Preparation of highly hindered polyenes with tert-butyl groups in internal positions

Article abstract of DOI:10.1002/chem.201001250

The conjugated tetraenes 3 and 4 a-c have been prepared and shown to possess an orthogonal structure. This was not only demonstrated by their spectroscopic properties and X-ray structural analysis of solid representatives (e.g., 4 a-c) but also by the res

Full text of DOI:10.1002/chem.201001250

FULL PAPER
DOI: 10.1002/chem.201001250
Preparation of Highly Hindered Polyenes with tert-Butyl Groups in
Internal Positions**
Markus Betz,[a] Henning Hopf,*[a] Ludger Ernst,[b] Peter G. Jones,[c] and
Yoshio Okamoto[d]
In memory of Professor Wilfried A. Kçnig
Abstract: The conjugated tetraenes 3 and 4a–c have been prepared and shown to
possess an orthogonal structure. This was not only demonstrated by their spectro-
scopic properties and X-ray structural analysis of solid representatives (e.g., 4a–c)
but also by the resolution of these chiral compounds by GC and HPLC chroma-
tography using various chiral selector systems. The chemical behavior of the typi-
cal tetraene 4a has been studied using bromination, hydrogenation, epoxidation,
and photo equilibration reactions.
Keywords: bromination · chirality ·
conjugation · epoxidation · polyole-
fins · tetraenes
Introduction
In the two preceding papers of this series we described the
preparation and structural properties of long oligoenes 1,
which were stabilized by placing tert-butyl groups in their a-
and w-positions;[2] in several of these molecules we also re-
placed up to four double bonds by acetylene moieties, creat-
ing oligoene/oligoyne hybrids[1] (Scheme 1).
[a] Dr. M. Betz, Prof. Dr. H. Hopf
Institut fꢀr Organische Chemie
Technische Universitꢁt Braunschweig
Hagenring 30, 38106 Braunschweig (Germany)
Fax : (+49)531-391-5388
Scheme 1. Terminally and “internally” tert-butylated oligoenes.
E-mail: H.Hopf@tu-bs.de
[b] Prof. Dr. L. Ernst
NMR-Laboratorium der Chemischen Institute der
Technischen Universitꢁt Braunschweig
Hagenring 30, 38106 Braunschweig (Germany)
Fax : (+49)531-391-8192
Single-crystal X-ray structural analysis of the hydrocar-
bons 1 revealed that most of the molecules studied have a
planar structure.[2] This situation should be vastly different if
the bulky blocking groups are bonded to interior positions
of the polyolefin. In this case they would not only prevent
an “external attack” on the normally highly reactive polyene
chain,[3] but would also cause intramolecular repulsive
forces, eventually leading to nonplanar polyolefins in which
the lateral overlap of the p orbitals would be impaired or
even completely removed. This could not only lead to re-
duced—or even annihilated—conjugation; but also to a
chiral oligo- or polyolefin. Applied to the most famous poly-
[c] Prof. Dr. P. G. Jones
Institut fꢀr Anorganische und Analytische Chemie
Technische Universitꢁt Braunschweig
Postfach 3329, 38023 Braunschweig (Germany)
Fax : (+49)531-391-5387
[d] Prof. Dr. Y. Okamoto
EcoTopia Science Institute, Nagoya University
Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)
Fax : (+81)52-789-3188
[**] Highly hindered olefins and polyolefins, XVI. Part XV: ref. [1].
Chem. Eur. J. 2011, 17, 231 – 247
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231

olefin, “polyacetylene”[4] this would mean “insulation” to-
wards the attack of external reagents, that is, stabilization,
but only at the price of reduced electric conductivity if these
polyolefins are employed as substrates for molecular
metals.[5] In fact, one of the simplest conjugated hydrocar-
bons carrying internal tert-butyl substituents, 2,3-di-tert-
butyl-buta-1,3-diene (2, 2,2,5,5-tetramethyl-3,4-bismethylen-
hexane) has already been described by Backer and co-work-
ers in the late 1930s.[6] Structural work on this hydrocarbon
was performed much later and demonstrated the orthogonal
geometry of the molecule: as determined by X-ray structur-
al elucidation the dihedral angle between the two planes
passing through the two double bonds of 2 amounts to 968,[7]
whereas an angle of 101.58 is obtained from a gas-phase
electron diffraction (GED) study of the molecule.[8] Clearly,
the Newman representation of 2 (right half of the formula
in Scheme 1) is a more realistic representation of the mole-
cule. Note that orthogonal 2 is a chiral molecule possessing
a chiral axis, just like numerous allenes, biphenyls or spiro-
compounds.[9]
Scheme 2. Failed attempts to prepare 4,5-di-tert-butyl-octa-1,3,5,7-tet-
raene (3).
Because the preparation of internally substituted oli-
goenes is hence an interesting question in its own right, but
could also be of considerable practical importance (organic
metals stabilized by bulky or functional groups), we decided
to prepare higher vinylogues of 2. In this publication we not
only describe the synthesis of the (formally) conjugated tet-
raene 3 (3,4-di-tert-butyl-octa-1,3,5,7-tetraene), but also of a
few of its derivatives 4a–c carrying tert-butyl groups both
terminally and internally.
Results and Discussion
Synthesis: Since 3 is structurally a simple molecule, we
hoped that we could prepare it by a short synthesis using
simple reagents and transformations. As it turned out, all of
our initial attempts, a selection of which is summarized in
Scheme 2, failed.
Although the bromodiene 7 could be obtained easily from
tert-butyl methyl ketone 5 via the intermediate a,b-unsatu-
rated aldehyde 6[10] in good yields, we were unable to homo-
couple two of these molecules to 3. Although we could
detect the hydrocarbon by GC/MS analysis of the complex
product mixture, we failed to isolate the target molecule
therefrom. Likewise, double Wittig olefination of the di-
Scheme 3. Successful preparation of 4,5-di-tert-butyl-octa-1,3,5,7-tetraene
(3).
The rather involved route began with propane-1,3-diol
(12), which was first monoprotected to the corresponding
tetrahydropyranyl (THP) ether, which in a subsequent oxi-
dation step with pyridinium chlorochromate (PCC) provided
13, a previously described aldehyde.[11,12] The next inter-
mediate, propargyl alcohol 14, obtained from 13 by ethynyl-
ACHTUNGTRENNUNGketone 9 with the ylid generated from allyltriphenylphos-
phonium bromide did not furnish the target molecule. The
reaction of 9 with allyl magnesium bromide started hopeful-
ly and yielded the tertiary alcohol 10, which, disappointingly,
could not be induced to react a second time with the
Grignard reagent, however. The intended double dehydra-
tion of the desired diol 11 could hence not be performed.
After these failures we decided to concentrate our efforts
on a multistep synthesis in which the carbon framework of 3
was first generated step by step and the complete set of
double bonds was only produced at the very end of the se-
quence. This approach is summarized in Scheme 3.
AHCTUNGTREGaNNUN tion with an acetylene Grignard, is also a known com-
pound.[13,14] When the former was treated with excess n-
butyl lithium in THF and the resulting organolithio species
quenched with 13, the symmetrical diol 15, a highly viscous,
colorless oil, was produced. With its four stereogenic centers
this compound should be formed as a mixture of diastereo-
mers, and this is indeed the case as shown by its 13C NMR
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Chiral Linear Polyenes
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spectrum (multiple signals for the majority of carbon
atoms); no attempt, however, was made to separate these
stereoisomers.
For the next step, tert-butylation, as described by us previ-
ously,[15] the two hydroxyl groups of 15 first had to be con-
verted into better leaving groups. This was accomplished by
esterification of 15 with acetic anhydride in pyridine. The di-
acetate 16, formed in good yield (90%), was then subjected
to the reagent produced from tert-butyl magnesium bromide
and CuBr/LiBr.[15] The desired diene 17 was obtained in
60% yield as a highly viscous oil. We believe that the con-
figuration of the two new double bonds is that shown in
Scheme 3; however, this could not be derived unambiguous-
ly from its spectroscopic data (see experimental section),
but follows from the crystal structure determination of the
diol 18 (see below), isolated in 73% yield after the protect-
ing groups of 17 had been removed by acid cleavage. The
bis-THP ether 17 contains three stereogenic centers (two
chiral centers, one chiral axis), and is hence produced as a
diastereomeric mixture by the above transformation. The
conversion of 16 into 17 involves two consecutive SN2’-sub-
stitution processes, taking place via an allenic intermediate.
This can be isolated as the main product if the substitution
is carried out with substoichiometric amounts of the metal
organic reagent; its spectroscopic data are given in the ex-
perimental section.
Figure 1. Olefinic region of the 1H NMR spectrum of 3 (400 MHz, sol-
vent CDCl3; top: experimental spectrum, bottom: simulated spectrum).
obtain the chemical shifts and coupling constants (Table 1).
The coupling constant of highest interest, JACTHNURTGNEU(GN 2-H, 3-H), was
determined to be 10.75 Hz, slightly larger than the corre-
Since the direct dehydration of 18 with p-toluene sulfonic
acid or sodium hydrogensulfate failed, the diol was first con-
verted into its bis-tosylate (62%). When this was treated
with potassium tert-butoxide in diethyl ether at room tem-
perature double elimination took place and yielded the tet-
raene 3 in 54% yield. The hydrocarbon is a colorless oil,
which forms a glasslike polymer when exposed neat to air
for several weeks at room temperature. Its structure follows
from the usual spectroscopic and analytical data as well as
its chiroptical properties (see below).
Table 1. 1H NMR chemical shifts and coupling constants of 3[a] compared
to butadiene.[b]
Proton d(3)
[ppm]
d(butadiene) Protons J(HH) in J(HH) in
G
[ppm]
3 [Hz]
butadiene [Hz]
1E
1Z
2
3
tBu
4.955
5.110
6.244
6.224
1.146
5.02
5.13
6.23
6.23
1E, 1Z
1E, 2
1E, 3
1Z, 2
1Z, 3
2, 3
2.09
10.12
ꢀ0.79
16.98
ꢀ0.83
10.75
1.74
10.17
ꢀ0.86
17.05
ꢀ0.83
10.41
Particularly revealing is its electronic spectrum (see
below), which shows a single absorption maximum at
228 nm, much shorter than expected for a conjugated tet-
raene: the fully conjugated parent hydrocarbon octa-1,3,5,7-
tetraene displays the typical “finger pattern” of absorption
maxima between 267 and 304 nm, the last two bands being
the most intense,[16] and its derivative carrying four tert-butyl
substituents in its 1- and 8-position shows a very similar pat-
tern with the four bands shifted to the range between 300
and 342 nm.[2] In fact, the absorption of 3 resembles more
that observed for its “half” 1,1-di-tert-butylbuta-1,3-diene
(lmax =242 nm, single maximum).[17] Parent buta-1,3-diene
absorbs at 217 nm, and its 1,1,4,4-tetramethyl derivative also
at 228 nm.[18] We conclude from these data, that the two
diene subsystems of 3 are practically uncoupled and that the
hydrocarbon possesses an orthogonal, chiral structure.
[a] Solvent CDCl3, reference TMS, observation frequency 400 MHz,
quality of fit: R=0.22%. [b] From reference [19]; solvent CCl4, reference
cyclohexane converted to the TMS scale using dACTHUNRGTNEUNG(C6H12)=1.40 ppm, com-
pare with reference [20]).
sponding value in 1,3-butadiene (10.41 Hz).[19] This shows
that the two butadiene halves of 3 are essentially planar, at
least as much as in butadiene itself. Hence, the conceivable
unfavorable interaction between 2-H and 5-tBu (or between
7-H and 4-tBu) does not play a major role. It is prevented
ꢀ
by the twist of the molecule about the C4 C5 bond as dis-
cussed above. It should be noted that the Z,Z-configuration
of 3 shown in Scheme 3 does not follow from these data. We
assume that the configuration shown is correction because
the stereochemistry of precursor diol 18 was established by
X-ray structural analysis (see below).
1
The H NMR spectrum of 3 also deserves comment. Its
olefinic region (Figure 1) shows a highly second-order four-
proton spin system. Its second-order character is caused
mainly by the closeness of the chemical shifts of 2-H and 3-
H. The spectrum needed an iterative analysis in order to
All other spectroscopic and analytical data of 3 are col-
lected in the experimental section and agree with the pro-
posed structure.
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233

H. Hopf et al.
Although with the synthesis of 3 we had been successful
in preparing the double vinylogue of the parent hydrocar-
bon 2, we did not have enough material to study its chemi-
cal properties and because of its oily nature we were unable
to carry out an X-ray diffraction study. Since the compound
was also somewhat labile (see above), we decided to intro-
duce tert-butyl groups at the ends of its olefinic system as
well, that is, use the same approach employed for the stabili-
zation of the parent polyolefin.[2]
reaction conditions (large excess of bromine, extended reac-
tion time). The separation of the product mixture containing
the substrate 4a and varying amounts of 24 and 27 was ac-
complished by column chromatography on silver nitrate im-
pregnated silica gel (Scheme 5).
Towards this end the a,b-unsaturated ketone 19, available
from our previous work in multigram quantities[1,2] was ethy-
nylated to provide the propargyl alcohol 20 (89%,
Scheme 4). When this was metalated as described above for
Scheme 5. The bromination of (5Z,7Z)-4a.
Whereas the structure of 24 could be derived by two-di-
mensional NMR analysis and its other spectroscopic data
(see Experimental Section), the dibromide 27 on high
vacuum sublimation provided crystals suitable for an X-ray
structural analysis (see below). It shows that the two diene
“halves” of 27 indeed adopt an orthogonal configuration
with respect to each other. The extensive 2D-NMR experi-
ments on 24 (COSY, HSQC, HMBC, NOESY) allowed us
to determine constitution, configuration, and conformation
of the molecule. Nuclear Overhauser effects were observed
between all tert-butyl protons and their respective cis-proton
at the same double bond. The NOE between 4-H and the 3-
tert-butyl group established the Z configuration of the C3=
C4 double bond. Moreover, a NOESY cross-peak was found
between 8-H and the (Z)-tert-butyl protons at C-10, in ac-
Scheme 4. Preparation of the terminally and internally tert-butylated tet-
raene (5Z,7Z)-4a.
the 14!15 conversion, and the formed organolithio inter-
mediate quenched by the addition of 19, the diol 21 was iso-
lated (77%) as a mixture of diastereomers as shown by its
1H NMR spectrum (see Experimental Section). The conver-
sion of 21 via 22 into the tetraene 4a was routine (see
Scheme 4), and we were pleased to obtain this hydrocarbon
not only in gram amounts, but also as a stable, crystalline
material.
The structure determination of 4a was carried out by the
usual spectroscopic and analytical methods, in particular by
single-crystal X-ray diffraction, the required crystals being
obtained by slow high-vacuum sublimation. As discussed
below, 4a possesses an orthogonal structure and is therefore
chiral.
ꢀ
cordance with an s-trans conformation at the C8 C9 bond.
Yet no NOE was discernible between protons in the differ-
ent halves of the molecule in agreement with an orthogonal
ꢀ
conformation at the C6 C7 bond.
Formally the above substitution resembles the ipso-substi-
tution in highly alkylated benzene derivatives. For example
on bromination of tert-butyl benzene small amounts of bro-
mobenzene are generated,[22] and in the case of 1,3,5-tri-tert-
butylbenzene the ipso-substitution product bromo-3,5-di-
tert-butylbenzene is the main product.[23] If the addition–
elimination mechanism postulated for these cases is applied
to 4a, the picture summarized in Scheme 5 results. Accord-
ing to molecular models and PM3 calculations, the terminal
double bonds of 4a are more accessible to an attacking ex-
ternal reagent than the internal ones, and as a primary inter-
mediate the bromonium ion 23 could be formed. Any trans-
attack by bromide ion is prevented by the severely crowded
environment, and therefore 23 stabilizes itself by loss of a
tert-butyl cation. In fact, the trapping product of this leaving
Chemical behavior of highly tert-butylated octatetraenes:
With sufficient amounts of 4a in hand, the first experiment
we tried was its bromination. As in the case of 1,2,3-tri-tert-
butylbuta-1,3-diene, another “orthogonal diene” studied by
us earlier,[17,21] we found that the intuitively expected elec-
trophilic addition had not taken place, but that 4a had un-
dergone a substitution reaction yielding the monobromide
24 (55%) when one equivalent of bromine was used. If a
threefold excess of bromine is used, the dibromide 27 is
formed in good yield (88%). It appears likely that 24 is an
intermediate en route to 27. This double substitution prod-
uct could not be converted into a more highly brominated
product, as shown by repeating the process under rougher
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group with bromide, that is, tert-butylbromide, could be de-
tected in the product mixture of this experiment by GC/MS
analysis as well as 1H NMR spectroscopy (singlet at d=
1.81 ppm). We could not find any evidence for the also pos-
sible production of isobutene. Even if the cyclic structure 23
opened up to the allyl cation 25$26, no additional room for
external bromide trapping would become available, the
ipso-substitution route still being the most favorable one.
Both vinyl bromides, 24 and 27, are, in principle, useful for
further transformations; in particular it would be of interest
to incorporate them into larger structures by metal-mediat-
ed coupling and cross-coupling reactions. The “polyacety-
lenes” thus obtained might well possess a helical structure.
The reason for the observed stereospecific formation of
both 24 and 27 is unclear at present. It could well be that
during the product-forming step from, for example, 23 or 26,
the incoming bromine substituent might find it sterically
easier to point towards the next double bond in a cisoid
fashion. If the tert-butyl substituent were to replace the bro-
mine atom, we might expect strong steric interactions be-
tween the bulky substituent and the neighboring olefinic hy-
drogen atom.
50% yield; its structure follows from the spectroscopic data
(see Experimental Section).
We next turned to the hydrogenation of the highly tert-bu-
tylated octatetraenes 4a–c. In a first series of experiments
catalytic hydrogenation reactions over various precious
metal catalysts were carried out.
Whereas 4a did not add hydrogen when Pd on charcoal
or in situ prepared Pt (from PtO2) was used, hydrogen
uptake took place over Pt/C although it proceeded very
slowly and provided the monohydrogenated triene (5Z,7Z)-
29 after one week at 1 atm of hydrogen pressure at room
temperature in 14% yield only. Although a doubly hydro-
genated product was also produced in trace amounts (hints
from the MS data), we could not separate and identify it.
Analytically pure triene was obtained by recrystallizing the
hydrocarbon several times from ethanol; the crystals were
suitable for an X-ray structure determination (see below).
The other spectroscopic data are given in the Experimental
Section. Under more rigorous conditions (37 atm H2 pres-
sure, 1508C, acetic acid, 3 days) the two terminal double
bonds of 4a were saturated and the hydrocarbon 30 was iso-
lated in 33% yield. Again, recrystallization from ethanol
provided single crystals of X-ray quality and the structure of
the diene in the solid state is reported below. Both hydrocar-
bons have the expected orthogonal structure (Scheme 7).
Tetraenes with a smaller number of tert-butyl substituents,
namely 4b and 4c, are readily available from 24 and 27 by
halogen–metal exchange followed by hydrolysis. Although
this process is slow and required heating in a THF/hexane
solvent mixture (probably because of steric hindrance
again), the two debrominated hydrocarbons 4b and 4c
could be prepared in good yields (90 and 65%, respectively;
Scheme 6).
Scheme 6. Debromination of the bromides 24 and 27.
On slow recrystallization from ethanol, single crystals of
4b and 4c were obtained which allowed X-ray structural de-
termination (see below). As expected, both compounds
show a twisted structure; their full spectroscopic and analyti-
cal details can be found in the Experimental Section.
Scheme 7. Hydrogenation of (5Z,7Z)-4a under different conditions.
When the debromination of 27 was performed at ꢀ788C
(excess n-butyl lithium) and the resulting intermediate
quenched with water, the monobromide 28 was isolated in
Comparable results were obtained when 4a was subjected
to the conditions of a Birch reduction (liquid ammonia,
sodium, ammonium chloride, THF). In this case, two reduc-
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235

H. Hopf et al.
tion products are formed, both
being trienes according to their
mass spectra. The first one is
the 5Z,7Z-diasteromer of 29 al-
ready discussed above (21%)
and the second one its 5Z,7E-
isomer (49%, see Scheme 7).
The hydrocarbons could be sep-
arated by column chromatogra-
phy on silver nitrate impregnat-
ed silica gel, and their struc-
Scheme 8. Structure-relevant
NOEs observed in (5Z,7E)-29.
tures determined by NMR spectroscopy (NOESY spectra).
As the structure of (5Z,7Z)-29 was also determined by X-
ray diffraction, only the NOEs relevant for the structure of
(5Z,7E)-29 are given in Scheme 8.
After these results with 4a, the hydrogenation of 4b and
4c offered no surprises. Under high pressure conditions the
two “internal” dienes were produced in 53 and 98% yield,
respectively (Scheme 7). Not only do the higher yields and
the milder conditions—the unpolar hexane serving as the
solvent—in these cases indicate less steric shielding, but ac-
cording to a GC/MS analysis of the hydrogenation mixture a
monoene was also produced in trace amounts; its concentra-
tion was, however, so small that its structure could not be
derived from its NMR spectra.
In summary, the hydrogenation experiments demonstrate
that these oligoenes posses an “external part” at which the
reducing agent (hydrogen plus catalyst surface) can more or
less readily attack and an inner unsaturated core which is so
strongly sterically protected that it survives even severe hy-
drogenation conditions. The unsaturation is “buried” by a
saturated sheet and survives chemical transformations, that
is, we are dealing with a “hidden functionality”.
Scheme 9. Epoxidation of (5Z,7Z)-4a, 4b, and 4c.
genic elements, a mixture of diasteromers is produced (ratio
1
1:9 as shown by H NMR analysis). In this case, however, a
separation of the two isomers failed. When the alternative
terminal double bond is attacked, the isomeric ketone 38 is
produced. For its formation a proton shift must have been
faster than the migration of a tert-butyl group.
In 4c the termini of the tetraene are equally substituted
again and one product, ketone 39, is produced on epoxida-
tion, as expected. The structures of all these new compounds
follow from their spectroscopic data which are listed in the
Experimental Section.
In one of our earlier studies on the preparation of tert-bu-
tylated di- and oligoenes, we described the photochemical
behavior of 2.[24] It was found that this hydrocarbon, on
direct irradiation with a high-pressure mercury lamp, cy-
clized to the bicyclobutane derivative 40. The surprisingly
high yield of 60% was attributed by us to the orthogonal
structure of 2. On further irradiation the central bond of 40
is cleaved and by a 1,2-hydrogen shift the cyclobutene deriv-
ative 41 is produced (Scheme 10)
The terminal double bonds of the tetraenes 4 also reacted
in the next series of experiments performed: epoxidations.
To our surprise, however, we could not isolate the expected
adducts. As shown in Scheme 9, in all cases ketones with a
rearranged carbon skeleton were produced.
We nevertheless assume that an epoxide, 33, generated at
the periphery of 4a, is produced initially and that this opens
up under the acidic conditions via 34 and 35; a terminating
Wagner–Meerwein shift of a tert-butyl substituent finally
provides the isolated ketone 36. Since this product possesses
two stereogenic elements (an axis and a center) it should be
formed as a mixture of two diastereomers. This is indeed the
To investigate whether the “extended” oligoenes 3 and 4
show a comparable behavior, we selected (5Z,7Z)-4a as a
model compound and irradiated it in hexane for three days
with a 150 W low-pressure mercury lamp. Two products
were formed and they could be separated by repeated re-
crystallization from ethanol. These hydrocarbons were the
5E,7Z and 5E,7E isomers of the substrate (5Z,7Z)-4a, and
not cyclization products such as 42 and 43, as demonstrated
by their NOESY-spectra (see Scheme 11).
1
case as shown by H NMR analysis, and although the two
products, formed in 9:1 ratio, could be separated by column
chromatography, no attempt was made to establish their
exact stereostructure. To avoid the presence of acid during
epoxidation, we repeated the process using dimethyldioxir-
ane as the oxidation reagent. However, in this case no epox-
idation of 4a was observed.
Tetraene 4b offers the interesting possibility to study two
competing oxidation reactions, since its two terminal double
bonds are differently substituted. Evidently, the more elec-
tron-rich double bond is attacked preferentially and 37 is
formed as the main product. Since this contains two stereo-
According to B3LYP-DFT calculations[25] (5E,7Z)-4a is
16 kJmolꢀ1 and (5E,7E)-4a is 26 kJmolꢀ1 less stable than
the substrate. No hints could be derived from the photoly-
sate that 42 or 43 had been produced during irradiation. Fol-
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Chiral Linear Polyenes
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Scheme 10. Photoisomerization of (5Z,7Z)-4a.
Scheme 11. NOEs observed in (5E,7Z)-4a and (5E,7E)-4a.
lowing the photoreaction by continuous monitoring (TLC
analysis) did not reveal any additional products at shorter
reaction times.
The structures of 4a–c, 18, 27, (5Z,7Z)-29, and 30 in the
solid state: All compounds crystallize solvent-free and with-
out imposed crystallographic symmetry; the asymmetric unit
of compounds 18 and 27 consists of two independent mole-
cules. Approximate twofold symmetry (r.m.s. deviations in
brackets) is displayed by the molecules 4a (0.1 ꢃ), 4c
(0.2 ꢃ), 18 (first molecule only, 0.1 ꢃ), 27 (both molecules;
0.07, 0.08 ꢃ), and 30 (0.04 ꢃ).
Molecular structures are presented in Figures 2–5. Table 2
presents a summary for all structures of molecular dimen-
sions along the central C8 chain. The most striking feature is
Figure 2. The molecular structures of compounds 4a (top), 4b (middle),
and 4c (bottom) in the crystal. Ellipsoids represent 30% probability
levels for 4a and 4b and 50% for 4c.
ꢀ
the geometry associated with the central single bond C4
C5. The torsion angles (absolute values) about this bond lie
in the range 77 to 938, thus demonstrating that the double
tert-butyl substitution has forced the orthogonality of the
two halves of the chain. The bond length itself ranges from
1.495 to 1.511 ꢃ (av. 1.503 ꢃ), which may be compared with
lengths C1=C2, which are significantly longer if C1 bears
two tert-butyl substituents. The double bonds C3=C4 are
shorter, effectively isolated double bonds, in compounds 18,
(one half of) 29, and 30 than in the other molecules. Bond
angles are consistent with some of the trends noted in our
polyene and mixed polyene/polyyne systems;[1,2] thus the
angles C1-C2-C3 are extremely wide (>1308) if C1 bears
two tert-butyl substituents, and angles C2-C3-C4 are also
consistently wider than the ideal 1208 by some 68. The
angles C3-C4-C5 at the center of the chain are however
close to ideal.
ꢀ
typical values for the system C=C C=C quoted as 1.455 ꢃ
for conjugated and 1.478 ꢃ for nonconjugated systems.[26]
ꢀ
The formally analogous bond lengths C2 C3, when lying be-
tween two double bonds as in compounds 4a–c, 27 and (one
half of) 29, correspond well to the conjugated value, because
the torsion angles about this bond are essentially zero. The
extra elongation of C4 C5 may be attributed to the steric
effects of the bulky substituents; compare with the bond
ꢀ
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
237

H. Hopf et al.
Figure 4. Top: One of two independent molecules of compound 27 in the
crystal. Ellipsoids represent 30% probability levels. Bottom: Packing dia-
Figure 3. Top: The two independent molecules of compound 18 in the
crystal. Ellipsoids represent 50% probability levels. Bottom: Packing dia-
1
gram of compound 27; thick dashed lines indicate bromine–bromine con-
gram of compound 18 in the region zꢁ = ; thick dashed lines indicate hy-
4
1
tacts. This is the region at xꢁ = and contains only the second independ-
8
drogen bonds. Molecule 1 is drawn with thick and molecule 2 with thin
bonds. Hydrogen atoms not involved in H bonds are omitted. The 19-
membered rings (see text) are seen as a horizontal series along the yz
faces and the 33-membered rings across the center of the cell.
ent molecule (see text).
ent types of rings; rings of graph set R55(19) involving the
complete backbone of molecule 2, and larger rings R33(33)
involving two backbones of molecule 1 and one of mole-
cule 2.
The two independent molecules of 18 differ primarily in
the conformation of the C-C-C-OH chains, for which the
torsion angles are extended (ꢁꢂ1808) except for C6’-C7’-
C8’-O2’ 75.48. For compound 27, differences in torsion
angles combine to make the r.m.s. deviation of a least-
squares fit 0.32 ꢃ, reducing to 0.11 ꢃ if only the atoms Br1,
Br2, C1–8, C13, C17 are considered.
The packing of the rod-shaped molecules of our polyene
and mixed polyene/polyyne systems[1,2] often involved paral-
lel molecular chains (which were generally linear) and asso-
ciated layer structures. The more equidimensional form of
the molecules studied here, associated with the orthogonali-
The packing of compound 27 is determined largely (ignor-
ꢀ
ing borderline C H···Br contacts) by the Br···Br interactions
ꢀ
Br1···Br2 3.5907(7) and Br1’···Br2’ 3.5597(7) ꢃ, with all C
Br···Br angles in the range 165–1758. Each independent mol-
ecule thereby forms chains of molecules related by y axis
translation, neighboring chains forming layers at xꢁ = ,7=
1
8
8
(molecule 2), 3= ,5= (molecule 1; Figure 4, bottom).
8
8
Chirality of 3, 4b, and 4c: Excluding the meso-forms, all
nonplanar di- and oligoenes are chiral. This is evident for
butadiene, the only achiral conformations of which are its
syn- and the anti-forms. As soon as the dihedral angle be-
tween the two double bonds differs from 0 or 1808, chirality
is generated. Whether, however, optically active enantio-
mers can be isolated depends on the racemization barrier
(activation energy for rotation about the single bond con-
necting the double bounds). In fact, resolvable derivatives
of chiral dienes have been known for a long time, the most
famous examples coming from the classical studies of Kç-
ꢀ
ty about C4 C5, renders the packing devoid of special fea-
tures unless other functional groups are present. For com-
pound 18 (Figure 3, bottom) each of the four independent
OH groups forms one classical hydrogen bond to another
OH group as the acceptor. Each independent molecule, con-
sidered alone, forms an undulating chain of graph set C(11)
with overall direction parallel to the y axis. The combination
of both chains leads to a corrugated layer structure parallel
to the xy plane. The layer contains two topologically differ-
238
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 231 – 247

Chiral Linear Polyenes
FULL PAPER
As far as we are aware, we are presenting here the first
experimental proof that nonplanar conjugated tetraenes are
chiral and can be resolved by either gas chromatography or
HPLC on chiral phases. For this purpose the di-tert-butylat-
ed octatetraene 3 and the two derivatives 4b and 4c were
resolved by various chromatographic methods using differ-
ent chiral selectors.
Beginning with the tetraenes 4b and 4c, these could be
resolved by analytical gas chromatography on a capillary
column coated with 6-O-TBDMS-2,3-di-O-methyl-b-cyclo-
dextrin. As shown in Figure 6 in both cases base-line separa-
tion was accomplished.[29]
Figure 6. Gas chromatographic separation of the two enantiomers of the
tetraenes 4b and 4c with 6-O-TBDMS-2,3-di-O-methyl-b-cyclodextrin as
chiral selector.
Figure 5. The molecular structures of compounds 29 (Z,Z isomer; top)
and 30 in the crystal. Ellipsoids represent 30% probability levels.
brich and of Mannschreck and involve polyhalogenated di-
and trienes.[27,28]
These separations were carried out at 1508C, the highest
operating temperature of the used columns, showing that
Table 2. Selected geometric parameters [bond lengths in ꢃ, bond angles and torsion angles in 8] for the central carbon chains of compounds 4a, 4b, 4c,
18, 27, (Z,Z)-29 and 30. The chains are numbered from C1 to C8. Values for both halves of the chain, which are in general chemically equivalent unless
ꢀ
ꢀ
otherwise stated, are presented together (e.g., C1 C2 with C7 C8).
ꢀ
C1 C2
ꢀ
C2 C3
ꢀ
C3 C4
ꢀ
C4 C5
C1-C2-C3
C2-C3-C4
C3-C4-C5
C1-C2-C3-C4
C2-C3-C4-C5
C3-C4-C5-C6
4a
1.359(1)
1.356(1)
1.354(2)
1.332(2)
1.342(4)
1.343(4)
1.518(3)
1.503(3)
1.504(3)
1.523(3)
1.338(5)
1.331(5)
1.336(5)
1.331(5)
1.351(2)
1.553(2)
1.552(1)
1.550(1)
1.460(1)
1.457(1)
1.451(2)
1.460(2)
1.458(4)
1.456(4)
1.500(3)
1.508(3)
1.501(3)
1.497(3)
1.442(5)
1.440(5)
1.442(5)
1.451(5)
1.459(2)
1.502(2)
1.509(1)
1.507(1)
1.352(1)
1.350(1)
1.353(2)
1.336(2)
1.355(4)
1.364(4)
1.332(3)
1.333(3)
1.334(3)
1.340(3)
1.344(5)
1.356(5)
1.338(5)
1.349(5)
1.348(2)
1.337(2)
1.334(1)
1.334(1)
1.503(1)
1.496(2)
1.511(4)
1.506(3)
1.507(3)
1.495(5)
1.499(5)
1.504(2)
1.507(1)
131.5(1)
131.3(1)
131.7(2)
123.4(2)
124.2(3)
124.0(3)
112.0(2)
115.2(2)
110.8(2)
113.0(2)
127.7(4)
127.4(4)
127.9(4)
127.9(4)
131.7(2)
115.6(1)
115.8(1)
115.6(1)
125.7(1)
124.7(1)
125.0(2)
126.7(2)
125.9(3)
125.0(3)
127.2(2)
127.4(2)
127.4(2)
126.7(2)
125.2(4)
125.3(4)
125.6(4)
124.1(4)
125.5(2)
127.4(2)
126.4(1)
126.2(1)
121.2(1)
121.1(1)
120.6(2)
119.8(1)
118.9(2)
118.3(2)
120.8(2)
120.8(2)
119.1(2)
119.0(2)
120.0(4)
119.7(3)
119.8(4)
119.3(4)
120.9(1)
119.5(1)
120.4(1)
120.3(1)
173.5(1)
169.5(1)
163.9(2)
0.7(1)
3.4(1)
ꢀ78.9(1)
4b[a]
4c
ꢀ0.9(2)
ꢀ77.3(2)
ꢀ91.8(3)
87.9(2)
178.8(2)
4.4(2)
ꢀ174.3(3)
0.0(4)
0.7(4)
176.9(3)
18
ꢀ130.6(2)
ꢀ126.0(2)
ꢀ157.7(2)
134.9(2)
ꢀ1.1(3)
0.5(3)
1.0(3)
1.8(3)
ꢀ8.1(6)
ꢀ3.8(6)
3.1(6)
1.4(6)
4.4(3)
ꢀ0.4(3)
ꢀ0.9(2)
ꢀ0.3(1)
ꢀ80.7(3)
90.4(5)
27
ꢀ178.0(4)
177.8(4)
ꢀ175.9(4)
ꢀ171.9(5)
ꢀ162.9(2)
ꢀ166.6(2)
176.7(1)
ꢀ92.4(5)
88.2(2)
G
ꢀ86.1(1)
180.0(1)
[a] The two halves of the molecule are not equivalent; C1 bears two tert-butyl substituents, C8 only one. [b] The two halves of the molecule are not
ꢀ
equivalent; C1=C2 is a double bond, C7 C8 a single bond.
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
239

H. Hopf et al.
the two hydrocarbons are configurationally stable at least
up to this temperature. Various attempts to resolve the
enantiomers on a preparative GC scale failed. On the above
column the two signals overlap far too strongly to allow a
successful separation. Turning to cellulose-tris-(3,5-dimethyl-
phenylcarbamate) as the chiral selector, a material that has
been used for the separation of numerous racemates, includ-
ing hydrocarbons and molecules with an axis of chirality[30]
also failed, although many different conditions (variation of
solvents and solvent mixtures) were tried.
Finally, the Nagoya group was able to separate 4c on a
Chiralpak OT(+)-column, which employs (+)-poly(triphe-
nylmethylmethacrylate) as the chiral selector.[31] The result
of a preparative HPLC separation of 4c with ethanol as sol-
vent at 08C is shown in Figure 7.
Figure 8. Top: CD spectrum of hydrocarbon 3 in hexane at room temper-
ature; conc. of S-(+)-3: 10.2 mgmLꢀ1, conc. of R-(ꢀ)-3: 8.6 mgmLꢀ1
Bottom: UV spectrum of 3 in hexane.
.
Figure 7. Separation of 4c by preparative HPLC on Chiralpak OT(+);
solvent: ethanol, flow rate 0.2 mLminꢀ1, 08C.
Altogether 3 mg of the first fraction, and 1 mg of the
second were obtained. As shown by analytical HPLC analy-
sis, the enantiomeric excess of the first fraction exceeded
99%, whereas the second fraction had an ee of ꢁ95%. The
specific rotation of the first fraction [a]2D0 was determined as
+1308.
Preparative gas chromatography on a 6-O-TBDMS-2,3-di-
O-methyl-b-cyclodextrin impregnated column turned out to
be the method of choice for separation of the di-tert-butylat-
ed tetraene 3. In this case a specific rotation of [a]2D0 =ꢂ2848
was measured.
For two of the tetraenes prepared in this study the abso-
lute configuration was determined by the exciton chirality
method: 3 and 4b.[32] The necessary CD and UV spectra are
shown in Figures 8 and 9, respectively, and the assignment
of the absolute configurations is given in Table 3. It is evi-
dent from the UV spectra that the two chromophores of
these hydrocarbons are not in conjugation (see above). In
both cases the dextrorotatory enantiomer is thus in the S
configuration.
Figure 9. Top: CD spectrum of hydrocarbon 4b in ethanol at room tem-
perature. Bottom: UV spectrum of 4b in ethanol.
Experimental Section
General: Melting points: below 2008C: Bꢀchi 510 melting point appara-
tus; above 2008C: Kofler apparatus. The m.p. are uncorrected. NMR:
240
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Chem. Eur. J. 2011, 17, 231 – 247

Chiral Linear Polyenes
FULL PAPER
Table 3. Assignment of the absolute configurations of 3 and 4b.
bined organic phases were dried (MgSO4) and the solvent removed by
distillation. The raw product was purified by column chromatography
(silica gel; hexane/diethyl ether 1:1). Yield: 2.29 g (50%); colorless oil;
1H NMR (400.1 MHz, CDCl3): d=1.43–1.83 (m, 12H; 10-, 11-, 12-, 15-,
16-, 17-H), 1.93–2.06 (m, 4H; 2-, 7-H), 3.54–4.03 (m, 8H; 1-, 8-, 13-, 18-
H), 4.58–4.63 ppm (m, 4H; 3-, 6-, 9-, 14-H); 13C NMR (100.6 MHz,
CDCl3): d=99.01, 99.00, 98.81 (d, C-9, -14), 85.39, 85.36 (s, C-4, -5),
64.27, 64.21 (t, C-1, -8), 62.46, 62.44, 62.14, 62.12 (t, C-13, -18), 60.31,
60.16 (d, C-3, -6), 37.09, 37.04 (t, C-2, -7), 30.47, 30.43 (t, C-10, -15),
25.22, 25.19 (t, C-12, -17), 19.46, 19.27 ppm (t, C-11, -16); IR (ATR): n˜ =
3042 (br, w), 2940 (m), 2872 (m), 1440 (m), 1352 (m), 1201 (m), 1136
(m), 1118 (s), 1062 (s), 1020 (s), 981 (s), 904 (m), 867 (m), 809 cmꢀ1 (m);
ESI-MS: m/z: 366.1 [M+ +H+Na] (25), 365.1 [M+ +Na] (100); UV
(acetonitrile): lmax (loge)=191 nm (3.05); HRMS/ESI: C18H30O6Na:
calcd 365.1940; found: 365.1933.
UV
CD
lmax [nm] lext [nm] (y [mdeg])
S-(+)-3 (positive exciton chirality)
244.2 (84.2)
231.9 (0.0)
228
A=160.1 mdeg
221.4 (ꢀ75.9)
R-(ꢀ)-3 (negative exciton chirality)
244.2 (ꢀ73.4)
228
232.3 (0.0)
A=ꢀ142.7 mdeg
220.4 (69.3)
3,6-Diacetoxy-1,8-bis-(tetrahydropyran-2-yloxy)-oct-4-yne (16):
A mix-
S-(+)-4b (positive exciton chirality)
251 (13.8)
ture of 15 (1.48 g, 4.32 mmol), acetic anhydride (50 mL), and pyridine
(6 mL, 74 mmol) was left at RT for 12 h under nitrogen. After neutraliza-
tion with aqueous bicarbonate solution, the reaction mixture was extract-
ed with diethyl ether (4ꢄ30 mL portions), and the combined organic
phases dried over magnesium sulfate. The oil obtained after solvent re-
moval in vacuo was purified by column chromatography on silica gel
(hexane/diethyl ether 1:1). Colorless oil, yield: 1.66 g (90%); 1H NMR
(400.1 MHz, CDCl3): d=1.48–1.87 (m, 12H; 10-, 11-, 12-, 19-, 20-, 21-H),
1.98–2.17 (m, 4H; 2-, 7-H), 2.072 and 2.075 (s, 6H; 15-, 17-H), 3.42–3.91
(m, 8H; 1-, 8-, 13-, 22-H), 4.56–4.59 (m, 2H; 9-, 18-H), 5.52–5.63 ppm (m,
2H; 3-, 6-H); 13C NMR (100.6 MHz, CDCl3): d=169.70, 169.68 (s, C-14,
-16), 98.68, 98.64 (d, C-9, -18), 82.77 (s, C-4, -5), 62.93, 62.85, 61.94, 61.91
(t, C-1, -18, -13, -22), 61.36, 61.26, 61.24 (d, C-3, -6), 34.94, 34.86 (t, C-2,
-7), 30.49, 30.45 (t, C-10, -19), 25.39 (t, C-12, 21), 20.92 (q, C-15, -17),
19.23, 19.18 ppm (t, C-11, -20); IR (ATR): n˜ =2942 (m), 2871 (w), 1739
(s), 1439 (w), 1369 (m), 1222 (s), 1200 (w), 1160 (m), 1119 (m), 1076 (m),
1035 (s), 1017 (s), 981 (s), 961 (s), 903 (m), 868 (m), 814 cmꢀ1 (m); ESI-
MS: m/z (%): 450 [M+ +H+Na] (22), 449 [M+ +Na] (100); UV (aceto-
nitrile): lmax (loge)=193 nm (3.15); HRMS/ESI: C22H34O8Na (449.22):
calcd 449.2151; found: 449.2154.
232
192
236 (0.0)
229 (ꢀ3.5)
A=17.3 mdeg
R-(ꢀ)-4b (negative exciton chirality)
251 (ꢀ5.8)
232
192
236 (0.0)
226 (1.9)
A=ꢀ7.7 mdeg
Bruker AC-200: 1H NMR (200.1 MHz), 13C NMR (50.3 MHz); Bruker
1
AM-400 and DRX-400: H NMR (400.1 MHz), 13C NMR (100.6 MHz) in
1
deuteriochloroform. H chemical shifts in ppm to high frequency of inter-
nal tetramethylsilane, 13C chemical shifts relative to CDCl3 (d=
77.01 ppm). IR: Nicolet 320 FT-IR spectrometer as KBr pellets or thin
films; ATR-IR: Bruker Tensor 27 Spectrometer. UV/Vis: HP 8452 A
Diode Array spectrophotometer; Varian Cary 100 BIO. MS: Finnigan
MAT 8430 (EI, 70 eV and FAB). GC/MS: Finnigan MAT 4515 (EI,
40 eV) attached to a Carlo Erba HRGC 5160. Analytical enantioselective
GC: Carlo Erba Fractovap 2150 with a 25 m fused silica capillary column
with octakis-(2,6-di-O-methyl-3-O-pentyl-g-cyclodextrin or heptakis-(6-
O-tert-butyldimethylsilyl-2,3-di-O-methyl)-b-cyclodextrin in OV-1701
(1:1; w/w) as the stationary phase. Preparative enantioselective GC:
Varian 1400 with heptakis-(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-
b-cyclodextrin/SE-52 (1:1; w/w) on Chromosorb W-HP. Optical rotation:
Propol polarimeter (Dr. Kernchen). CD: AVIV Model 215 Circular Di-
chroism Spectrometer (University of Hamburg); JASCO-1595 CD-Spec-
trometer (Nagoya University). HPLC columns for enantioselective chro-
matography: Chiracell OD-H; Chiralpak OT(+) using a Merck L-4250
or JASCO MD-2010 UV/Vis detector. Elemental analyses: Institut fꢀr
Pharmazeutische Chemie, TU Braunschweig. X-ray analysis: Siemens
R3; Stoe STADI-4; Bruker SMART 1000 CCD. The X-ray data were
processed and refined with the SHELXS-86 and SHELXS-93 programs,
respectively.
AHCTUNGTRENGN(UN 3Z,5Z)-4,5-Di-tert-butyl-1,8-bis-(tetrahydropyran-2-yloxy)-octa-3,5-diene
(17): A solution of tert-butyl magnesium chloride in anhydrous diethyl
ether (150 mL) was prepared from magnesium turnings (6.9 g, 0.28 mol)
and tert-butylchloride (9.4 mL, 86 mmol). The Grignard solution was
added under nitrogen at ꢀ508C to a suspension of anhydrous CuBr
(3.51 g, 24.5 mmol) and LiBr (2.12 g, 24.4 mmol) in THF (50 mL). After
stirring at this temperature, a solution of 16 (2.26 g, 5.30 mmol) in THF
(50 mL) was added at ꢀ708C. After 1 h stirring at this temperature more
Grignard solution was added (prepared from magnesium (7.3 g, 0.3 mol),
tert-butylchloride (10 mL, 91.8 mmol) at ꢀ708C. After stirring for 16 h at
room temperature, saturated aqueous ammonium chloride solution was
added for hydrolysis. The hydrolysate was filtered to remove any solid
precipitates, the phases were separated, and the aqueous phase was
washed with diethyl ether (3ꢄ30 mL). The combined organic phases
were dried with magnesium sulfate and the solvent was removed by
rotary evaporation. The remaining oily residue was purified by silica gel
column chromatography with hexane/diethyl ether 8:2 as the eluent.
1
Yield: 1.35 g (60%); H NMR (400.1 MHz, CDCl3): d=1.11 (s, 18H; 15-,
17-H), 1.52–1.86 (m, 12H; 10-, 11-, 12-, 19-, 20-, 21-H), 2.17–2.24 (m, 4H;
2-, 7-H), 3.33–3.89 (m, 8H; 1-, 8-, 13-, 22-H), 4.59 (t, J=3.5 Hz, 2H; 9-,
18-H), 5.54 ppm (t, J=7.0 Hz, 2H; 3-, 6-H); 13C NMR (100.6 MHz,
CDCl3): d=149.65, 149.61 (s, C-4, -5), 122.99, 122.86 (d, C-3, -6), 98.60,
98.56 (d, C-9, -18), 67.21, 67.14 (t, C-1, -8), 61.94, 61.89 (t, C-13, -22),
35.34 (s, C-14, -16), 32.15 (q, C-15, -17), 31.26 (t, C-2, -7), 30.63 (t, C-10,
-19), 25.51 (t, C-12, -21), 19.43, 19.40 ppm (t, C-11, -20); IR (ATR): n˜ =
2945 (m), 2900 (m), 2868 (m), 1471 (w), 1388 (w), 1362 (w), 1200 (m),
1138 (m), 1119 (m), 1075 (m), 1028 (s), 986 (m), 967 (m), 870 (m),
813 cmꢀ1 (m); MS (70 eV): m/z (%): 422 [M+] (<1), 192 (3), 179 (8), 164
(16), 149 (13), 119 (14), 105 (14), 85 (100), 67 (12), 57 (74); ESI/MS : m/z
(%): 445 [M+ +Na] (100), 446 [M+ +Na+H] (28); UV (acetonitrile):
lmax (loge)=193 nm (4.23); HRMS/ESI: m/z calcd for: C26H46O4Na:
445.3294; found: 445.3293.
The aldehydes 13[11, 12] and 19[16] and the alcohol 14[14] were prepared ac-
cording to the procedure described in the literature; all other reagents
were commercial compounds.
1,8-Bis-(tetrahydropyran-2-yloxy)-oct-4-yne-3,6-diol (15): A solution of
nBuLi (1.6m) in hexane (18.4 mL, 29.5 mmol) was added under nitrogen
to a solution of the propargyl alcohol 14 (2.47 g, 13.4 mmol) in anhydrous
THF (70 mL) at 08C . The mixture was heated to reflux for 1 h and after
cooling to 08C a solution of aldehyde 13 (2.33 g, 14.75 mmol) in anhy-
drous THF (10 mL) was added. The reaction mixture was stirred at room
temperature and subsequently hydrolyzed with sat. ammonium chloride
solution in water (100 mL). The phases were separated and the aqueous
phase was carefully extracted with diethyl ether (4ꢄ30 mL). The com-
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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241

H. Hopf et al.
3-Acetoxy-4-tert-butyl-1,8-bis-(tetrahydropyran-2-yloxy)-octa-4,5-diene:
With shorter reaction times and/or insufficient amounts of the metal or-
ganic reagent in the preparation of 17, the mono-tert-butylated intermedi-
ate could be isolated. Colorless oil; 1H NMR (400.1 MHz, CDCl3): d=
1.06, 1.07 (s, 9H; 17-H), 1.50–1.85 (m, 12H; 10-, 11-, 12-, 19-, 20-, 21-H),
2.01, 2.02 (s, 3H; 15-H), 1.91–2.06 (m, 2H; 2-H), 2.33 (q, J=6.9 Hz, 2H;
7-H), 3.31–3.38 (m, 2H; 1-H), 3.44–3.89 (m, 6H; 8-, 13-, 22-H), 4.55–4.61
(m, 2H; 9-, 18-H), 5.37 (t, J=6.9 Hz, 1H; 6-H), 5.51–5.55 ppm (m, 1H;
3-H); 13C NMR (100.6 MHz, CDCl3): d=202.26, 202.23, 202.20, 202.17 (s,
C-5), 170.07, 170.01 (s, C-14), 113.44, 113.40, 113.34, 113.29 (s, C-4),
98.60, 98.53, 98.47, 98.37 (d, C-9, -18), 92.15, 92.12 (d, C-6), 68.55, 68.22
(d, C-3), 66.64, 66.62 (t, C-8), 64.07, 63.87 (t, C-1), 61.94, 61.88, 61.60 (t,
C-13, -22), 35.08 (t, C-2), 33.15 (s, C-16), 30.45 (t, C-10, -19), 29.68, 29,63
(t, C-7), 29.32, 29.28 (q, C-17), 25.29 (t, C-12, -21), 21.15 (q, C-15), 19.32,
19.28, 19.25, 19.09 ppm (t, C-11, -20); IR (ATR): n˜ =2943 (m), 2869 (w),
1735 (m), 1440 (w), 1366 (m), 1233 (s), 1201 (m), 1138 (m), 1120 (s), 1078
(m), 1064 (m), 1030 (s), 984 (m), 906 (m), 813 cmꢀ1 (m); MS (70 eV): m/z
(%): 424 [M+] (<1), 178 (8), 165 (8), 121 (4), 85 (100), 67 (7), 57 (12), 43
(9); UV (acetonitrile): lmax (loge)=192 nm (4.22); elemental analysis
calcd (%) for C24H40O6 (424.6): C 67.89, H 9.50; found: C 67.51, H 9.64.
100 mL). The combined organic phases were dried (MgSO4), the solvent
was removed in vacuo, and the remaining oil purified by column chroma-
tography (hexane): 80 mg (54%) of 3 as a colorless oil. On standing, the
hydrocarbon polymerized within several weeks yielding a glassy polymer.
1H NMR (400.1 MHz, CDCl3): see Table 1; 13C NMR (100.6 MHz,
CDCl3): d=151.95 (s, C-4, -5), 136.32 (d, C-2, -7), 127.71 (d, C-3, -6),
115.28 (t, C-1, -8), 35.96 (s, C-9, -11), 31.73 ppm (q, C-10, -12); IR
(ATR): n˜ =3084 (w), 2965 (m), 2868 (w), 1717 (w), 1624 (w), 1474 (w),
1391 (w), 1364 (m), 1195 (w), 1158 (w), 1089 (m), 1043 (s), 997 (s), 899
(s), 663 cmꢀ1 (s); GC/MS (70 eV): m/z (%): 218 [M+] (<1), 145 (6), 131
(5), 119 (13), 105 (26), 91 (11), 77 (6), 57 (100), 41 (17); UV (hexane):
lmax (loge)=228 nm (4.53); elemental analysis calcd (%) for C16H26
(218.4): C 88.00 H 12.00; found: C 87.21 H 12.10; specific rotation:
[a]2D0 =+284ꢂ3 (c=0.34 in hexane, l=0.1 dm), ꢀ280ꢂ1 (c=0.33 in
hexane, l=0.1 dm).
5-tert-Butyl-6,6-dimethylhept-4-en-1-yn-3-ol (20): A solution of ethynyl
magnesium bromide (85.6 mL, 42.8 mmol) in THF (50 mL) was added
under nitrogen to a solution of the aldehyde 19 (6.0 g, 35.7 mmol)[33] in
anhydrous THF (100 mL) at 08C over a period of 30 min. After stirring
for 2 h at 08C, the reaction mixture was hydrolyzed by the addition of an
ice-cold saturated ammonium chloride solution (100 mL). The aqueous
phase was separated, thoroughly extracted with diethyl ether (3ꢄ
100 mL), and the combined organic phases were dried over magnesium
sulfate. After solvent removal in vacuo, the solid residue was purified by
column chromatography (silica gel; dichloromethane). Yield: 6.2 g
(89%), colorless solid; m.p. 60–618C; 1H NMR (400.1 MHz, CDCl3): d=
1.23, 1.34 (s, 9H; 7-, 9-H), 1.83 (s, 1H; OH), 2.50 (d, J=2.0 Hz, 1H; 1-
H), 5.42 (d, J=9.8 Hz, 1H; 4-H), 5.51 ppm (dd, J=9.8, 1.2 Hz, 1H; 3-H);
13C NMR (100.6 MHz, CDCl3): d=157.15 (s, C-5), 124.5 (d, C-4), 84.58
(s, C-2), 72.91 (d, C-1), 60.55 (d, C-3), 38.64, 37.47 (s, C-6/8), 33.93,
31.58 ppm (q, C-7/9); IR (KBr): n˜ =3355 (s), 3278 (s), 3013 (w), 2979
(m), 2960 (s), 2925 (m), 2877 (w), 1610 (w), 1394 (w), 1369 (w), 1020 (s),
697 (m), 674 (m), 670 (m), 653 cmꢀ1 (s); GC/MS (70 eV): m/z (%): 194
[M+] (<1), 139 (23), 137 (3), 126 (8), 123 (13), 111 (31), 105 (54), 97 (4),
95 (20), 91 (15), 84 (50), 69 (37), 67 (17), 59 (24), 57 (100), 55 (19), 43
(15), 41 (28); UV (acetonitrile): lmax (loge)=198 nm (4.02); elemental
analysis calcd (%) for C13H22O (194.36): C 80.35, H 11.41; found: C
80.42, H 11.62.
ACHTUNGTRENNUNG(3Z,5Z)-4,5-Di-tert-butylocta-3,5-diene-1,8-diol (18): The diene 17
(660 mg, 1.56 mmol) was heated under nitrogen in the presence of p-tol-
uenesulfonic acid (10 mg, 0.05 mmol) in ethanol (30 mL) for 2 h under
reflux. The solvent was removed in vacuo, and the solid residue purified
by silica gel column chromatography with diethyl ether: 290 mg (73%)
of 18 as colorless plates. M.p. 1088C; 1H NMR (400.1 MHz, CDCl3): d=
1.11 (s, 18H; 10-, 12-H), 2.02–2.09 (m, 2H; 2-, 7-HA), 2.30–2.39 (m, 2H;
2-, 7-HB), 2.69 (s, 2H; -OH), 3.57–3.63 (m, 2H; 1-, 8-HA), 3.67–3.72 (m,
2H; 1-, 8-HB), 5.50 ppm (dd, J=9.5, 4.3 Hz, 2H; 3-, 6-H); 13C NMR
(100.6 MHz, CDCl3): d=150.74 (s, C-4, -5), 123.43 (d, C-3, -6), 62.60 (t,
C-1, -8), 35.60 (s, C-9, -11), 34.10 (t, C-2, -7), 32.09 (q, C-10, -12); IR
(ATR): n˜ =3295 (m), 3027 (w), 2958 (s), 2904 (m), 2867 (m), 1475 (m),
1460 (m), 1388 (m), 1361 (m), 1226 (w), 1195 (m), 1054 (s), 1022 (s), 947
(m), 731 (m), 655 (s), 607 cmꢀ1 (m); MS (70 eV): m/z (%): 236 [M+] (5),
180 (4), 179 (8), 165 (9), 164 (20), 149 (18), 137 (6), 135 (10), 121 (15),
105 (15), 93 (12), 81 (8), 69 (9), 57 (100), 55 (11); UV (acetonitrile): lmax
(loge)=192 nm (4.21); elemental analysis calcd (%) for C16H30O2
(254.43): C 75.54, H 11.89; found: C 75.49, H 11.98; X-ray structural anal-
ysis: see below.
3,10-Di-tert-butyl-2,2,11,11-tetramethyldodeca-3,9-dien-6-yne-5,8-diol
(21): A solution of n-butyl lithium (25.4 mL, 40.6 mmol) in hexane (1.6m)
was slowly added to a solution of 20 (3.6 g, 18.5 mmol) in anhydrous di-
ethyl ether (100 mL) at 08C. After the mixture had been heated to reflux
for 1 h, it was cooled to ꢀ788C and a solution of the aldehyde 19 (4.0 g,
23.8 mmol) in anhydrous ether (20 mL) was added. The mixture was
warmed to room temperature, stirred for 12 h, and hydrolyzed with satu-
rated aqueous ammonium chloride solution (80 mL). The phases were
separated, the aqueous phase was extracted carefully with diethyl ether
(150 mL), and the combined organic phases were dried over magnesium
sulfate. After solvent removal the solid residue was purified by column
chromatography (silica gel; dichloromethane, then diethyl ether) and re-
crystallization (dichloromethane/hexane). Yield: 5.2 g (77%), slightly
ACHTUNGTRENNUNG(3Z,5Z)-4,5-Di-tert-butyl-1,8-bis-(toluene-4-sulfonyloxymethyl)-octa-3,5-
diene: A mixture of the diol 18 (160 mg, 0.63 mmol) and p-toluenesulfon-
yl chloride (900 mg, 4.72 mmol) in pyridine (8 mL) was stirred for 16 h
under nitrogen at room temperature. After completion of the reaction,
the mixture was poured into saturated aqueous bicarbonate solution
(50 mL), the aqueous phase was extracted with ether thoroughly, and the
combined organic phases were dried (MgSO4). After solvent removal by
rotary evaporation the oily residue was purified by column chromatogra-
phy (silica gel, hexane/dichloromethane 1:1). Yield: 0.22 g (62%) of the
ditosylate; colorless oil; 1H NMR (400.1 MHz, CDCl3): d=1.00 (s, 18H;
17-, 19-H), 2.13–2.19 (m, 4H; 2-, 7-H), 2.44 (s, 6H; 15-, 26-H), 3.89–4.00
(m, 4H; 1-, 8-H), 5.35 (t, J=6.9 Hz, 2H; 3-, 6-H), 7.34 (AA’XX’, 4H; 11-
,13-, 22-, 24-H), 7.77 ppm (AA’XX’, 4H; 10-, 14-, 21-, 25-H); 13C NMR
(100.6 MHz, CDCl3): d=151.30 (s, C-4, -5), 144.61 (s, C-9, -20), 133.91 (s,
C-12, -23), 129.73 (d, C-11, -13, -22, -24), 127.70 (d, C-10, -14, -21, -25),
120.75 (d, C-3, -6), 69.83 (t, C-1, -8), 35.33 (s, C-16, -18), 31.81 (q, C-17,
-19), 30.10 (t, C-2, -7), 21.42 ppm (q, C-15, -26); IR (ATR): n˜ =2965 (w),
2901 (w), 2867 (w), 1598 (w), 1467 (w), 1356 (s), 1173 (s), 1097 (w), 1055
(m), 963 (m), 908 (s), 835 (m), 813 (s), 757 (m), 731 (m), 661 cmꢀ1 (s);
ESI/MS : m/z (%): 586 [M+ +Na+H], 585 [M+ +Na]; UV (acetonitrile):
lmax (loge)=197 (4.69), 224 nm (4.38); HRMS (ESI): m/z calcd for
C30H42O6S2Na: 585.2321; found: 585.2327.
1
yellow, amorphous solid; m. p. 1128C; H NMR (400.1 MHz, CDCl3): d=
1.205, 1.208, 1.32 (s, 36H; 1-, 12-, 14-, 16-H), 1.92 (s, 1H; OH), 5.38 (d,
J=9.5 Hz, 2H; 4-, 9-H), 5.53 ppm (d, J=9.5 Hz, 2H; 5-, 8-H); 13C NMR
(100.6 MHz, CDCl3): d=156.24, 156.20 (s, C-3, -10), 124.92, 124.88 (d, C-
4, -9), 88.50 (s, C-6, -7), 60.82 (d, C-5, -8), 38.64, 37.44 (s, C-2, -11, -13,
-15), 33.87, 33.85, 31.64 (q, C-1, -12, -14, -16); IR (KBr): n˜ =3386 (s),
2959 (s), 2918 (s), 2875 (m), 1392 (m), 1371 (m), 1216 (m), 1017 cmꢀ1 (s);
MS (CI, NH3, pos.): m/z (%): 380 [M+ +NH4] (13), 346 (10), 345 (36),
322 (3), 289 (43), 271 (73), 261 (6), 233 (100), 186 (35), 177 (13), 169 (11),
126 (5), 121 (3), 111 (3); UV (acetonitrile): lmax (loge)=200 nm (4.34);
elemental analysis calcd (%) for C24H42O2 (362.64): C 79.50H, 11.68;
found: C 79.38, H 11.70.
ACHTUNGTRENNUNG(3Z,5Z)-4,5-Di-tert-butylocta-1,3,5,7-tetraene (3): A solution of the above
ditosylate (0.380 g, 0.675 mmol) in anhydrous diethyl ether (50 mL) was
stirred under nitrogen at room temperature for 2 d in the presence of po-
tassium tert-butoxide (1.0 g, 8.91 mmol) The progress of the reaction was
monitored by TLC analysis. The reaction mixture was hydrolyzed with
aqueous bicarbonate solution (50 mL), the phases were separated, and
the aqueous phase was thoroughly extracted with diethyl ether (3ꢄ
5,8-Diacetoxy-3,10-di-tert-butyl-2,2,11,11-tetramethyldodeca-3,9-dien-6-
yne (22): As described above for 16, from the diol 21 (3.7 g, 10.1 mmol),
acetic anhydride (40 mL) and pyridine (2.2 mL, 27.2 mmol) 22 was pre-
pared. The raw product was purified by column chromatography (silica
gel, dichloromethane): 4.43 g (98%) of 22, colorless crystals. m.p. 828C;
242
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 231 – 247

Chiral Linear Polyenes
FULL PAPER
1H NMR (400.1 MHz, CDCl3): d=1.19, 1.20, 1.31 (s, 36H; 1-, 12-, 14-,
20-H), 2.08 (s, 6H; 16-, 18-H), 5.35, 5.37 (d, J=9.4 Hz, 2H; 4-, 9-H),
6.46 ppm (d, J=9.4 Hz, 2H; 5-, 8-H); 13C NMR (100.6 MHz, CDCl3): d=
169.66, 169.62 (s, C-15, -17), 157.53, 157.44 (s, C-3, -10), 120.72, 120.66 (d,
C-4, -9), 82.97, 82.89 (s, C-6, -7), 62.94, 62.89 (d, C-5, -8), 38.89, 37.42 (s,
C-2, -11, -13, -19), 33.52, 31.64 (q, C-1, -12, -14, -20), 21.19 ppm (q, C-16,
-18); IR (KBr): n˜ =3018 (w), 2961 (s), 2920 (w), 2877 (w), 1750 (s), 1393
(m), 1370 (m), 1013 cmꢀ1 (s); MS (70 eV): m/z (%): 446 [M+] (6), 389
(5), 347 (37), 306 (3), 307 (15), 287 (12), 273 (24), 249 (21), 231 (66), 203
(10), 175 (8), 149 (8), 137 (8), 123 (15), 111 (13), 57 (100), 41 (16); UV
(acetonitrile): lmax (loge)=202 nm (4.34); elemental analysis calcd (%)
for C28H46O4 (446.73): C 75.29, H 10.38; found: C 75.35, H 10.50.
Bromination of (5Z,7Z)-4a—synthesis of (3Z,5Z,7Z,9Z)-3,10-dibromo-
6,7-di-tert-butyl-2,2,11,11-tetramethyldodeca-3,5,7,9-tetraene (27): Ac-
cording to the above procedure, 4a (3.0 g, 6.75 mmol) in CCl4 (75 mL)
was treated with bromine (3.3 g, 20.63 mmol) in CCl4 (10 mL). Since in
this case the reaction was slow (TLC monitoring on AgNO3-treated silica
gel; hexane) another portion of bromine (0.300 g, 1.88 mmol) was added
and the mixture stirred for another day at room temperature. After sol-
vent removal the remainder was purified by sublimation (508C,
0.011 mbar). Yield: 2.92 g (88%), colorless plates; m.p. 988C; 1H NMR
(400.1 MHz, CDCl3): d=1.15 (s, 18H; 1-, 12-H), 1.17 (s, 18H; 14-, 16-H),
6.16 (d, J=9.8 Hz, 2H; 4-, 9-H), 6.52 ppm (d, J=9.7 Hz, 2H; 5-, 8-H);
13C NMR (100.6 MHz, CDCl3): d=154.72 (s, C-6, -7), 140.55 (s, C-3, -10),
125.69 (d, C-5, -8), 123.43 (d, C-4, -9), 39.87 (s, C-2, -11), 36.53 (s, C-13,
-15), 31.99 (q, C-14, -16), 29.79 ppm (q, C-1, -12); IR (KBr): n˜ =2869 (w),
2908 (w), 2936 (m), 2968 (s), 3053 (w), 1392 (w), 1385 (w), 1363 (m),
1262 (s), 1225 (m), 785 cmꢀ1 (m); MS (70 eV): m/z (%): 490/488/486 [M+
] (7/15/8), 433/431/429 (<1/1/<1), 373/375/377 (1/2/1), 337 (2), 295/293
(3/1), 215 (2), 199 (2), 173 (3), 159 (5), 128 (3), 105 (3), 91 (3), 83 (2), 57
(100), 41 (15); UV (acetonitrile): lmax (loge)=246 (4.41), 254 nm (4.37,
sh); HRMS: m/z calcd for C24H40Br2: 486.1497; found: 486.1500; X-ray
structural analysis: see below and main section. The formation of tert-
butyl bromide as a reaction product was established by 1H NMR spec-
troscopy (singlet at d=1.81 ppm, tBu) and GC/MS analysis (m/z=135
and 133 [M+] and comparison with the data of an authentic sample.
ACHTUNGTRENNUNG(5Z,7Z)-2,2,11,11-Tetramethyl-3,6,7,10-tetra-tert-butyldodeca-3,5,7,9-tet-
raene ((5Z,7Z)-4a): As described above for the conversion of 18 to 3,
the metal organic alkylating reagent was prepared from magnesium turn-
ings (4.9 g, 0.20 mol), tert-butyl bromide (6.7 mL, 61.5 mmol) in diethyl
ether (50 mL) and CuBr (2.5 g, 17 mmol) and LiBr (1.5 g, 17 mmol) in
THF (150 mL). This reagent was used to tert-butylate 22 (2.3 g,
5.1 mmol) in THF (20 mL). After stirring for 12 h at room temperature
the process was complete (monitoring by TLC), and the reaction mixture
was hydrolyzed by the addition of saturated aqueous ammonium chloride
solution (150 mL). Most of the solvent was removed by rotary evapora-
tion, the obtained concentrated product solution filtered through a pad
of silica gel, and the final product obtained by gradient high vacuum sub-
limation at 1008C/0.011 mbar. Yield: 1.8 g (80%) as colorless crystals;
m.p. 1668C; 1H NMR (400.1 MHz, CDCl3): d=1.13 (s, 18H; 1-, 12-H=
terminal (E)-tBu), 1.15 (s, 18H; 16-, 18-H), 1.36 (s, 18H; 14-, 20-H=ter-
minal (Z)-tBu), 5.87 (d, J=11.1 Hz, 2H; 4-, 9-H), 6.73 (d, J=11.1 Hz,
2H; 5-, 8-H); 13C NMR (100.6 MHz, CDCl3): d=153.01 (s, C-3, -10),
148.91 (s, C-6, -7), 125.44 (d, C-5, -8), 122.89 (d, C-4, -9), 39.16 (s, C-2,
-11=terminal (E)-tBu), 37.39 (s, C-13, -19=terminal (Z)-tBu), 36.48 (s,
C-15, -17), 33.68 (q, C-14, -20=terminal (Z)-tBu), 32.07 ppm (q, C-1,
-12=terminal (E)-tBu), 31.94 (q, C-16, -18); IR (KBr): n˜ =3003 (w), 2956
(s), 2924 (m), 2907 (m), 2869 (m), 1637 (w), 1389 (w), 1364 cmꢀ1 (m); MS
(70 eV): m/z (%): 442 [M+] (17), 386 (16), 343 (2), 330 (3), 274 (6), 273
(18), 203 (4), 181 (7), 131 (7), 109 (13), 83 (19), 69 (25), 57 (100); UV
(acetonitrile): lmax (loge)=238 (4.25, sh), 246 (4.30), 254 nm (4.23, sh); el-
emental analysis calcd (%) for C32H58 (442.83): C 86.80, H 13.20; found:
C 86.81, H 13.35; X-ray structure analysis: see main section and below.
AHCTUNGTRENGN(UN 5Z,7Z)-3,6,7-Tri-tert-butyl-2,2,11,11-tetramethyl-dodeca-3,5,7,9-tetraene
(4b): A solution of nBuLi in hexane (30 mL, 48 mmol, 1.6m) was added
under nitrogen and ice cooling to a solution of the bromide 24 (0.74 g,
1.59 mmol) in anhydrous THF (50 mL). The reaction mixture was heated
to reflux for 2 h and then hydrolyzed under ice cooling with saturated
aqueous bicarbonate solution (50 mL). The phases were separated, the
aqueous phase thoroughly extracted with diethyl ether (3ꢄ100 mL) and
the combined organic layers were dried (MgSO4). After solvent removal
by rotary evaporation the solid residue was purified by column chroma-
tography (AgNO3 impregnated silica gel; hexane) and gradient sublima-
tion (1108C, 0.6 mbar). Yield: 552 mg (90%), colorless plates; m.p. 618C;
1H NMR (400.1 MHz, CDCl3): d=0.97 (s, 9H; 12-H), 1.122 (s, 9H; 16-
H), 1.125 (s, 9H; 1-H), 1.16 (s, 9H; 18-H), 1.36 (s, 9H; 14-H), 5.59 (d, J=
15.5 Hz, 1H; 10-H), 5.87 (dd, J=10.5 Hz, 15.5 Hz, 1H; 9-H), 5.87 (d, J=
10.9 Hz, 1H; 4-H), 6.13 (d, J=10.5 Hz, 1H; 8-H), 6.72 ppm (d, J=
10.9 Hz, 1H; 5-H); 13C NMR (100.6 MHz, CDCl3): d=153.03 (s, C-3),
149.11 (s, C-6), 148.84 (s, C-7), 143.03 (d, C-10), 126.44 (d, C-8), 126.14
(d, C-5), 125.16 (d, C-9), 122.89 (d, C-4), 39.10 (s, C-2), 37.41 (s, C-13),
36.16, 36.13 (s, C-15/17), 33.61 (q, C-14), 33.16 (s, C-11), 32.05 (q, C-1),
31.89, 31.88 (q, C-16/18), 29.85 ppm (q, C-12); IR (KBr): n˜ =2994 (m),
2953 (s), 2926 (m), 2904 (m), 2867 (m), 1390 (w), 1363 (m), 974 cmꢀ1 (m);
MS (70 eV): m/z (%): 386 [M+] (42), 329 (26), 273 (100), 246 (5), 231
(3), 217 (17), 203 (8), 189 (5), 165 (8), 133 (5), 109 (23), 95 (3), 83 (10),
69 (5), 57 (95), 41 (13); UV (acetonitrile): lmax (loge)=238 (4.54),
258 nm (4.40, sh); elemental analysis calcd (%) for C28H50 (386.68): C
86.97, H 13.03; found: C 86.82, 13.25; X-ray structural analysis: see
below and main section.
Bromination of (5Z,7Z)-4a—synthesis of (3Z,5Z,7Z)-3-bromo-6,7,10-tri-
tert-butyl-2,2,11,11-tetramethyldodeca-3,5,7,9-tetraene (24): A solution of
bromine (0.42 g, 2.63 mmol) in CCl4 (5 mL) was slowly added to a solu-
tion of 4a (1.0 g, 2.26 mmol) in CCl4 (80 mL) at 08C. Even after 12 h at
room temperature the color of the solution was still red, indicating the
slow rate of the reaction. The reaction mixture was washed with aqueous
bisulfite solution (25 mL), the phases were separated and after thorough
extraction of the aqueous layer with diethyl ether (3ꢄ100 mL) the com-
bined organic fractions were dried over magnesium sulfate. The solvent
was removed in vacuo and the resulting solid raw product was purified
by column chromatography (silver nitrate impregnated silica gel;
hexane). Yield: 0.577 g (55%), colorless plates; m.p. 738C (150 mg
(3E,5Z,7Z,9E)-6,7-Di-tert-butyl-2,2,11,11-tetramethyldodeca-3,5,7,9-tet-
raene (4c): A solution of nBuLi in hexane (40 mL, 64 mmol, 1.6m) was
added under nitrogen and ice cooling to a solution of the dibromide 27
(2.9 g, 5.94 mmol) in anhydrous THF (100 mL). After heating under
reflux for 2 h, the reaction mixture was cooled to room temperature and
a saturated aqueous solution of ammonium chloride (100 mL) was added
for hydrolysis. After the usual work-up (see above, experiment 14) the
resulting raw hydrocarbon was purified by recrystallization from ether/
ethanol or by sublimation (478C, 0.001 mbar). Yield: 1.3 g (65%) of 4c,
colorless plates; m.p. 558C; 1H NMR (400.1 MHz, CDCl3): d=0.99 (s,
18H; 1-, 12-H), 1.14 (s, 18H; 14-, 16-H), 5.60 (d, J=15.5 Hz, 2H; 3-, 10-
H), 5.89 (dd, J=10.4, 15.5 Hz, 2H; 4-, 9-H), 6.15 ppm (d, J=10.4 Hz,
2H; 5-, 8-H); 13C NMR (100.6 MHz, CDCl3): d=149.19 (s, C-6, -7),
143.12 (d, C-3, -10), 127.04 (d, C-5, -8), 125.23 (d, C-4, -9), 35.86 (s, C-13,
-15), 33.16 (s, C-2, -11), 31.88 (q, C-14, -16), 29.88 ppm (q, C-1, -12); IR
(KBr): n˜ =3041 (w), 3022 (w), 2967 (s), 2956 (s), 2903 (m), 2865 (m),
1638 (m), 1475 (m), 1460 (m), 1390 (w), 1360 (m), 1316 (w), 1258 (w),
1228 cmꢀ1 (m); MS (70 eV): m/z (%): 330 [M+] (96), 315 (8), 274 (32),
1
(15%) of the starting tetraene 4a was recovered); H NMR (400.1 MHz,
CDCl3): d=1.13 (s, 9H; 10-tBu(E)), 1.15 (s, 9H; 3-tBu), 1.16 (s, 9H; 7-
tBu), 1.17 (s, 9H; 6-tBu), 1.36 (s, 9H; 10-tBu(Z)), 5.83 (d, J=11.1 Hz,
1H; 9-H), 6.19 (d, J=9.7 Hz, 1H; 4-H), 6.52 (d, J=9.7 Hz, 1H; 5-H),
6.74 ppm (d, J=11.1 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=
154.87 (s, C-6), 154.12 (s, C-10), 148.84 (s, C-7), 139.61 (s, C-3), 126.13 (d,
C-8), 125.12 (d, C-5), 123.88 (d, C-4), 122.34 (d, C-9), 39.77 (s, Cq of 3-
tBu), 39.22 (s, Cq of 10-tBu(E)), 37.44 (s, Cq of 10-tBu(Z)), 36.82 (s, Cq of
6-tBu), 36.14 (s, Cq of 7-tBu), 33.67 (q, CH3 of 10-tBu(Z)), 32.04 (q, CH3
of 10-tBu(E)), 31.96 (q, CH3 of 6-tBu), 31.93 (q, CH3 of 7-tBu),
29.77 ppm (q, CH3 of 3-tBu); IR (KBr): n˜ =2966 (s), 2921 (m), 2909 (m),
2869 (m), 1390 (w), 1363 cmꢀ1 (m); MS (70 eV): m/z (%): 466/464 [M+]
(20/21), 410 (4), 409/407 (18/19), 353/351 (28/31), 326 (2), 297/295 (3/4),
271 (4), 245/243 (9/9), 215 (3), 173 (4), 164 (8), 159 (3), 121 (3), 83 (16),
57 (100), 41 (13); UV (acetonitrile): lmax (loge)=246 nm (4.48), 260
(4.42, sh); HRMS: m/z calcd for C28H49Br: 464.3018; found: 464.3014.
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
243

H. Hopf et al.
259 (40), 245 (24), 231 (77), 217 (98), 189 (24), 175 (35), 161 (79), 133
(29), 105 (26), 95 (12), 91 (17), 83 (22), 69 (21), 57 (100), 43 (20), 41 (55);
UV (acetonitrile): lmax (loge)=222 (4.49, sh), 232 (4.60), 250 nm (4.43,
sh); elemental analysis calcd (%) for C24H42 (330.58): C 87.19, H 12.81;
found: C 87.20, H 12.93; specific rotation [a]2D0 =ꢂ130ꢂ28 (c=0.19 in
hexane l=0.1 dm), ꢂ135.38 (c=0.3 in hexane, l=1 dm); X-ray structural
analysis: see below and main section.#
C-3, -10), 36.76, 36.74 (s, C-2, -11, -13, -19), 35.00 (s, C-15, -17), 32.86 (q,
C-16, -18), 31.13, 31.09 (q, C-1, -12, -14, -20), 30.11 ppm (t, C-4, -9); IR
(KBr): n˜ =2970 (s), 2959 (s), 2923 (m), 2910 (m), 2870 (m), 1488 (w),
1474 (m), 1459 (w), 1394 (m), 1385 (w), 1367 cmꢀ1 (m); MS (70 eV): m/z
(%): 446 [M+] (5), 389 (40), 375 (3), 333 (100), 319 (25), 278 (7), 277
(35), 263 (54), 249 (4), 221 (10), 207 (46), 193 (30), 179 (20), 165 (11), 151
(38), 137 (64), 123 (53), 97 (31), 83 (50), 71 (77); UV (acetonitrile): lmax
(loge)=198 nm (4.26); elemental analysis calcd (%) for C32H62 (446.8): C
86.01H; 13.99; found: C 86.07, H 14.33; X-ray structural analysis: see
below and main section.
(3Z,5Z,7Z,9E)-3-Bromo-6,7,10-tri-tert-butyl-2,2,11,11-tetramethyldodeca-
3,5,7,9-tetraene (28): A solution of nBuLi in hexane (6.25 mL, 10 mmol,
1.6m) was added under nitrogen to a solution of the dibromide 27
(100 mg, 0.205 mmol) in anhydrous THF (30 mL) at ꢀ788C . The reac-
tion mixture was stirred for 30 min at ꢀ788C and subsequently hydro-
lyzed by addition of a saturated ammonium chloride solution (20 mL).
After the usual work-up (see above, preparation of 4b) the raw product
was purified by column chromatography (AgNO3 impregnated silica gel;
hexane). Yield:42 mg (50%), colorless oil. 1H NMR (400.1 MHz,
CDCl3): d=0.91 (s, 9H; 12-H), 1.05 (s, 9H; 16-H), 1.08 (s, 9H; 1-H), 1.10
(s, 9H; 14-H), 5.54 (d, J=15.5 Hz, 1H; 10-H), 5.77 (dd, J=10.5, 15.5 Hz,
1H; 9-H), 6.07 (d, J=10.5 Hz, 1H; 8-H), 6.13 (d, J=9.7 Hz, 1H; 4-H),
6.45 ppm (d, J=9.7 Hz, 1H; 5-H); 13C NMR (100.6 MHz, CDCl3): d=
154.93 (s, C-6), 149.05 (s, C-7), 144.02 (d, C-10), 139.70 (s, C-3), 127.03 (d,
C-8), 125.60 (d, C-5), 124.65 (d, C-9), 123.95 (d, C-4), 39.78 (s, C-2), 36.55
(s, C-13), 35.84 (s, C-15), 33.23 (s, C-11), 31.94 (q, C-14), 31.90 (q, C-16),
29.82 (q, C-12), 29.78 ppm (q, C-1); IR (KBr): n˜ =2868 (s), 2905 (s), 2963
(s), 1572 (w), 1477 (m), 1463 (m), 1391 (m), 1362 (s), 1262 (m), 1227 (m),
1196 (m), 975 cmꢀ1 (m); MS (70 eV): m/z (%): 410/408 [M+] (65/68), 395/
393 (5/4), 353/351 (9/9), 339/337 (8/8), 325/323 (5/4), 311/309 (8/8), 297/
295 (12/13), 285/282 (5/7), 257 (5), 241/239 (4/4), 215 (7), 187/185 (4), 173
(8), 159 (14), 133 (5), 95 (4), 83 (7), 57 (100), 41 (15); UV (acetonitrile):
lmax (loge)=238 (4.35), 254 nm (4.23, sh); HRMS: m/z calcd for
C24H41Br: 408.2392; found: 408.2401.
Birch reduction of (5Z,7Z)-4a—formation of (5Z,7E)-29: Ammonia
(50 mL) was condensed into a three-necked flask and small pieces of
sodium (1.0 g, 43.5 mmol) were added. After stirring the intensely blue
solution for 30 min (5Z,7Z)-4a (0.200 g, 0.45 mmol) in THF (5 mL) and
ammonium chloride (1.0 g, 18.7 mmol) were added. After stirring for
10 min the reaction mixture was brought to room temperature, while the
ammonia evaporated. Ice water (50 mL) was carefully added to the re-
maining solid (caution! there may be traces of sodium left over) and the
suspension extracted carefully with diethyl ether (3ꢄ30 mL). The solvent
was removed in vacuo and the raw product was purified by column chro-
matography (AgNO3 impregnated silica gel; hexane). Yield: 98 mg
(49%) of the triene (5Z,7E)-29, 41 mg (21%) of (5Z,7Z)-29, and 30 mg
of a mixture of hydrocarbons (m/z=446), the composition of which was
not determined; m.p. 958C; data for (5Z,7E)-29: 1H NMR (400.1 MHz,
CDCl3): d=1.01, 1.02 (s, 9 H each, 12-, 20-H), 1.07 (t, J=4.2 Hz, 1H; 10-
H), 1.12 (s, 9H; 16-H), 1.169 (s, 9H; 18-H), 1.171 (s, 9H; 1-H), 1.35 (s,
9H; 14-H), 2.23–2.37 (m, 2H; 9-H), 5.01 (t, J=5.4 Hz, 1H; 8-H), 6.10 (d,
J=10.4 Hz, 1H; 4-H), 6.53 ppm (d, J=10.4 Hz, 1H; 5-H); 13C NMR
(100.6 MHz, CDCl3): d=154.03 (s, C-6), 152.91 (s, C-3), 143.66 (s, C-7),
133.99 (d, C-8), 124.18 (d, C-5), 122.94 (d, C-4), 60.99 (d, C-10), 39.11 (s,
C-2), 37.45 (s, C-13), 36.86 (s, C-11, -19), 36.78 (s, C-15), 35.23 (s, C-17),
33.48 (q, C-14), 32.17 (q, C-1), 31.74 (q, C-16), 31.19, 31.14 (q, C-12, -20),
29.99 (q, C-18), 29.96 ppm (t, C-9); IR (ATR): n˜ =2952 (s), 2903 (m),
2868 (m), 1477 (m), 1460 (m), 1392 (m), 1364 (s), 1237 (m), 1211 (m),
1193 (m), 664 cmꢀ1 (m); MS (70 eV): m/z (%): 444 [M+] (5), 387 (7), 332
(5), 331 (19), 275 (4), 219 (2), 205 (6), 83 (11), 69 (7), 57 (100); UV (ace-
tonitrile): lmax (loge)=197 (4.13), 257 nm (4.27); HRMS: m/z calcd for
C32H60: 444.4695; found: 444.4694.
Hydrogenation of 4a to (5Z,7Z)-3,6,7,10-tetra-tert-butyl-2,2,11,11-tetra-
methyldodeca-3,5,7-triene ((5Z,7Z)-29): A suspension of the tetraene 4a
(0.200 g, 0.45 mmol), and Pt on C (20 mg) in hexane (20 mL) was hydro-
genated at room temperature for 7 d under normal pressure. The catalyst
was removed by filtration through a pad of silica gel, and the solvent was
removed in vacuo. The raw hydrogenation product was purified by
column chromatography (silver nitrate impregnated silica gel; hexane),
yielding 170 mg of hydrogenated products and 30 mg of substrate 4a
(15%). Threefold recrystallization from ethanol provided (5Z,7Z)-29
(29 mg, 14%) as colorless needles. M.p. 968C; 1H NMR (400.1 MHz,
CDCl3): d=0.93, 0.98 (s, 9H each; 12-, 20-H), 1.0–1.1 (m, 1H; 10-H),
1.11 (s, 9H; 1-H), 1.15 (s, 9H; 16-H), 1.20 (s, 9H; 18-H), 1.37 (s, 9H; 14-
H), 1.83 (dt, J=18.5, ꢁ4.6 Hz, 1H; 9-HA), 1.92 (ddd, J=4.1, 6.1, 18.5 Hz,
1H; 9-HB), 5.46 (dd, J=4.3, 6.1 Hz, 1H; 8-H), 5.91 (d, J=11.3 Hz, 1H;
4-H), 6.69 ppm (d, J=11.3 Hz, 1H; 5-H); 13C NMR (100.6 MHz, CDCl3):
d=152.85 (s, C-3), 149.30 (s, C-6), 146.30 (s, C-7), 131.89 (d, C-8), 125.91
(d, C-5), 122.38 (d, 4-C), 58.58 (d, C-10), 39.06 (s, C-2), 37.40 (s, C-13),
36.74, 36.57 (s, C-11/19), 35.86 (s, C-15), 35.65 (s, C-17), 33.69 (q, C-14),
32.34 (q, C-1), 32.25 (q, C-18), 32.02 (q, C-16), 31.28, 31.11 (q, C-12/20),
30.67 ppm (t, C-9); IR (KBr): n˜ =3008 (s), 2962 (s), 2904 (s), 2867 (s),
1476 (s), 1392 (s), 1365 (s), 1212 cmꢀ1 (m); MS (70 eV): m/z (%): 444
[M+] (9), 387 (24), 275 (7), 205 (7), 163 (2), 135 (5), 109 (4), 91 (4), 83
(10), 69 (7), 57 (100), 41 (21); UV (acetonitrile): lmax (loge)=198 (4.06),
254 (4.32, sh), 260 nm (4.33); elemental analysis calcd (%) for C32H60
(444.8): C 86.40, H 13.60; found: C 86.14 H 13.81; X-ray structural analy-
sis: see below and main section.
Hydrogenation of 4b to (5Z,7Z)-3,6,7-tri-tert-butyl-2,2,11,11-tetramethyl-
dodeca-5,7-diene (31): Using the same procedure as for the hydrogena-
tion of 4a to give 30, the tetraene 4b (0.191 g, 0.49 mmol) in hexane
(5 mL) was hydrogenated over Pt/C (20 mg) for 3 d at 1508C and 37 atm
pressure. After purification by column chromatography, 31 (100 mg,
53%) was obtained as a colorless oil. 1H NMR (400.1 MHz, CDCl3): d=
0.85 (s, 9H; 12-H), 0.97, 0.99 (s, 9H each; 1-, 14-H), 1.09 (s, 9H; 16-H),
1.13 (s, 9H; 18-H), 1.15–1.17 (m, 1H; 3-H), 1.18–1.28 (m, 2H; 10-H),
1.85–1.91 (m, 4H; 4-, 9-H), 5.35–5.41 ppm (m, 2H; 5-, 8-H); 13C NMR
(100.6 MHz, CDCl3): d=148.09 (s, C-7), 146.81 (s, C-6), 131.87 (d, C-5),
127.11 (d, C-8), 58.90 (d, C-3), 44.05 (t, C-10), 36.83, 36.61 (s, C-2, -13),
35.09 (s, C-17), 35.06 (s, C-15), 32.79 (q, C-18), 32.38 (q, C-16), 31.23,
31.17 (q, C-1, -14), 29.49 (q, C-12), 26.28, 30.58 (t, C-4, -9), 30.40 ppm (s,
C-11); IR (ATR): n˜ =2953 (s), 2904 (m), 2868 (m), 1475 (m), 1393 (m),
1364 (s), 1227 (w), 1196 cmꢀ1 (w); GC/MS (70 eV): m/z (%): 388 [M+]
(11), 332 (3), 331 (13), 276 (15), 275 (72), 219 (9), 135 (6), 111 (6), 83
(23), 57 (100); UV (acetonitrile): lmax (loge)=193 (4.21), 197 nm (4.16).
Hydrogenation of 4c to (5Z,7Z)-6,7-di-tert-butyl-2,2,11,11-tetramethyl-
dodeca-5,7-diene (32): Using the same procedure as for the hydrogena-
tion of 4a to give 30, compound 4c (227 mg, 0.69 mmol) was hydrogenat-
ed in hexane (5 mL) over Pt/C (20 mg) at 1508C and 37 atm of hydrogen
Hydrogenation of 4a to (5Z,7Z)-3,6,7,10-tetra-tert-butyl-2,2,11,11-tetra-
methyldodeca-5,7-diene (30): A suspension of 4a (0.130 g, 0.29 mmol)
and Pt on C (20 mg) in glacial acetic acid (5 mL) was hydrogenated at
1508C for 3 d at a hydrogen pressure of 37 atm. The solvent was removed
by distillation and the remaining solid residue recrystallized several times
from ethanol. Yield: 43 mg (33%) as colorless needles; m.p. 1078C;
1H NMR (400.1 MHz, CDCl3): d=0.98, 0.99 (s, 18H each; 1-, 12-, 14-,
20-H), 1.13 (s, 18H; 16-, 18-H), 1.17 (dd, J=5.3, 3.7 Hz, 2H; 3-, 10-H),
1.93 (ddd, J=19.1, 5.3, 4.7 Hz, 2H; 4-, 9-HA), 2.00 (ddd, J=19.1, 4.9,
3.7 Hz, 2H; 4-, 9-HB), 5.35 ppm (“t”, Jꢁ4.8 Hz, 2H; 5-, 8-H); 13C NMR
(100.6 MHz, CDCl3): d=146.94 (s, C-6, -7), 132.16 (d, C-5, -8), 59.11 (d,
pressure: diene 32 (220 mg, 95%) was obtained as
a colorless oil;
1H NMR (400.1 MHz, CDCl3): d=0.79 (s, 18H; 1-, 12-H), 1.02 (s, 18H;
14-, 16-H), 1.03–1.18 (m, 4H; 3-, 10-H), 1.69–1.84 (m, 4H; 4-, 9-H),
5.32 ppm (dd, 2H; J=6.2, 7.9 Hz, 5-, 8-H); 13C NMR (100.6 MHz,
CDCl3): d=147.31 (s, C-6, -7), 126.75 (d, C-5, -8), 43.74. (t, C-3, -10),
34.83 (s, C-13, -15), 32.04 (q, C-14, -16), 30.10 (s, C-2, -11), 29.22 (q, C-1,
-12), 25.95 ppm (t, C-4, -9); IR (ATR): n˜ =2952 (s), 2904 (m), 2867 (m),
1709 (w), 1472 (m), 1391 (m), 1363 cmꢀ1 ( s); GC/MS (70 eV): m/z (%):
334 [M+] (19), 277 (29), 263 (9), 235 (15), 221 (47), 207 (22), 194 (23),
244
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 231 – 247

Chiral Linear Polyenes
FULL PAPER
179 (11), 151 (8), 137 (16), 123 (20), 95 (8), 83 (9), 71 (6), 57 (100), 55
(5), 43 (9); UV (acetonitrile): lmax (loge)=192 nm (3.95).
(s, 9 H each; 1-, 12-, 14-, 16-H), 1.35 (s, 9H; 18-H), 2.94 (dd, J=5.1,
19.2 Hz, 1H; 4-HA), 3.25 (dd, J=7.9, 19.2 Hz, 1H; 4-HB), 5.84 (d, J=
11.2 Hz, 1H; 9-H), 5.87 (dd, J=5.1, 7.9 Hz, 1H; 5-H), 6.73 ppm (d, J=
11.2 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=214.14 (s, C-3),
153.79 (s, C-10), 150.63 (s, C-6), 148.48 (s, C-7), 126.27 (d, C-8), 122.06 (d,
C-9), 119.11 (d, C-5), 43.95 (s, C-2), 39.12 (s, C-11), 38.13 (t, C-4), 37.41,
36.42, 35.78 (s, C-13, -15, -17), 33.64 (q, C-18), 32.09, 31.92, 31.97 (q, C-
12, -14, -16), 28.56 ppm (q, C-1); IR (KBr): n˜ =3442 (w), 2870 (m), 2907
(m), 2928 (m), 2965 (s), 1709 (m), 1478 (m), 1467 (m), 1365 (m), 1213
(m), 1066 cmꢀ1 (m); MS (70 eV): m/z (%): 402 [M+] (4), 345 (6), 289
(16), 261 (24), 205 (25), 189 (12), 133 (11), 85 (11), 57 (100), 41 (21); UV
(acetonitrile): lmax (loge)=194 (3.98), 258 nm (4.15); HRMS: m/z calcd
for C28H50O: 402.3862; found: 402.3853.
Epoxidation of 4a to (5Z,7Z)-4,6,7,10-tetra-tert-butyl-2,2,11,11-tetrame-
thyldodeca-5,7,9-trien-3-one (36): m-Chloroperbenzoic acid (136 mg,
0.45 mmol) was added to a solution of 4a (200 mg, 0.45 mmol) in di-
chloromethane (15 mL) and the mixture stirred for 1 h at room tempera-
ture. The solvent was removed in vacuo and the remainder purified by
column chromatography (silica gel; hexane/dichloromethane 9:1) yielding
two diastereomers of 36: diastereomer I (131 mg, 63%) as a colorless
solid (m.p. 748C) and diastereomer II (19 mg, 5%) as a colorless oil;
49 mg (25%) of the starting material 4a was recovered.
Diastereomer I of 36: 1H NMR (400.1 MHz, CDCl3): d=0.90 (s, 9H; 14-
H), 1.12 (s, 9H; 18-H), 1.18 (s, 9H; 1-H), 1.19 (s, 9H; 12-H), 1.24 (s, 9H;
16-H), 1.36 (s, 9H; 20-H), 3.58 (d, J=10.3 Hz, 1H; 4-H), 5.79 (d, J=
10.3 Hz, 1H; 5-H), 5.94 (d, J=11.9 Hz, 1H; 9-H), 6.80 ppm (d, J=
11.9 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=219.68 (s, C-3),
153.26 (s, C-10), 148.23 (s, C-6), 147.09 (s, C-7), 128.90 (d, C-5), 128.56 (d,
C-8), 123.47 (d, C-9), 56.5 (d, C-4), 44.49 (s, C-2), 39.19 (s, C-11), 37.43 (s,
C-13), 37.32, 37.29 (s, C-13, -19), 35.87 (s, C-15), 33.79 (q, C-20), 32.83 (q,
C-16), 32.68 (q, C-18), 32.02 (q, C-12), 29.29 (q, C-14), 28.02 ppm (q, C-
1); IR (ATR): n˜ =2955 (s), 2904 (m), 2870 (m), 1685 (m), 1476 (m), 1462
(m), 1391 (m), 1364 (s), 1211 (s), 1192 (m), 1051 (m), 996 (m), 928 (m),
670 cmꢀ1 (m); MS (70 eV): m/z (%): 459 [M+ +1] (45), 404 (2), 402 (17),
374 (25), 346 (15), 318 (23), 289 (17), 261 (100), 233 (12), 219 (15), 205
(29), 153 (10), 133 (6), 109 (9), 85 (21), 83 (32); UV (acetonitrile): lmax
(loge)=192 (4.20), 260 nm (4.35); elemental analysis calcd (%) for
C32H58O (458.83): C 83.77, H 12.74; found: C 83.64 H 12.80.
Epoxidation of 4c to (5Z,7Z)-6,7-di-tert-butyl-2,2,11,11-tetramethyl-
dodeca-5,7,9-trien-3-one (39): As described above (experiment 23) the
tetraene 4c (200 mg, 0.606 mmol) was epoxidized in dichloromethane
(15 mL) with m-chloroperbenzoic acid (183 mg, 0.604 mmol; reaction
time 3 h). After work-up (see above) were isolated: ketone 39 (30 mg,
14%, colorless oil) and 30 mg (15%) of the substrate 4c. 1H NMR
(400.1 MHz, CDCl3): d=0.96 (s, 9H; 12-H), 1.08 (s, 9H; 1-H), 1.13 (s,
9H; 16-H), 1.14 (s, 9H; 14-H), 2.91 (dd, J=5.1, 18.7 Hz, 1H; 4-HA), 3.30
(dd, J=8.5, 18.7 Hz, 1H; 4-HB), 5.57 (d, J=15.6 Hz, 1H; 10-H), 5.85 (dd,
J=5.1, 8.5 Hz, 1H; 5-H), 5.88 (dd, J=10.7, 15.7 Hz, 1H; 9-H), 6.12 ppm
(d, J=10.7 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=214.24 (s,
C-3), 150.91 (s, C-6), 148.86 (s, C-7), 143.58 (d, C-10), 127.19 (d, C-8),
119.81 (d, C-5), 44.00 (s, C-2), 38.18 (t, C-4), 36.15 (s, C-13), 35.44 (s, C-
15), 33.24 (s, C-11), 32.08 (q, C-14), 31.89 (q, C-16), 29.72 (q, C-12),
26.49 ppm (q, C-1); IR (film): n˜ =2964 (s), 2906 (s), 2870 (s), 1710 (s),
1677 ( m), 1478 (s), 1466 (s), 1393 (m), 1365 (s), 1227 (m) 1198 (m), 1065
(m), 981 cmꢀ1 (s); MS (70 eV): m/z (%): 346 [M+] (7), 289 (37), 233 (16),
231 (5), 205 (9), 189 (6), 135 (6), 133 (7), 85 (12), 69 (4), 57 (100), 55 (7),
41 (18); UV (acetonitrile): lmax (loge)=194 (4.04), 240 nm (4.23); ele-
mental analysis calcd (%) for C24H42O (346.64): C 83.17, H 12.21; found:
C 83.17 H 12.25.
1
Diastereomer II of 36: H NMR (400.1 MHz, CDCl3): d=1.02, 1.10, 1.12,
1.13 (s, 9H each; 1-, 12-, 14-, 16-H), 1.26 (s, 9H; 18-H), 1.34 (s, 9H; 20-
H), 3.61 (d, J=10.5 Hz, 1H; 4-H), 5.69 (d, J=11.8 Hz, 1H; 9-H), 5.86 (d,
J=10.5 Hz, 1H; 5-H), 6.79 (d, J=11.8 Hz, 1H; 8-H); 13C NMR
(100.6 MHz, CDCl3): d=219.56 (s, C-3), 153.06 (s, C-10), 148.55 (s, C-6),
147.39 (s, C-7), 127.94, 127.70 (d, C-5, -8), 122.68 (d, C-9), 54.53 (d, C-4),
44.22 (s, C-2), 39.05 (s, C-11), 37.27, 37.02, 36.01, 35.44 (s, C-13, -15, -17,
-19), 33.67 (q, C-12), 32.54, 32.49, 31.55, 29.59, 28.75 (q, C-1, -14, -16, -18,
-20); IR (ATR): n˜ =2959 (s), 2923 (s), 2870 (m), 1690 (s), 1478 (m), 1391
(m), 1364 (s), 1212 (s), 1193 cmꢀ1 (m); MS (70 eV): m/z (%): 458 [M+]
(4), 317 (8), 261 (20), (2), 205 (14), 177 (5), 135 (6), 109 (7), 83 (17), 69
(8), 57 (100), 55 (9); UV (acetonitrile): lmax (loge)=195 (4.02), 254
(4.26), 260 nm (4.26); HRMS: m/z calcd for C32H50O: 458.4488; found:
458.4493.
Photoisomerization of 4a: In a quartz NMR tube a solution of 5Z,7Z-4a
(100 mg, 0.226 mmol) in hexane (2 mL) was irradiated for 3 d with a
150 W low-pressure mercury lamp. Removal of the solvent and recrystal-
lization from ethanol provided two diastereomers.
AHCTUNGTRENGN(UN 5E,7Z)-2,2,11,11-tetramethyl-3,6,7,10-tetra-tert-butyldodeca-3,5,7,9-tet-
raene ((5E,7Z)-4a): Yield: 15 mg (15%); m.p. 658C; 1H NMR
(400.1 MHz, CDCl3): d=1.15 (s, 18H; 18-, 20-H), 1.22 (s, 9H; 16-H),1.25
(s, 9H; 1-H), 1.32 (s, 9H; 14-H), 1.36 (s, 9H; 12-H), 6.04 (d, J=10.5 Hz,
1H; 9-H), 6.17 (d, J=11.3 Hz, 1H; 5-H), 6.49 (d, J=11.3 Hz, 1H; 4-H),
6.56 ppm (d, J=10.5 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=
153.89 (s, C-7), 153.85 (s, C-3), 153.20 (s, C-10), 145.98 (s, C-6), 126.84 (d,
C-5), 124.11 (d, C-8), 122.80 (d, C-9), 120.48 (d, C-4), 39.37 (s, C-2), 39.07
(s, C-19), 37.46 (s, C-11), 37.24 (s, C-13), 36.92 (s, C-17), 35.08 (s, C-15),
33.54 (q, C-14), 33.47 (q, C-12), 32.12, 31.65 (q, C-18, -20), 32.06 (q, C-1),
31.19 ppm (q, C-16); IR (KBr): n˜ =2953 (s), 2903 (s), 2869 (m), 1476 (m),
1391 (m), 1363 (s), 1213 (s), 1193 cmꢀ1 (m); MS (70 eV): m/z (%): 442
[M+] (15), 385 (15), 329 (6), 301 (2), 273 (30), 245 (8), 203 (11), 133(6),
109 (11), 83 (15), 57 (100); UV (acetonitrile): lmax (loge)=244 (4.47),
Epoxidation of 4b to (5Z,7Z)-4,6,7-tri-tert-butyl-2,2,11,11-tetramethyldo-
deca-5,7,9-trien-3-one (37) and (5Z,7Z)-6,7,10-tri-tert-butyl-2,2,11,11-tet-
ramethyldodeca-5,7,9-trien-3-one (38): As described under the epoxida-
tion of 4a to give 36, the tetraene 4b (200 mg, 0.517 mmol) was epoxi-
dized for 1 h at RT in dichloromethane (15 mL) with m-chloroperbenzoic
acid (156 mg, 0.515 mmol). After work-up and chromatographic purifica-
tion (silica gel, hexane/dichloromethane 1:1) were obtained: ketone 37
(39 mg, 18%) as an oily mixture of diastereomers, ketone 38 (8 mg, 4%)
as a colorless solid (m.p. 708C), and unreacted substrate 4b (50 mg,
25%).
ACHTUNGTRENNUNG(5Z,7Z)-4,6,7-tri-tert-butyl-2,2,11,11-tetramethyldodeca-5,7,9-trien-3-one
(37): 1H NMR (400.1 MHz, CDCl3): d=0.90 (s, 9H; 14-H), 1.00 (s, 9H;
12-H), 1.12 (s, 9H; 16-H), 1.18 (s, 9H; 1-H), 1.20 (s, 9H; 18-H), 3.57 (d,
J=10.5 Hz, 1H; 4-H), 5.53 (d, J=15.3 Hz, 1H; 10-H), 5.81 (d, J=
10.5 Hz, 1H; 5-H), 6.01 (dd, J=10.9, 15.3 Hz, 1H; 9-H), 6.12 ppm (d, J=
10.9 Hz, 1H; 8-H); 13C NMR (100.6 MHz, CDCl3): d=219.58 (s, C-3),
148.32 (s, C-6), 147.89 (s, C-7), 142.79 (d, C-10), 129.11 (d, C-8), 128.92
(d, C-5), 126.48 (d, C-9), 56.5 (d, C-4), 44.53 (s, C-2), 37.18 (s, C-13),
35.32 (s, C-17), 33.28 (s, C-11), 32.70 (q, C-18), 32.61 (q, C-16), 29.72 (q,
C-12), 29.46 (q, C-14), 28.02 ppm (q, C-1); IR (film): n˜ =2962 (s), 2906
(s), 2870 (m), 1691 (m), 1476 (m), 1465 (m), 1392 (m), 1365 cmꢀ1 (s); MS
(70 eV): m/z (%): 403 [M+ +1] (<1), 318 (6), 289 (7), 261 (55), 233 (4),
205 (64), 191 (6), 135 (7), 91 (4), 83 (16), 57 (100); UV (acetonitrile): lmax
(loge)=192 (4.04), 246 nm (4.31); HRMS: m/z calcd for C28H50O:
402.3862; found: 402.3859.
259 nm (4.41, sh); HRMS: m/z calcd for C32H58
: 442.4539; found:
442.4534.
AHCTUNGTRENGN(UN 5E,7E)-2,2,11,11-tetramethyl-3,6,7,10-tetra-tert-butyldodeca-3,5,7,9-tet-
raene ((5E,7E)-4a): Yield: 5 mg (5%); m. p. 1238C; 1H NMR
(400.1 MHz, CDCl3): d=1.22 (s, 18H; 16-, 18-H), 1.24 (s, 18H; 1-, 20-H),
1.33 (s, 18H; 12-, 14-H), 6.15 (d, J=11.0 Hz, 2H; 5-, 8-H), 6.43 ppm (d,
J=11.0 Hz, 2H; 4-, 9-H); 13C NMR (100.6 MHz, CDCl3): d=153.21 (s,
C-3, -10), 151.93 (s, C-6, -7), 125.72 (d, C-5, -8), 120.77 (d, C-4, -9), 39.31
(s, C-2, -19), 37.19 (s, C-11, -13), 35.41 (s, C-15, -17), 33.40 (q, C-12, -14),
32.07 (q, C-1, -20), 31.27 ppm (q, C-16, -18); IR (ATR): n˜ =3015 (m),
2987 (m), 2953 (s), 2900 (s), 2864 (m), 1479 (m), 1453 (m), 1390 (m),
1362 (s), 1234 (m), 1214 (s), 1193 cmꢀ1 (s); MS (70 eV): m/z (%): 442
[M+] (7), 385 (7), 273 (8), 245 (5), 203 (6), 139 (4), 109 (9), 83 (12), 57
(100); UV (acetonitrile): lmax (loge)=246 (4.49), 260 nm (4.48); HRMS:
m/z calcd for C32H58: 442.4539; found: 442.4533.
ACHTUNGTRENNUNG
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
245

H. Hopf et al.
Table 4. Crystallographic data for compounds 4a, 4b, 4c, 18, 27, (Z,Z)-29 and 30.
4a
4b
4c
18
27
G
30
formula
Mr
habit
cryst. size (mm)
crystal system
space group
a [ꢃ]
b [ꢃ]
c [ꢃ]
a [8]
b [8]
C32H58
442.78
C28H50
386.68
C24H42
330.58
colorless plate
0.5ꢄ0.25ꢄ0.07
monoclinic
Cc
18.630(4)
11.838(2)
10.587(2)
90
100.693(4)
90
2294.4
4
0.957
0.05
C16H30O2
254.40
colorless tablet
0.3ꢄ0.3ꢄ0.17
orthorhombic
P212121
8.7348(8)
12.0757(11)
30.160(3)
90
90
90
3181.3
8
1.067
C24H40Br2
488.38
colorless tablet
0.15ꢄ0.13ꢄ0.10
monoclinic
P21/c
29.578(4)
12.0343(14)
14.6191(18)
90
90.699(5)
90
5203.3
8
1.247
3.1
C32H60
444.80
colorless prism
0.25ꢄ0.2ꢄ0.15
orthorhombic
Pbca
11.480(2)
15.661(2)
33.685(5)
90
90
90
6056.5
8
0.976
C32H62
446.82
colorless tablet
0.4ꢄ0.3ꢄ0.2
triclinic
colorless tablet
0.25ꢄ0.2ꢄ0.08
triclinic
colorless tablet
0.4ꢄ0.3ꢄ0.2
triclinic
¯
¯
¯
P1
P1
P1
8.6943(8)
11.8507(11)
15.5774(14)
82.849(3)
89.937(3)
68.991(3)
1485.0
2
9.072(2)
11.884(2)
12.707(2)
101.075(6)
90.646(6)
91.046(6)
1344.0
2
8.7800(12)
11.7302(16)
15.928(2)
86.785(6)
84.032(6)
70.598(5)
1538.5
2
g [8]
V [ꢃ3]
Z
1calcd [Mgmꢀ3
]
0.990
0.05
500
0.955
0.05
436
0.965
0.05
500
m [mmꢀ1
(000)
]
0.07
1136
0.05
2016
F
A
744
2032
T [8C]
2qmax
ꢀ140
ꢀ140
ꢀ140
ꢀ140
ꢀ140
ꢀ140
ꢀ140
60
56.6
56.6
57.4
56.6
53.8
60
reflns measured
independent reflns
Rint
23100
8559
0.028
307
0
0.147
0.049
1.03
0.38
13823
6598
0.036
268
7994
2846
0.159
229
61
0.172
0.068
1.03
33534
4601
0.048
363
33
0.117
0.044
1.07
0.38
61759
12876
0.075
493
118
0.120
0.047
0.94
0.68
51304
6206
0.062
307
0
0.163
0.053
1.03
0.32
17651
8818
0.027
307
0
0.129
0.045
1.04
0.33
parameters
restraints
0
wR (F2, all reflns)
R [F>4s(F)]
S
0.170
0.058
1.06
max. D1 [eꢃꢀ3
]
0.32
0.52
X-ray structure determinations: Numerical details are presented in
Table 4. Data collection and reduction: Crystals were mounted in inert
oil on glass fibers and transferred to the cold gas stream of the diffrac-
tometer (Bruker SMART 1000 CCD). Measurements were performed
with monochromated MoKa radiation (l=0.71073 ꢃ). Absorption correc-
tions were performed for the brominated derivative 27 only, on the basis
of multi-scans (program SADABS). Structure refinement: The structures
were refined anisotropically against F2 (program SHELXL-97[34]). Hy-
droxyl hydrogen atoms were refined freely but with OH distance re-
straints; other H atoms were included as rigid methyl groups or with a
riding model. Special features: For 4c and 18, which crystallize in non-
centrosymmetric space groups, anomalous scattering was negligible and
Friedel opposite reflections were therefore merged. For 18, the tert-butyl
group at C9’ is disordered over two positions; the disordered methyl
groups were refined ideally staggered using a riding model.
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 231 – 247

Chiral Linear Polyenes
FULL PAPER
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Received: May 10, 2010
Published online: December 1, 2010
Chem. Eur. J. 2011, 17, 231 – 247
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
247