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13C nmr and conformational analysis of some 1,4-dithiepane spiranes
oo4o-m0/85 s3.00+ shl Pergamon Pm8 Ltd.
Tem,,e&m Vol. 41, No. 5, pp. 889 to 894, 1985 Rinted in Oreat Britain.
“C
NMRAND CONFORMATIONAL ANALYSIS OF SOME1,4-DITHIEPANE SPIRANES
Jagiellonian
BARBARARYS University Krakow, Department of Chemistry, Karaaia 3, PL-30060 Krakow, Poland and
Ruhr-Univeraittit Poatfach 102148,
HELMUT DUDDECK * Bochum, Abteilung D-4630 Bochum 1,
fiir West
Chemie, Germany
(Received in Germany 29 November 1984)
Abstract The l3 C NMR spectra of four series of diand tricyclic 1,4-dithiepane apiranea presented. The are cia-fused tricyclic derivatives 4a 4d exhibit two coaleacences in their 100.6 MHz spectra. These are discussed and assigned to conformational proceaaea, namely a conversion of the molecules into their mirror images and a restricted pseudorotation of the dithiepane ring, respectively.
The chemistry want
to
including
report
of
1,4-dithiepanea has not been investigated in great 13 C NMR spectra of a number of biand tricyclic
detail.
the
investigations
have been published
on
their
conformational
behaviour.
In this
1,4-dithiepane
The syntheses
of
these
paper
compounds
earlier’.
2* I
*
a
d
b
The numbering in 2-4 does not correspond to the IUPAC-nomenclature and has been chosen for sake of better comparibility.
§ The cia-fused
for
bicyclic
molecules
tricyclic compounds 4 are racemates. The numbfrfng,of the atoms refers to the enantiomer shown above where the hydrogen atoms are a and S ia in axial position with respect to the cia-fused cyclohexane ring (cf. Fig. 3).
889
we
apiranea
B. RYS and H. DUDDECK
890
RESULTS
AND DISCUSSIDN
l3 C chemical
The
signal
shifts
assignments
relative
were
intensities
1:
TABLE
of the compounds la-lc, aided
recorded
shifts
2a-2d, 3a-3d and 4a-4d are listed
“off-resonance”
and the consistency
l3 C chemical
I
by
of
spectra,
signal
the
1,4-dithiepane
spiranes
MHz and ca +3D°C, relative
C-1’
C-2’
C-3’
C-4’
la-lc,
2a-2d,
to internal
C-l”
C-2”
c-2
c-3
c-5
la
38.4
38.4
44.5
45.9
44.5
--
--
--
--
32.1
14.2
lb
38.2
38.2
41.2
46.9
41.2
--
--
--
--
81.3
--
C-7
3a-3d
TMS
C-3”
C-4”
C-5”
32.7
--
--
81.3
--
--
38.6
38.6
44.6
51.1
44.6
--
--
--
--
38.6
24.9
24.9
30.6
--
2a
58.9
58.9
43.5
46.4
43.5
30.7
22.3
30.7
--
32.9
14.0
32.9
--
--
2b
59.3
59.3
40.7
41.4
40.7
30.7
22.4
30.7
--
82.0
--
82.0
--
--
2c
59.4
59.4
43.8
51.9
43.8
30.5
22.4
30.5
--
30.1
24.8
24.8
30.7
-36.0
2d
59.1
59.1
42.6
41.3
42.6
30.5
22.4
30.5
--
36.0
21.8
26.1
21.8
3a
56.0
56.0
43.7
44.4
43.1
33.4
26.2
26.2
33.4
32.5
14.1
32.5
--
--
3b
51.2
57.2
40.8
45.8
40.8
33.4
26.1
26.1
33.4
81.6
--
81.6
--
--
3c
57.0
57.0
43.9
49.6
43.9
33.3
26.2
26.2
33.3
38.4
25.0
25.0
30.4
--
3d
56.6
56.6
42.5
39.1
42.5
33.3
26.3
26.3
33.3
36.0
21.9
26.2
21.9
36.0
14.2
32.1
--
--
--
81.4a
--
--
4a
51.4
51.4
40.7
45.9
40.7
31.4
24.3
24.3
31.4
32.7
4b
51.5
51.5
37.7
47.0
37.7
31.2
24.1
24.1
31.2
B1.6a
4c
51.6
51.8
40.6
51.2
40.6
31.3
4d
50.Sb
50.Sb
38.9b
40.8
3B.9b 31.1b
May be interchanged.
b
Signals
are broadened
The
shifts,
and 4a-4d,
lc
a
1.
of the whole data body.
in CDC13 at 22.64
C-6
in Table
substituent-induced
24.3
24.3
31.3
3B.Ba 24.9
24.9
38.2’
24.3b
24.3b
31.1b
36.2a
22.0
26.1
22.0
for
the
due to coalescence
-35.5a
effects.
Bicyclic1,4-dithiepane spiraneala-lc The assignment it
relies
(lb)
on the
we observe
endocyclic group2. (6
of
the
following
A further in
in
Fig.
1:
the
and
moat stable
behaviour
as well
than
of
for
it
as
of
except
When the methylene the
C”’
a stereochemical
confirmation
The conformational
possible
shift
such
straightforward
this
6-hydroxyl-1,4-dithiepane3
Cycloheptsnes4 rather
is
argument:
an upfield
oxygen
= 37.9)
13C signals
signal
group C-2”in (-3.4
orientation
assignment which is
is very
is the close
la
ppm) because smaller to those
replaced the
than
13C chemical
and C5’7pair.
is
8 effect
that
shift in la-lc
of
Here
by oxygen of
an
a methylene
of the C2’3 signal (8
q
38.2-38.6).
seven-membered saturated rings is rather well established. 596 have been found to prefer the twist-chair (TC)
1,4_dithiepanes
twist-boat
conformation.
was
that
(TB) reported 536
the
In the
symmetrical
heterocyclic TC form
one.
Symmetrical
C2/3
twist-chair
(TC) conformation
of 1,4-dithiepane
case (Fig.
several
1) is
TC forms
the energetically
are
W NMR and coaformational analysis of soare 1,4dithiepane spirancs In that
l,l-dimethylcycloheptane of
the
preferably
adopts
low temperatures From all la-lc
this
must
Fig.
2:
the they
evidence
be
two C6 hydrogen
the
the
TC pseudorotation
interconversion
TC-TB
must
isoclinal were not
position able
we conclude
symmetrical
to
that
TC with
be 497
freeze
barrier
higher 497
. Other out
the preferred a C2-axis
is
assumed
. Moreover, authors
any of
the
the
reported
to
391 be
5.5
as represented
and
carbon
atom
substituted that
even
TC stereoisomers
conformation
kcal/mol
of
at
extremely
cycloheptane’.
of the bicyclic
Spiro-compounds
by Fig.
X replacing
1 with
atoms.
Temperature-dependent
100.6
see
Formula
footnote
% of the
MHz l3 C NMRspectra
of 4d (in
CDC13); for
the
numbering
scheme.
2”+ 5”
T= 323
K
308
K
293
K
283
K
273
K
263
K
253
K
243
K
233
K
223
K
the
a92
B. RYS and H. DUDDECK
tricyclic1,4_dithiepsmspiranesZa-2d and 3a-3d
Trens-fused
For these tions
compounds signal
of
the
assignments
dithiepane
suggest
that
the
Hz and
Ii5 as
rings
can
symmetrical
well
as
are
unambiguous. No safe statement 13 C chemical shifts
TC conformations
H3 and
H’,
should
respectively, the
Cis-fused
4s-4d
The compounds Fig.
l+dithiepane
of
the
2 shows the
processes: of
the
Cl”_
that
of the first
Since
Spiro-ring
the
positions
for
two signals
coalescence
4a
of
and
conclude
the
analogues
This
the is
TB form
13
their
NOE
the respective
0.2 kcal/mol)
leading
hand,
C7,
the
Cl”,
between
C NMR spectra.
to
six
1:l
signals
AGf=lO-12 C2”,
in
the
of the Spiro-ring
kcal/mol)
C4’
and C5”
both coalescence. equal
which involves
splittings
we observe
; it should be
The second
process
intensity.
of 4d:
identical
positions
underlying
to that
and
the
conformational
accomplished
smaller
Models
the
Unfortunately,
because
in
13.7
q
riog
(243 t 20 K;
peaks
in
similar
with
AG+
each of approximately
stay
that
effects
in
by an inversion
of cis-decalin
Spiro-rings
are
others
process
exchange
their
interconverts
of-the
cis-fused
( AGO= 12.6
somewhat lower:
the
bicyclic
kcal/molj9. 12.3 f 0.3
kcal/mol
13.1 r 0.2 kcal/mol for 4~. In each instance four AX spin systems (C2/C3, , c5/c7, C1* /C”’ and C2’ /C3 1 were evaluated using approximation equations for the reaction ‘rates 10 at the coalescence temperature . Assiqnment During too
of
the
between
4b
K;
C5,
in the spectra
atoms
into its mirror image. f (AC= = 13.7tO.2 kcal/mol)
The barriers
G3,
show two distinct
into
we
310 210
C2,
space.
conforma-
series.
4d at 100.6 MHz. Here we found two coalescence
On the other
of
in
whereas
not promising
motion
At low temperature
signals
carbon
pairwise
of
in this
again
near
are
six-membered
coalescence.
the
splittings
(-
cis-fused
unaffected.
Assiqnment
system
this
of
spectra
favoured
rather
TB form
conformational
temperature the
C5 and C7 do not
again
molecule
of
coalescence
affords
and
region
C5* ) are
a second noted
at high
seven-
low-temperature
4 exhibit
temperature-dependent
The first
signals (C6,
series
spiranes
be
are
experiments which might be able to exclude 1 H signals are too close to each other.
tricyclic
on preferred
be made from the
the second
second
those
much to
csse
the
and
of be
are
mode.
I?”
rather
Moreover,
4 although
in the spectra of 4d: ” *, c2”, c4” the signals of C1 and C5 split into two and the distance L * ” and C4 is approximately 5 ppm (l-2 ppm for C2 and C5 ). This is clearly
explained
conformers
atoms
coalescence
process
by
are
small,
since
we found
their
a slowing
diastereomers the
down of
but
are
the
in
somewhat
only
the
lower
ring
differences
differ
effects
at
Spiro-cyclohexane
structural
diastereomers
corresponding
coalescences
the
for
in the fused
spectra
of
the
temperatures.
consistent with the known energies in the conformation processes 11 rings . Thus, the underlying process must be an interconversion
populated
conformations
the pseudorotation
of
TC conformations
of this
within
6 is are of
A is
a rigid in
energy
C1
orientation due to
I C4 and can therefore
The A S
flexible
TC with
gauche
high
a
dithiepane
ring one
depicted. Structure
the
is
a strong
be ruled
B interconversion
due to series
the
(cf.
steric
interference
out as a major contributor is
a pseudorotation
from
the
panes 5’6.
As models
show
the
C1
3)
which
D (Fig.
An inspection
of
of
however,
of ‘In
5
models
Fig.
of
is
the
series not
at
and five-membered
two different,
molecular
annelation. footnote
members of
four-
carbon
annelation
equally shows
that
3 some conceivable scheme)
formula
are
n ” TC with C1 being in rather similar positions. Structure and C5 ” and C5 in very different chemical environments since both sulfur atoms *, ” with respect to C1 C must be but antiperiplsnar to C5 . Structure
estimated
state
restricted
enantiomeric
kcal/mol,
transition
ring.
other
In that
Spiro-ring
cyclohexane
This,
all
inversion.
the
spectra) ” and has
is 4’ C to
so
the
endo-hydrogen
to the conformational
and the question much
methylene be
between
passed
higher groups during
than are the
arises that very
A
why its
in
the
close
Z
atoms
at
C7 and
process.
to
barrier
(lo-12
monocyclic
dithie-
each
in the
other
B interconversion.
This
893
“C NMR and conformational analysis of &noc l&dithiepsne spiraoes steric
compression
lower
barriers”
Cl”
-
C6 -
the ateric Fig.
can in
C4” ,
4a-4c
(see
the
are
with
extraordinarily
understandable are ,
respectively,
interference Conceivable
3:
explain
the C4
smaller methylene
TC conformations
footnote
high
since
here
due to
the
group is
of 4d within
§ of the formula
In addition,
barrier. the
bond
reduced
angles
n the potentially
C1
Spiro-ring
-
C6 -
size
C‘”
-and
and therefore
alleviated.
one enantiomeric
series
scheme)
EXPERIMENTAL
The syntheses
of
at ca +30°C in
the
compounds
approximately
The temperature-dependent
meter.
at 100.6
MHz (Bruker
AM-400).
l-4
has
been
0.2 molar CDC13 solutions 13 C NMR measurements All
chemical
shifts
The 13C NMRspectra
earlier’.
reported
at 22.64
MHz using
were carried
are referenced
a Bruker
out with
to internal
were recorded WH-90 apectro-
cs 1 molar solutions TMS.
ACKNOWLEDGEMENT
The
authors
assistance
auspices UniveraitSt
gratefully from
of
the
Dr.
acknowledge W. Dietrich
cooperation
helpful Dr.
and
program
Bochum and was supported
discussions H. Kaiser,
between
by the
the
Fonda
with Bochum.
Prof.
G.
This
work
Snatzke,
Jagiellonian
University
der Chemischen
Induatrie.
has
been
Bochum,
and
the
done under the
Krakow and the
Ruhr-
B. RYS and H. DUDDECK
894 REFERENCESAND FOOTNOTES 1
S. Snolihskiand B. Rys, -Monatsh.-Chem.
2
E.L. Eliel, W.F. Bailey,L.D. D.K. 97,
3
Kopp,
110,
R.L.
279
(1979).
Wilier,D.M.
Grant,
R.
Bertrand,
K.A.
Dalling,M.W. Duch, E. Wenkert,F.M. Schell and D.W. Cochran,2. fi. 322
(1975);
E.L. Eliel and K.M. Pietrusiewicz, Orq. Maqn. w.
R.E. Desimone,M.J. Albright,W.J. Kennedy
and
L.A.
Ochrymowicz,
--Chem.
Christensen, Sot.
13, 193 (19BO). m.
Maqn.
Reson.
6, 583 (1980). 4
G. Fsvini,_?.Mol. Struct.Theochem.93, 139 (19B3)and referencescited therein.
5
M.J. Cook, G. Ghaem-Maghami, F. Kaberisand K. Bsrgensen,b.
6
W.N.
Magn. m.
21, 339 (1983).
Seizer,G.S. Wilson and R.S. Glass, Tetrahedron37, 2735 (1981);W.N. Setzer,B.R.
Coleman,G.S. Wilson and R.S. Glass,ibid. 37, 2743 (1981). 7 B 9
G. Borgen and J. Dale,Acta -Chem. Stand. 26, 3593 (1972). D.F. Bocian and H.L. Strauss,2. &. e. &. 99, 2866 (1977). D.K.
Dalling,D.M.
D.M.
Am. Chem. Sot. 93, 3678 (1971);D.K. Dalling, Grant and L.F. Johnson, J. --95, 3718 (1973);B.E. Mann, 2. Maqn. Reson.
Grant and E.G. Paul,2. -Am. Chem. a. 21, 17 (1976).
10 J. Sandstrom,EndeavourXxX111,111, (1974);J. Sandstrom,Dynamicw
Spectroscopy,
AcademicPress, London (1982)and referencescited therein. 11 E.L. Eliel, N.L.
Allinger,S.J. Angyal and
G.A.
Analysis,Wiley Morrison,Conformational
Interscience, New York (1965);J. Dale, Stereochemie @
Konformationssnalyse, Verlag
Chemie,Weinheim (1978). 12
The
lower coalescencetemperaturesin the spectraof 4a-4c may also originatein smaller
distancesof the carbon signalsinvolvedin the low-temperature region.Since we measured in CDC13 solutionswe cannot definitelydecide whether this or a lower barrier is the reason.
Tem,,e&m Vol. 41, No. 5, pp. 889 to 894, 1985 Rinted in Oreat Britain.
“C
NMRAND CONFORMATIONAL ANALYSIS OF SOME1,4-DITHIEPANE SPIRANES
Jagiellonian
BARBARARYS University Krakow, Department of Chemistry, Karaaia 3, PL-30060 Krakow, Poland and
Ruhr-Univeraittit Poatfach 102148,
HELMUT DUDDECK * Bochum, Abteilung D-4630 Bochum 1,
fiir West
Chemie, Germany
(Received in Germany 29 November 1984)
Abstract The l3 C NMR spectra of four series of diand tricyclic 1,4-dithiepane apiranea presented. The are cia-fused tricyclic derivatives 4a 4d exhibit two coaleacences in their 100.6 MHz spectra. These are discussed and assigned to conformational proceaaea, namely a conversion of the molecules into their mirror images and a restricted pseudorotation of the dithiepane ring, respectively.
The chemistry want
to
including
report
of
1,4-dithiepanea has not been investigated in great 13 C NMR spectra of a number of biand tricyclic
detail.
the
investigations
have been published
on
their
conformational
behaviour.
In this
1,4-dithiepane
The syntheses
of
these
paper
compounds
earlier’.
2* I
*
a
d
b
The numbering in 2-4 does not correspond to the IUPAC-nomenclature and has been chosen for sake of better comparibility.
§ The cia-fused
for
bicyclic
molecules
tricyclic compounds 4 are racemates. The numbfrfng,of the atoms refers to the enantiomer shown above where the hydrogen atoms are a and S ia in axial position with respect to the cia-fused cyclohexane ring (cf. Fig. 3).
889
we
apiranea
B. RYS and H. DUDDECK
890
RESULTS
AND DISCUSSIDN
l3 C chemical
The
signal
shifts
assignments
relative
were
intensities
1:
TABLE
of the compounds la-lc, aided
recorded
shifts
2a-2d, 3a-3d and 4a-4d are listed
“off-resonance”
and the consistency
l3 C chemical
I
by
of
spectra,
signal
the
1,4-dithiepane
spiranes
MHz and ca +3D°C, relative
C-1’
C-2’
C-3’
C-4’
la-lc,
2a-2d,
to internal
C-l”
C-2”
c-2
c-3
c-5
la
38.4
38.4
44.5
45.9
44.5
--
--
--
--
32.1
14.2
lb
38.2
38.2
41.2
46.9
41.2
--
--
--
--
81.3
--
C-7
3a-3d
TMS
C-3”
C-4”
C-5”
32.7
--
--
81.3
--
--
38.6
38.6
44.6
51.1
44.6
--
--
--
--
38.6
24.9
24.9
30.6
--
2a
58.9
58.9
43.5
46.4
43.5
30.7
22.3
30.7
--
32.9
14.0
32.9
--
--
2b
59.3
59.3
40.7
41.4
40.7
30.7
22.4
30.7
--
82.0
--
82.0
--
--
2c
59.4
59.4
43.8
51.9
43.8
30.5
22.4
30.5
--
30.1
24.8
24.8
30.7
-36.0
2d
59.1
59.1
42.6
41.3
42.6
30.5
22.4
30.5
--
36.0
21.8
26.1
21.8
3a
56.0
56.0
43.7
44.4
43.1
33.4
26.2
26.2
33.4
32.5
14.1
32.5
--
--
3b
51.2
57.2
40.8
45.8
40.8
33.4
26.1
26.1
33.4
81.6
--
81.6
--
--
3c
57.0
57.0
43.9
49.6
43.9
33.3
26.2
26.2
33.3
38.4
25.0
25.0
30.4
--
3d
56.6
56.6
42.5
39.1
42.5
33.3
26.3
26.3
33.3
36.0
21.9
26.2
21.9
36.0
14.2
32.1
--
--
--
81.4a
--
--
4a
51.4
51.4
40.7
45.9
40.7
31.4
24.3
24.3
31.4
32.7
4b
51.5
51.5
37.7
47.0
37.7
31.2
24.1
24.1
31.2
B1.6a
4c
51.6
51.8
40.6
51.2
40.6
31.3
4d
50.Sb
50.Sb
38.9b
40.8
3B.9b 31.1b
May be interchanged.
b
Signals
are broadened
The
shifts,
and 4a-4d,
lc
a
1.
of the whole data body.
in CDC13 at 22.64
C-6
in Table
substituent-induced
24.3
24.3
31.3
3B.Ba 24.9
24.9
38.2’
24.3b
24.3b
31.1b
36.2a
22.0
26.1
22.0
for
the
due to coalescence
-35.5a
effects.
Bicyclic1,4-dithiepane spiraneala-lc The assignment it
relies
(lb)
on the
we observe
endocyclic group2. (6
of
the
following
A further in
in
Fig.
1:
the
and
moat stable
behaviour
as well
than
of
for
it
as
of
except
When the methylene the
C”’
a stereochemical
confirmation
The conformational
possible
shift
such
straightforward
this
6-hydroxyl-1,4-dithiepane3
Cycloheptsnes4 rather
is
argument:
an upfield
oxygen
= 37.9)
13C signals
signal
group C-2”in (-3.4
orientation
assignment which is
is very
is the close
la
ppm) because smaller to those
replaced the
than
13C chemical
and C5’7pair.
is
8 effect
that
shift in la-lc
of
Here
by oxygen of
an
a methylene
of the C2’3 signal (8
q
38.2-38.6).
seven-membered saturated rings is rather well established. 596 have been found to prefer the twist-chair (TC)
1,4_dithiepanes
twist-boat
conformation.
was
that
(TB) reported 536
the
In the
symmetrical
heterocyclic TC form
one.
Symmetrical
C2/3
twist-chair
(TC) conformation
of 1,4-dithiepane
case (Fig.
several
1) is
TC forms
the energetically
are
W NMR and coaformational analysis of soare 1,4dithiepane spirancs In that
l,l-dimethylcycloheptane of
the
preferably
adopts
low temperatures From all la-lc
this
must
Fig.
2:
the they
evidence
be
two C6 hydrogen
the
the
TC pseudorotation
interconversion
TC-TB
must
isoclinal were not
position able
we conclude
symmetrical
to
that
TC with
be 497
freeze
barrier
higher 497
. Other out
the preferred a C2-axis
is
assumed
. Moreover, authors
any of
the
the
reported
to
391 be
5.5
as represented
and
carbon
atom
substituted that
even
TC stereoisomers
conformation
kcal/mol
of
at
extremely
cycloheptane’.
of the bicyclic
Spiro-compounds
by Fig.
X replacing
1 with
atoms.
Temperature-dependent
100.6
see
Formula
footnote
% of the
MHz l3 C NMRspectra
of 4d (in
CDC13); for
the
numbering
scheme.
2”+ 5”
T= 323
K
308
K
293
K
283
K
273
K
263
K
253
K
243
K
233
K
223
K
the
a92
B. RYS and H. DUDDECK
tricyclic1,4_dithiepsmspiranesZa-2d and 3a-3d
Trens-fused
For these tions
compounds signal
of
the
assignments
dithiepane
suggest
that
the
Hz and
Ii5 as
rings
can
symmetrical
well
as
are
unambiguous. No safe statement 13 C chemical shifts
TC conformations
H3 and
H’,
should
respectively, the
Cis-fused
4s-4d
The compounds Fig.
l+dithiepane
of
the
2 shows the
processes: of
the
Cl”_
that
of the first
Since
Spiro-ring
the
positions
for
two signals
coalescence
4a
of
and
conclude
the
analogues
This
the is
TB form
13
their
NOE
the respective
0.2 kcal/mol)
leading
hand,
C7,
the
Cl”,
between
C NMR spectra.
to
six
1:l
signals
AGf=lO-12 C2”,
in
the
of the Spiro-ring
kcal/mol)
C4’
and C5”
both coalescence. equal
which involves
splittings
we observe
; it should be
The second
process
intensity.
of 4d:
identical
positions
underlying
to that
and
the
conformational
accomplished
smaller
Models
the
Unfortunately,
because
in
13.7
q
riog
(243 t 20 K;
peaks
in
similar
with
AG+
each of approximately
stay
that
effects
in
by an inversion
of cis-decalin
Spiro-rings
are
others
process
exchange
their
interconverts
of-the
cis-fused
( AGO= 12.6
somewhat lower:
the
bicyclic
kcal/molj9. 12.3 f 0.3
kcal/mol
13.1 r 0.2 kcal/mol for 4~. In each instance four AX spin systems (C2/C3, , c5/c7, C1* /C”’ and C2’ /C3 1 were evaluated using approximation equations for the reaction ‘rates 10 at the coalescence temperature . Assiqnment During too
of
the
between
4b
K;
C5,
in the spectra
atoms
into its mirror image. f (AC= = 13.7tO.2 kcal/mol)
The barriers
G3,
show two distinct
into
we
310 210
C2,
space.
conforma-
series.
4d at 100.6 MHz. Here we found two coalescence
On the other
of
in
whereas
not promising
motion
At low temperature
signals
carbon
pairwise
of
in this
again
near
are
six-membered
coalescence.
the
splittings
(-
cis-fused
unaffected.
Assiqnment
system
this
of
spectra
favoured
rather
TB form
conformational
temperature the
C5 and C7 do not
again
molecule
of
coalescence
affords
and
region
C5* ) are
a second noted
at high
seven-
low-temperature
4 exhibit
temperature-dependent
The first
signals (C6,
series
spiranes
be
are
experiments which might be able to exclude 1 H signals are too close to each other.
tricyclic
on preferred
be made from the
the second
second
those
much to
csse
the
and
of be
are
mode.
I?”
rather
Moreover,
4 although
in the spectra of 4d: ” *, c2”, c4” the signals of C1 and C5 split into two and the distance L * ” and C4 is approximately 5 ppm (l-2 ppm for C2 and C5 ). This is clearly
explained
conformers
atoms
coalescence
process
by
are
small,
since
we found
their
a slowing
diastereomers the
down of
but
are
the
in
somewhat
only
the
lower
ring
differences
differ
effects
at
Spiro-cyclohexane
structural
diastereomers
corresponding
coalescences
the
for
in the fused
spectra
of
the
temperatures.
consistent with the known energies in the conformation processes 11 rings . Thus, the underlying process must be an interconversion
populated
conformations
the pseudorotation
of
TC conformations
of this
within
6 is are of
A is
a rigid in
energy
C1
orientation due to
I C4 and can therefore
The A S
flexible
TC with
gauche
high
a
dithiepane
ring one
depicted. Structure
the
is
a strong
be ruled
B interconversion
due to series
the
(cf.
steric
interference
out as a major contributor is
a pseudorotation
from
the
panes 5’6.
As models
show
the
C1
3)
which
D (Fig.
An inspection
of
of
however,
of ‘In
5
models
Fig.
of
is
the
series not
at
and five-membered
two different,
molecular
annelation. footnote
members of
four-
carbon
annelation
equally shows
that
3 some conceivable scheme)
formula
are
n ” TC with C1 being in rather similar positions. Structure and C5 ” and C5 in very different chemical environments since both sulfur atoms *, ” with respect to C1 C must be but antiperiplsnar to C5 . Structure
estimated
state
restricted
enantiomeric
kcal/mol,
transition
ring.
other
In that
Spiro-ring
cyclohexane
This,
all
inversion.
the
spectra) ” and has
is 4’ C to
so
the
endo-hydrogen
to the conformational
and the question much
methylene be
between
passed
higher groups during
than are the
arises that very
A
why its
in
the
close
Z
atoms
at
C7 and
process.
to
barrier
(lo-12
monocyclic
dithie-
each
in the
other
B interconversion.
This
893
“C NMR and conformational analysis of &noc l&dithiepsne spiraoes steric
compression
lower
barriers”
Cl”
-
C6 -
the ateric Fig.
can in
C4” ,
4a-4c
(see
the
are
with
extraordinarily
understandable are ,
respectively,
interference Conceivable
3:
explain
the C4
smaller methylene
TC conformations
footnote
high
since
here
due to
the
group is
of 4d within
§ of the formula
In addition,
barrier. the
bond
reduced
angles
n the potentially
C1
Spiro-ring
-
C6 -
size
C‘”
-and
and therefore
alleviated.
one enantiomeric
series
scheme)
EXPERIMENTAL
The syntheses
of
at ca +30°C in
the
compounds
approximately
The temperature-dependent
meter.
at 100.6
MHz (Bruker
AM-400).
l-4
has
been
0.2 molar CDC13 solutions 13 C NMR measurements All
chemical
shifts
The 13C NMRspectra
earlier’.
reported
at 22.64
MHz using
were carried
are referenced
a Bruker
out with
to internal
were recorded WH-90 apectro-
cs 1 molar solutions TMS.
ACKNOWLEDGEMENT
The
authors
assistance
auspices UniveraitSt
gratefully from
of
the
Dr.
acknowledge W. Dietrich
cooperation
helpful Dr.
and
program
Bochum and was supported
discussions H. Kaiser,
between
by the
the
Fonda
with Bochum.
Prof.
G.
This
work
Snatzke,
Jagiellonian
University
der Chemischen
Induatrie.
has
been
Bochum,
and
the
done under the
Krakow and the
Ruhr-
B. RYS and H. DUDDECK
894 REFERENCESAND FOOTNOTES 1
S. Snolihskiand B. Rys, -Monatsh.-Chem.
2
E.L. Eliel, W.F. Bailey,L.D. D.K. 97,
3
Kopp,
110,
R.L.
279
(1979).
Wilier,D.M.
Grant,
R.
Bertrand,
K.A.
Dalling,M.W. Duch, E. Wenkert,F.M. Schell and D.W. Cochran,2. fi. 322
(1975);
E.L. Eliel and K.M. Pietrusiewicz, Orq. Maqn. w.
R.E. Desimone,M.J. Albright,W.J. Kennedy
and
L.A.
Ochrymowicz,
--Chem.
Christensen, Sot.
13, 193 (19BO). m.
Maqn.
Reson.
6, 583 (1980). 4
G. Fsvini,_?.Mol. Struct.Theochem.93, 139 (19B3)and referencescited therein.
5
M.J. Cook, G. Ghaem-Maghami, F. Kaberisand K. Bsrgensen,b.
6
W.N.
Magn. m.
21, 339 (1983).
Seizer,G.S. Wilson and R.S. Glass, Tetrahedron37, 2735 (1981);W.N. Setzer,B.R.
Coleman,G.S. Wilson and R.S. Glass,ibid. 37, 2743 (1981). 7 B 9
G. Borgen and J. Dale,Acta -Chem. Stand. 26, 3593 (1972). D.F. Bocian and H.L. Strauss,2. &. e. &. 99, 2866 (1977). D.K.
Dalling,D.M.
D.M.
Am. Chem. Sot. 93, 3678 (1971);D.K. Dalling, Grant and L.F. Johnson, J. --95, 3718 (1973);B.E. Mann, 2. Maqn. Reson.
Grant and E.G. Paul,2. -Am. Chem. a. 21, 17 (1976).
10 J. Sandstrom,EndeavourXxX111,111, (1974);J. Sandstrom,Dynamicw
Spectroscopy,
AcademicPress, London (1982)and referencescited therein. 11 E.L. Eliel, N.L.
Allinger,S.J. Angyal and
G.A.
Analysis,Wiley Morrison,Conformational
Interscience, New York (1965);J. Dale, Stereochemie @
Konformationssnalyse, Verlag
Chemie,Weinheim (1978). 12
The
lower coalescencetemperaturesin the spectraof 4a-4c may also originatein smaller
distancesof the carbon signalsinvolvedin the low-temperature region.Since we measured in CDC13 solutionswe cannot definitelydecide whether this or a lower barrier is the reason.