the
correlation is expected to be better with δ(Se: 2) than δ(Se: 1)
as the standard when δ(Se) from the π-framework in ArSeAr′
is examined and vice versa. This must be of great interest as
the R effect in p-YC6H4SeR on δ(Se), although the observed
magnitudes seem small.
9-[p-(N,N-Dimethylamino)phenylselanyl]triptycene (1b). Un-
der a nitrogen atmosphere, to a suspension of di-9-triptycyl
diselenide22 (900 mg, 1.38 mmol) and 40 mL of THF at 0 °C was
added NaBH4 (110 mg, 2.76 mmol) in a small amount of water. A
solution of 6.0 equiv of p-(N,N-dimethylamino)phenyldiazonium
chloride was added at 0 °C. If an orange precipitate appeared,
NaBH4 (110 mg, 2.76 mmol) in an aqueous THF solution was added
to the reaction solution. Dichloromethane (200 mL) and a 2%
aqueous solution of sodium hydroxide were added. The organic
layer was separated and washed with a 10% aqueous solution of
sodium bicarbonate and a saturated aqueous solution of sodium
hydrogen carbonate, then dried over potassium carbonate. The crude
product was purified by column chromatography (SiO2, benzene/
hexane 1:1 as eluent) and recrystallization from hexane. 1b was
isolated in 6% yield as pale yellow needles (19 mg): mp
227.5-229.0 °C; 1H NMR (300 MHz, CDCl3/TMS) δ 2.87 (s, 6H),
5.42 (s, 1H), 6.55 (d, J ) 9.0 Hz, 2H), 6.94 (dt, J ) 1.5, 7.5 Hz,
3H), 7.01 (dt, J ) 1.3, 7.3 Hz, 3H), 7.10 (d, J ) 9.1 Hz, 2H), 7.40
(dd, J ) 1.3 and 7.1 Hz, 3H), 7.60 (d, J ) 7.4 Hz, 3H); 13C NMR
(75.5 MHz, CDCl3/TMS) δ 40.5 (2C), 54.3, 60.5, 113.4 (2C), 123.1
(3C), 125.0 (3C), 125.1 (3C), 125.1, 125.6 (3C), 131.0 (2J(Se,C)
) 15.3 Hz, 2C), 144.5 (2J(Se,C) ) 6.2 Hz, 3C), 145.4 (3C), 148.6;
77Se (57.3 MHz, CDCl3/Me2Se) δ 238.5. Anal. Calcd for
C28H23NSe: C, 74.33; H, 5.12; N, 3.10. Found: C, 74.13; H, 5.11;
N, 3.14.
Conclusion
A new set of δ(Se) are proposed for pl, employing 9-(ar-
ylselanyl)triptycenes (1: p-YC6H4SeTpc, Y ) H (a), NMe2 (b),
OMe (c), Me (d), F (e), Cl (f), Br (g), COOEt (h), CN (i), and
NO2 (j)), in addition to the sets of δ(Se) proposed employing
9-(arylselanyl)anthracenes (2 (A: pl)) and 1-(arylselanyl)an-
thraquionones (3 (A: pd)). δ(Se: 2) and δ(Se: 3) must serve as
the standard for pl and pd in solutions, respectively. The
temperature dependence of δ(Se: 1) is substantially improved
relative to that for δ(Se: 2). The character of δ(Se) in 1 (pl) is
very similar to that in 2 (pl), although δ(Se: 1) are different
from δ(Se: 2) for Y of halogens, which is of great interest. The
character in 1 (pl) is very different from that of 3 (pd). δ(Se)
of 1-3 are demonstrated to serve as the standard to determine
the structures in solutions. Structures of various ArSeR for R
of the benzene and naphthalene systems are determined in
solutions from the viewpoint of the orientational effect based
on δ(Se) of 1-3. The rules of thumb derived from the characters
in δ(Se) of 1 (A: pl), 2 (A: pl), and 3 (A: pd) are also very
useful to determine the structures of ArSeR in solutions, in
addition to the analysis of the plots.
The preparations of 1c-1j are given in the SI.
QC Calculations. Quantum chemical (QC) calculations are
performed on 1a (Y ) H) with use of the Gaussian 03 program14
at the density functional theory (DFT) level of the Becke three-
parameter hybrid functional combined with the Lee-Yang-Parr
correlation functional (B3LYP)15,16 and the Møller-Plesset second
order energy correlation (MP2)17 levels.
Experimental Section
9-(Phenylselanyl)triptycene (1a). Under an argon atmosphere,
to a solution of 9-bromotriptycene21 (510 mg, 1.50 mmol) in 12
mL of benzene and 40 mL of diethyl ether at 0 °C was added 1.0
mL of n-BuLi (1.62 mmol, 1.62 M). After 1 h of stirring, the fine
suspension of 9-triptycyllithum was added to an ethereal solution
of 1.0 equiv of benzeneselenobromide. After being stirred for 1 h
at 0 °C, the reaction was quenched by acetone (4 mL), and the
solvent was removed in vacuo. A 100 mL sample of benzene and
a 6% aqueous solution of hydrochloric acid were added. The organic
layer was separated and washed with 50 mL of water, 50 mL of a
10% aqueous solution of sodium bicarbonate, 50 mL of a saturated
aqueous solution of sodium hydrogen carbonate, and 50 mL of water
and dried over anhydrous sodium sulfate. The crude product was
purified by column chromatography (SiO2, benzene/hexane 1:2 as
eluent) and recrystallized from dichloromethane and hexane. 1a
was isolated in 32% yield as a colorless solid (195 mg): mp
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research (Nos. 16550038, 19550041,
and 20550042) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan.
Supporting Information Available: Plots of δ(Se)SCS in 11
(11′) versus δ(Se: 1)SCS:213 and/or δ(Se: 2)SCS:213, experimental
procedure, preparations of 1c-1j, NMR spectra of 1, complete
reference 14, and optimized structures given by Cartesian
coordinates for 1a at the DFT (B3LYP) and MP2 levels. This
material is available free of charge via the Internet at
http://pubs.acs.org.
JO801786J
(21) Bartlett, P. D.; Cohen, S. G.; Cotman, J. D., Jr.; Kornblum, N.; Landry,
J. R.; Lewis, E. S. J. Am. Chem. Soc. 1950, 72, 1003–1004.
(22) Ishii, A.; Matsubayashi, S.; Takahashi, T.; Nakayama, J. J. Org. Chem.
1999, 64, 1084–1085.
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