Efficient synthesis of functionalized [7]helicenes

Article abstract of DOI:10.1021/jo981380y

[7]Helicenebisquinones can be made easily and in quantity by reacting the silyl enol ethers of a 9,10-dialkoxy-, or better a 9,10-disiloxy-, 3,6-diacetylphenanthrene, with p-benzoquinone. If an ethyl enol ether is used in place of the silyl enol ether, the transformation proceeds in much lower yield. The [7]helicenes are efficiently resolved into their enantiomers, and absolute configurations are assigned.

Full text of DOI:10.1021/jo981380y

7456
J . Org. Chem. 1998, 63, 7456-7462
Efficien t Syn th esis of F u n ction a lized [7]Helicen es
J oseph M. Fox, Naomi R. Goldberg, and Thomas J . Katz*
Department of Chemistry, Columbia University, New York, New York 10027
Received J uly 15, 1998
[7]Helicenebisquinones can be made easily and in quantity by reacting the silyl enol ethers of a
9,10-dialkoxy-, or better a 9,10-disiloxy-, 3,6-diacetylphenanthrene, with p-benzoquinone. If an
ethyl enol ether is used in place of the silyl enol ether, the transformation proceeds in much lower
yield. The [7]helicenes are efficiently resolved into their enantiomers, and absolute configurations
are assigned.
In 1967, the synthesis of [7]helicene1sthe first helicene
produce helicenes in large quantity and with useful
functional groups.
made using the photocyclization of a stilbene2 as the key
stepswas reported by Martin and co-workers. Prior to
this report, the only carbohelicenes synthesized were [5]-3
and [6]helicenes.4 Because the stilbene precursors are
easy to prepare and the photocyclizations are easy to
carry out, within 8 years of Martin’s initial report, this
procedure had been used to prepare all of the parent
helicenes between [6]- and [14]helicene.5 It soon became
possible to convert helicenes into materials with even
more unusual structures and even more interesting
optical properties.6 However, stilbene photocyclizations
have serious limitations. They must be carried out using
solutions that are very dilute.2a,7 For example, while
irradiating a 1.67 mM solution of 4,4′-dimethylstilbene
for 8 h produces 3,6-dimethylphenanthrene in 97% yield,
increasing the concentration to 4.7 mM lowers the yield
to 23%.7,8 (A 59% yield of unreacted starting material is
recovered.) Another limitation is that amino, nitro, and
other functional groups that relax the singlet excited
states of stilbenes inhibit photocyclizations.2a Thus, there
is a need for procedures that are operationally as simple
as photocyclizations, but that unlike photocyclizations
Although there are a number of syntheses of helicenes
that do not use light, the majority produce either [5]-
helicenes, which racemize at an appreciable rate at room
temperature,9 or heterohelicenes that are also likely to
have low barriers to racemization.10 The others4,11 have
given helicenes that are either unfunctionalized or func-
tionalized only by methyls11g,h,i or a carboxylic acid.11a
Recently, we showed that combining the enol ethers of
1,4-diacetylbenzene and 2,7-diacetylnaphthalene with
p-benzoquinone produces derivatives of [5]- and [6]-
helicene in large quantity.12 Furthermore, the helicenes
synthesized by this method contain a useful functional-
ity-alkoxyl side-chains, which render the compounds
soluble in a variety of organic solvents,12 and quinones,
which have rich chemistry13-and both these helicenes6fg,14
and materials made from them15 display interesting
properties. For these reasons and because there is no
nonphotochemical method for preparing [7]carboheli-
cenes, it would be significant if functionalized [7]helicenes
could be made in quantity by an analogous method.
We report below that enol ethers of appropriate and
easily accessible 3,6-diacetylphenanthrenes do indeed
combine with p-benzoquinone to produce [7]helicenebis-
quinones. We show how such preparations can be carried
out on a very large scale, and we show how the [7]-
helicene derivatives can be obtained in nonracemic
form.
(1) Flammang-Barbieux, M.; Nasielski, J .; Martin, R. H. Tetrahedron
Lett. 1967, 743.
(2) (a) Mallory, F. B.; Mallory, C. W. Organic Reactions; Wiley: New
York, 1984; Vol. 30, p 1. (b) Laarhoven, W. H.; Prinsen, W. J . C. Top.
Curr. Chem. 1984, 125, 63.
(3) (a) Weitzenbo¨ck, R.; Klingler, A. Monatsh. Chem. 1918, 39, 315.
(b) Cook, J . W. J . Chem. Soc. 1933, 1592. (c) Weidlich, H. A. Chem.
Ber. 1938, 71, 1203. (d) Altman, Y.; Ginsburg, D. J . Chem. Soc. 1959,
466. (e) Bergmann, E. D.; Szmuszkovicz, J . J . Am. Chem. Soc. 1951,
73, 5153. (f) Crawford, M.; Mackinnon, R. A. M.; Supanekar, V. R. J .
Chem. Soc. 1959, 2807. (g) Bell, F.; Waring, D. H. J . Chem. Soc. 1949,
2689.
(9) See refs 3f,g and: Goedicke, C.; Stegmeyer, H. Tetrahedron Lett.
1970, 937.
(10) See footnotes 1 and 6 in ref 12.
(11) (a) Bogaert-Verhoogen, D.; Martin, R. H. Tetrahedron Lett.
1967, 3045. (b) Teuber, H.-J .; Vogel, L. Chem. Ber. 1970, 103, 3319.
(c) Rau, H.; Schuster, O. Angew. Chem., Int. Ed. Engl. 1976, 15, 114.
(d) Pereira, D. E.; Neelima; Leonard, N. J . Tetrahedron 1990, 46, 5895.
(e) Staab, H. A.; Diehm, M.; Krieger, C. Tetrahedron Lett. 1994, 35,
8357. (f) Dore, A.; Fabbri, D.; Gladiali, S.; Valle, G. Tetrahedron:
Asymmetry 1995, 6, 779. (g) Pischel, I.; Grimme, S.; Kotila, S.; Nieger,
M.; Vo¨gtle, F. Tetrahedron: Asymmetry 1996, 7, 109. (h) Larsen, J .;
Bechgaard, K. J . Org. Chem. 1996, 61, 1151. (i) Tanaka, K.; Suzuki,
H.; Osuga, H. J . Org. Chem. 1997, 62, 4465.
(12) Katz, T. J .; Liu, L.; Willmore, N. D.; Fox, J . M.; Rheingold, A.
L.; Shi, S.; Nuckolls, C.; Rickman, B. H. J . Am. Chem. Soc. 1997, 119,
10054.
(13) (a) Patai, S. The Chemistry of the Quinonoid Compounds;
Wiley: London, 1974. (b) Patai, S.; Rappoport, Z. The Chemistry of
the Quinonoid Compounds; Wiley: Chichester, 1988; Vol. 2.
(14) (a) Nuckolls, C.; Katz, T. J .; Castellanos, L. J . Am. Chem. Soc.
1996, 118, 3767. (b) Lovinger, A. J .; Nuckolls, C.; Katz, T. J . J . Am.
Chem. Soc. 1998, 120, 264.
(4) Newman, M. S.; Lednicer, D. J . Am. Chem. Soc. 1956, 78, 4765.
(5) See ref 2b, p 71.
(6) Interesting materials prepared from helicenes in which a pho-
tocyclization was a key step: (a) Katz, T. J .; Pesti, J . J . Am. Chem.
Soc. 1982, 104, 346. (b) Sudhakar, A.; Katz, T. J . J . Am. Chem. Soc.
1986, 108, 179. (c) Katz, T. J .; Sudhakar, A.; Teasley, M. F.; Gilbert,
A. M.; Geiger, W. E.; Robben, M. P.; Wuensch, M.; Ward, M. D. J . Am.
Chem. Soc. 1993, 115, 3182. (d) Thulin, B.; Wennerstro¨m, O. Acta.
Chem. Scand. 1976, B30, 688. (e) Fox, J . M.; Lin, D.; Itagaki, Y.; Fujita,
T. J . Org. Chem. 1998, 63, 2031. (f) Yang, B.; Liu, L.; Katz, T. J .;
Liberko, C. A.; Miller, L. L. J . Am. Chem. Soc. 1991, 113, 8993. (g)
Liberko, C. A.; Miller, L. L.; Katz, T. J .; Liu, L. J . Am. Chem. Soc.
1993, 115, 2478.
(7) Liu, L.; Yang, B.; Katz, T. J .; Poindexter, M. K. J . Org. Chem.
1991, 56, 3769.
(8) The photodimerizations of stilbenes and the intermolecular
reactions of stilbenes with phenanthrenes also complicate photocy-
clizations that are not performed at high dilution. See ref 2a.
(15) Dai, Y.; Katz, T. J . J . Org. Chem. 1997, 62, 1274.
S0022-3263(98)01380-2 CCC: $15.00 © 1998 American Chemical Society
Published on Web 09/25/1998

Functionalized [7]Helicenes
Sch em e 1a
J . Org. Chem., Vol. 63, No. 21, 1998 7457
Sch em e 2a
a
a
Reagents and conditions: (a) diphenyldiazomethane, benzene
Reagents and conditions: (a) 1-ethoxyvinyltributylstannane,
Pd(Ph3P)4, dioxane, reflux, 3 h; then H+ (62% yield); (b) triisopro-
pylsilyl triflate, Et3N, CH2Cl2, rt, 2h (92% yield); (c) p-benzo-
quinone, toluene, 103 °C, 63 h (20-22% yield).
(89% yield); (b) 1-ethoxyvinyltributylstannane, Pd(Ph3P)4, dioxane,
reflux (72% yield); (c) p-benzoquinone, toluene, 100 °C, 48 h (10%
yield).
Resu lts a n d Discu ssion
6 possesses are notable. Unfortunately, the yield in the
reaction that produces 6 is only 10%, and our efforts to
improve it were unsuccessful. A typical reaction started
with 1 g of 5 and gave only 140 mg of 6. Thus, Scheme
1 offers, in terms of scale, no great advantage over the
photochemical methods previously used to make [7]-
helicenebisquinones.6f,23
As precursors we chose the enol ethers not of 3,6-
diacetylphenanthrene itself but of its 9,10-dialkoxy de-
rivatives (1) because these would lead to more highly
functionalized helicenebisquinones (2), because the ad-
ditional electron-donating substituents should facilitate
the Diels-Alder reactions in eq 1 and because, as shown
We therefore sought ways to improve the yield of the
Diels-Alder reaction in Scheme 1. Since in some cases,
Diels-Alder reactions of siloxy dienes proceed in high
yields when those of alkoxy dienes fail,24 presumably
because the electron-donating abilities of siloxyls are
greater than those of alkoxyls,25 the bis(triisopropylsilyl)
enol ether 7 was prepared (Scheme 2) and combined with
p-benzoquinone. In the latter reaction, the yield of
helicenebisquinone 8 was 20-22%, twice that in the
preparation of 6. More importantly, it proved possible
to prepare 8 in quantities (ca. 1 g) that are large when
compared to the amounts of helicenebisquinones prepa-
rable by photochemical methods.23
(1)
In view of this improvement, we prepared tetrasiloxy-
phenanthrene derivative 11 to see whether it reacted
even more efficiently with p-benzoquinone. The synthe-
sis of 12 was accomplished as outlined in Scheme 3.
Thus, 3,6-dibromo-9,10-phenanthrenequinone 3 with zinc
and TMEDA in the presence of tert-butyldimethylsilyl
chloride gave 9,26 which when subjected to Stille coupling
with 1-ethoxyvinyltributylstannane and hydrolysis gave
10. Reaction with triisopropylsilyl triflate and Et3N gave
below, these, unlike the parent 3,6-diacetylphenanthrene,
could be synthesized easily. Compounds of structure 1
should be preparable from suitably functionalized 9,10-
phenanthrenequinones. Initially, 3,6-dibromo-,16 3,6-
dicyano-,16 3,6-dimethyl-,17 and 3,6-diacetoxyphenan-
threne18 were considered as potential precursors. How-
ever, to synthesize these requires several steps, and to
introduce the phenanthrenequinone functionality re-
quires more yet. In contrast, 3,6-dibromo-9,10-phenan-
threnequinone19 (3) can be prepared by brominating
commercially available 9,10-phenanthrenequinone in ni-
trobenzene, a process we used to make 185 g of 3 in the
course of 1 day. This makes 3 an excellent precursor for
the synthesis of [7]helicenes. Indeed, as summarized in
Scheme 1, 3 reacts with diphenyldiazomethane to give
3,6-dibromo-9,10-(diphenylmethylenedioxy)phenanth-
rene, 4,20 a compound that with 1-ethoxyvinyltributyl-
stannane21,22 undergoes Stille coupling to give bis-enol
ether 5 in 72% yield. Reaction of 5 with p-benzoquinone
then gives [7]helicenebisquinone 6. The brevity of the
sequence and the significant functionality that helicene
(21) 1-Ethoxyvinyltributylstannane can be purchased from Aldrich
chemical company or prepared as described in: (a) Gadwood, R. C.;
Rubino, M. R.; Nagarajan, S. C.; Michel, S. T. J . Org. Chem. 1985, 50,
3255. (b) Soderquist, J . A.; Hsu, G. J .-H. Organometallics 1982, 1, 830.
For its use in the conversion of arylbromides to arylmethylketones,
see: (c) Kosugi, M.; Sumiya, T.; Obara, Y.; Suzuki, M.; Sano, H.; Migita,
T. Bull. Chem. Soc. J pn. 1987, 60, 767.
(22) 1-Ethoxyvinyltributylstannane had previously been used in our
lab to produce a bis-ethyl enol ether, which was used to synthesize a
[6]helicenebisquinone. Nuckolls, C. Unpublished results.
(23) The photocyclization shown in Scheme 2 of ref 6f produced, after
a solution in 400 mL of benzene had been irradiated for 8 h, 120 mg
of 1,18-dimethoxy[7]helicene, a compound that was converted in 39%
yield to 1,4,15,18-tetrahydro-1,4,15,18-tetraoxo[7]helicene: Yang, B.
V. Ph.D. Dissertation, Columbia University, 1987.
(24) (a) Semmelhack, M. F.; Tomoda, S.; Hurst, K. M. J . Am. Chem.
Soc. 1980, 102, 7567. (b) Savard, J .; Brassard, P. Tetrahedron Lett.
1979, 4911.
(25) (a) Petrzilka, M.; Grayson, J . I. Synthesis 1981, 753. (b)
Danishefsky, S. Acc. Chem. Res. 1981, 14, 400.
(16) Barber, H. J .; Stickings, C. E. J . Chem. Soc. 1945, 167.
(17) Staab, H. A.; Meissner, U. E.; Meissner, B. Chem. Ber. 1976,
109, 3875.
(18) Fieser, L. F. J . Am. Chem. Soc. 1929, 51, 2471.
(19) Schmidt, J .; Eitel, M. J . Prakt. Chem. 1932, 134, 167.
(20) Borodkin, G. I.; Shakirov, M. M.; Shubin, V. G.; Koptyug, V. A.
Zh. Org. Khim. (Engl. Transl.) 1976, 12, 1298.
(26) For a related procedure in which p-benzoquinones are reduced
by Zn in the presence of TMSCl but in the absence of an amine, see:
Rasmussen, J . K.; Krepski, L. R.; Heilmann, S. M.; Smith, H. K.;
Tumey, M. L. Synthesis 1983, 457.

7458 J . Org. Chem., Vol. 63, No. 21, 1998
Fox et al.
Sch em e 3a
F igu r e 1. CD (upper curve, ordinate on left) and UV-vis
(lower curve, ordinate on right) of a 2.0 × 10-5 M solution of
(+)-14 in CH2Cl2.
(+)-14, in CH2Cl2 are displayed in Figure 1. Those of
(-)-14 are shown in the Supporting Information.
a
Reagents and conditions: (a) Zn, tert-butyldimethylsilyl chlo-
ride, TMEDA, CH2Cl2, 16 h, rt (79% yield); (b) 1-ethoxyvinyltribu-
tylstannane, Pd(Ph3P)4, dioxane, reflux, 7 h; then H+ (72% yield);
(c) triisopropylsilyl triflate, Et3N, CH2Cl2, rt, 1.5 h (94% yield);
(d) p-benzoquinone, toluene, 100 °C, 86 h (37% yield).
The absolute configurations of (+)- and (-)-14 were
assigned by comparing their CD spectra and specific
rotations with those of other helicenes. The CD spectra
of helicenes possess two intense long-wavelength π-π*
transitions: the p-band and the higher energy â-band.29,30
For helicenes with the P-configuration, the circular
dichroisms of the p- and â-bands are positive, and for
helicenes with the M-configuration they are negative. At
wavelengths longer than their lowest energy absorptions,29c
helicenes with the P-configuration have dextrorotatory-
specific rotations, and those with the M-configuration
have levorotatory rotations.
Sch em e 4a
The CD spectrum of (+)-14 (Figure 1) includes two
intense positively dichroic maxima at 405 (∆ꢀ ) 69) and
367 nm (∆ꢀ ) 103), which were assigned to the p- and
â-bands, respectively. Accordingly, (+)-14 was assigned
the P-configuration. Similarly, (-)-14, which is diaster-
eomeric with (+)-14, was assigned the M-configuration.
The peaks in its CD spectrum at 402 (∆ꢀ ) -73) and 365
nm (∆ꢀ ) -95), assigned to the p- and â-bands, respec-
tively, are negatively dichroic.
a
Reagents and conditions: (a) CsF, C12H25I, DMF, 70 °C, 2.5 h
(88% yield); (b) Zn, TMEDA, (S)-(-)-camphanoyl chloride, toluene
1 h, reflux (99% yield).
Steps similar to those applied above to 8 were applied
to tetrasiloxybisquinone 12. Thus (Scheme 5), CsF/
dodecyl iodide converted 12 into tetraalkoxybisquinone
15, which when reduced with zinc in the presence of (S)-
(-)-camphanoyl chloride gave a mixture of diastereomeric
helicenes 16 that could be separated by chromatography
into materials with de g 98%. The UV-vis absorption
and CD spectra of the dextrorotatory diastereomer, (+)-
16, are displayed in Figure 2. Those of (-)-16 are shown
in the Supporting Information.
11. Enol ether 11 does indeed react even more efficiently
than 9 with p-benzoquinone, producing [7]helicenebis-
quinone 12 in 37% yield. The consequence is that 30 g
of helicene 12 can be prepared in a single 1 L round-
bottomed flask.
Resolu tion of [7]Helicen ebisqu in on es. As outlined
in Scheme 4, treating 8 with CsF and C12H25I in DMF
converted its siloxy groups into alkoxyls.27 Subsequent
reduction with zinc and TMEDA28 in the presence of (S)-
(-)-camphanoyl chloridesa reagent previously used to
resolve [6]helicenebisquinones14asconverted bisdodecy-
loxyhelicene 13 into diastereomeric helicene tetracam-
phanates 14, which column chromatography separated
in high optical purity (de g 98%). The UV-vis absorp-
tion and CD spectra of the dextrorotatory diastereomer,
The maxima at 401 (∆ꢀ ) 67) and 366 nm (∆ꢀ ) 94) in
the CD spectrum of (+)-16 were assigned to the p- and
â-bands, respectively, and therefore, (+)-16 was assigned
(29) (a) Brown, A.; Kemp, C. M.; Mason, S. F. J . Chem. Soc. (A) 1971,
751. (b) Newman, M. S.; Darlak, R. S.; Tsai, L. J . Am. Chem. Soc. 1967,
89, 6191. (c) Brickell, W. S.; Brown, A.; Kemp, C. M.; Mason, S. F. J .
Chem. Soc. (A) 1971, 756. (d) Martin, R. H.; Marchant, M. J .
Tetrahedron 1974, 30, 343. (e) Groen, M. B.; Wynberg, H. J . Am. Chem.
Soc. 1971, 93, 2968.
(27) For a related procedure that uses MeI or BnBr and KF in DMF
to convert tert-butyldimethylsilylaryl ethers into methyl- or benzylaryl
ethers, see: Sinhababu, A. K.; Kawase, M.; Borchardt, R. T. Tetrahe-
dron Lett. 1987, 28, 4139.
(30) In addition, the CD spectra of [6]helicenes29b and thiahelicenes29e
possess an additional, low-intensity transition at longer wavelengths
the R-bandsbut this transition cannot be distinguished from the
p-band in the CD spectra of [7]-, [8]-, and [9]helicenes,29d nor can it be
recognized in the CD of (+)- and (-)-14 and 16.
(28) The previous procedure14a employs Na2S2O4 as the reducing
agent. For the [7]helicenebisquinones studied here Zn/TMEDA in
toluene generally effected cleaner conversion.

Functionalized [7]Helicenes
Sch em e 5a
J . Org. Chem., Vol. 63, No. 21, 1998 7459
a
Reagents and conditions: (a) CsF, C12H25I, DMF, 65 °C, 2.5 h
(78% yield); (b) Zn, TMEDA, (S)-(-)-camphanoyl chloride, toluene
1 h, reflux (75% yield).
F igu r e 3. CD (upper curves, scale at left) and UV-vis (lower
curves, scale at right) of CH2Cl2 solutions of (P)-13 (s, 2.0 ×
10-5 M), (P)-15 (- - -, 2.1 × 10-5 M), and (P)-17 (‚‚‚, 2.2 × 10-5
M). The insets show long-wavelength dichroisms and absorp-
tions in the CD (upper right) and UV-vis (lower right) spectra
of CH2Cl2 solutions of (P)-13 (s, 8.7 × 10-4 M), (P)-15 (- - -,
8.7 × 10-4 M), and (P)-17 (‚‚‚, 8.7 × 10-4 M).
F igu r e 2. CD (upper curve, ordinate on left) and UV-vis
(lower curve, ordinate on right) of a 2.0 × 10-5 M solution of
(+)-16 in CH2Cl2.
Ta ble 1. P ea k s in th e CD Sp ectr a of (P )-13, (P )-15, a n d
(P )-17a
(P)-13
(P)-15
(P)-1712
the P-configuration. The M-configuration was assigned
to (-)-16. The corresponding peaks are at 398 (∆ꢀ ) -87)
and 364 nm (∆ꢀ ) -109).
Each of the nonracemic tetracamphanates 14 and 16
was combined with n-BuLi to give a bis-hydroquinone,
which after workup was oxidized by chloranil to give
nonracemic bisquinones 13 and 15 in yields, for the two
steps, of 74-89%. The UV-vis absorption and CD
spectra of the resulting (P)-13 and (P)-15 are displayed
in Figure 3.
In Table 1 and Figure 3, the peaks in the CD spectra
of these bisquinones are compared to that of (+)-[6]-
helicenebisquinone (17), which is known to have the
P-configuration.12 The sign of the specific rotation of 13
can be changed by changing the solvent (see the Experi-
mental Section), and accordingly the structures of 13 and
15 displayed in Figure 3 are referred to in Table 1 as
(P)-13 and (P)-15. All three of the CD spectra sum-
marized in the table have positive dichroisms at ca. 265
and 360 nm and a negative dichroism at ca. 300 nm.
These similarities verify that 13 and 15 have P-helicity.
The n-π* transtion in the UV-vis spectrum of 15 is
assigned to the peak at 450 nm,31 and like that in the
CD spectrum of 17,12 it gives rise to a positive dichroism.
264 (42)
296 (-98)
363 (74)
450 (-9)
483 (-2)
602 (10)
267 (71)
305 (-106)
366 (69)
450 (6)
259 (40)
296 (-80)
351 (90)
440 (15)
570 (5)
a
The positions of peaks are given in nm, ∆ꢀ in parentheses.
The n-π* transtion of 13 is assigned similarly to a peak
in the UV-vis spectrum at 460 nm, but it is difficult to
locate in the CD spectrum because a negative dichroism
falls just to the blue, at 450 nm. A notable observation
is that 13 and 15 each display a CD peak at even longer
wavelengths, observed neither in the spectrum of 17 nor
in the spectra of the parent [5]-, [6]-, [7]-, and [8]-
helicenebisquinones.6f,32,33 The dichroisms are weak and
positive and maximize at 602 and 570 nm, respectively.
Possibly they arise from charge transfer between the
second and seventh rings.
Con clu sion s
[7]Helicenes can be synthesized by nonphotochemical
methods in only five steps from 9,10-phenanthrene-
(32) (a) Liu, L.; Katz, T. J . Tetrahedron Lett. 1990, 31, 3983. (b)
Yang, B. V. Dissertation, Columbia University, 1987. (c) Liu, L. Ph.D.
Dissertation, Columbia University, 1991.
(33) The peaks at longest wavelengths (λ, nm) in the CD spectra of
the (+)- or (-)-[n]-helicenebisquinones are as follows [n, λ (∆ꢀ)]: (+)-
5, 495 (2.8); (-)-6, 440 (-20); (-)-7, 430 (-3); (-)-8, 450 (-15).32b,c
(31) n-π* transitions in the UV-vis spectra of p-quinones generally
occur at 420-460 nm. See: Berger, S.; Rieker, A. In The Chemistry of
the Quinonoid Compounds; Patai, S., Ed.; Wiley: London, 1974;
Chapter 4.

7460 J . Org. Chem., Vol. 63, No. 21, 1998
Fox et al.
again stripped until the total volume was ca. 20 mL. The flask
was cooled briefly in a dry ice/acetone bath, and the precipi-
tated pasty solid was filtered on a bed of Celite and washed
with additional cold MeOH. Washing the filter cake with CH2-
Cl2 and stripping the solvent gave 3.72 g (92%) of 7, a sticky,
1
pale yellow solid. IR(CCl4): 2946, 2868, 1685, 1656 cm-1. H
NMR (C6D6, 400 MHz): δ 9.30 (d, 2H, J ) 1.3 Hz), 8.10 (d,
2H, J ) 8.5 Hz), 7.97 (dd, 2H, J ) 1.5, 8.5 Hz), 7.81 (m, 4H),
7.08 (m, 6H), 5.11 (d, 2H, J ) 1.8 Hz), 4.65 (d, 2H, J ) 1.8
Hz), 1.31 (m, 6H), 1.20 (m, 36H) ppm. 13C NMR (C6D6, 75
MHz): δ 157.1, 141.0, 138.2, 134.8, 129.3, 128.5, 127.0, 124.9,
121.8, 120.7, 120.5, 118.6, 91.0, 18.1, 12.9 ppm.
quinone. Large quantities can be produced, the struc-
tures are usefully functionalized, and resolutions into
optically active materials are easy to carry out. The
absolute configurations have been assigned.
6,13-Bis(tr iisop r op ylsiloxy)-9,10-(d ip h en ylm eth ylen e-
d ioxy)[7]h elicen ebisqu in on e (8). A flask containing 7 (3.72
g, 4.84 mmol) and p-benzoquinone (10.45 g, 96.7 mmol) and
fitted with a reflux condenser was evacuated and filled with
N2 three times. Toluene (24 mL) was syringed in, and the
mixture was heated in an oil bath at 103 °C for 63 h. The
reaction mixture was then cooled, and the toluene was
stripped. Excess p-benzoquinone was removed into a trap by
vacuum sublimation at 100 °C. The residue was chromato-
graphed on silica (4:1 CH2Cl2/hexanes), giving 0.94 g (20%) of
8, a brown-red solid, mp > 225 °C. A similar reaction starting
from 1.51 g of 7 gave 0.42 (22%) of 8. IR(CCl4): 2948, 2869,
Exp er im en ta l Section
THF and toluene were distilled from Na/benzophenone; CH2-
Cl2 and Et3N, from CaH2. TMEDA (Aldrich, anhydrous,
99.5+%) was used without purification. DMF (Aldrich, an-
hydrous, 99.8%) was boiled and cooled under N2 to free it of
oxygen. Zn dust (Aldrich, <10 µm, 98+%) was activated prior
to use.34 1,4-Benzoquinone (Aldrich, 98%) was purified by
slurrying it in CH2Cl2 with 4 times its weight of basic alumina,
filtering through Celite, and drying under vacuum. Manipula-
tions involving stannanes were performed in a fume hood.
Glassware was flame-dried under vacuum and cooled under
N2. Reactions were run under N2. Additions by syringe were
through rubber septa. “Chromatography” refers to “flash
chromatography”.35 FAB was used for high-resolution mass
spectra.
1663, 1613 cm-1 1H NMR (CDCl3, 400 MHz): δ 8.39 (d, 2H,
.
J ) 8.8 Hz); 8.25 (d, 2H, 8.8 Hz); 7.76 (m, 4H); 7.43 (m, 6H);
7.34 (s, 2H); 6.47 (d, 2H, J ) 10.1 Hz); 5.94 (d, 2H, J ) 10.1
Hz); 1.51 (m, 6H); 1.25 (s, 9H); 1.23 (s, 9H); 1.21 (s, 9H); 1.19
(s, 9H) ppm. 13C NMR (CDCl3, 75 MHz): δ 184.6, 183.3, 157.6,
140.7, 140.1, 140.0, 133.9, 133.2, 129.5, 129.3, 128.7, 128.3,
126.5, 124.6, 124.4, 122.0, 121.4, 120.7, 119.3, 107.7, 18.0, 13.0
ppm. HRMS calcd for C61H63O8Si2: (M + 1) 979.4062, found
979.4106.
3,6-Bis(1-(tr iisop r op ylsiloxy)eth en yl)-9,10-(d ip h en yl-
m eth ylen ed ioxy)p h en a n th r en e (7). Pd(Ph3P)4 (1.0 g, 0.87
mmol) was added to a solution of 3,6-dibromo-9,10-(diphenyl-
methylenedioxy)phenanthrene 420 (7.80 g, 14.7 mmol) and
1-ethoxyvinyltributylstannane21 (11.65 g, 32 mmol) in 80 mL
of dioxane. After the mixture had refluxed for 3 h, it was
cooled to room temperature and the solvent was stripped.
Acetone (20 mL), H2O (1 mL), and acetic acid (1 mL) were then
added, and the mixture was heated for 20 min at 60 °C, cooled
to room temperature, and partitioned between CH2Cl2 and
H2O. The organic layer was washed with saturated aqueous
NaHCO3 and dried (Na2SO4), and the solvent was removed
under reduced pressure. Hexane was added, and the hexane-
soluble portion was loaded onto a short column of silica gel.
The column was washed with hexane to remove the majority
of the (C4H9)3SnCl. The eluent was changed to CH2Cl2 until
fluorescent material was near the bottom of the column and
then to EtOAc. The eluted material was combined with the
material that had not dissolved in hexane, and this was
dissolved in CH2Cl2, filtered, and chromatographed (5% EtOAc/
hexane), giving 4.14 g (62%) of 3,6-diacetyl-9,10-(diphenylm-
ethylenedioxy)phenanthrene, an off-white solid, mp > 225 °C.
6,13-Bis(d od ecyloxy)-9,10-(d ip h en ylm eth ylen ed ioxy)-
[7]h elicen ebisqu in on e (13). DMF (50 mL) and dodecyl
iodide (4.54 g, 15.3 mmol, 3.78 mL) were sequentially syringed
into a flask containing 8 (0.500 g, 0.511 mmol) and CsF (0.466
g, 3.07 mmol). After 2 h at 70 °C, the mixture was cooled to
room temperature and partitioned between CH2Cl2 and H2O.
The organic layer was dried (Na2SO4), and the solvent was
stripped. The residue, loaded onto a chromatography column
with ca. 10% CH2Cl2/hexane, was washed with excess hexane
and then eluted with CH2Cl2. Further purification by tritu-
ration with MeOH gave 0.453 g (88%) of 13, a red-brown solid,
mp 161-162 °C. IR(CCl4): 2928, 2856, 1662, 1612 cm-1 1H
.
NMR (CDCl3, 500 MHz): δ 8.39 (d, 2H, J ) 8.8 Hz), 8.22 (d,
2H, J ) 8.8 Hz), 7.78 (m, 4H), 7.41 (m, 6H), 7.37 (s, 2H), 6.47
(d, 2H, J ) 10.1 Hz); 5.96 (d, 2H, J ) 10.1 Hz); 4.36 (m, 2H),
4.26 (m, 2H), 2.01 (m, 4H), 1.61 (m, 4H), 1.5-1.2 (m, 32H),
0.87 (t, 6H, J ) 7.0 Hz) ppm. 13C NMR (CDCl3, 75 MHz): δ
184.9, 183.3, 159.7, 141.0, 140.1, 140.0, 133.8, 133.5, 129.4,
128.3, 128.1, 127.5, 126.6, 124.4, 124.2, 122.0, 120.9, 120.8,
119.4, 100.7, 69.5, 31.9, 29.7, 29.65, 29.60, 29.57, 29.38, 29.35,
29.0, 26.2, 22.7, 14.1 ppm. HRMS calcd for C67H72O8: (M +
2)36 1004.5227, found 1004.5226.
IR (CCl4): 3070, 1685, 1653, 1612 cm-1 1H NMR (CDCl3, 400
.
MHz): δ 9.38 (d, 2H, J ) 1.4 Hz), 8.24 (dd, 2H, J ) 8.5, 1.4
Hz), 8.17 (d, 2H, J ) 8.4 Hz), 7.73 (m, 4H), 7.42 (m, 6H), 2.82
(s, 6H) ppm. 13C NMR (CDCl3, 75 MHz): δ 197.7, 139.7, 139.4,
133.6, 129.5, 128.4, 127.4, 126.5, 126.4, 124.4, 124.0, 120.9,
119.0, 26.9 ppm. HRMS calcd for C31H22O4: 458.1518, found
458.1535.
Triisopropylsilyl triflate (3.37 g, 11.0 mmol, 2.92 mL) was
added to a solution of the above diacetyl compound (2.40 g,
5.25 mmol) in CH2Cl2 (36 mL) and Et3N (6.8 mL), cooled in
an ice bath, and the mixture was then warmed to room
temperature and stirred for 2 h. Additional CH2Cl2 was added,
and after the solution had been washed with saturated
aqueous NaHCO3 and dried (Na2SO4), the solvents were
removed and the residue was dissolved in CH2Cl2 (25 mL).
MeOH (50 mL) was added. Solvents were then removed under
reduced pressure until the total volume was ca. 20 mL.
Additional MeOH (50 mL) was added, and the solvents were
Resolu tion of 13. Toluene (23 mL) and TMEDA (5.80 g,
50 mmol, 7.53 mL) were sequentially syringed into a flask
containing 13 (0.533 g, 0.53 mmol), Zn (0.533 g, 8.2 mmol),
and (S)-(-)-camphanoyl chloride (1.70 g, 7.9 mmol). The
mixture was refluxed for 1 h, cooled to room temperature, and
filtered. CH2Cl2 was added, and after it had been washed with
HCl (1 M) and saturated aqueous NaHCO3 and dried (Na2-
SO4), the solvent was stripped and the residue was combined
with the crude product from a similar reaction that had started
with 0.092 g of 13. Chromatography on silica gel, eluting first
with CH2Cl2, then with 3% EtOAc in CH2Cl2, and finally with
5% EtOAc in CH2Cl2, gave the levorotatory diastereomer, (M)-
14 (0.530 g, 99%), mp 92-94 °C, followed by the dextrorotatory
diastereomer, (P)-14 (0.534 g, 99%), mp 108-110 °C. The
latter was further purified by chromatography (10% EtOAc/
benzene). Both diastereomers are yellow solids.
(34) Shriner, R. L.; Neumann, F. W. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. 3, p 73.
(35) Still, W. C.; Kahn, M.; Mitra, A. J . Org. Chem. 1978, 43, 2923.
(36) M + 2 peaks are often seen in the mass spectra of quinones.
See: Zeller, K.-P. In The Chemistry of the Quinonoid Compounds;
Patai, S., Ed.; Wiley: London, 1974; Chapter 5.

Functionalized [7]Helicenes
J . Org. Chem., Vol. 63, No. 21, 1998 7461
(P )-14: [R]D +723 (c 0.066, CH2Cl2); IR (CCl4) 2960, 2929,
was added to the residue. A large crop of white crystals of
pure 9 that did not dissolve was removed by filtration, and
the filtrate was directly loaded onto a large plug of silica gel
(6 in. × 6 in.). Elution with hexane was continued until TLC
indicated that the eluant contained no more product. The
solvents were then stripped, and the residual solid was slurried
with 1:1 CH2Cl2/hexane. The precipitate plus the crystals
obtained earlier amounted to 129 g (79%) of pure 9, a white
crystalline solid, mp 224-226 °C. IR (CCl4): 2959, 2932, 2860,
1
2873, 1799, 1750 cm-1; H NMR (CDCl3, 500 MHz) δ 8.38 (d,
2H, J ) 8.5 Hz); 8.18 (d, 2H, J ) 8.5 Hz); 7.74 (m, 4H); 7.42
(m, 6H); 7.04 (d, 2H, J ) 8.4 Hz); 6.84 (s, 2H); 5.99 (d, 2H, J
) 8.4 Hz); 4.29 (m, 2H); 4.13 (m, 2H); 2.64 (m, 2H); 2.24 (m,
2H); 2.1-1.9 (m, 6H); 1.82 (m, 2H); 1.64-1.50 (m, 8H); 1.48-
1.11 (m, 54H); 0.89 (m, 12H); 0.63 (s, 6H); 0.40 (s, 6H) ppm;
13C NMR (CDCl3, 75 MHz) δ 178.0, 177.0, 165.1, 165.0, 154.5,
143.1, 142.3, 140.0, 138.4, 129.5, 128.4, 126.9, 126.5, 126.3,
123.7, 123.4, 122.8, 121.7, 120.2, 120.0, 118.9, 116.6, 115.5,
96.2, 91.2, 90.2, 68.8, 55.0, 54.5, 54.3, 54.0, 31.9, 31.0, 29.7
(m), 29.5, 29.4, 29.2, 28.9, 28.7, 26.4, 22.7, 17.0, 16.8, 16.7, 16.3,
14.1, 9.8, 9.4 ppm; HRMS calcd for C107H122O20 1727.8564,
found 1727.8605.
1589 cm-1
.
1H NMR (CDCl3, 400 MHz): δ 8.61 (d, 2H, J )
1.8 Hz); 8.04 (d, 2H, J ) 8.8 Hz); 7.67 (dd, 2H, J ) 1.8, 8.8);
1.12 (s, 18H); 0.07 (s, 12 H) ppm. 13C NMR (CDCl3, 75 MHz):
δ 137.6, 129.8, 129.4, 128.0, 125.2, 124.8, 119.5, 26.4, 18.7, -3.7
ppm. Anal. Calcd for
Found: C, 52.5; H, 6.2.
C26H36Br2Si2O2: C, 52.3; H, 6.1.
(M)-14: [R]D -801 (c 0.073, CH2Cl2); IR (CCl4) 2961, 2930,
2856, 1799, 1798, 1750 cm-1 1H NMR (CDCl3, 500 MHz) δ
;
3,6-Dia cetyl-9,10-bis(ter t-bu tyld im eth ylsiloxy)p h en a n -
th r en e (10). A solution of 9 (71 g, 0.12 mol), 1-ethoxyvinyl-
tributylstannane (95 g, 0.26 mol), and Pd(PPh3)4 (5.0 g, 4.3
mmol) in 600 mL of dioxane was refluxed for 4 h. Additional
Pd(PPh3)4 (1.0 g, 0.87 mmol) was added as a solution in
dioxane, and after it had refluxed for another 3 h, the mixture
was cooled to room temperature. Acetic acid (5 mL) and H2O
(10 mL) were added, and the mixture was stirred for 1 h. The
solvent was then stripped, and the residue was added to a
large column of silica gel (6 in. × 8 in.), which, to remove the
majority of the (C4H9)3SnCl, was washed first with hexanes
and then with ca. 1 L of 20% EtOAc in hexane (TLC monitor-
ing!). Elution with pure EtOAc, followed by 20% EtOAc in CH2-
Cl2, removed the product from the column. Trituration with
hexanes gave 44.6 g (72%) of 10, an off-white solid, mp > 225
8.46 (d, 2H, J ) 8.5 Hz); 8.29 (d, 2H, J ) 8.5 Hz); 7.82 (m,
4H); 7.4-7.3 (m, 6H); 7.06 (d, 2H, J ) 8.4 Hz); 6.80 (s, 2H);
6.12 (d, 2H, J ) 8.4 Hz); 4.32 (m, 2H); 4.03 (m, 2H); 2.65 (m,
2H); 2.33 (m, 2H); 2.1-1.9 (m, 6H); 1.83 (m, 2H); 1.59 (m, 4H);
1.5-1.0 (m, 54H); 0.89 (t, 6H, J ) 7.0 Hz); 0.84 (s, 6H); 0.82
(m, 2H); 0.69 (m, 2H); 0.52 (s, 6H); 0.30 (s, 6H) ppm; 13C NMR
(CDCl3, 75 MHz) δ 178.5, 178.1, 165.5, 165.4, 155.0, 143.2,
142.4, 141.6, 138.5, 129.4, 128.7, 127.2, 126.5, 126.1, 124.0,
123.6, 122.3, 122.2, 121.5, 120.4, 118.5, 116.5, 115.3, 96.5, 91.7,
89.9, 69.3, 55.4, 54.8, 54.7, 54.5, 32.4, 31.5, 30.1 (m), 29.9, 29.8,
29.6, 29.5, 28.6, 26.7, 23.1, 17.5, 17.3, 16.6, 16.3, 14.6, 10.2,
9.9 ppm; HRMS calcd for
1727.8601.
C107H122O20 1727.8564, found
P r ep a r a tion of Non r a cem ic Helicen es 13 fr om Tet-
r a ester s 14. n-BuLi (2.64 mL of a 2.5 M solution in hexane,
6.6 mmol) was added to a solution of (M)-14 (0.456 g, 0.264
°C. IR (CCl4): 2960, 2932, 2861, 1686, 1600 cm-1 1H NMR
.
(CDCl3, 400 MHz): δ 9.31 (d, 2H, J ) 1.4 Hz); 8.29 (d, 2H, J
) 8.6 Hz); 8.17 (dd, 2H, J ) 1.5, 8.6 Hz); 2.82 (s; 6H); 1.14 (s,
18H); 0.09 (s, 12H) ppm. 13C NMR (CDCl3, 75 MHz): δ 198.0,
139.8, 133.9, 133.6, 127.5, 125.5, 123.6 (2 peaks), 27.0, 26.4,
18.7, -3.5 ppm. Anal. Calcd for C30H42Si2O4: C, 68.9; H, 8.1.
Found: C, 68.9; H, 8.1.
mmol) in THF (20 mL) that had been cooled in
a dry
ice/acetone bath. After the mixture had stirred for 20 min at
-78 °C, the reaction was quenched at this temperature with
saturated aqueous NH4Cl, and ca. 20 mL of HCl (1 M) and
CH2Cl2 were added. After a wash with HCl (0.5 M) and two
washes with H2O, the organics were dried (Na2SO4). Chloranil
(0.200 g, 0.81 mmol) was added, whereupon the solution turned
brown-red. After standing for 15 min, the solution was
filtered, washed twice with saturated aqueous NaHCO3, and
dried (Na2SO4). The solvent was stripped, and the residue was
chromatographed (2:1 CH2Cl2/hexanes), giving after trituration
with a small amount of MeOH 0.220 g (83%) of (M)-13, mp
3,6-Bis(1-(tr iisop r op ylsiloxy)eth en yl)-9,10-bis(ter t-bu -
tyld im eth ylsiloxy)p h en a n th r en e (11). Triisopropylsilyl
triflate (54.9 g, 0.179 mol, 48.1 mL) was added to an ice-bath-
cooled solution of 10 (44.6 g, 0.085 mol) in 400 mL of CH2Cl2
and 71 mL of Et3N. The ice bath was then removed, and after
the mixture had stirred for 1.5 h, it was washed three times
with saturated aqueous NaHCO3 and dried (Na2SO4). Solvent
was then removed under reduced pressure until product began
to precipitate. MeOH (ca. 300 mL) was added, and the
solvents were again concentrated under reduced pressure until
the total volume was ca. 100 mL. More MeOH was added, and
the volume was once again reduced to ca. 100 mL. The solid
that had precipitated was filtered and rinsed with cold MeOH,
dissolved in hexane, washed with saturated aqueous NaHCO3,
and dried (Na2SO4). The solution was filtered into a 2 L flask.
Removal of solvents and drying in vacuo gave 66.6 g (94%) of
11, a white, fibrous material, mp 119-121 °C. IR (CCl4): 2947,
1
112-113 °C. The H NMR spectrum was identical to that of
the racemic material. [R]D: +260 (c 0.070, CH2Cl2).37 UV-
vis (CH2Cl2, c ) 1.8 × 10-5 M): λmax (nm) (log ꢀ) 250 (4.79), 306
(4.65), 365 (4.16), 395 (4.09), 454 (3.81), 600 (2.71). CD (c )
1.8 × 10-5 M): nm ([θ]), 243 (2.44 × 10-5), 267 (-2.24 × 10-5),
306 (3.73 × 10-5), -332 (3.63 × 10-4), 365 (-2.18 × 10-5), 397
(-1.06 10-5), 448 (3.3 × 10-4), 480 (3.3 × 10-3), 602 (-2.64 ×
10-4). The same reaction conditions applied to the other
diastereomer, (P)-14, gave (P)-13 in 76% yield. [R]D: -260 (c
0.077, CH2Cl2); +340° (c 0.070,THF); -170° (c 0.070, benzene);
+280° (c 0.070, hexanes).37
2867, 1599, 1472 cm-1 1H NMR (C6D6, 300 MHz): δ 9.45 (s,
.
2H); 8.57 (d, 2H, J ) 8.6 Hz); 8.16 (d, 2H, J ) 8.7 Hz); 5.25 (d,
2H, J ) 1.6 Hz); 4.76 (d, 2H, J ) 1.5 Hz); 1.5-1.2 (m, 60H);
0.22 (s, 12H) ppm. 13C NMR (C6D6, 75 MHz): δ 157.1, 138.4,
135.3, 130.9, 128.4, 124.1, 123.4, 120.1, 90.9, 26.6, 18.9, 18.3,
13.1, -3.4 ppm.
3,6-Dibr om o-9,10-bis(ter t-bu tyldim eth ylsiloxy)ph en an -
th r en e (9). Zn (268 g, 4.12 mol), TMEDA (200 mL, 154 g,
1.33 mol), and tert-butyldimethylsilyl chloride (168 g, 1.12 mol)
were sequentially added to a three-necked 2 L round-bottomed
flask containing 3,6-dibromo-9,10-phenanthrenequinone19 (100
g, 0.273 mol) in CH2Cl2 (1 L). After the mixture had been
stirred mechanically for 16 h at room temperature, it was
filtered on Celite, which was rinsed exhaustively with hot
CHCl3 to recover any product that had precipitated from
solution. After they had been washed with HCl (1 M) and H2O,
the organics were dried over Na2SO4 and solid NaHCO3 and
filtered. The solvent was stripped, and CH2Cl2 (ca. 0.75 L)
6,13-Bis(tr iisopr opylsiloxy)-9,10-bis(ter t-bu tyldim eth yl-
siloxy)[7]h elicen ebisqu in on e (12). A 1 L round-bottomed
flask that contained 11 (66.6 g, 0.080 mol) and p-benzoquinone
(173 g, 1.60 mol) was fitted with a reflux condenser and
evacuated and filled with N2 three times. Toluene (400 mL)
was added (via cannula), and the mixture was heated in an
oil bath at 100 °C for 86 h. The reaction mixture was then
cooled to room temperature and the solvent stripped. Excess
p-benzoquinone was removed to a trap by vacuum sublimation
at 100 °C. The residue, dissolved in CH2Cl2, was loaded onto
a large plug of silica gel (5 in. × 6 in.) and sequentially eluted
with 1:1 CH2Cl2/hexane, CH2Cl2, and 25% EtOAc/CH2Cl2.
After the solvents had been removed, the material was divided
into three parts, each of which was chromatographed (1:1 CH2-
Cl2/hexane). The yield of 12, a red-brown solid, mp > 225 °C,
(37) The small value of 14’s [R]D and the solvent dependence of its
sign are probably a consequence of the CD spectrum peaking at the
wavelength of the sodium D-line (589 nm). A Cotton effect in the ORD
spectrum is expected to coincide with the λmax of an isolated transition
in the CD spectrum. See: Eliel, E. L.; Wilen, S. H.; Mander, L. N.
Stereochemistry of Organic Compounds; Wiley: New York, 1994;
Chapter 13.

7462 J . Org. Chem., Vol. 63, No. 21, 1998
Fox et al.
was 30.5 g (37%). IR (CCl4): 2950, 2932, 2868, 1665 cm-1. 1H
NMR (CDCl3, 400 MHz): δ 8.37 (d, 2H, J ) 9.0 Hz); 8.33 (d,
2H, J ) 9.0 Hz); 7.34 (s, 2H); 6.44 (d, 2H, J ) 10.1 Hz); 5.94
(d, 2H, J ) 10.1 Hz); 1.52 (m, 6H); 1.25-1.23 (m, 18H); 1.20-
1.18 (m, 36H); 0.32 (s, 6H); 0.13 (s, 6H) ppm. 13C NMR (CDCl3,
75 MHz): δ 184.7, 184.1, 157.2, 140.3, 139.9, 134.0, 132.8,
130.2, 129.3, 127.9, 125.6, 125.0, 123.8, 120.4, 107.3, 26.4, 18.7,
18.1, 13.0, -3.1, -4.1 ppm. Anal. Calcd for C60H82Si4O4: C,
69.1; H, 7.9. Found: C, 69.0; H, 8.0.
28.8, 28.7, 26.4, 26.3, 22.7, 17.0, 16.8, 16.7, 16.5, 14.1, 9.8, 9.5
ppm; HRMS calcd for C118H162O20 1899.1659, found 1899.1586.
(M)-16: [R]D -790 (c 0.090, CH2Cl2); IR (CCl4) 2928, 2856,
1
1798, 1750 cm-1; H NMR (CDCl3, 400 MHz) δ 8.44 (m, 4H);
7.06 (d, 2H, J ) 8.5 Hz); 6.81 (s, 2H); 6.11 (d, 2H, J ) 8.4 Hz);
4.40-4.28 (m, 4H); 4.15 (m, 2H); 4.04 (m, 2H); 2.66 (m, 2H);
2.34 (m, 2H); 2.1-1.94 (m, 12H); 1.84 (m, 2H); 1.59 (m, 8H);
1.5-1.1 (m, 88H); 0.94-0.86 (m, 18H); 0.60 (s, 6H); 0.44 (s,
6H) ppm; 13C NMR (CDCl3, 75 MHz) δ 178.1, 177.6, 165.2,
165.0, 154.6, 143.7, 142.8, 142.0, 128.4, 127.5, 125.6, 124.8,
123.1, 122.4, 122.1, 121.1, 115.8, 114.5, 96.0, 91.2, 89.4, 74.0,
68.7, 55.0, 54.4 (2 peaks), 54.3, 31.9, 31.0, 30.7, 29.7 (m), 29.5,
29.3, 29.2, 29.0, 28.5, 26.3, 22.7, 17.0, 16.8, 16.2, 16.0, 14.1,
9.8, 9.5 ppm; HRMS calcd for C118H162O20 1900.1694, found
1900.1702.
6,9,10,13-Te t r a k is(d od e cyloxy)[7]h e lice n e b isq u in -
on e (15). DMF (24 mL) and dodecyl iodide (7.2 g, 24 mmol,
6.0 mL) were sequentially syringed into a flask containing 12
(0.500 g, 0.48 mmol) and CsF (0.58 g, 3.84 mmol), and the
mixture was heated in an oil bath at 65 °C for 2.5 h. After
cooling the mixture to room temperature, CH2Cl2 was added.
This was washed with H2O, dried (Na2SO4), and stripped, and
the residue was loaded onto a chromatography column, which
was washed first with hexane. The product was then eluted
with 4:1 CH2Cl2/hexane, triturated with MeOH, and then
dissolved in a minimum amount of CH2Cl2. MeOH (ca. 30 mL)
was then added, and the solvent was stripped until the total
volume was ca. 10 mL. Again, MeOH (ca. 30 mL) was added,
and the volume was again reduced to ca. 10 mL. The
precipitated solid was then filtered and washed with excess
cold MeOH, yielding 0.440 g (78%) of 15, a red solid, mp 77-
P r ep a r a tion of Non r a cem ic Helicen es 15 fr om Tet-
r a ester s 16. n-BuLi (1.24 mL of a 2.5 M solution in hexane,
3.1 mmol) was added to a solution of (P)-16 (0.236 g, 0.124
mmol) in THF (10 mL) that had been cooled in
a dry
ice/acetone bath. After this had stirred for 25 min at -78 °C,
the reaction was quenched at this temperature by the addition
of saturated aqueous NH4Cl, and ca. 20 mL of HCl (1 M) and
CH2Cl2 were added. After a wash with HCl (0.5 M) and two
washes with H2O, the organics were dried (Na2SO4). Chloranil
(0.100 g, 0.40 mmol) was then added, whereupon the solution
turned brown-red. After 15 min, the solution was filtered,
washed twice with saturated aqueous NaHCO3, and dried (Na2-
SO4). The solvent was removed under reduced pressure, and
the residue chromatographed (4:1 CH2Cl2/hexanes), giving
after trituration with MeOH 0.130 g (89%) of (P)-15, mp 65-
67 °C. The 1H NMR spectrum was identical to that of the
racemic material. [R]D: +1480 (c 0.050, CH2Cl2). The same
reaction conditions applied to the other diastereomer, (M)-16,
gave (M)-15 in 74% yield. [R]D: -1480 (c 0.050, CH2Cl2). UV-
vis (CH2Cl2, c ) 2.0 × 10-5 M): λmax (nm) (log ꢀ) 252 (4.79), 300
(4.51), 358 (4.17), 445 (3.69), 570 (2.85). CD (c ) 2.0 × 10-5
M): nm ([θ]), 243 (1.42 × 10-5), 264 (-1.25 × 10-5), 295 (3.53
× 10-5), 328 (-1.02 × 10-4), 360 (-2.57 × 10-5), 454 (-2.9 ×
10-4), 571 (-1.65 × 10-4).
78 °C. IR (CCl4): 2928, 2856, 1663, 1608 cm-1
.
1H NMR
(CDCl3, 400 MHz): δ 8.46 (d, 2H, J ) 9.0 Hz); 8.40 (2H, d, J
) 9.0 Hz); 7.36 (s, 2H); 6.46 (d, 2H, J ) 10.1 Hz); 5.92 (d, 2H,
J ) 10.1 Hz); 4.43 (m, 4H); 4.25 (m, 4H); 1.99 (m, 8H); 1.60
(m, 8H); 1.29 (m, 64 H); 0.89 (m, 12H) ppm. 13C NMR (CDCl3,
75 MHz): δ 184.8, 183.5, 159.5, 144.6, 140.6, 133.8, 133.2,
130.0, 127.7, 127.4, 125.7, 124.7, 123.5, 120.3, 100.5, 74.0, 69.3,
31.9, 30.5, 29.6 (m), 29.4, 29.0, 26.2, 26.1, 22.7, 14.1 ppm.
HRMS calcd for C78H111O8: (M + 1) 1175.8279, found 1175.8269.
Resolu tion of 15. Toluene (16 mL) and TMEDA (4.40 g,
37.9 mmol, 5.71 mL) were syringed into a flask containing 15
(0.445 g, 0.379 mmol), Zn (0.382 g, 5.87 mmol), and (-)-
camphanoyl chloride (1.23 g, 5.68 mmol). The mixture was
refluxed for 2 h, cooled to room temperature, washed with HCl
(1 M) and then saturated aq NaHCO3, dried (Na2SO4), and
chromatographed (5% EtOAc/CH2Cl2). The levorotatory dias-
tereomer (M)-16 (0.275 g, 76%, mp 51-53 °C) eluted first. The
dextrorotatory diastereomer (P)-16 eluted second and was
rechromatographed (25% EtOAc in hexane). The yield was
0.271 g (75%), mp 90-92 °C.
Ack n ow led gm en t. We thank the NSF for grant
support (CHE98-02316 and its REU program) and
Pfizer Inc. for a Pfizer Undergraduate Summer Fellow-
ship to N.R.G.
(P )-16: [R]D +715 (c 0.057, CH2Cl2); IR (CCl4) 2928, 2856,
Su p p or tin g In for m a tion Ava ila ble: Graphs showing the
1H and 13C NMR and IR spectra of 3,6-diacetyl-9,10-(diphe-
nylmethylenedioxy)phenanthrene, 7-13, (P)-(+)-14, (M)-(-)-
14, 15, (P)-(+)-16, and (M)-(-)-16, and the UV-vis and CD
spectra of (M)-13, (M)-(-)-14, (M)-15, and (M)-(-)-16. (43
pages). This material is contained in libraries on microfiche,
immediately follows this article in the microfilm version of the
journal, and can be ordered from the ACS; see any current
masthead page for ordering information.
1
1798, 1750 cm-1; H NMR (CDCl3, 400 MHz) δ 8.38 (d, 2H, J
) 8.7 Hz); 8.36 (d, 2H, J ) 8.7 Hz); 7.03 (d, 2H, J ) 8.4 Hz);
6.86 (s, 2H); 6.05 (d, 2H, J ) 8.4 Hz); 4.37-4.28 (m, 4H); 4.20-
4.12 (m, 4H); 2.67 (m, 2H); 2.25 (m, 2H); 2.11-1.95 (m, 10H);
1.83 (m, 2H); 1.74 (m, 2H); 1.63 (m, 8H); 1.5-1.2 (m, 88H);
0.98 (s, 6H); 0.90 (m, 12 H); 0.72 (s, 6H); 0.52 (s, 6H) ppm; 13
C
NMR (CDCl3, 75 MHz) δ 178.0, 177.1, 165.0, 164.8, 154.3,
143.9, 142.9, 142.3, 128.9, 127.4, 126.2, 124.7, 123.3, 122.7,
122.0, 121.1, 116.5, 115.2, 96.2, 91.2, 90.3, 74.1, 68.7, 55.0,
54.41, 54.37, 54.25, 31.9, 31.0, 30.7, 29.7 (m), 29.5, 29.3, 29.2,
J O981380Y