The effect of high pressure on the diastereoselectivity of intermolecular all-carbon Diels-Alder reactions

Article abstract of DOI:10.1002/(SICI)1521-3765(19990104)5:1<297::AID-CHEM297>3.0.CO;2-5

The influence of high pressure on the diastereoselectivity of the intermolecular all-carbon Diels-Alder reaction of the phenylbutadienes 1 a- c with the dicyanoethylenes 2a-d to give the cyclohexenes 3-8 is described. The differences in activation volume, ΔΔV(≠), for the two pathways leading to cis and trans diastereomers range from - (0.7 ± 0.8) to - (6.4 ± 0.6) cm³mol^-1 indicating a pressure-induced increase of diastereoselectivity in favour of the cis adducts 3a-d, 5a-d and 7b-d.

Full text of DOI:10.1002/(SICI)1521-3765(19990104)5:1<297::AID-CHEM297>3.0.CO;2-5

FULL PAPER
The Effect of High Pressure on the Diastereoselectivity of Intermolecular
All-Carbon Diels ± Alder Reactions
Lutz F. Tietze,*[a] Marielouise Henrich,[a] Anja Niklaus,[b] and Michael Buback*[b]
Abstract: The influence of high pressure on the diastereoselectivity of the
intermolecular all-carbon Diels ± Alder reaction of the phenylbutadienes 1a ± c with
Keywords: activation volume
asymmetric synthesis cyclo-
additions diastereoselectivity
high pressure chemistry
´
the dicyanoethylenes 2a ± d to give the cyclohexenes 3 ± 8 is described. The
´
differences in activation volume, DDV=, for the two pathways leading to cis and
´
´
1
trans diastereomers range from (0.7 Æ 0.8) to (6.4 Æ 0.6) cm3 mol , indicating a
pressure-induced increase of diastereoselectivity in favour of the cis adducts 3a ± d,
5a ± d and 7b ± d.
ment of diastereoselectivity. For this purpose, we have
determined the DDV= value of the described cycloadditions
in a laborious procedure; this allows a prediction of the
selectivity over a wide range of pressures up to 10 kbar.
Introduction
The Diels ± Alder reaction is one of the most important in
synthesis, since it provides an efficient route not only to
carbocycles, but also to a multitude of heterocycles.[1] In many
cases the cycloadditions can be accelerated markedly by
applying high pressure[1a, 2] since both the intermolecular and
intramolecular Diels ± Alder reactions are associated with
Results and Discussion
large negative volumes of activation, between
25 to
45 cm3 mol ,[3, 4] and with large negative reaction volumes.
In contrast, synthetically useful improvements of stereo-
selectivity under high pressure have been found only for a
very few systems so far, for example for the intermolecular
hetero-Diels ± Alder reaction of enamino ketones with enol
ethers to give dihydropyrans with a difference in activation
1
The phenylbutadienes 1a ± c and the dicyanoethylenes 2a ± d
were allowed to react to yield the cis and trans cyclo-
adducts 3a ± d, 5a ± d, 7a ± d and 4a ± d, 6a ± d, 8a ± d,
respectively (Scheme 1). Assuming a pressure-dependent
volume of up to DDV=ˆ 7.3 cm3 mol .
1 [5, 6]
In this paper we present the first synthetically useful
examples of a pressure-induced increase of diastereoselectiv-
ity for all-carbon Diels ± Alder reactions. It is the aim of this
work to show that the application of high pressure in organic
transformations is not only useful for the acceleration of
reactions for which DV= is negative, but also for the improve-
Scheme 1. Diels ± Alder reactions of 1a ± c and 2a ± d.
[a] Prof. Dr. Dr. h. c. L. F. Tietze, Dr. M. Henrich
Institut für Organische Chemie
der Georg-August Universität Göttingen
Tammannstrasse 2, D-37077 Göttingen (Germany)
Fax: (‡49)551-399476
diastereoselectivity to be primarily due to differences in steric
interaction of the two diastereomeric transition structures and
not to a change in reaction mechanism,[2d] we expected an
increase in DDV= with increasing bulkiness of the substitu-
ents R1 and R2.
The dienes 1a ± c were easily prepared in a three-step
sequence starting from trans-cinnamaldehyde 9 (Scheme 2).
Alkylation of 9 with MeLi and with the Grignard reagents of
E-mail: ltietze@gwdg.de
[b] Prof. Dr. M. Buback, Dr. A. Niklaus
Institut für Physikalische Chemie
der Georg-August Universität Göttingen
Tammannstrasse 6, D-37077 Göttingen (Germany)
Fax: (‡49)551-393144
E-mail: mbuback@gwdg.de
Chem. Eur. J. 1999, 5, No. 1
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0297 $ 17.50+.50/0
297

L. F. Tietze, M. Buback et al.
FULL PAPER
With increasing bulkiness of the substituents on either the
diene or dienophile (R1 ˆ iPr or/and R2 ˆ iPr, tBu; entries 3 ±
4, 7 ± 8, 11 ± 12), the amount of the cis product decreases
significantly. Thus, the cycloaddition of the substrates 1c and
2d leads exclusively to the trans product 8d (entry 12). These
results are in agreement with the expectation that the cis
diastereomers are formed via an endo-E-syn transition
structure I, which is energetically favoured unless the
substituents R1 and R2 are too bulky (Scheme 3). Under
conditions of a strong steric interaction the exo-E-anti
transition structure II is preferred.
Scheme 2. Synthesis of the 1,3-butadienes 1a ± c.
bromoethane and 2-bromopropane, respectively, led to the
alcohol 10, which, after oxidation to the ketone 11, gave the
desired butadienes 1a ± c in good overall yields on Wittig
reaction with methyltriphenylphosphonium iodide.
The cycloadditions of 1a ± c to 2a ± d were carried out in
toluene at 1208C for 12 ± 48 h at ambient pressure to give the
cyclohexenes 3 ± 8 as a mixture of two diastereomers. Under
these conditions, the reactions of the bulkier substrates to give
the cycloadducts 5d/6d, 7c/8c and 7d/8d gave only low yield.
However, the yields could be easily improved by running the
cycloadditions of 1b and 2d, of 1c and 2c and of 1c and 2d
under high pressure; for example, at 10 kbar yields between
31 and 98% were achieved.[7]
Scheme 3. Transition structures for the Diels ± Alder reactions of 1 and 2.
The cycloadditions of 1a ± c and 2a ± d under high pressure
were carried out in dichloromethane with a large excess of the
diene (30 equiv). The experimental set-up, including the high-
pressure cell, has already been described.[5g, 8]
It should be noted that 1) the Diels ± Alder reactions of
1a ± c with 2a ± d are kinetically controlled and 2) isomer-
ization of the double bond in the butadienes 1a ± c and in the
products does not take place under reaction conditions. For
the cycloadditions two effects have to be discussed, namely
steric and electronic influences on the Diels ± Alder reaction.
The cycloaddition belongs to the normal type, for which the
overlap of the LUMO of the dienophile and the HOMO of
the diene is dominating. Whereas steric hindrance obviously
increases for the diene and the dienophile when going from
methyl to ethyl, isopropyl and tert-butyl substituents, the
electronic effects are different for the diene and the dien-
ophile. As a consequence of the interaction between the ‡I
effect of the alkyl substituents with the relevant molecular
orbitals, the reaction rate decreases from dienophile 2a to
dienophile 2d for the same diene and increases from diene 1a
to diene 1c for the same dienophile. Furthermore, the
electronic effect on the reaction rate should be more obvious
for the formation of the trans product, whereas the formation
of the cis product should be influenced by steric interaction to
a higher extent.
The diastereomers of 3 ± 8 could partially be separated by
column chromatography. The relative configuration of the
1
diastereomers was deduced either from the H ± 1H NOSY
spectra or from X-ray analysis. The ratio of the diastereomers
was determined from the crude product mixture by GC, with
the exception of the cycloadducts 7a and 8a, for which
13C NMR spectra of the product mixture were analysed.
The obtained ratios of the cis to trans diastereomer of 3 ± 8
at ambient pressure clearly depend on the steric demand of
the substituents R1 and R2 (Table 1). With R1 and R2 being
methyl or ethyl (entries 1 ± 2, 5 ± 6), and with R1 ˆ iPr and
R2 ˆ Me (entry 9) the formation of the cis adducts is favoured.
Table 1. Yields and diastereoselectivities of the Diels ± Alder reactions of
1a ± c and 2a ± d.
Entry Diene Dieno- Meth- Time Products Yield Selectivity[b]
phile od[a]
[h]
[%]
cis/trans
1
2
3
4
5
6
7
8
9
1a
1a
1a
1a
1b
1b
1b
1b
1c
1c
1c
1c
2a
2b
2c
2d
2a
2b
2c
2d
2a
2b
2c
2d
IV
IV
IV
IV
IV
IV
IV
V
12
12
12
48
12
12
24
48
12
24
36
24
3a/4a
3b/4b
3c/4c
3d/4d
5a/6a
5b/6b
5c/6c
5d/6d
7a/8a
7b/8b
7c/8c
7d/8d
70
80
66
90
73
95
69
96
54
98
31
70
1.86:1
1.56:1
1.18:1
1:5.56
1.17:1
1.13:1
1:1.56
1:5.88
ꢀ 2:1[c]
1:1.89
1:3.33
< 1:99
ˆ
The differences in activation volume, DDV=ˆ DVcis
ˆ
DVtrans, were derived from the pressure dependence of the
product ratios ccis/ctrans (Table 2).
Figures 1 ± 3 show plots of ln(ccis/ctrans) against the Elꢁyanov
parameter Y[9] for the cycloaddition reactions of dienes 1a ± c
with dienophiles 2a ± d in dichloromethane solution at
pressures from 250 to 3000 bar.
As can be seen from Table 2, DDV= is negative for the entire
set of cycloadditions. According to the well-established rule
that high pressure favours sterically hindered processes, this
IV
IV
V
10
11
12
V
[a] General procedure IV: reaction in toluene at 1208C and ambient
pressure; general procedure V: reaction in dichloromethane at 508C and
10 kbar. [b] Determined by GC. [c] Determined by 13C NMR.
298
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0298 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 1

Diels±Alder Reactions
297±304
ˆ
ˆ
Table 2. Differences in activation volume DDV=ˆ DVcis DVtrans deter-
mined from product ratios of the Diels ± Alder reactions of phenyl-
butadienes 1a ± c with dicyanoethylenes 2a ± d in dichloromethane sol-
ution.
1
Reactants
T [8C][a]
DDV= [cm3 mol
]
1a ‡ 2a
1a ‡ 2b
1a ‡ 2c
1a ‡ 2d
30
30
70
90
(1.9 Æ 0.1)
(1.9 Æ 0.2)
(4.3 Æ 0.3)
(6.4 Æ 0.6)
(1.3 Æ 0.1)
(1.6 Æ 0.1)
(2.9 Æ 0.3)
(3.9 Æ 0.3)
1b ‡ 2a
1b ‡ 2b
1b ‡ 2c
1b ‡ 2d
30
30
50
70
1c ‡ 2a[a]
1c ‡ 2b
1c ‡ 2c
30
30
70
70
±
(0.7 Æ 0.8)
(1.9 Æ 0.4)
±
1c ‡ 2d[b]
Figure 3. Dependence of the product ratio ccis/ctrans on the Elꢁyanov
parameter Y for the cycloaddition reactions of phenylbutadiene 1c with
the dicyanoethylenes 2b and 2c at 308C.
[a] The cis/trans product ratio could not be determined. [b] The cis adduct
could not be detected.
indicates that steric hindrance is greater for cycloadditions via
an endo transition structure than for the reaction via an exo
transition structure. A corresponding pressure-induced selec-
tivity in favour of the cis adduct is what one would expect.
Fully consistent with this argument is the clear increase of
DDV= with steric bulkiness of the substituent at the
dienophile. Thus, for the cycloaddition of 1a (R1 ˆ Me) with
2a (R2 ˆ Me), 2b (R2 ˆ Et), 2c (R2 ˆ iPr), and 2d (R2 ˆ tBu) a
significant increase in DDV=, from (1.9 Æ 0.1) to (6.4 Æ
1
0.6) cm3 mol , is found. The same trend is observed within
the series of cycloadditions of 1b (R1 ˆ Et) with dienophiles
2a ± d, where DDV= continuously increases from (1.3 Æ 0.1)
1
to (3.9 Æ 0.3) cm3 mol . For the cycloadditions of 1c (R1 ˆ
iPr), too, an enhancement of DDV= is found with increasing
1
steric bulkiness, (0.7 Æ 0.8) cm3 mol for 1c ‡ 2b and (1.9 Æ
1
0.4) cm3 mol for 1c ‡ 2c.
However, an important point to note from the data in
Table 2 is that the attempts to increase steric hindrance by
adding bulky substituents on both diene and dienophile do not
yield DDV= values that exceed, for example, the number
found for the 1a ‡ 2d cycloaddition. For a particular dien-
ophile, 2b or 2c, variation of the diene from 1a to 1c leads to a
Figure 1. Dependence of the product ratio ccis/ctrans on the Elꢁyanov
parameter Y for the cycloaddition reactions of phenylbutadiene 1a with
the dicyanoethylenes 2a ± d at 308C.
decrease in
DDV= although the steric demand of the
transition structures would be expected to increase. The
values of
DDV= are (1.9 Æ 0.2), (1.6 Æ 0.1) and (0.7 Æ
1
0.8) cm3 mol for the respective cycloadditions of 2b. For
the cycloadditions of 1a ‡ 2c, 1b ‡ 2c and 1c ‡ 2c they are
1
(4.3 Æ 0.3), (2.9 Æ 0.3) and (1.9 Æ 0.4) cm3 mol . These data
indicate that sterically overloading the transition structure
may lead to a situation where the geometries with favourable
interactions characteristic of endo transition structures cannot
be organized. We argue that this is the reason that a cis
product does not result from the cycloaddition of 1c ‡ 2d.
It must be assumed that the expression endo transition
structure and perhaps also exo transition structure does not
refer to well-defined species, such as a set of species with
identical geometry at the reactive site. The activation volume
data indicate that, depending on the type of substitution at the
diene and the dienophile, the overlap of the dominating
orbitals varies, in particular in the endo transition structure.
Figure 2. Dependence of the product ratio ccis/ctrans on the Elꢁyanov
parameter Y for the cycloaddition reactions of phenylbutadiene 1b with
the dicyanoethylenes 2a ± d at 308C.
Chem. Eur. J. 1999, 5, No. 1
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0299 $ 17.50+.50/0
299

L. F. Tietze, M. Buback et al.
FULL PAPER
The effect of an interchange of the substituents R1 and R2 at
the diene and dienophile, as indicated by the differences of
the activation volumes, for example, for the reactions of 1c ‡
were isolated by column chromatography on silica gel (Silica gel 60, particle
size 0.04 ± 0.063 mm, Merck).
3-Hydroxy-1-phenyl-1-butene (10a): A solution of methyl lithium in
diethyl ether (1.6m, 39.7 mmol, 24.8 mL) was added to a solution of
cinnamaldehyde (9, 5.00 g, 37.8 mmol) in 50 mL THF at 108C. After
stirring of the mixture for 1 h at RT, aqueous saturated ammonium chloride
solution (50 mL) was added and the organic phase was separated. The
aqueous layer was extracted with dichloromethane (3 Â 50 mL) and the
combined organic phases were washed with brine, dried with MgSO4,
filtered and evaporated in vacuo. Distillation of the residue afforded 5.41 g
of the alcohol 16a (97%) as a colourless oil. Rf ˆ 0.22 (petroleum ether/
ethyl acetate 6:1); b.p. 808C (0.5 mbar); UV (CH3CN): lmax (lge) ˆ 204 nm
(4.193), 251 (4.081); 1H NMR (200 MHz, CDCl3): d ˆ 1.21 (d, J ˆ 6.0 Hz,
3H, 4-H), 1.55 (s, 1H, OH), 4.42 (quint, J ˆ 6.0 Hz, 1H, 3-H), 6.19 (dd, J ˆ
15.8, 6.3 Hz, 1H, 2-H), 6.48 (d, J ˆ 15.8 Hz, 1H, 1-H), 7.20 ± 7.41 (m, 5H,
Ph-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 23.39 (C-4), 68.89 (C-3), 126.4,
127.6, 128.5, 129.3, 133.5 (Ph-C, C-1, C-2), 136.6 (Ph-Ci); MS (70 eV): m/z
1
2b (DDV=ˆ (0.7 Æ 0.8) cm3 mol ) and of 1b ‡ 2c (DDV=ˆ
1
(2.9 Æ 0.3) cm3 mol ), demonstrates that the endo transition
structure of the cycloaddition of 1c ‡ 2b having the bulky iPr
substituent as R1 at the diene is of ªlower qualityº. It is thus
only within a series in which the diene remains unchanged
that the numerical size of the DDV= value, which corresponds
to a pressure-induced enhancement of diastereoselectivity,
increases towards larger steric hindrance. This is seen in the
series in which the substituent R2 at the dienophile increases
in steric size. The measured differences in activation volume
1
are fairly large, DDV= up to (6.4 Æ 0.7) cm3 mol , which may
‡
‡
‡
‡
allow for applications in selective synthesis. It should be noted
that the results of our previous investigations on hetero
Diels ± Alder reactions[5] also apply to the all-carbon Diels ±
Alder reactions of the present study.[10]
(%) ˆ 43 (52) [C3H7 ], 77 (23) [C6H5 ], 91 (44) [C7H7 ], 105 (100) [M
‡
‡
‡
C3H7], 115 (22) [C9H7 ], 133 (26) [C9H8OH ], 148 (62) [M ]; C10H12O
(148.2): calcd 148.0888, found 148.0888 (HRMS).
General procedure I. Grignard reaction of 9: A 2.0m solution of the alkyl
magnesium bromide (100 mmol) in THF was added dropwise to a solution
of cinnamaldehyde (9, 100 mmol) in 15 mL THF at 08C. The reaction
mixture was heated to 708C for 2.5 h and then cooled to RT. The mixture
was poured into an identical volume of ice-water and hydrolysed by
addition of 6n HCL (until pH reached 7). The aqueous phase was extracted
with diethyl ether (3 Â 50 mL), and the combined organic extracts were
washed with aqueous saturated sodium bicarbonate solution and brine. The
resulting solution was dried with Na2SO4, the solvents were evaporated and
the crude product purified by distillation.
Conclusion
The Diels ± Alder reactions of the phenylbutadienes 1a ± c
and the dicyanoethylenes 2a ± d with substituents R1 and R2 of
different size clearly demonstrate that under high pressure an
endo transition structure to give the cis products is increas-
ingly stabilized with increasing bulkiness of R2 at the
dienophile. Thus, for the cycloaddition of 1a (R1 ˆ Me) with
2a (R2 ˆ Me), 2b (R2 ˆ Et), 2c (R2 ˆ iPr), and 2d (R2 ˆ tBu) a
significant enlargement in DDV=, from (1.9 Æ 0.1) to (6.4 Æ
3-Hydroxy-1-phenyl-1-pentene (10b): Grignard reaction of
9 (10.0 g,
75.7 mmol) and ethyl bromide (8.20 g, 75.7 mmol) according to General
Procedure I gave 12.3 g of the alcohol 10b (quant). Rf ˆ 0.29 (petroleum
ether/ethyl acetate 5:1); IR (film): ˆ 3360 cm 1 (OH), 966, 694 (monosub-
stituted aromatic); UV (CH3CN): lmax (lge) ˆ 191 nm (4071), 204 (4110),
1
1
0.6) cm3 mol , in favour of the cis adducts is found. However,
252 (3980); H NMR (200 MHz, CDCl3): d ˆ 0.98 (t, J ˆ 7.2 Hz, 3H, 5-H),
1.70 (s, 1H, OH), 1.69 (quint, J ˆ 7.2 Hz, 2H, 4-H), 4.21 (q, J ˆ 7.2 Hz, 1H,
3-H), 6.20 (dd, J ˆ 16.0, 7.2 Hz, 1H, 2-H), 6.60 (d, J ˆ 16.0 Hz, 1H, 1-H),
7.20 ± 7.41 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 9.75 (C-5),
30.19 (C-4), 74.35 (C-3), 126.4, 127.5, 128.5, 130.3, 132.2 (Ph C, C-1, C-2),
this effect is limited by steric overload, which can prevent the
formation of a proper endo transition structure. Thus,
increasing the bulkiness of R1 at the diene results in a
DDV=; indeed, for the cycloadditions of 2c
‡
‡
136.7 (Ph Ci); MS (70 eV): m/z (%) ˆ 77 (65) [C6H5 ], 91 (42) [C7H7 ], 115
decrease of
‡
‡
‡
(R2 ˆ iPr) with 1a (R1 ˆ Me), 1b (R1 ˆ Et) and 1c (R1 ˆ
iPr) DDV= is found to be (4.3 Æ 0.3), (2.9 Æ 0.3), and (1.9 Æ
0.4) cm3/mol, respectively. Thus, we have shown for the first
time that a steric overload phenomena in pressure dependent
diastereoselectivity exists. We are confident that the observed
effects are not associated with a change in the reaction
mechanism where the exo adduct is formed by a concerted
and the endo adduct by a two-step pathway. That such a
change in mechanism is possible has been demonstrated by
Klärner[2d, 11] for the dimerisation of 1,3-cyclohexadiene.
(50) [C9H7 ], 133 (100) [C9H8OH ], 162 (30) [M ]; C11H14O (162.2), calcd C
81.44, H 8.70; found C 81.62, H 8.75.
3-Hydroxy-4-methyl-1-phenyl-1-pentene (10c): Grignard reaction of 9 and
2-bromopropane (12.6 mL, 100 mmol) with isopropylmagnesium bromide
(50 mL of a 2.0m solution in THF) according to General Procedure I gave
11.5 g of the alcohol 10c (65%). Rf ˆ 0.35 (petroleum ether/ethyl acetate
1
4:1); b.p. 708C (0.2 mbar); IR (film): ˆ 3404 cm (OH), 968, 696 (mono-
substituted aromatic); UV (CH3CN): lmax (lge) ˆ 192 nm (4.124), 204
(3.976); 1H NMR (200 MHz, CDCl3): d ˆ 0.92, 0.99 (2d, J ˆ 7.5 Hz, 6H, 2 Â
CH3), 1.62 (s, 1H, OH), 1.82 (hept, J ˆ 7.5 Hz, 2H, 4-H), 4.10 (t, J ˆ 7.2 Hz,
1H, 3-H), 6.21 (dd, J ˆ 16.0, 7.5 Hz, 1H, 2-H), 6.54 (d, J ˆ 16.0 Hz, 1H,
1-H), 7.21 ± 7.42 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 37.92,
35.94 (2 Â CH3), 78.11 (C-3), 126.4, 127.6, 128.5, 130.8, 131.1 (Ph C, C-1,
‡
‡
C-2), 136.8 (Ph Ci); MS (70 eV): m/z (%) ˆ 43 (4) [C3H7 ], 77 (12) [C6H5 ],
‡
‡
‡
‡
91 (8) [C7H7 ], 115 (19) [C9H7 ], 133 (100) [C9H8OH ], 176 (12) [M ];
Experimental Section
C12H16O (176.3), calcd 176.1201, found 176.1201 (HRMS).
General: The high-pressure cells and details of the experimental set-up and
procedures have already been described.[5g, 8] The experimental pressures
were determined to better than Æ10 bar. The uncertainty in temperature
was below Æ0.58C. GC: Varian Star 3400CX with a Merck ± Hitachi
Integrator D-2000. Column SGEBPX-5, 0.22 mm  30 m. 1H NMR and
13C NMR: Varian XL-200, Bruker AMX-300, Varian XL-500; multiplicities
were determined with APT pulse sequence. MS: Varian MAT311A; high
resolution: Varian MAT731. IR: Bruker IFS25. UV: Perkin Elmer Lambda
9. Elemental analyses were carried out in the analytical laboratory of the
university. All solvents were distilled prior to use. Reagents and materials
were obtained from commercial suppliers and were used without further
purification. All reactions were carried out under argon pressure and
monitored by TLC (Macherey ± Nagel, Polygram SILG/UV254). Products
1-Phenylbut-1-ene-3-one (11a): To a solution of alcohol 10a (4.90 g,
33.3 mmol) in 10 mL dichloromethane was added MnO2 (28.9 g, 333 mmol,
10 equiv). After stirring for 12 h at RT the mixture was filtered, the solvent
evaporated, and the crude product (4.21 g, 29.0 mmol, 87%) used in the
olefination without further purification. Rf ˆ 0.37 (petroleum ether/ethyl
1
acetate 6:1); b.p. 928C (2.5 mbar); IR (film): ˆ 3004 cm (C H), 1610
ˆ
(C O), 976, 692 (monosubstituted aromatic); UV (CH3CN): lmax (lge) ˆ
282 nm (4.167); 1H NMR (300 MHz, CDCl3): d ˆ 2.40 (s, 3H, CH3), 6.72 (d,
J ˆ 16.0 Hz, 1H, 2-H), 7.36 ± 7.60 (m, 5H, Ph H), 7.44 (d, J ˆ 16.0 Hz, 1H,
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 27.49 (C-1), 127.1, 128.9, 130.5 (Ph
ˆ
C, C-2), 134.4 (Ph Ci), 143.4 (C-1), 198.0 (C O); MS (70 eV): m/z (%) ˆ 77
‡
‡
‡
‡
(31) [C6H5 ], 103 (69) [C8H7 ], 131 (100) [M
C3H7], 146 (12) [M ];
C10H10O (146.2): calcd C 82.16, H 6.25; found C 82.00, H 6.96.
300
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0300 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 1

Diels±Alder Reactions
297±304
General procedure II. Swern oxidation of 10: A cooled solution of DMSO
(4.5m, 3.2 equiv) in dry dichloromethane was added to a 0.5m solution of
oxalyl chloride (1.6 equiv) in dry dichloromethane at a temperature below
788C. After stirring for 10 min, a solution of the alcohols 10 (1.0 equiv) in
dichloromethane (4.0 mL) was added dropwise over 30 min. After
continued stirring for 2 h at 788C, triethylamine (6.4 equiv) was added.
The resulting mixture was stirred for another 5 min, then slowly warmed to
08C and poured onto an identical volume of ice-water. After separation of
the organic layer, the aqueous phase was extracted with dichloromethane
(3 Â 50 mL). The combined organic phases were washed with water and
aqueous saturated sodium chloride solution, and dried with Na2SO4. After
filtration, the solvent was removed in vacuo to afford the crude ketone,
which was purified by distillation.
1'-H), 5.08, 5.14 (2d, J ˆ 1.5 Hz, 2H, 4-H), 6.59 (d, J ˆ 16.0 Hz, 1H, 2-H),
6.83 (d, J ˆ 16.0 Hz, 1H, 1-H), 7.18 ± 7.50 (m, 5H, Ph H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 12.75 (CH3), 24.71 (C-1'), 115.1 (C-4), 126.6 (Ph
Co), 127.3, 127.7, 128.5 (Ph C, C-2), 131.1 (C-1), 137.4 (Ph Ci), 147.6 (C-3);
‡
‡
‡
MS (70 eV): m/z (%) ˆ 51 (23) [C4H3 ], 77 (38) [C6H5 ], 115 (62) [C9H7 ],
‡
‡
‡
129 (100) [C10H9 ], 143 (30) [M
C11H11], 158 (82) [M ]; C12H15 (159.3):
calcd C 91.08, H 8.92; found C 91.20, H 8.93.
1-Phenyl-3-isopropylbuta-1,3-diene (1c): Ketone 11c (1.00 g, 5.74 mmol,
0.80 equiv) was transformed into the butadiene 1c (0.99 g, 5.22 mmol,
91%) according to General Procedure III by means of methyl triphenyl-
phosphonium iodide (2.90 g, 7.18 mmol, 1.0 equiv). B.p. 608C (2 mbar); IR
1
(film): ˆ 2964 cm
(C H), 754, 692 (monosubstituted aromate), 962
(RHC CHR); UV (CH3CN): lmax (lge) ˆ 282 nm (4.116); 1H NMR
(200 MHz, CDCl3): d ˆ 1.15 (d, J ˆ 6.4 Hz, 6H, 2  CH3), 2.80 (hept, J ˆ
6.4 Hz, 1H, C-1'), 5.05, 5.15 (2s, 2H, 4-H), 6.65 (d, J ˆ 15.0 Hz, 1H, 2-H),
6.78 (d, J ˆ 15.0 Hz, 1H, 1-H), 7.15 ± 7.50 (m, 5H, Ph H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 22.34 (2  CH3), 29.25 (C-1'), 112.8 (C-4), 126.4
(Ph Co), 127.3, 127.4, 128.5 (Ph C, C-2), 130.9 (C-1), 137.4 (Ph Ci), 152.6 (C-
ˆ
1-Phenylpent-1-ene-3-one (11b): Reaction of 10b (6.00 g, 37.0 mmol) with
oxalyl chloride (7.50 g, 59.2 mmol, 1.6 equiv), DMSO (9.25 g, 118 mmol,
3.2 equiv) and triethylamine (24.0 g, 237 mmol, 6.4 equiv) according to
General Procedure II gave 3.97 g of the ketone 11b (67%). Rf ˆ 0.24
(petroleum ether/ethyl acetate 10:1); b.p. 808C (0.6 mbar); IR (film): ˆ
1
‡
‡
ˆ
1666 cm (C O), 980, 692 (monosubstituted aromatic); UV (CH3CN): lmax
3); MS (70 eV): m/z (%) ˆ 115 (6) [C9H7 ], 129 (100) [M
C3H7], 172 (20)
(lge) ˆ 282 nm (4.031); 1H NMR (200 MHz, CDCl3): d ˆ 1.19 (t, J ˆ 8.0 Hz,
3H, CH3), 2.70 (q, J ˆ 8.0 Hz, 2H, 4-H), 6.72 (d, J ˆ 16.0 Hz, 1H, 2-H),
7.33 ± 7.53 (m, 5H, Ph H), 7.54 (d, J ˆ 16.0 Hz, 1H, 1-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 8.14 (CH3), 33.94 (C-4), 125.9, 128.1, 128.5, 128.8,
‡
[M ]; C13H16 (172.3): calcd 172.1252, found 172.1252 (HRMS).
General procedure IV. Diels ± Alder reaction under ambient pressure: A
solution of the butadiene 1a, 1b or 1c (0.58 mmol) and the dienophile 2a,
2b, 2c or 2d (0.58 mmol) in 5 mL of toluene was heated at 1208C for 12 ±
48 h in a pressure flask. After removal of the solvent in vacuo, the residue
was purified by column chromatography on silica gel (petroleum ether/
diethyl ether 20:1).
ˆ
130.2 (Ph C, C-2), 134.5 (Ph Ci), 142.1 (C-1), 200.7 (C O); MS (70 eV): m/z
‡
‡
‡
(%) ˆ 103 (100) [C8H7 ], 131 (80) [M
C3H7], 160 (17) [M ]; C11H12O
(160.2): calcd 160.0888, found 160.0888 (HRMS).
4-Methyl-1-phenylpent-1-ene-3-one (11c): Treatment of 10c (5.00 g,
28.4 mmol) according to General Procedure II gave 4.65 g of the ketone
General procedure V. Diels ± Alder reaction under high pressure: A
solution of diene 1b or 1c (0.58 mmol) and dienophile 2c or 2d
(0.58 mmol) in dichloromethane (2.5 mL) was filled by syringe into a
teflon tube. The tube was sealed and placed in a high-pressure cell[7] at
508C, 10 kbar for 24 ± 48 h. Afterwards, the solvent was evaporated and the
residue purified by column chromatography on silica gel (petroleum ether/
diethyl ether 20:1).
11c (94%) as a pale yellow oil. Rf ˆ 0.29 (petroleum ether/ethyl acetate
1
ˆ
50:1); b.p. 738C (0.5 mbar); IR (film): ˆ 2970 cm (C H), 1612 (C O),
984, 686 (monosubstituted aromatic); UV (CH3CN): lmax (lge) ˆ 285 nm
(4.089); 1H NMR (200 MHz, CDCl3): d ˆ 1.20 (d, J ˆ 7.2 Hz, 6H, 2  CH3),
2.95 (hept, 1H, 4-H), 6.82 (d, J ˆ 16.0 Hz, 1H, 2-H), 7.20 ± 7.41 (m, 5H, Ph
H), 7.62 (d, J ˆ 16.0 Hz, 1H, 1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.50
1,1-Dicyano-4,6-dimethyl-2-phenylcyclohex-3-ene (3/4a): Diene 1a
(200 mg, 1.38 mmol) and dienophile 2a (128 mg, 1.38 mmol) were cyclized
according to General Procedure IV at 1208C in 5 mL toluene over 12 h.
The ratio of 3a to 4a was 1.86:1 (GC). Column chromatography gave
43.0 mg of 3a, 13.0 mg of 4a and 170 mg of a mixture of 3a/4a (70%).
trans-1,1-Dicyano-4,6-dimethyl-2-phenylcyclohex-3-ene (4a): Rf ˆ 0.21
(2 Â CH3), 39.29 (C-4), 124.4, 128.2, 128.9 (Ph C, C-2), 134.7 (Ph Ci), 142.4
‡
ˆ
(C-1), 203.8 (C O); MS (70 eV): m/z (%) ˆ 77 (34) [C6H5 ], 103 (46)
‡
‡
‡
[C8H7 ], 131 (100) [M
C3H7], 174 (12) [M ]; C12H14O (174.2): calcd
174.1044, found 174.1044 (HRMS).
General procedure III. Wittig reaction of 11: A 0.5m suspension of methyl
triphenylphosphonium iodide (7.18 mmol, 1.0 equiv) in THF was added to
2.4m nBuLi in hexane (7.90 mmol, 1.1 equiv) at 788C and stirred for
30 min at 08C and for a further 30 min at RT. Subsequently, a 0.5m solution
of ketone 11 (5.74 mmol, 0.8 equiv) in 10 mLTHF was added at 788C, the
mixture was stirred for 15 min at 788C and then allowed to warm to RT.
The reaction mixture was stirred until the reaction was complete (TLC)
and then poured onto an identical volume of ice-water. Pentane (50 mL)
and water (10 mL) were added, and the aqueous phase was extracted twice
with pentane. The combined organic phases were washed with water and
aqueous saturated sodium potassium tartrate solution, dried with MgSO4,
filtered and evaporated in vacuo. The residue was distilled to give the
butadienes 1a ± c.
1
(petroleum ether/ethyl acetate 30:1); IR (film): ˆ 2928 cm (C H), 2242
ꢁ
ˆ
(C N), 1452 (Ar C C), 700, 762 (monosubstituted aromatic); UV
(CH3CN): lmax (lge) ˆ 191 nm (4.189); 1H NMR (300 MHz, CDCl3): d ˆ
1.29 (d, J ˆ 6.5 Hz, 3H, CH3), 1.88 (brs, 3H, CH3), 2.07 (mc, 1H, 5-H),
2.35 ± 2.51 (m, 2H, 6-H, 5-H), 3.97 (mc, 1H, 2-H), 5.48 (mc, 1H, 3-H), 7.31 ±
7.41 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 17.23, 23.30 (2 Â
ꢁ
CH3), 31.53 (C-5), 34.55 (C-6), 43.27 (C-1), 47.12 (C-2), 114.6, 115.0 (C N),
118.3 (C-3), 128.5, 128.9, 130.2 (Ph C), 135.4, 135.9 (C-4, Ph Ci); MS
‡
‡
(70 eV): m/z (%) ˆ 129 (100) [diene CH3 ], 144 (80) [diene ], 236 (8)
‡
[M ]; Rt (1808C, 18Cmin 1) ˆ 13.4 min; C16H16N2 (236.3): calcd 236.1313,
found 236.1313 (HRMS). cis-1,1-Dicyano-4,6-dimethyl-2-phenylcyclohex-
3-ene (3a): Rf ˆ 0.19 (petroleum ether/ethyl acetate 30:1); IR (film): ˆ
1
ꢁ
ˆ
2934 cm (C H), 2252 (C N), 1456 (Ar C C), 700, 764 (monosubstituted
aromatic); UV (CH3CN): lmax (lge) ˆ 242 nm (3.164); 1H NMR (200 MHz,
CDCl3): d ˆ 1.41 (d, J ˆ 6.5 Hz, 3H, CH3), 1.82 (brs, 3H, CH3), 2.10 ± 2.32
(mc, 2H, 5-H2), 2.46 (quintd, J ˆ 11.2, 6.5 Hz, 1H, 6-H), 3.91 (mc, 1H, 2-H),
5.42 (mc, 1H, 3-H), 7.38 ± 7.47 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3):
d ˆ 18.23, 23.06 (2  CH3), 34.86 (C-5), 37.30 (C-6), 46.02 (C-1), 50.06 (C-2),
3-Methyl-1-phenylbuta-1,3-diene (1a): According to General Proce-
dure III, ketone 11a (4.00 g, 27.6 mmol, 0.8 equiv) was transformed into
the butadiene 1a (2.01 g, 14.1 mmol, 51%) by means of methyl triphenyl-
phosphonium iodide (13.9 g, 34.5 mmol, 1.0 equiv); b.p. 748C (6.5 mbar);
IR (film): ˆ 2982, 2934 cm 1 (C H), 748, 694 (monosubstituted aromatic),
962 (RHC CHR); UV (CH3CN): lmax (lge) ˆ 281 nm (4.155); 1H NMR
ˆ
ꢁ
112.4, 115.4 (C N), 120.0 (C-3), 128.7, 128.8, 129.1 (Ph C), 136.3, 137.3 (C-4,
(200 MHz, CDCl3): d ˆ 1.98 (s, 3H, CH3), 5.07, 5.12 (2s, 2H, 4-H), 6.52 (d,
J ˆ 15.0 Hz, 1H, 2-H), 6.89 (d, J ˆ 15.0 Hz, 1H, 1-H), 7.20 ± 7.43 (m, 5H, Ph
H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.58 (CH3), 117.3 (C-4), 126.4 (Ph
Co), 127.4, 128.6 (Ph C, C-2), 131.6 (C-1), 137.3 (Ph Ci), 142.0 (C-3); MS
‡
‡
Ph Ci); MS (70 eV): m/z (%) ˆ 129 (100) [diene CH3 ], 144 (90) [diene ],
236 (12) [M ]; Rt (1808C, 18Cmin 1) ˆ 13.6 min; C16H16N2 (236.3): calcd C
‡
81.32, H 6.82; found C 81.25, H 6.82.
‡
‡
‡
(70 eV): m/z (%) ˆ 115 (11) [C9H7 ], 129 (100) [M
C3H7], 144 (44) [M ];
1,1-Dicyano-6-ethyl-4-methyl-2-phenylcyclohex-3-ene (3/4b): Diene 1a
(124 mg, 0.87 mmol) and dienophile 2b (92.0 mg, 0.87 mmol) were cyclized
according to General Procedure IV at 1208C in 5 mL toluene over 12 h.
The ratio of 3b/4b was 1.56:1 (GC). Column chromatography gave 105 mg
of 3b (49%) and 68 mg of 4b (31%). trans-1,1-Dicyano-6-ethyl-4-methyl-
C11H12 (144.2): calcd 144.0939, found 144.0939 (HRMS).
3-Ethyl-1-phenylbuta-1,3-diene (1b): Ketone 11b (3.85 g, 24.0 mmol,
0.80 equiv) was transformed into the butadiene 1b (2.16 g, 13.7 mmol,
57%) according to General Procedure III by means of methyl triphenyl-
phosphonium iodide (12.1 g, 30.0 mmol, 1.00 equiv). B.p. 808C (4 mbar);
IR (film): ˆ 2968, 2936 cm 1 (C H), 754, 694 (monosubstituted aromatic),
2-phenylcyclohex-3-ene (4b): Rf ˆ 0.44 (petroleum ether/ethyl acetate
1
ꢁ
30:1); IR (film): ˆ 2932, 2970 cm (C H), 2246 (C N), 702, 766 (mono-
962 (RHC CHR); UV (CH3CN): lmax (lge) ˆ 282 nm (4.217); 1H NMR
substituted aromatic); UV (CH3CN): lmax (lge) ˆ 191 nm (4.215); 1H NMR
(300 MHz, CDCl3): d ˆ 0.95 (t, J ˆ 7.0 Hz, 3H, CH2CH3), 1.36 ± 1.50 (m,
ˆ
(200 MHz, CDCl3): d ˆ 1.18 (t, J ˆ 7.2 Hz, 3H, CH3), 2.36 (q, J ˆ 7.2 Hz, 2H,
Chem. Eur. J. 1999, 5, No. 1
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0301 $ 17.50+.50/0
301

L. F. Tietze, M. Buback et al.
FULL PAPER
ꢁ
1H, CH2CH3), 1.75 ± 1.90 (m, 1H, CH2CH3), 1.92 ± 2.14 (m, 1H, 5-Hax), 2.06
(mc, 1H, 6-H), 2.42 (brd, J ˆ 16.0 Hz, 1H, 5-Heq), 3.90 (brs, 1H, 2-H), 5.41
(brs, 1H, 3-H), 7.38 ± 7.46 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3):
d ˆ 11.18 (CH2CH3), 23.40 (CH3), 24.63 (CH2CH3), 31.41 (C-5), 37.51 (C-6),
53.27 (C-2), 113.8, 116.4 (C N), 120.4 (C-3), 128.4, 128.9, 129.8 (Ph C),
‡
136.4 (C-4), 137.0 (Ph Ci); MS (70 eV): m/z (%) ˆ 91 (9) [C7H7 ], 77 (6)
‡
‡
‡
‡
[C6H5 ], 129 (65) [diene CH3 ], 144 (100) [diene ], 278 (18) [M ]; Rt
(1808C, 58Cmin 1) ˆ 16.5 min; C19H22N2 (278.4): calcd C 81.97, H 7.96;
found C 81.77, H 7.76.
ꢁ
45.81 (C-1), 47.46 (C-2), 114.6, 115.2 (C N), 118.4 (C-3), 128.5, 130.2 (Ph
C), 135.3, 135.9 (C-4, Ph Ci); MS (70 eV): m/z (%) ˆ 129 (90) [diene
1,1-Dicyano-4-ethyl-6-methyl-2-phenylcyclohex-3-ene (5/6a): Diene 1b
(150 mg, 0.95 mmol) and dienophile 2a (105 mg, 1.14 mmol, 1.2 equiv)
were cyclized according to General Procedure IVat 1208C in 5 mL toluene
over 12 h. The ratio of 5a/6a was determined to be 1.17:1 (GC). Column
chromatography gave 18.0 mg of 5a, 18.0 mg of 6a and 174 mg of a mixture
5a/6a (73%). trans-1,1-Dicyano-4-ethyl-6-methyl-2-phenylcyclohex-3-ene
‡
‡
‡
CH3 ], 144 (100) [diene ], 251 (15) [M ]; Rt (1508C, 58Cmin 1) ˆ 15.2 min;
C17H18N2 (250.3). cis-1,1-Dicyano-6-ethyl-4-methyl-2-phenylcyclohex-3-
ene (3b): Rf ˆ 0.40 (petroleum ether/ethyl acetate 30:1); IR (film): ˆ
1
ꢁ
2934, 2970 cm (C H), 2248 (C N), 702, 772 (monosubstituted aromatic);
UV (CH3CN): lmax (lge) ˆ 191 nm (4.188); 1H NMR (300 MHz, CDCl3):
d ˆ 1.08 (t, J ˆ 7.5 Hz, 3H, CH2CH3), 1.50 ± 1.65 (m, 2H, 6-H, CH2CH3),
1.85 (brs, 3H, CH3), 2.00 ± 2.30 (m, 3H, 5-H, CH2CH3, 6-H), 3.90 (mc, 1H,
2-H), 5.43 (mc, 1H, 3-H), 7.38 ± 7.46 (m, 5H, Ph H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 10.95 (CH2CH3), 23.19 (CH3), 25.97 (CH2CH3), 31.94 (C-5),
(6a): Rf ˆ 0.52 (petroleum ether/ethyl acetate 10:1); IR (film, mixture with
1
ꢁ
ˆ
5a): ˆ 2968 cm (C H), 2248 (C N), 1458 (Ph C C), 768, 702 (mono-
substituted aromatic); UV (CH3CN, mixture with 5a): lmax (lge) ˆ 191 nm
(4.247); 1H NMR (200 MHz, CDCl3): d ˆ 1.10 (t, J ˆ 7.2 Hz, 3H, CH2CH3),
1.28 (d, J ˆ 6.5 Hz, 3H, CH3), 2.00 ± 2.21 (m, 5H, 5-H2, CH2CH3, 6-H),
2.35 ± 2.55 (m, 1H, CH2CH3), 3.99 (brs, 1H, 2-H), 5.46 (brs, 1H, 3-H),
7.28 ± 7.45 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 12.15, 17.22
(2 Â CH3), 29.82, 32.91 (C-5, CH2CH3), 31.50 (C-6), 43.42 (C-1), 46.97 (C-2),
ꢁ
43.25 (C-6), 45.81 (C-1), 50.29 (C-2), 112.7, 115.5 (C N), 120.1 (C-3), 128.7,
128.8, 129.1 (Ph C), 136.1, 137.2 (C-4, Ph Ci); MS (70 eV): m/z (%) ˆ 129
‡
‡
‡
(100) [diene CH3 ], 144 (80) [diene ], 251 (10) [M ]; Rt (1508C,
58Cmin 1) ˆ 15.8 min; C17H18N2 (250.3): calcd 250.1470, found 250.1470
(HRMS).
ꢁ
114.6, 114.9 (C N), 116.6 (C-3), 128.6, 128.9, 130.1 (Ph C), 136.0 (C-4),
140.7 (Ph Ci); MS (70 eV, mixture with 5a): m/z (%) ˆ 129 (100) [diene
1,1-Dicyano-6-isopropyl-4-methyl-2-phenylcyclohex-3-ene (3/4c): Diene
1a (150 mg, 1.04 mmol) and dienophile 2c (125 mg, 1.04 mmol) were
cyclized according to General Procedure IVat 1208C in 5 mL toluene over
12 h. The ratio of 3c to 4c was 1.18:1 (GC). Column chromatography gave
20.0 mg of 4c and 181 mg of a mixture of 3c/4c (66%). trans-1,1-Dicyano-
6-isopropyl-4-methyl-2-phenylcyclohex-3-ene (4c): Rf ˆ 0.20 (petroleum
C2H5 ], 158 (62) [diene ], 250 (10) [M ]; Rt (1908C, 18Cmin 1) ˆ 13.0 min;
C17H18N2 (250.3), calcd C 81.56, H 7.25; found C 81.52, H 7.33. cis-1,1-
Dicyano-4-ethyl-6-methyl-2-phenylcyclohex-3-ene (5a): Rf ˆ 0.46 (petro-
leum ether/ethyl acetate 10:1); IR see 6a; UV see 5a; 1H NMR (200 MHz,
CDCl3): d ˆ 1.15 (t, J ˆ 7.0 Hz, 3H, CH2CH3), 1.48 (d, J ˆ 7.5 Hz, 3H, CH3),
2.01 ± 2.58 (m, 5H, 5-H2, CH2CH3, 6-H), 2.35 ± 2.55 (m, 1H, CH2CH3), 3.89
(mc, 1H, 2-H), 5.41 (mc, 1H, 3-H), 7.28 ± 7.45 (m, 5H, Ph H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 12.03, 18.29 (2  CH3), 29.62, 33.38 (C-5, CH2CH3),
‡
‡
‡
1
ether/ethyl acetate 50:1); IR (film, mixture with 3c): ˆ 2970 cm (C H),
ꢁ
2248 (C N), 706, 762 (monosubstituted aromatic); UV (CH3CN, mixture
with 3c): lmax (lge) ˆ 191 nm (4.241); 1H NMR (300 MHz, CDCl3): d ˆ 1.09,
1.11 (2d, J ˆ 7.0 Hz, 6H, 2  CH3), 2.09 ± 2.19 (m, 2H, 6-H, HCMe2), 2.20 ±
2.28 (m, 2H, 5-H2), 4.06 (brd, J ˆ 4.5 Hz, 1H, 2-H), 5.47 (mc, 1H, 3-H),
7.37 ± 7.43 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 16.21, 21.91,
23.41 (3 Â CH3), 26.98 (C-5), 29.09 (CMe2), 39.26 (C-1), 41.46 (C-6), 50.00
ꢁ
37.32 (C-6), 46.21 (C-1), 50.02 (C-2), 112.4, 115.4 (C N), 118.3 (C-3), 128.7,
128.8, 129.1 (Ph C), 137.5 (C-4), 141.7 (Ph Ci); MS see 6a; Rt (1908C,
18Cmin 1) ˆ 13.4 min; C17H18N2 (250.3): calcd 250.1470, found 250.1470
(HRMS).
ꢁ
(C-2), 114.4, 116.2 (C N), 118.3 (C-3), 128.5, 129.0, 130.7 (Ph C), 136.5 (C-
1,1-Dicyano-4,6-diethyl-2-phenylcyclohex-3-ene (5/6b): Diene 1b (150 mg,
0.95 mmol) and dienophile 2b (121 mg, 1.14 mmol, 1.2 equiv) were cyclized
according to General Procedure IV at 1208C in 5 mL toluene over 12 h.
The ratio of 5b to 6b was 1.13:1 (GC). Column chromatography gave
12.0 mg of 5b, 18.0 mg of 6b and 209 mg of a mixture 5b/6b (95%). trans-
1,1-Dicyano-4,6-diethyl-2-phenylcyclohex-3-ene (6b): Rf ˆ 0.54 (petroleum
‡
4, Ph Ci); MS (70 eV, mixture with 3c): m/z (%) ˆ 129 (72) [diene CH3 ],
144 (100) [diene ], 264 (10) [M ]; Rt (1808C, 58Cmin 1) ˆ 11.6 min;
C18H19N2 (263.4): calcd C 81.78, H 7.62; found C 81.70, H 7.60. cis-1,1-
Dicyano-6-isopropyl-4-methyl-2-phenylcyclohex-3-ene (3c): Rf ˆ 0.16 (pe-
troleum ether/ethyl acetate 50:1); IR see 4c; UV see 4c; 1H NMR
(500 MHz, CDCl3, 1:1 mixture with 4c): d ˆ 0.70, 1.09 (2d, J ˆ 7.0 Hz, 6H,
2 Â CH3), 2.09 ± 2.19 (m, 1H, 6-H), 2.29 ± 2.39 (m, 2H, 5-H2), 2.46 (dsept,
J ˆ 7.0, 3.0 Hz, 1-H, HCMe2), 3.94 (mc, 1H, 2-H), 5.42 (mc, 1H, 3-H), 7.34 ±
7.43 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 16.11, 21.94, 23.35
(3 Â CH3), 26.74 (C-5), 29.86 (CMe2), 44.97 (C-1), 46.99 (C-6), 51.89 (C-2),
‡
‡
1
ether/ethyl acetate 10:1); IR (film, mixture with 5b): ˆ 2934, 2968 cm
ꢁ
ˆ
(C H), 2248 (C N), 1456 (Ar C C), 702, 766 (monosubstituted aromat-
1
ic); UV (CH3CN, mixture with 5b): lmax (lge) ˆ 192 nm (4.199); H NMR
(300 MHz, CDCl3): d ˆ 1.01, 1.10 (t, J ˆ 7.0 Hz, 6H, 2  CH3), 1.40 ± 1.57 (m,
1H, CH2CH3), 1.80 ± 1.96 (m, 1H, CH2CH3), 2.00 ± 2.20 (m, 4H, CH2CH3,
6-H, 5-H), 2.44 ± 2.55 (m, 1H, 5-H), 3.95 (brs, 1H, 2-H), 5.46 (brs, 1H, 3-H),
7.39 ± 7.43 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 11.23, 12.17
(2 Â CH3), 25.56 (C-5), 29.75, 29.94 (CH2CH3), 37.66 (C-6), 43.41 (C-1),
ꢁ
113.4, 115.0 (C N), 120.1 (C-3), 128.6, 128.8, 129.3 (Ph C), 136.4 (C-4), 137.0
(Ph Ci); MS see 4c; Rt (1808C, 58Cmin 1) ˆ 12.3 min; C18H19N2 (263.4).
6-tert-Butyl-1,1-dicyano-4-methyl-2-phenylcyclohex-3-ene (3/4d): Diene
1a (200 mg, 1.40 mmol) and dienophile 2d (187 mg, 1.40 mmol) were
cyclized according to General Procedure IVat 1208C in 5 mL toluene over
48 h. The ratio of 3d to 4d was 1:5.56 (GC). Column chromatography gave
20.0 mg of 3d (containing 20% 4d), 90.0 mg of 4d and 216 mg of a mixture
3d/4d (90%). trans-6-tert-Butyl-1,1-dicyano-4-methyl-2-phenylcyclohex-
3-ene (4d): Rf ˆ 0.23 (petroleum ether/ethyl acetate 30:1); IR (film): ˆ
ꢁ
47.33 (C-2), 114.6, 115.2 (C N), 116.9 (C-3), 128.6, 128.9, 130.2 (Ph C), 136.1
‡
(C-4), 140.7 (Ph Ci); MS (70 eV): m/z (%) ˆ 129 (100) [diene C2H5 ], 158
(36) [diene ], 264 (8) [M ]; Rt (1808C, 58Cmin 1) ˆ 12.4 min; C18H20N2
(264.4): calcd C 81.78, H 7.62; found C 81.73, H 7.63. cis-1,1-Dicyano-4,6-
diethyl-2-phenylcyclohex-3-ene (5b): Rf ˆ 0.50 (petroleum ether/ethyl
acetate 10:1); IR see 6b; UV see 6b; 1H NMR (300 MHz, CDCl3): d ˆ
1.08, 1.09 (t, J ˆ 7.0 Hz, 6H, 2  CH3), 1.50 ± 1.61 (m, 1H, CH2CH3), 2.00 ±
2.27 (m, 1H, CH2CH3, 5-H, 6-H), 2.40 (mc, 1H, 5-H), 3.90 (mc, 1H, 2-H),
5.40 (mc, 1H, 3-H), 7.35 ± 7.42 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3):
d ˆ 10.95, 12.01 (2  CH3), 26.00 (C-5), 29.70, 30.46 (CH2CH3), 43.25 (C-6),
‡
‡
1
ꢁ
2936 cm (C H), 2244 (C N), 704, 756 (monosubstituted aromatic); UV
(CH3CN): lmax (lge) ˆ 258 nm (2.100); 1H NMR (300 MHz, CDCl3): d ˆ
1.09 (s, 9H, tBu), 1.89 (s, 3H, CH3), 2.10 (t, J ˆ 8.0 Hz, 1H, 5-Hax), 2.30 (brd,
J ˆ 8.0 Hz, 2H, 6-H, 5-Heq), 4.06 (brd, J ˆ 5.0 Hz, 1H, 2-H), 5.48 (brd, J ˆ
5.0 Hz, 1H, 3-H), 7.38 ± 7.42 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3):
d ˆ 23.24 (CH3), 28.49 (tBu); 30.99 (C-5), 33.40 (CMe3), 39.08 (C-6), 43.21
ꢁ
45.97 (C-1), 50.21 (C-2), 112.7, 115.5 (C N), 118.4 (C-3), 128.7, 128.8, 129.1
(Ph C), 137.4 (C-4), 141.5 (Ph Ci); MS (70 eV): m/z (%) ˆ 129 (100)
[diene C2H5 ], 158 (24) [diene ], 264 (3) [M ]; Rt (1808C, 58Cmin 1) ˆ
‡
‡
‡
ꢁ
(C-1), 51.87 (C-2), 116.4, 116.5 (C N), 118.4 (C-3), 128.3, 128.9, 130.9 (Ph
12.8 min; C18H20N2 (264.4) calcd 264.1626, found 264.1626 (HRMS).
C), 135.3 (C-4), 136.5 (Ph Ci); MS (70 eV): m/z (%) ˆ 129 (58) [diene
CH3 ], 144 (100) [diene ], 278 (8) [M ]; Rt (1808C, 58Cmin 1) ˆ 17.9 min;
1,1-Dicyano-4-ethyl-6-isopropyl-2-phenylcyclohex-3-ene (5/6c): Diene 1b
(150 mg, 0.95 mmol) and dienophile 2c (137 mg, 1.14 mmol, 1.2 equiv)
were cyclized according to General Procedure IVat 1208C in 5 mL toluene
over 24 h. The ratio of 5c to 6c was 1:1.56 (GC). Column chromatography
gave 40.0 mg of 5c, 46.0 mg of 6c and 96.0 mg of a mixture 5c/6c (69%).
trans-1,1-Dicyano-4-ethyl-6-isopropyl-2-phenylcyclohex-3-ene (6c): Rf ˆ
‡
‡
‡
C19H22N2 (278.4): calcd 278.1782, found 278.1782 (HRMS). cis-6-tert-Butyl-
1,1-dicyano-4-methyl-2-phenylcyclohex-3-ene (3d): Rf ˆ 0.19 (petroleum
1
ꢁ
ether/ethyl acetate 30:1); IR (film): ˆ 2940, 2966 cm (C H), 2246 (C N),
702 (monosubstituted aromatic); UV (CH3CN): lmax (lge) ˆ 252 nm
(1.948); 1H NMR (300 MHz, CDCl3): d ˆ 1.22 (s, 9H, tBu), 1.82 (s, 3H,
CH3), 2.26 (dd, J ˆ 12.5, 4.5 Hz, 1H, 6-H), 2.31 (brdd, J ˆ 17.0, 12.5 Hz, 1H,
5-Hax), 2.43 (brd, J ˆ 17.0 Hz, 1H, 5-Heq), 3.87 (mc, 1H, 2-H), 5.37 (mc, 1H,
3-H), 7.35 ± 7.48 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 23.18
(CH3), 28.79 (tBu); 30.73 (C-5), 34.13 (CMe3), 41.51 (C-6), 51.12 (C-1),
0.31 (petroleum ether/ethyl acetate 20:1); IR (KBr, mixture with 5c): ˆ
1
ꢁ
ˆ
2928, 2966 cm (C H), 2244 (C N), 1464 (Ar C C), 700, 760 (mono-
substituted aromatic); UV (CH3CN, mixture with 5c): lmax (lge) ˆ 191 nm
(4.152); 1H NMR (300 MHz, CDCl3): d ˆ 0.98, 1.10, 1.15 (d, J ˆ 6.8 Hz, 9H,
302
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0302 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 1

Diels±Alder Reactions
297±304
3 Â CH3), 2.08 ± 2.30 (m, 6H, 4-H2, 5-H, CH3CH2, HCMe2), 4.08 (mc, 1H,
2-H), 5.48 (mc, 1H, 3-H), 7.29 ± 7.45 (m, 5H, Ph H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 12.24, 16.21, 21.89 (3  CH3), 25.33, 29.98 (C-5, CH3CH2), 29.11
1,1-Dicyano-4,6-diisopropyl-2-phenylcyclohex-3-ene (7/8c): Diene 1c
(100 mg, 0.58 mmol) and dienophile 2c (70 mg, 0.58 mmol) were cyclized
according to General Procedure V at 508C, 10 kbar in 2.5 mL dichloro-
methane within 36 h. The ratio of 7c/8c was determined to be 1:3.33 (GC).
Column chromatography gave 37.0 mg of 8c and 16 mg of a mixture 7c/8c
(31%). trans-1,1-Dicyano-4,6-diisopropyl-2-phenylcyclohex-3-ene (8c):
ꢁ
(CMe2), 39.16 (C-6), 41.58 (C-1), 49.81 (C-2), 114.4, 116.1 (C N), 116.6 (C-
3), 128.4, 128.9, 130.6 (Ph C), 135.6 (C-4), 141.8 (Ph Ci); MS (70 eV): m/z
‡
‡
‡
(%) ˆ 129 (100) [diene C2H5 ], 158 (38) [diene ], 278 (4) [M ]; Rt (1808C,
58Cmin 1) ˆ 12.2 min; C19H22N2 (278.4): calcd C 81.97, H 7.96; found C
81.84, H 7.86. cis-1,1-Dicyano-4-ethyl-6-isopropyl-2-phenylcyclohex-3-ene
(5c): Rf ˆ 0.28 (petroleum ether/ethyl acetate 20:1); IR see 6c; UV see 6c;
1H NMR (300 MHz, CDCl3): d ˆ 1.10, 1.12 (d, J ˆ 7.0 Hz, 6H, 2  CH3),
1.11 (t, J ˆ 7.0 Hz, 3H, CH2CH3), 2.10 ± 2.52 (m, 6H, 4-H2, 6-H, CH3CH2,
HCMe2), 3.93 (mc, 1H, 2-H), 5.41 (mc, 1H, 3-H), 7.37 ± 7.46 (m, 5H, Ph H);
13C NMR (50.3 MHz, CDCl3): d ˆ 12.08, 16.12, 21.95 (3  CH3), 25.24 (C-5)
29.88 (CH3CH2), 29.91 (CMe2), 44.23 (C-1), 46.96 (C-6), 51.79 (C-2), 113.4,
Rf ˆ 0.28 (petroleum ether/ethyl acetate 30:1); IR (KBr, mixture with
1
ꢁ
7c): ˆ 2964 cm (C H), 2248 (C N) 702, 764 (monosubstituted aromatic);
UV (CH3CN, mixture with 7c): lmax (lge) ˆ 191 nm (4.183); 1H NMR
(300 MHz, CDCl3): d ˆ 1.01, 1.11, 1.14, 1.16 (4d, J ˆ 6.5 Hz, 12H, 4  CH3),
2.02 ± 2.34 (m, 4H, 5-H2, 6-H, HCMe2), 2.42 (sept, J ˆ 6.5 Hz, 1H, HCMe2),
4.08 (brd, J ˆ 5.0 Hz, 1H, 2-H), 5.49 (mc, 1H, 3-H), 7.20 ± 7.42 (m, 5H, Ph
H); 13C NMR (50.3 MHz, CDCl3): d ˆ 16.29, 21.20, 21.64, 21.91 (4  CH3),
23.15 (C-5), 29.20, 35.04 (2 Â CMe2), 39.18 (C-6), 41.70 (C-1), 49.67 (C-2),
ꢁ
ꢁ
115.0 (C N), 118.3 (C-3), 128.6, 128.9, 129.3 (Ph C), 137.1 (C-4), 142.4 (Ph
115.8 (C-3), 114.4, 116.0 (C N), 128.5, 128.9, 130.6 (Ph C), 135.7 (C-4),
‡
‡
Ci); MS (70 eV): m/z (%) ˆ 129 (100) [diene C2H5 ], 158 (28) [diene ],
146.0 (Ph Ci); MS (70 eV, mixture with 7c): m/z (%) ˆ 129 (100) [diene
278 (3) [M ]; Rt (1808C, 58Cmin 1) ˆ 12.9 min; C19H22N2 (278.4): calcd
iPr ], 172 (55) [diene ], 292 (10) [M ]; Rt (1808C, 38Cmin 1) ˆ 16.8 min;
C20H24N2 (292.4): calcd C 82.14, H 8.27; found C 82.05, H 8.28. cis-1,1-
Dicyano-4,6-diisopropyl-2-phenylcyclohex-3-ene (7c): Rf ˆ 0.26 (petrole-
‡
‡
‡
‡
278.1783, found 278.1783 (HRMS).
6-tert-Butyl-1,1-dicyano-4-ethyl-2-phenylcyclohex-3-ene (5/6d): Diene 1b
(100 mg, 0.63 mmol) and dienophile 2d (254 mg, 2.00 mmol, 3 equiv) were
cyclized according to General Procedure V at 508C, 10 kbar in 2.5 mL
dichloromethane over 48 h. The ratio of 5d to 6d was 1:5.88 (GC). Column
chromatography gave 39.0 mg of 6d and 85 mg of a mixture 5d/6d (96%).
trans-6-tert-Butyl-1,1-dicyano-4-ethyl-2-phenylcyclohex-3-ene (6d): Rf ˆ
0.36 (petroleum ether/ethyl acetate 30:1); IR (KBr, mixture with 5d): ˆ
1
um ether/ethyl acetate 30:1); IR see 8c; UV see 8c; H NMR (300 MHz,
CDCl3 d ˆ 0.94, 1.02, 1.10, 1.18 (4d, J ˆ 6.5 Hz, 12H, 4  CH3), 2.04 ± 2.50
(m, 5H, 5-H2, 6-H, 2 Â HCMe2), 3.95 (mc, 1H, 2-H), 5.44 (brs, 1H, 3-H),
7.20 ± 7.43 (m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 16.19, 21.20,
21.64, 21.91 (4 Â CH3), 23.15 (C-5), 30.01, 34.90 (2 Â CMe2), 44.31 (C-1),
ꢁ
47.01 (C-6), 51.77 (C-2), 113.3, 115.1 (C N), 117.6 (C-3), 128.3, 128.7, 128.9
(Ph C), 137.1 (C-4), 146.6 (Ph Ci); MS see 8c; Rt (1808C, 38Cmin 1) ˆ
1
ꢁ
2968 cm (C H), 2242 (C N) 700, 754 (monosubstituted aromatic); UV
18.3 min; C20H24N2 (292.4): calcd 292.1939, found 292.1939 (HRMS).
(CH3CN, mixture with 5d): lmax (lge) ˆ 191 nm (4.142); 1H NMR
(300 MHz, CDCl3): d ˆ 1.10 (s, 9H, tBu), 2.08 (dd, J ˆ 9.0, 8.0 Hz, 1H,
5-Hax), 2.18 (brq, J ˆ 7.0 Hz, 2H, CH2CH3), 2.33 (brd, J ˆ 8.0 Hz, 2H,
5-Heq, 6-H), 4.09 (mc, 1H, 2-H), 5.49 (mc, 1H, 3-H), 7.29 ± 7.45 (m, 5H, Ph
H); 13C NMR (50.3 MHz, CDCl3): d ˆ 12.20 (CH3), 28.50 (tBu), 29.93, 29.78
(C-5, CH3CH2), 33.42 (CMe3), 39.22 (C-6), 43.15 (C-1), 51.73 (C-2), 116.4,
trans-6-tert-Butyl-1,1-dicyano-4-isopropyl-2-phenylcyclohex-3-ene (8d):
Diene 1c (100 mg, 0.63 mmol) and dienophile 2d (84.8 mg, 0.63 mmol)
were cyclized according to General Procedure Vat 508C, 10 kbar in 2.5 mL
dichloromethane over 24 h. Column chromatography gave 39 mg of 8d as a
single product (96%). Traces of the cycloadduct 7d may have been
determined by GC, 8d:7d >99:1). Rf ˆ 0.37 (petroleum ether/ethyl acetate
ꢁ
116.5 (C N), 116.8 (C-3), 128.3, 128.9, 130.9 (Ph C), 135.4 (C-4), 141.9 (Ph
1
ꢁ
20:1); IR (KBr): ˆ 2968 cm (C H), 2242 (C N) 702, 770 (monosubsti-
‡
Ci); MS (70 eV, mixture with 5d): m/z (%) ˆ 129 (100) [diene C2H5 ], 158
tuted aromatic); UV (CH3CN): lmax (lge) ˆ 191 nm (4.170); 1H NMR
(300 MHz, CDCl3): d ˆ 1.09 (s, 9H, tBu), 1.13, 1.15 (2d, J ˆ 6.5 Hz, 6H, 2 Â
CH3), 2.05 (dd, J ˆ 10.0, 6.5 Hz, 1H, 5-Hax), 2.33 (td, J ˆ 10.0, 1.0 Hz, 1H,
5-Heq), 2.35 (brd, J ˆ 6.5, 1.0 Hz, 1H, 6-H), 2.38 (sept, J ˆ 6.5 Hz, 1H,
HCMe2), 4.08 (brd, J ˆ 4.0 Hz, 1H, 2-H), 5.50 (mc, 1H, 3-H), 7.31 ± 7.45 (m,
5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 21.17, 21.67 (2  CH3), 27.23
(C-5), 28.25 (tBu), 33.48 (CMe3), 34.82 (CMe2), 39.29 (C-1), 39.29 (C-6),
(45) [diene ], 292 (10) [M ]; Rt (1808C, 58Cmin 1) ˆ 12.5 min; C20H24N2
(292.4): calcd C 82.43, H 7.95; found C 82.51, H 8.07. cis-6-tert-Butyl-1,1-
dicyano-4-ethyl-2-phenylcyclohex-3-ene (5d): Rf ˆ 0.30 (petroleum ether/
ethyl acetate 30:1); IR see 6d; UV see 6d; 13C NMR (50.3 MHz, CDCl3,
mixture with 6d): d ˆ 12.07 (CH3), 28.78 (tBu), 29.27, 29.69 (C-5, CH3CH2),
‡
‡
ꢁ
34.15 (CMe3), 41.65 (C-6), 51.05 (C-1), 53.11 (C-2), 113.8 (C N), 118.7 (C-
3), 128.4, 128.8, 129.8 (Ph C), 136.8 (C-4), 142.4 (Ph Ci); MS see 6d; Rt
ꢁ
43.11 (C-6), 51.55 (C-2), 115.9 (C-3), 116.3, 116.5 (C N), 128.3, 128.9, 130.9
(1808C, 58Cmin 1) ˆ 13.1 min; C20H24N2 (292.4).
(Ph C), 135.4 (C-4), 146.1 (Ph Ci); MS (70 eV): m/z (%) ˆ 129 (100)
‡
‡
‡
1,1-Dicyano-6-ethyl-4-isopropyl-2-phenylcyclohex-3-ene (7 ± 8b): Diene 1c
(100 mg 113, 0.58 mmol) and dienophile 2b (61.5 mg, 0.58 mmol) were
cyclized according to General Procedure IV at 1208C in 5 mL toluene
within 24 h. The ratio of 7b/8b was determined to be 1:1.89 (GC). Column
chromatography gave 3.0 mg of 7b, 14.0 mg of 8b and 148 mg of a mixture
7b/8b (98%). trans-1,1-Dicyano-6-ethyl-4-isopropyl-2-phenylcyclohex-3-
[diene iPr ], 172 (41) [diene ], 306 (12) [M ]; C21H26N2 (306.5): calcd C
82.27, H 8.55; found C 82.37, H 8.70.
Acknowledgements
ene (8b): Rf ˆ 0.23 (petroleum ether/ethyl acetate 20:1); IR (film, mixture
1
ꢁ
with 7b): ˆ 2966 cm (C H), 2248 (C N) 702, 768 (monosubstituted
We thank the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie for financial support. This work was performed
under the auspices of the Graduiertenkolleg ªKinetik und Selektivität
chemischer Prozesse in verdichteter fluider Phaseº.
aromatic); UV (CH3CN, mixture with 7b): lmax (lge) ˆ 191 nm (4.188);
1H NMR (200 MHz, CDCl3): d ˆ 0.93 (t, J ˆ 7.2 Hz, 3H, CH2CH3), 0.96 (d,
J ˆ 6.8 Hz, 6H, 2  CH3), 1.34 ± 1.52 (m, 1H, CH2CH3), 1.72 ± 1.93 (m, 1H,
CH2CH3), 1.96 ± 2.10 (m, 2H, 5-H, 6-H), 2.31 (sept, J ˆ 6.8 Hz, 1H,
HCMe2), 3.90 (brd, J ˆ 4.0 Hz, 1H, 2-H), 5.39 (mc, 1H, 3-H), 7.21 ± 7.39
(m, 5H, Ph H); 13C NMR (50.3 MHz, CDCl3): d ˆ 11.28 (CH2CH3), 21.21,
21.42 (2 Â CH3), 24.47 (CH2CH3), 27.41 (C-5), 34.90 (CMe2), 37.74 (C-6),
ꢁ
43.50 (C-1), 47.13 (C-2), 114.7, 115.2 (C N), 116.1 (C-3), 128.6, 128.9, 130.2
[1] a) L. F. Tietze, G. Kettschau, J. A. Gewert, A. Schuffenhauer, Curr.
Org. Chem. 1998, 2, 19 ± 62; b) L. F. Tietze, G. Kettschau, Top. Curr.
Chem. 1997, 189, 1 ± 120; c) C. O. Kappe, S. S. Murphree, A. Padwa,
Tetrahedron 1997, 53, 14179 ± 14233; d) L. C. Dias, J. Braz. Chem. Soc.
1997, 8, 289 ± 332; e) C. Cativela, J. I. Garcia, J. A. Mayoral, L.
Salvatella, Chem. Soc. Rev. 1996, 25, 209 ± 218; f) A. Whiting, Adv.
Asymmetric Synth. 1996, 126 ± 145; g) J. D. Winkler, Chem. Rev. 1996,
96, 167 ± 176; h) J. Streith, A. Defoin, Synthesis 1994, 1107 ± 1117; i) H.
Waldmann, Synthesis 1994, 535 ± 551; j) J. Sauer, R. Sustmann, Angew.
Chem. 1980, 92, 773 ± 801; Angew. Chem. Int. Ed. Engl. 1980, 19, 779 ±
806.
(Ph C), 136.2 (C-4), 144.8 (Ph Ci); MS (70 eV, mixture with 8d): m/z (%) ˆ
‡
‡
‡
129 (100) [diene C3H7 ], 172 (24) [diene ], 278 (2) [M ]; Rt (1808C,
58Cmin 1) ˆ 11.9 min; C19H22N2 (278.4): calcd C 81.97, H 7.96; found C
82.12, H 7.99. cis-1,1-Dicyano-6-ethyl-4-isopropyl-2-phenylcyclohex-3-ene
(7b): Rf ˆ 0.19 (petroleum ether/ethyl acetate 20:1); IR see 8b; UV see 8b;
1H NMR (500 MHz, CDCl3): d ˆ 1.09, 1.10 (2d, J ˆ 6.8 Hz, 6H, 2  CH3),
1.11 (t, J ˆ 7.0 Hz, 3H, CH2CH3), 1.55 ± 1.60 (m, 1H, CH2CH3), 2.06 ± 2.24
(m, 3H, 6-H, 5-H, CH2CH3), 2.34 (sept, J ˆ 6.8 Hz, 1H, HCMe2), 3.90 (mc,
1H, 2-H), 5.44 (mc, 1H, 3-H), 7.39 ± 7.42 (m, 5H, Ph H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 10.99 (CH2CH3), 21.11, 21.50 (2  CH3), 26.08
(CH2CH3), 28.31 (C-5), 34.68 (CMe2), 43.20 (C-6), 46.01 (C-1), 50.01 (C-2),
[2] a) R. Winter, J. Jonas, High Pressure Chemistry, Biochemistry and
Materials Science, Kluwer Academic, Dordrecht, 1993; b) N. S. Isaacs,
Tetrahedron 1991, 47, 8463 ± 8497; c) K. Matsumoto, R. M. Acheson,
ꢁ
112.6, 115.5 (C N), 117.5 (C-3), 128.5, 128.8, 129.1 (Ph C), 137.4 (C-4), 145.7
(Ph Ci); MS see 8b; Rt (1808C, 58Cmin 1) ˆ 12.2 min; C19H22N2 (278.4).
Chem. Eur. J. 1999, 5, No. 1
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0303 $ 17.50+.50/0
303

L. F. Tietze, M. Buback et al.
FULL PAPER
Organic Synthesis at High Pressures, Wiley, Interscience, New York
1991; d) F. G. Klärner, Chem. Unserer Zeit 1989, 23, 53 ± 63; e) R.
van Eldik, T. Asano, W. J. le Noble, Chem. Rev. 1989, 89, 549 ± 688;
f) K. Matsumoto, A. Sera, T. Uchida, Synthesis 1985, 1 ± 26; g) K.
Matsumoto, A. Sera, Synthesis 1985, 999 ± 1027.
[6] a) M. Buback, J. Abeln, T. Hübsch, C. Ott, L. F. Tietze, Liebigs Ann.
1995, 9 ± 11; b) M. Buback, K. Gerke, C. Ott, L. F. Tietze, Chem. Ber.
1994, 127, 2241 ± 2248; c) L. F. Tietze, C. Ott, U. Frey Liebigs Ann.
Chem. 1996, 63 ± 67; d) L. F. Tietze, C. Ott, K. Gerke, M. Buback,
Angew. Chem. 1993, 105, 1536 ± 1538; Angew. Chem. Int. Ed. Engl.
1993, 32, 1485 ± 1486.
[3] J. R. McCabe, C. A. Eckert, Acc. Chem. Res. 1974, 7, 251 ± 257.
[4] C. Brun, G. Jenner, A. Deluzarche, Bull. Soc. Chim. Fr. 1972, 2332 ±
2337.
[7] D. Dudek, B. Baranowski, Pol. J. Chem. 1991, 65, 1357 ± 1364.
[8] W. Tost, Thesis, Universität Göttingen, 1988.
[5] a) L. F. Tietze, M. Henrich, I. Rothert, G. Kuchta, M. Buback, Pol. J.
Chem. 1997, 71, 1749 ± 1762; b) M. Buback, G. Kuchta, A. Niklaus, M.
Henrich, L. F. Tietze, Liebigs Ann. 1996, 1151 ± 1158; c) L. F. Tietze, T.
Hübsch, C. Ott, G. Kuchta, M. Buback, Chem. Ber. 1994, 127, 1 ± 7;
d) L. F. Tietze, T. Hübsch, J. Oelze, C. Ott, W. Tost, G. Wörner, M.
Buback, Chem. Ber. 1992, 125, 2249 ± 2269; e) L. F. Tietze, T Hübsch,
M. Buback, W. Tost, High-Pressure Res. 1990, 5, 638 ± 640; f) M.
Buback, W. Tost, T. Hübsch, E. Voss, L. F. Tietze, Chem. Ber. 1989,
122, 1179 ± 1186; g) M. Buback, W. Tost, L. F. Tietze, E. Voss, Chem.
Ber. 1988, 121, 781 ± 795.
[9] a) B. S. Elꢁyanov, G. M. Gonikberg, J. Chem. Soc. Faraday Trans. I
1979, 75, 172 ± 191; b) B. S. Elꢁyanov, G. M. Gonikberg, G. Jenner, J.
Chem. Soc. Perkin Trans. 2 1992, 137 ± 142.
[10] L. F. Tietze, T. Hübsch, E. Voss, M. Buback, W. Tost, J. Am. Chem.
Soc. 1988, 110, 4065 ± 4066.
[11] F. G. Klärner, Angew. Chem. 1986, 98, 109 ± 111; Angew. Chem. Int.
Ed. Engl. 1986, 25, 108 ± 110; see also: F. G. Klärner, B. R. Krawczyk,
V. Ruster, U. Deiters, J. Am. Chem. Soc. 1994, 116, 7646 ± 7657.
Received: March 12, 1998 [F1044]
304
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0501-0304 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 1