Addition and cyclization reactions in the thermal conversion of hydrocarbons with an enyne structure, 7. - Cycloisomerization of 1-phenyl-1- buten-3-yne to naphthalene via cinnamylidene carbenes - A complex reaction involving 1,2-C switches and 1,2-styryl migrations

Article abstract of DOI:10.1002/(sici)1099-0690(199912)1999:12<3407::aid-ejoc3407>3.0.co;2-6

The thermal conversion of [4-¹³C,4-D]- (1) and [4-¹³C]-1-phenyl-1- buten-3-yne (7) has been studied in a quartz tubular reactor at 650 °C (1, in the presence of N₂ and N₂/toluene, respectively) and at 600 and 620 °C (mixture of 1 and 7, in N₂ only) at a reaction time of approximately 0.3 s. The liquid pyrolyzates were analyzed spectroscopically. By means of a special calculation method reported recently, the naphthalene isotopomers formed by reaction pathways other than those proceeding via cinnamylidene carbenes were arithmetically eliminated and the reaction events proceeding via carbene intermediates were mechanistically analyzed. The result of this analysis undoubtedly suggests a complex reaction in which the rates of the partial reactions may be placed in the following order: 1,2-D(H) >> 1,2-styryl > 1,6- C,H.

Full text of DOI:10.1002/(sici)1099-0690(199912)1999:12<3407::aid-ejoc3407>3.0.co;2-6

FULL PAPER
Addition and Cyclization Reactions in the Thermal Conversion of
Hydrocarbons with an Enyne Structure, 7[°]
Cycloisomerization of 1-Phenyl-1-buten-3-yne to Naphthalene via
Cinnamylidene Carbenes – A Complex Reaction Involving 1,2-C Switches and
1,2-Styryl Migrations
Kathrin Schulz,[a] Jörg Hofmann,[a,b] and Gerhard Zimmermann*[a,b]
Keywords: Enyne pyrolysis / 13C,D labelling / Alkenylidene carbenes / 1,2-Styryl migration
The thermal conversion of [4-13C,4-D]- (1) and [4-13C]-1-
phenyl-1-buten-3-yne (7) has been studied in a quartz
tubular reactor at 650 °C (1, in the presence of N2 and N2/
toluene, respectively) and at 600 and 620 °C (mixture of 1
and 7, in N2 only) at a reaction time of approximately 0.3 s.
The liquid pyrolyzates were analyzed spectroscopically. By
than those proceeding via cinnamylidene carbenes were
arithmetically eliminated and the reaction events proceeding
via carbene intermediates were mechanistically analyzed.
The result of this analysis undoubtedly suggests a complex
reaction in which the rates of the partial reactions may be
placed in the following order: 1,2-D(H) ϾϾ 1,2-styryl Ͼ 1,6-
means of a special calculation method reported recently, the C,H.
naphthalene isotopomers formed by reaction pathways other
1,3-Hexadien-5-ynes, in which one or both of the CϪC
Although the mechanistic details of the formation of 6π-
double bonds of the dienyl skeleton are integral parts of 6π- ring systems by electrocyclic ring closure and the sub-
systems, have turned out to be useful precursors in high- sequent 1,5(1,3)-H shift[6] are now known, this route is in
temperature syntheses of planar[2] and bowl-shaped[3] poly- fact almost negligible if the terminal CϪC double bond of
cyclic aromatics. At first glance, cycloisomerizations of this the 1,3-hexadien-5-yne is part of a phenyl group. This is
type seem to follow a simple mechanistic pattern, as de- because in the cyclization step the resonance stabilization
picted in Scheme 1. However, sophisticated experiments energy of the phenyl group has to be overcome.[4] Sub-
aimed at proving other pathways, which are envisaged as sequently, the thermal conversion in question is mainly sup-
occurring competitively in the thermal conversion of 1-phe- ported by the vinyl radical and, at higher temperatures, by
nyl-1-buten-3-ynes, clearly show that this is indeed the case reversibly formed carbenes. Both routes represent intrin-
at temperatures between 550 and 750°C.[1,2c,4,5] There is no sically complex reactions. Their details, however, are as yet
longer any doubt that electrocyclic ring closures[6] and only well-known for the radical cycloisomerizations.[1]
A
cyclization steps proceeding via alkylidenecarbenes (cf. for coherent analysis of the complex reaction controlled by the
example, refs.[2][3]) as well as via vinyl-type radicals[1,2c,4] corresponding cinnamylidene carbenes is not yet available,
compete not only with each other, but also with carbene- though some important features are already known.[2c,3c,4,5]
mediated 1,2-C switches within the enyne fragment of the
Against this background, we became interested in deline-
employed phenylbutenynes,[5] which are themselves inde- ating a more complete picture by carrying out further stud-
pendently operative in the preliminary stages of the naph- ies in this field. We report herein on repeatedly performed
thalene formation.
thermal conversions of [4-13C,4-D]-1-phenyl-1-buten-3-yne
1 (cf. ref.[1]) at 650°C in the presence of nitrogen and nitro-
gen/toluene, respectively, as well as on the co-pyrolysis of a
mixture of 1 and [4-13C]-1-phenyl-1-buten-3-yne 7 at 600
and 620°C, in this case exclusively in the presence of nitro-
gen. The results are discussed in relation to already pub-
lished mechanistic assumptions and proposals.
Scheme 1. Naphthalene formation by electrocyclic ring closure
[°]
Part 6: Ref.[1]
Abteilung Hochtemperaturreaktionen am Institut für
Results
[a]
Technische Chemie der Universität Leipzig,
Permoserstraße 15, D-04303 Leipzig, Germany
Fax: (internat.) ϩ49(0)341/235Ϫ2701
Thermal Conversion of
[1-13C,4-D]-1-Phenyl-1-buten-3-yne (1)
E-mail: zimmerma@sonne.tachemie.uni-leipzig.de
[b]
Present address: Institut für Nichtklassische Chemie an der
Labelled 1-phenyl-1-buten-3-yne (1) was available from
our earlier research[1] and was used as a 1:99 cis/trans mix-
Universität Leipzig,
Permoserstraße 15, D-04303 Leipzig, Germany
Eur. J. Org. Chem. 1999, 3407Ϫ3412
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ193X/99/1212Ϫ3407 $ 17.50ϩ.50/0
3407

K. Schulz, J. Hofmann, G. Zimmermann
FULL PAPER
ture (GC purity: 98.6%, D and 13C content: 99 atom-% Table 1. Dependence of the products formed from 1 in the presence
of N2 and N2/tol at 650°C
each). It was used directly as the starting compound for
the pyrolysis experiments in the form of a 10% solution
in benzene.
In each run, between 0.7 and 0.9 mL of this solution was
slowly evaporated into a stream of nitrogen (N2) gas or a
nitrogen/toluene vapour mixture (N2/tol), respectively. Prin-
cipally, the gas streams served as diluents (d) carrying 1 in
low concentrations (nd/n1 ഠ 50:1) through a quartz flow
system (cf. for example, ref.[2c]). The reaction temperature
was 650°C, and the reaction time was calculated to be ap-
proximately 0.3 s. Under the applied conditions, however,
the nitrogen/toluene mixture served not only as a diluent
but also as an auxiliary agent lowering the stationary con-
centrations of the unavoidably formed chain carrier rad-
icals.[4] The effluents were cooled, collected, and analyzed
by GC/FID, GC/FT-IR, GC/MS, 1H, 2H, and 13C NMR as
detailed previously.[1][5] The yields of the liquid pyrolyzates
(essentially isotopomers of naphthalene, benzofulvene, azu-
lene, and phenylbutenyne) boiling at temperatures higher
than benzene amounted to Ն 95% of the solution employed
in each case. With strictly comparable parameters, each of
the experiments was repeated to guarantee the reproduc-
ibility of the composition of the formed isotopomers in the
liquid pyrolyzates. The results, representing averaged values
for each compound, are listed in Table 1. The product com-
positions of the fractions (upper part) were analyzed by GC
and GC/MS. The proportions of the remaining 1 and its
isotopomers (2, 7, 8) were calculated from the correspond-
1
ing H- and 13C-NMR as well as GC/FT-IR spectra of the
liquid pyrolyzates according to ref.[5], while the proportions
[a]
[b]
5 mol-% toluene in nitrogen. Ϫ
In% of the liquid pyrolyzate
of the naphthalene isotopomers 5, 6, 11, and 12 as well
as those of [1-13C,1-D]- and [2-13C,1-D]naphthalene were
determined solely from the 13C-NMR data (see, for ex-
ample, ref.[1] and the Experimental Section). The percentage
of each component in the liquid pyrolyzates of the repeated
experiments varied only marginally. The deviations were es-
timated to be ± 2% absolute at most, referred to the average
values listed in Table 1.
[c]
[minus benzene (solvent)]. Ϫ At 750°C in the presence of hydro-
gen, the proportion of 7 ϩ 8 amounts only to Յ 3%.
Thermal Conversion of a Mixture of
[1-13C,4-D]-1-Phenyl-1-buten-3-yne (1) and
[1-13C]-1-Phenyl-1-buten-3-yne (7)
To check the role that primary kinetic H/D isotope effects
may play in the reaction cascade according to Scheme 2, a
10% benzene solution of a 46:54 mixture of 1 and 7 was
thermally converted in nitrogen. Experiments were carried
out at 600 and 620°C (0.3 s) only to guarantee that the
found composition of the phenylbutenyne isotopomer frac-
tion is still far below the equilibration point, which is
known to be reached at approximately 750°C.[5] The experi-
ments were carried out in the same way as described pre-
viously for the thermal conversion of 1, with the same par-
ameter ranges. The obtained results are compiled in Tables
2.1 and 2.2.
Scheme 2. Main reaction cascades in the conversion of 1 (7)
Eur. J. Org. Chem. 1999, 3407Ϫ3412
3408

Addition and Cyclization Reactions in the Thermal Conversion of Hydrocarbons with an Enyne Structure, 7
FULL PAPER
Table 2.1. Degrees of conversion and selectivities of the formed
products (S[a]) in the thermal conversion of a mixture of 1 and 7[b]
at 600 and 620°C in the presence of nitrogen
Table 3. Molar percentages [x] with x ϭ 5 and 6 available in the
pyrolyzates from 1 and formed by radical ([x]rad) and carbene-like
processes ([x]carb) in the presence of both N2 and N2/tol at 650°C
Temperature [°C]
600
6
620
9
Degree of conversion (%)[c]
Product selectivities (S):
Naphthalenes
1-Methylene-1H-indenes
Azulenes
Others
96
3
91
8
1
1
trace
trace
[x]carb ϭ [x] Ϫ [x]rad
(1)
[a]
S ϭ mol of product formed from 100 mol of the fed sum of 1
[b]
ϩ 7 converted. Ϫ
Percentage composition of the 1-phenyl-1-
buten-3-ynes 1/7 ϭ 46:54. Ϫ [c] Referred to the sum of 1 ϩ 7 intro-
Discussion
duced.
The product balance of the liquid pyrolyzates from the
conversion of 1 at 650°C (Table 1) clearly reveals that the
sum of the formed compounds having a structure funda-
mentally different from that of 1 amounts to just 18 and
10%, with naphthalene as the main product. Of the remain-
der, the 1-phenyl-1-buten-3-yne fraction consists of a mix-
ture of four (1, 2, 7, and 8) and the naphthalene fraction a
mixture of six isotopomers (5, 6, 11, 12, [1-13C,1-D]- and
[2-13C,1-D]naphthalene).
Taking the composition of the 1-phenyl-1-buten-3-yne
fraction into account, it immediately becomes clear that the
observed automerization 1 v 2 cannot be a radical-assisted
process like that for which the mechanism is outlined in
Scheme 3. If such a process were to be operative, a signifi-
cant dedeuteration of 1 and 2 ought to be expected. The
non-deuterated 13C-phenylbutenynes 7 and 8 are, however,
formed only in trace amounts. This supports our previously
drawn conclusion, according to which the automerization 1
v 2 runs as a cyclic quadrangular process as outlined in
the core of Scheme 2. The formation of 2 from 1 constitutes
the main reaction event at 650°C. Consequently, the 1,2-D
and even the 1,2-styryl migration are undoubtedly much
more favored compared to the 1,6-C,H insertion of the
carbenes 3, 4 and 9, 10 into the naphthalenes 5, 6 and 11,
12, respectively.
Table 2.2. Composition of the remaining phenylbutenyne and the
formed naphthalene fraction ( ϭ 100% each) in the pyrolyzates of
the copyrolysis of 1 ϩ 7 according to the summarized data given
in Table 2.1
Temperature [°C]
600
620
1-Phenyl-1-buten-3-ynes[a]
[4-13C,4-D]-
[3-13C,4-D]-
[4-13C]-
:
(1)
(2)
(7)
(8)
39
34.5
11
7.5
45
41
[3-13C]-
8.5
13.5
Naphthalenes[a]
[1-13C,2-D]-
[2-13C,2-D]-
[1-13C]-
:
(5)
ca. 17
ca. 12
ca. 39
ca. 25
ca. 6
ca. 16
ca. 13
ca. 37
ca. 26.5
ca. 6
(6)
(11)
(12)
[2-13C]-
[1-13C,1-D]-
[2-13C,1-D]-
< 1
ca. 1.5
[a]
The composition was calculated on the basis of characteristic
spectroscopic data of the corresponding pyrolyzate components (cf.
Experimental Section and ref.[1]
)
Calculation of the Amounts of the Naphthalenes 5
and 6 Formed via Cinnamylidenecarbenes
Of the six naphthalene isotopomers listed in Table 1, only
two of them can in fact be straightforwardly formed via
cinnamylidenecarbenes, i.e. 5 and 6 (cf. Scheme 2), but, un-
fortunately, the matter is more complicated as they can also
be formed by radical-controlled ring closures.[1]
Therefore, the percentages of 5 and 6 immediately formed
from the cinnamylidene carbenes 3 and 4, respectively, have
to be calculated as the difference between the molar per-
centages of 5 ([5]) and 6 ([6]), respectively, in the corre-
sponding liquid pyrolyzate, and the amounts formed
through vinyl-type radicals.[1]
Scheme 3. Considered radical mechanism of the automerization
1 o 2
This observation is somewhat surprising because it seems
to be tacitly accepted that the activation parameters of the
For this, we used the computational method detailed in unimolecularly occurring 1,5- and 1,6-C,H insertion (but
ref.[4], starting from the experimental results obtained in the not the 1,4-C,H insertion[7]) of the corresponding alkenylid-
thermal conversion of 1-phenyl-1-buten-3-ynes in the pres- ene carbenes are considered to be almost negligible in com-
ence of diluent gases of different nature, and using Equa- parison to those for the 1,2-R migration.[7][8] This assump-
tion 1 with x ϭ 5 and 6, respectively. The results obtained tion is, however, speculative since experiment-based acti-
in this way are compiled in Table 3.
vation parameters of unimolecularly proceeding 1,5- and
Eur. J. Org. Chem. 1999, 3407Ϫ3412
3409

K. Schulz, J. Hofmann, G. Zimmermann
FULL PAPER
Table 4. Molar proportions of 5 and 6 formed in the pyrolysis of 1 from 1 and 2 by 1,2-D and 1,2-styryl migrations in the presence of
nitrogen and nitrogen/toluene, respectively, at 650°C (0.3 s)
Product
Parent compound
Formed according to
mol-% formed via carbene species
Calculated by Equation
5
6
6
5
1
2
2
1
r1Ј(1,2-D) ϩ r1ЈЈ(1,6-C,H)
r4Ј(1,2-D) ϩ r4ЈЈ(1,6-C,H)
r3Ј(1,2-styryl) ϩ r3ЈЈ(1,6-C,H)
r2Ј(1,2-styryl) ϩ r2ЈЈ(1,6-C,H)
3.57
1.08
0.20
0.06
4
9
5
8
1,6-C,H insertions of alkenylidenecarbenes have still to be the solutions of which are described by Equations 8 and
reported. The preceding reflections clearly show that the 9.[10]
mechanism of the naphthalene formation from 1-phenyl-1-
buten-3-ynes can only be adequately discussed when it is
known how the preceding automerization process works.
Therefore, the proportions of 5 and 6 formed from the car-
bene intermediates 3 and 4 should be considered first.
In accordance with the data listed in Table 3, approxi-
mately 4.9 mol-% of the combined total amount of 5 and 6
is generated from 3 and 4. This corresponds to about 30%
in the presence of nitrogen and 60% in the presence of nitro-
gen/toluene. In this process (cf. Scheme 2), 5 is formed from
1 by the partial reaction r1Ј ϩ r1ЈЈ (ϭ r1) and from 2 by r2Ј
ϩ r2ЈЈ (ϭ r2). Therefore,
The molar proportions of 5 and 6 formed from 1 accord-
ing the reaction steps r1Ј ϩ r1ЈЈ (ϭ r1) and from 2 according
to r2Ј ϩ r2ЈЈ (ϭ r2) were calculated from the experimentally
determined proportions of 5 and 6 in the liquid pyrolyzates.
The results obtained in this way are summarized in Table 4.
From the above data, it can be concluded unequivocally
that the formation of 5 and 6 from 1 and 2 is predetermined
to approximately 95% by 1,2-D (r1 ϩ r4) and to only about
5% by 1,2-styryl migrations (r2 ϩ r3).
and, by analogy,
This statement seems to be largely in line with DreidingЈs
observation,[11] according to which the thermal cyclization
of [3-13C]-1-(1-methylcyclopentyl)-2-propynone at 530°C
occurs almost exclusively by 1,2-H shift and 1,5-C,H inser-
tion reactions of the initially formed carbene species, while
the alternative 1,2-acyl migration becomes important only
at higher temperatures.
To round off this picture, it is worthwhile to gain some
insight into the relative rates at which the reversed 1,2-D
and the 1,2-styryl migration as well as the 1,6-C,H insertion
compete with each other when starting from the corre-
sponding carbene intermediates 3 and 4. To this end, the
results of the copyrolysis of 1 and 7 (Tables 2.1 and 2.2)
were analyzed.
Taking the different portions of 1 and 7 in the feedstock
mixture into account, the data in Table 2.2 clearly reveal
that the automerizations 1 v 2 and 7 v 8 proceed at almost
the same rate under intrinsic conditions. A kinetic H/D iso-
tope effect is not measurable. The formed cinnamylidene-
carbenes 3, 4 and 9, 10 (from 7, 8) evidently undergo a back
reaction at a rate much faster than the 1,2-styryl migrations.
Consequently, the 1,2-styryl and not the 1,2-D(H) mi-
grations must be the rate-determining step of the 1,2-C
switches.
holds for the formation of 6, where the index ri in
notes the reaction steps from 1 and 2 to x ϭ 5 and x ϭ
6, respectively.
Taking into account that the average percentages in
which 1 and 2 are available in the reactor volume depend
on the residence time effective at every differential reactor
segment,[1] and assuming that 12C/13C isotope effects are
de-
consistently very small, the molar portions
and
have to be larger than those of
and
by the factor
Reff[9] defined as the ratio of the steady-state concentrations
at which 1 and 2 become effective in the whole reactor.[1]
Therefore, it holds that
and
which finally gives the following system of Equations:
From the same experiment, the molar proportion of 2
has been determined to be significantly higher (31%) than
the sum of the molar proportions of the naphthalenes 5 and
6 in the liquid pyrolyzate formed from 1 via cinnamylidene
carbenes at 650°C, which amounts only to just less than 5%
(Table 3, column 6). Despite the lack of kinetic data for the
3410
Eur. J. Org. Chem. 1999, 3407Ϫ3412

Addition and Cyclization Reactions in the Thermal Conversion of Hydrocarbons with an Enyne Structure, 7
FULL PAPER
Figure 1. Energy profile diagram
1,2-styryl migrations and 1,6-C,H insertions, the pro- ance with previous results,[4] one can conclude that the im-
portions of 5 and 2 in the liquid pyrolyzate from 1 make it portance of the 1,6-C,H insertion increases with increasing
possible to roughly assess the ratio of the rate constants at temperature, while the opposite holds true for the other par-
which 5 and 2 are formed from the common precursor 3, tial reactions.
provided that the consecutive reaction of 2 to 4 and its sub-
Finally, it seems to be very plausible that the 1,2-styryl
sequent reactions are ignored. Under this assumption, the migration, first discussed as an alternative reaction by
1,2-styryl migration of 3 to 2 is estimated to be faster than Wentrup, Zeller and co-workers[2c] and experimentally pro-
the 1,6-C,H insertion of 3 to 5 by a factor of about 8. Al- ven by ourselves,[5] has to be considered as the first example
though this deduction is rather limited with reference to any of a family of hitherto undiscovered 1,2-vinyl-type mi-
quantitative conclusions, it is sufficiently reliable to realize grations, which are purported to take place commonly, not
semi-quantitatively the important role 1,2-styryl migrations only in high-temperature chemistry of compounds with en-
play in the thermal conversion of 1-phenyl-1-buten-3-ynes yne structure fragments, but also in hydrocarbon flames
at temperatures above 600°C or even 550°C[5] in the gas
phase. Apparently, the activation energy for the 1,6-C,H in-
sertion of the cinnamylidene carbenes (here 3, 4, 9, 10) to
the naphthalenes (here 5, 6, 11, 12) has to be significantly
higher than that for the 1,2-styryl migration of the corre-
sponding carbenes to the phenylbutenynes (here 1, 2, 7, 8).
These facts are qualitatively summarized in the energy pro-
file diagram (Figure 1).
Experimental Section
General: NMR: Varian Unity 400, 1H NMR (400 MHz,
CD3COCD3, int. CH3COCH3, δ ϭ 2.08), 2H NMR (61 MHz,
CH3COCH3, int. CD3COCD3, δ ϭ 2.08), 13C NMR (100 MHz,
CD3COCD3, int., δ ϭ 29.8 (CD3), δ ϭ 206.0 (CϭO); inversed gated
decoupling). Ϫ Analytical GC: HP 5890 Series II (FID, H2, col-
umn: PS 255 Ϫ quartz, 25 m ϫ 0.32 mm ϫ 1.2 µm, 50°C Ϫ 5 min,
10°C/min, 200°C Ϫ 10 min). Ϫ GC/MS: HP 5890 Series II (MSD
HP 5971A Ϫ 70 eV, He; column: SE 54, 15 m ϫ 0.20 mm ϫ 0.25
µm, 50°C Ϫ 5 min, 10°C/min, 200°C Ϫ 10 min). Ϫ GC/FT-IR: HP
Conclusions and Prospects
5890 Series II (IRD: HP 5965 B, ν ϭ 750Ϫ4000 cmϪ1, N2, column:
SE 30: 25 m ϫ 0.32 mm ϫ 1.2 µm, 50°C Ϫ 5 min, 10°C/min, 200°C
Ϫ 10 min).
˜
The reaction course depicted in Scheme 2 that qualitat-
ively describes naphthalene formation from phenylbut-
enynes proceeding via cinnamylidene carbenes proved to be
correct. Moreover, at 650°C, the relative rates of partial re-
actions such as 1,2-D(H) and 1,2-styryl migrations as well
as 1,6-C,H insertions decrease in the following order:
cis/trans-[4-13C]-1-Phenyl-1-buten-3-yne (7): The synthesis of 7 by
reaction of [13C]dichloromethane (Promochem, 13C content: 99
atom-%) with a mixture of n-butyllithium, cinnamyl bromide, and
HMPT in diethyl ether solution at Ϫ78°C, followed by a double
dehydrohalogenation with potassium tert-butoxide, has already
been described in detail.[1] Ϫ trans-[4-13C]-1-Phenyl-1-buten-3-yne:
1,2-D(H) >> 1,2-styryl > 1,6-C,H
Consequently, their energies of activation inevitably have
to increase in the reversed order. From this and in accord- MS: m/z (%): 130 (10), 129 (100) [Mϩ], 128 (26), 127 (9), 103 (12),
Eur. J. Org. Chem. 1999, 3407Ϫ3412
3411

K. Schulz, J. Hofmann, G. Zimmermann
FULL PAPER
102 (6), 78 (6), 63 (4). Ϫ FT-IR: ν˜ ϭ 3312 cmϪ1 (13C4؊H4 valence
Pyrolysis: The pyrolyses were carried out as already described else-
vibration), 3092, 3039, 2076, 1951, 1880, 1786, 1492, 1198, 953. Ϫ where[2c] by passing the starting materials together with nitrogen
2
NMR: For NMR data (1H-, H-, 13C NMR), see under “Analysis
or a nitrogen/toluene mixture as diluent gas at a given temperature
through a quartz tube, which was placed in an electrical heating
system. The tube was connected to a cold trap (Ϫ195.8°C), in
which the liquid pyrolyzates were collected. After warming to am-
bient temperature, the pyrolyzates were analyzed by analytical gas
chromatography, GC/MS analysis, and NMR spectroscopy as de-
scribed previously.[1] The phenylbutenynes were introduced into the
reactor as 0.7Ϫ0.9-mL samples of a 10% solution in benzene.
of the Pyrolyzates”.
cis/trans-[4-13C,4-D]-1-Phenyl-1-buten-3-yne (1): Compound 1 was
synthesized by deuteration of 7 according to the procedure that we
have described previously.[1] The residue obtained following distil-
lation was used directly for the pyrolysis experiments. The spectro-
scopic data were in complete agreement with those from the pre-
viously carried out synthesis. Ϫ trans-1: MS; m/z (%): 131 (10), 130
(100) [Mϩ], 129 (26), 128 (10), 104 (11), 78 (7), 65 (4), 51 (8). Ϫ
FT-IR: ν˜ ϭ 3083 cmϪ1, 3039, 2559 (13C4ϪD4 valence vibration),
1951, 1880, 1786, 1591, 1492, 1264, 1016, 952. Ϫ NMR: See under
“Analysis of the Pyrolyzates”.
Acknowledgments
The authors are grateful to the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie for the financial support
of the presented investigations.
Analysis of the Pyrolyzates: The compositions of the 1-phenyl-1-
buten-3-yne and naphthalene isotopomer fractions were deter-
mined from the NMR spectra, which were recorded directly from
the relevant liquid pyrolyzates and the molar masses of the deuter-
ated (m/z ϭ 130) and the non-deuterated (m/z ϭ 129) [13C]phenyl-
butenynes and naphthalenes. The analyses were carried out on the
[1]
K. Schulz, J. Hofmann, M. Findeisen, G. Zimmermann, Eur. J.
Org. Chem. 1998, 2195Ϫ2142.
[2]
[3]
[2a]
Cf. for example:
R. F. C. Brown, F. W. Eastwood, K. J.
basis of well-known 13C-, H- and H-NMR data [chemical shifts
δ (ppm), coupling constants J (Hz)] already detailed in ref.[1] (see
ref.[9] therein), taking the intensities of the signals in the recorded
spectra into account. In this way, it is possible to distinguish the
trans as well as the cis configurations of 1, 7 and 2, 8 on the basis
of the different coupling constants of the olefinic H and D atoms
(H1, H2, D1, D2), respectively, with the 13C atoms in the C-3 and
C-4 positions.
1
2
Harrington, G. L. McMullen, Aust. J. Chem. 1974, 27,
[2b]
2393Ϫ2402. Ϫ
J. Am. Chem. Soc. 1980, 102, 5110Ϫ5112. Ϫ
Hofmann, G. Zimmermann, Liebigs Ann. 1997, 2535Ϫ2539.
J. Becker, C. Wentrup, E. Katz, K.-P. Zeller,
[2c]
K. Schulz, J.
[3a]
Cf. for example:
L. T. Scott, M. M. Hashemi, D. T. Meyer,
H. W. Warren, J. Am. Chem. Soc. 1991, 113, 7082Ϫ7084. Ϫ
[3b] P. W. Rabideau, A. H. Abdourazak, H. E. Folson, Z. Marzi-
now, A. Sygula, R. Sygula, J. Am. Chem. Soc. 1994, 116,
[3c]
7891Ϫ7892. Ϫ
G. Zimmermann, U. Nüchter, S. Hagen, M.
Nüchter, Tetrahedron Lett. 1994, 35, 4747Ϫ4750.
J. Hofmann, K. Schulz, A. Altmann, M. Findeisen, G. Zimmer-
mann, Liebigs Ann. 1997, 2541Ϫ2548.
[4]
[5]
Representative relevant NMR data are listed below for the trans-
1-phenyl-1-buten-3-ynes: 1H NMR: trans-1(7): H1: 7.1 (d,
K. Schulz, J. Hofmann, G. Zimmermann, M. Findeisen, Tetra-
hedron Lett. 1995, 36, 3829Ϫ3830.
3
3
3JH1,H2 ϭ 16.4), H2: 6.4 (dd, JH2,H1 ϭ 16.4, JH2,C4 ϭ 4.4); trans-
3
3
2(8): H1: 7.1 (dd, JH1,H2 ϭ 16.4, JH1,C3 ϭ 8.4), H2: 6.4 (dd,
[6] [6a]
W. R. Roth, H. Hopf, C. Horn, Chem. Ber. 1994, 127,
3JH2,H1 ϭ 16.4, JH2,C3 ϭ 0.4). Ϫ 2H NMR: trans-1: D4: 3.4 (d,
3
[6b]
1765Ϫ1779. Ϫ
U. Nüchter, G. Zimmermann, V. Franke, H.
Hopf, Liebigs Ann. 1997, 1505Ϫ1515. Ϫ[6c] H. Hopf, H. Berger,
G. Zimmermann, U. Nüchter, P. G. Jones, J. Dix, Angew. Chem.
1997, 109, 1236Ϫ1238; Angew. Chem. Int. Ed. Engl. 1997, 34,
1187Ϫ1190.
1JD4,C4 ϭ 38.6); trans-2: D4: 3.4 (d, JD4,C3 ϭ 7.6). Ϫ 13C NMR:
2
1
2
trans-1: C4: 80.8 (t, JC4,D4 ϭ 38.6); trans-2: C3: 83.0 (t, JC3,D4
ϭ
7.6); trans-7: C4: 81.1 (s); trans-8: C3: 83.5 (s).[12]
[7]
[8]
J. Hofmann, G. Zimmermann, M. Findeisen, Tetrahedron Lett.
1995, 36, 3831Ϫ3832.
The proportions of the naphthalene isotopomers were determined
from the intensities of the signals of the 13C-labelled atoms in the
1H-decoupled 13C-NMR spectra and of the D atoms in the 2H-
NMR spectra (see below), taking into account the relevant mass-
spectrometrically determined data.
B. Ondruschka, M. Remmler, G. Zimmermann, Ch. Krüger, J.
Prakt. Chem. 1987, 329, 49Ϫ54.
Approximately 3.3 (cf. ref.[1]).
[9]
Derivation: cf. Equation 2Ϫ5 in ref.[1]
[10]
[11]
J. Kaneti, M. Karpf, A. S. Dreiding, Helv. Chim. Acta 1982,
65, 2517Ϫ2525.
1
13C NMR: [1-13C,1-D]naphthalene: C1: 128.7 (t, JC1,D1 ϭ 24.4);
[12]
[2-13C,1-D]naphthalene: C2: 126.9 (s); 5: C1: 128.9 (s); 6: C2: 126.7
(t, 1JC2,D2 ϭ 24.4); 11: C1: 127.0 (s); 12: C2: 129.0(s). Ϫ 2H NMR:
The different chemical shifts of the isotope-labelled C atoms in
the H-decoupled 13C-NMR spectra make it possible to differ-
1
entiate between the [13C]phenylbutenynes 1, 2, 7 and 8.
1
[1-13C,1-D]naphthalene: D1: 7.9 (d, JD1,C1 ϭ 24.4); [2-13C,1-
Received April 13, 1999
[O99209]
D]naphthalene: D1: 7.9 (s); 5: D2: 7.5 (s); 6: 7.5 (d, 1JD2,C2 ϭ 24.4).
3412
Eur. J. Org. Chem. 1999, 3407Ϫ3412