[4+2] Cycloadditions of 1,2,4,5-tetrazines and cyclopropenes - Synthesis of 3,4-diazanorcaradienes and tetracyclic aliphatic azo compounds

Article abstract of DOI:10.1002/1099-0690(200107)2001:14<2629::aid-ejoc2629>3.0.co;2-2

1,2,4,5-Tetrazines 1 readily react with cyclopropenes 2 to form 3,4-diazanorcaradienes 3, 4, 7 and 8 in a cycloaddition - cycloelimination sequence. Compounds 3 and 4 still act as 1,3-dienes with cyclopropenes 2, producing aliphatic azo compounds 5 and 6, versatile starting compounds in thermolysis and photolysis reactions.

Full text of DOI:10.1002/1099-0690(200107)2001:14<2629::aid-ejoc2629>3.0.co;2-2

FULL PAPER
[4؉2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes ؊ Synthesis of
3,4-Diazanorcaradienes and Tetracyclic Aliphatic Azo Compounds
Jürgen Sauer,*[a] Peter Bäuerlein,[a] Wolfgang Ebenbeck,[a] Charalampos Gousetis,[a]
Heinz Sichert,[a] Theodor Troll,[a] Ferdinand Utz,[a] and Uwe Wallfahrer[a]
Dedicated to Prof. Siegfried Hünig on the occasion of his 80th birthday
Keywords: Azo compounds / Cycloadditions / Cyclopropenes / Nitrogen heterocycles / 1,2,4,5-Tetrazines
1,2,4,5-Tetrazines 1 readily react with cyclopropenes 2 to
form 3,4-diazanorcaradienes 3, 4, 7 and 8 in a cycloaddition
− cycloelimination sequence. Compounds 3 and 4 still act as
1,3-dienes with cyclopropenes 2, producing aliphatic azo
compounds 5 and 6, versatile starting compounds in thermo-
lysis and photolysis reactions.
Introduction
(dioxane, 20 °C).[11] The fading of the colour here again
indicates the progress of the reaction at room temperature
[General Procedure (2)].
Forty years have passed since the first report on the diene
activity of 1,2,4,5-tetrazines was published.[1] In the mean-
time this heterocyclic system has proved to be a valuable
electron-poor diene in [4ϩ2] cycloadditions with angle-
strained and electron-rich dienophiles.[2] A large variety of
heterocyclic and carbocyclic compounds are accessible in a
few steps; examples include 3,4-diazanorcaradienes,[3]
homotropilidenes,[4Ϫ6] syn-bis-σ-homobenzenes[7] and semi-
bullvalenes.[8,9] Here we give a full report on the synthesis
of 3,4-diazanorcaradienes 3, 4, 7 and 8, as well as for the
aliphatic azo compounds 5 and 6. Diazanorcaradienes 3
and 4 were also needed for a detailed kinetic study.[10]
3,4-Diazanorcaradienes 3 and 4 are much less reactive
dienes than 1,2,4,5-tetrazines, by a factor of 103 to 104 for
the rate constants derived from kinetic data.[2] Con-
sequently, only those diazadienes 3 and 4 with electron-
withdrawing substituents R1 react readily with an excess of
cyclopropene (2a) at Ϫ78 °C, forming the so-called ‘‘bisad-
ducts’’ 5 and 6. The reaction can be driven to final comple-
tion by warming the reaction mixture to room temperature.
Again, the disappearance of the tetrazine or diazanorcarad-
iene colour is a simple indicator that the reaction is success-
fully going to completion [General Procedure (3)]. For the
less reactive 3,3-dimethylcyclopropene (2b), more forcing
conditions were required: high pressure (up to 8 kbar) and
slightly elevated temperatures (56Ϫ100 °C) [General pro-
cedure (4)]. The highly negative ∆V϶ values, well known in
concerted cycloaddition reactions, are responsible for the
accelerating pressure effect.[12] We were unsuccessful, how-
ever, in forcing 3,4-diazanorcaradienes 7 and 8 to undergo
addition reactions to form ‘‘bisadducts’’ of type 5 and 6. In
this cycloaddition step, the resonance energy of one or two
imino ester units has to be sacrificed.
Results and Discussion
Schemes 1 and 2 summarize all reactions performed. As
already indicated, [4ϩ2] cycloaddition reactions between
tetrazines 1 and cyclopropenes 2 occur readily. After the
addition step, the sequence is completed by loss of nitro-
gen in a cycloelimination, with diazanorcaradienes 3, 4, 7
and 8 being formed in reasonable yields, mostly between
70 and 90%. The cyano derivatives 5c and 6c could not be
obtained directly from the labile dicyanotetrazine 1c, so
we instead used the conventional transformations 5a/6a Ǟ
5b/6b Ǟ 5c/6c. The highly reactive cyclopropene (2a)[11]
was introduced into a solution of tetrazine 1 in a stream
of nitrogen at Ϫ78 °C; the reaction can be monitored by
the disappearance of the tetrazine colour [General Proced-
ure (1)]. 3,3-Dimethylcyclopropene (2b) is far less reactive,
by a factor of approximately 5000Ϫ6000 in rate constants
NMR spectra provided structural proof for all com-
1
pounds obtained. Tables 1 and 2 show selected H NMR
spectroscopic data for 3,4-diazanorcaradienes 3 and 4,
while the corresponding values for the tetracyclic azo com-
pounds 5 and 6 are to be found in Tables 2 and 3. The
typical pronounced chemical shift difference between 7-Hsyn
and 7-Hanti in 3, in conjunction with the characteristic set
of coupling constants for the ABX2 spin system,[3] is in ac-
cordance with the diazanorcaradiene structure (Figure 1).
1
Simpler H NMR spectra were observed for the dimethyl
derivatives 4, with the chemical shift differences between
methyl groups, syn and anti, again being considerable. De-
tailed analysis of the H NMR spectroscopic data for the
[a]
Institut für Organische Chemie der Universität Regensburg,
Universitätsstraße 31, 93040 Regensburg, Germany
Fax: (internat.) ϩ 49-(0)941/943-4946
1
E-mail: rudolf.vasold@chemie.uni-regensburg.de
‘‘bisadducts’’ 5 and 6, including chemical shifts and coup-
Eur. J. Org. Chem. 2001, 2629Ϫ2638
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ193X/01/0714Ϫ2629 $ 17.50ϩ.50/0
2629

J. Sauer et al.
FULL PAPER
Scheme 1. Cycloadditions between 1,2,4,5-tetrazines 1aϪ1u and cyclopropenes 2, giving 3,4-diazanorcaradienes 3 and 4, with subsequent
formation of tetracyclic azo compounds 5 and 6
Table 1. 1H NMR chemical shifts (δ values, CDCl3/TMS, 80 or
n
250 MHz) and coupling constants J(1H,1H) [Hz] of 3,4-diazanor-
caradienes 3 and 7
1-H, 6-H 3J7s,1/6 J7a,1/6 J7,7
8.9 3.8
3
2
Cmpd.
7-Hsyn
7-Hanti
3a[a][3]
Ϫ0.03 (dt)
2.28 (dt) 3.05 (dd) 4.8
3d[b] 0.32Ϫ0.41 (m) 2.41Ϫ2.51 (m) 2.71 (m)
Ϫ
Ϫ
Ϫ
3e
3f
3g
3h
3i
3j
3k
3l
3n
3o
3q
3r
3s
3t
3u
7v
7x
0.35 (dt)
0.31 (dt)
0.27 (dt)
0.33 (dt)
0.30 (dt)
0.35 (dt)
0.36 (dt)
0.41 (dt)
0.41 (dt)
0.43 (dt)
0.40 (dt)
0.29 (dt)
0.43 (dt)
0.38 (dt)
0.27 (dt)
0.42 (dt)
0.51 (dt)
2.16 (dt)
2.71(dd) 4.9
9.0 3.8
9.0 3.8
9.0 3.8
9.1 3.8
9.0 3.8
9.1 3.9
9.0 3.9
9.0 3.9
9.0 4.1
9.1 4.0
9.1 4.7
9.2 3.6
9.0 3.9
9.0 4.0
9.1 3.6
8.9 4.5
9.1 4.6
2.15 (dt) 2.68 (dd) 4.9
2.09 (dt) 2.63 (dd) 4.9
2.15 (dt) 2.70 (dd) 4.9
2.08 (dt) 2.48 (dd) 4.9
2.22 (dt) 2.69 (dd) 4.9
2.19 (dt) 2.71 (dd) 4.9
2.28 (dt) 2.77 (dd) 4.9
2.04 (dt) 2.74 (dd) 4.9
2.27 (dt) 3.39 (dd) 4.8
2.40 (dt) 3.35 (dd) 4.8
2.32 (dt) 3.48 (dd) 4.8
2.31 (dt) 2.80 (dd) 4.9
2.30 (dt) 2.78 (dd) 4.9
2.29 (dt) 3.42 (dd) 4.7
1.73 (dt) 2.21 (dd) 4.7
1.49 (dt) 2.14 (dd) 4.6
Scheme 2. Cycloadditions between 1,2,4,5-tetrazines 1vϪ1z and
cyclopropenes 2, giving 3,4-diazanorcaradienes 7 and 8
ling constants (Tables 2 and 3), proves the syn,syn arrange-
ment, relative to the azo bridge, in both cyclopropane units.
As 13C NMR spectra did not change dramatically over
compounds 3Ϫ8, 13C NMR spectra were measured only for
a limited number of compounds (see Exp. Sect.).
[a]
[b]
At 248 K. Ϫ At 233 K.
2630
Eur. J. Org. Chem. 2001, 2629Ϫ2638

[4ϩ2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes
Table 2. 1H NMR chemical shifts (δ values, CDCl3/TMS, 80 or 250 MHz) of 3,4-diazanorcaradienes 4, 8 and tetracyclic azo compounds 6
FULL PAPER
3,4-Diazanorcaradienes 4 and 8
Tetracyclic azo compounds 6
Cmpd.
7-CH3-syn
7-CH3-anti
1-H, 6-H
Cmpd.
7-CH3-syn
7-CH3-anti
2,4,6,8-H
4a[a][3]
4d
4e
4g
4i
0.59 (s)
0.69 (s)
0.63 (s)
0.68 (s)
0.67 (s)
0.70 (s)
0.79 (s)
0.65 (s)
0.72 (s)
0.80 (s)
0.70 (s)
0.72 (s)
0.67 (s)
0.74 (s)
0.71 (s)
0.68 (s)
0.67 (s)
0.67 (s)
1.55 (s)
1.53 (s)
1.61 (s)
1.66 (s)
1.67 (s)
1.68 (s)
1.80 (s)
1.51 (s)
1.80 (s)
1.76 (s)
1.56 (s)
1.65 (s)
1.68 (s)
1.72 (s)
1.71 (s)
1.68 (s)
1.27 (s)
1.20 (s)
2.88 (s)
2.49 (s)
2.45 (s)
2.46 (s)
2.45 (s)
2.43 (s)
2.61 (s)
2.35 (s)
2.55 (s)
3.28 (s)
2.58 (s)
3.17 (s)
3.33 (s)
2.58 (s)
2.57 (s)
3.26 (s)
1.94 (s)
1.90 (s)
6a[b]
6b[c]
6c
0.92 (s)
0.93 (s)
1.02 (s)
0.96 (s)
1.11 (s)
0.91 (s)
1.02 (s)
0.92 (s)
1.01 (s)
0.97 (s)
1.10 (s)
1.02 (s)
1.23 (s)
1.08 (s)
1.09 (s)
1.08 (s)
1.78 (s)
1.88 (s)
1.86 (s)
1.72 (s)
1.75 (s)
2.20 (s)
1.99 (s)
2.18 (s)
6d
6e
4k
4l
6o
6q[b]
6r
4m
4n
4o
4p
4q
4r
4s
4t
4u
8v
8w
[a]
[b]
[c]
At 253 K. Ϫ Solvent CD2Cl2. Ϫ Solvent CD3OD.
Table 3. 1H NMR chemical shifts (δ values, CDCl3/TMS, 80 or
250 MHz) and coupling constants J(1H,1H) [Hz] of tetracyclic azo
compounds 5
Conclusion
3,4-Diazanorcaradienes such as 3, 4, 7 and 8, and also
the ‘‘bisadducts’’ 5 and 6, required for preparative and kin-
etic studies, are accessible in good yields in wide structural
variety with the aid of simple [4ϩ2] cycloadditions. The re-
action conditions required vary from Ϫ78 °C at normal
pressure to ϩ100 °C at 8 kbar, depending on the reactivity
of the 4π and 2π components.
Cmpd. 3,7-Hsyn 3,7-Hanti 2,4,6,8-H 3J3s,2/4 3J3a,2/4 2J3,3
5a[3]
5b[a]
5c
0.13 (dt) 0.56 (dt) 1.93 (dd)
0.00 (dt) 0.55 (dt) 2.00 (dd)
0.37 (m) 0.85 (m) 2.07 (m)
0.10 (dt) 0.60 (dt) 1.80 (dd)
0.27 (dt) 0.55 (dt) 2.29 (dd)
0.33 (dt) 0.79 (dt) 2.12 (dd)
0.21 (dt) 0.54 (dt) 2.22 (dd)
0.49 (dt) 0.90 (dt) 1.95 (dd)
0.43 (dt) 0.83 (dt) 1.93 (dd)
3.7
3.6
Ϫ
3.6
3.6
3.6
3.6
3.7
3.7
7.4
7.6
Ϫ
7.7
7.7
7.7
7.7
7.7
7.7
6.8
7.2
Ϫ
7.2
7.0
7.0
6.4
6.5
6.6
5d
5o
5q[b]
5r
5s
5t
Experimental Section
[a]
[b]
Solvent CD3OD. Ϫ Solvent CD2Cl2.
General Remarks: IR spectra were recorded with a Beckman Accu-
lab 1 machine and UV/Vis spectra with a Carl Zeiss Specord M500
UV spectrophotometer. Ϫ NMR spectra were obtained with
Bruker AW 80 and AC 250 machines (80 MHz/250 MHz for 1H
and 63 MHz for 13C); δ values are reported in ppm downfield from
tetramethylsilane; s, d, dd, dt and m indicate singlet, doublet, doub-
let of doublets, doublet of triplets and multiplet. The degree of
substitution of the C atoms was determined by DEPT-135 and
DEPT-90 methods and indicated as quat. C, ϭCH, ϪCH2Ϫ,
ϪCH3. Ϫ Mass spectra were measured with a Varian MAT311A
instrument by electron impact, at an ionizing voltage of 70 eV. Ϫ
Melting points were determined either with a Büchi melting point
apparatus (Ͻ 280 °C) or with a copper block (Ͼ 280 °C) and are
uncorrected. Ϫ Elemental analyses were performed in the microan-
alytical laboratory of the University of Regensburg with Heraeus
Mikro U/E and CHN-Rapid instruments. In some cases Ϫ such as
for 3d, 3e, 4d and 4e Ϫ correct elemental analyses could not be
obtained. Ϫ For analytical thin layer chromatography, precoated
plastic sheets (POLYGRAM SIL G/UV254, MachereyϪNagel &
Co.) were used. Ϫ Silica gel 60 (particle size 0.040Ϫ0.063 nm,
Merck) was used for flash column chromatography (FC). Ϫ Reac-
tions were carried out under nitrogen. Solvents for reactions were
dried according to standard procedures. The petroleum ether (PE)
used had a boiling range of 40Ϫ60 °C.
Figure 1. Significant coupling constants nJ(1H,1H) observed for
3,4-diazanorcaradienes 3 and tetracyclic azo compounds 5
Eur. J. Org. Chem. 2001, 2629Ϫ2638
2631

J. Sauer et al.
FULL PAPER
Synthesis of 3,4-Diazanorcaradienes and Tetracyclic Azo Com-
pounds
(KBr): ν
˜ ϭ 3090, 3040, 1530, 1490, 1410, 1385, 1045, 1015, 765,
1
2
680 cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.35 (dt, J ϭ 3.8,
2
3
3J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.16 (dt, J ϭ 3.8, J ϭ 9.0 Hz, 1 H, 7-
General Procedure (1) for the Synthesis of 3,4-Diazanorcaradienes
3d؊3l, 3n, 3o, 3q؊3u and 7v؊7z, and Tetracyclic Azo Compounds
5d, 5o and 5q: A ca. 30-fold excess of gaseous cyclopropene (2a),
generated using an optimized procedure by Closs and Krantz,[13]
was condensed (ca. 6 h) into a trap maintained at dry ice temper-
ature and containing a stirred suspension of tetrazine 1 in an inert
solvent (vide infra). The trap was allowed to warm to room temper-
ature and stirring was continued until the red colour of the tetra-
zine 1 had disappeared (reaction times: see below). After comple-
tion of the reaction, the solvent was removed in vacuo and the
crude reaction product was purified as described below.
3
3
Hanti), 2.71 (dd, J ϭ 4.9, J ϭ 9.0 Hz, 2 H, 1-H, 6-H), 7.45Ϫ7.53
(m, 6 H, Ar-H), 8.13Ϫ8.19 (m, 4 H, Ar-H). Ϫ UV/Vis (CH3CN):
λmax (ε) ϭ 312 (21400) nm.
2,5-Bis(m-tolyl)-3,4-diazanorcaradiene (3f): This compound was
prepared according to General Procedure (1). Compounds 1f
(3.00 g, 11.4 mmol) and 2a, after stirring in CH2Cl2 (80 mL) at Ϫ78
°C for 10 min, purification by FC (CH2Cl2/EtOAc ϭ 1:1) and
recrystallization (CH2Cl2/EtOAc), yielded 3f (1.90 g, 6.90 mmol,
˜
61%) as yellow crystals, m.p. 132 °C. Ϫ IR (KBr): ν ϭ 3040, 2980,
1610, 1590, 1550, 1515, 1430, 1400, 1280, 1200, 805, 715, 685 cmϪ1
1H NMR (250 MHz, CDCl3): δ ϭ 0.31 (dt, 2J ϭ 3.8, 3J ϭ
.
Ϫ
2
3
General Procedure (2) for the Synthesis of 7,7-Dimethyl-3,4-diaz-
anorcaradienes 4d, 4e, 4g, 4i, 4k؊4u, 8v and 8w, and Tetracyclic Azo
Compounds 6a and 6d: The tetrazine 1 was dissolved in an inert
solvent (vide infra). The dienophile 3,3-dimethylcyclopropene (2b)
synthesized using a procedure described by Huber and Sauer,[14]
was added and the reaction mixture was stirred until the character-
istic red colour of the tetrazine 1 had disappeared (reaction times:
see below). The solution was concentrated to dryness and the crude
product was purified as described below.
4.9 Hz, 1 H, 7-Hsyn), 2.15 (dt, J ϭ 3.8, J ϭ 9.0 Hz, 1 H, 7-Hanti),
3
3
2.44 (s, 6 H, Ar-CH3), 2.68 (dd, J ϭ 4.9, J ϭ 9.0 Hz, 2 H, 1-H,
6-H), 7.30Ϫ8.00 (m, 8 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ
317 (21400) nm. Ϫ C19H18N2 (274.4): calcd. C 83.18, H 6.61, N
10.21; found C 83.14, H 6.64, N 10.23.
2,5-Bis(p-tolyl)-3,4-diazanorcaradiene (3g): This compound was
prepared according to General Procedure (1). Compounds 1g
(3.00 g, 11.4 mmol) and 2a, after stirring in CH2Cl2 (80 mL) at 0
°C for 1 h and purification by FC (CH2Cl2/EtOAc ϭ 1:1), yielded
3g (1.82 g, 6.60 mmol, 58%) as yellow crystals, m.p. 224 °C. Ϫ IR
General Procedure (3) for the Synthesis of Tetracyclic Azo Com-
pounds 5r؊5t: A ca. 100-fold excess of gaseous cyclopropene (2a)
was generated according to General Procedure (1) and condensed
(ca. 6 h) into a trap maintained at dry ice temperature.[13] A solu-
tion of diazanorcaradiene 3 in CH2Cl2 was added and the reaction
mixture was stirred for 3 h at Ϫ78 °C. The mixture was then al-
lowed to warm to room temperature and stirring was continued for
24 h until the colour of 3 had disappeared (vide infra). After re-
moval of the solvent the colourless residue was purified as de-
scribed below.
˜
(KBr): ν ϭ 3040, 2910, 1605, 1530, 1400, 1385, 1180, 1170, 1040,
1010, 810, 710 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.27
2
3
2
3
(dt, J ϭ 3.8, J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.09 (dt, J ϭ 3.8, J ϭ
9.0 Hz, 1 H, 7-Hanti), 2.41 (s, 6 H, Ar-CH3), 2.63 (dd, 3J ϭ 4.9,
3J ϭ 9.0 Hz, 2 H, 1-H, 6-H), 7.26Ϫ8.05 (m, 8 H, Ar-H). Ϫ UV/
Vis (CH3CN): λmax (ε) ϭ 321 (25700) nm. Ϫ C19H18N2 (274.4):
calcd. C 83.18, H 6.61, N 10.21; found C 83.41, H 6.35, N 10.22.
2,5-Bis(m-methoxyphenyl)-3,4-diazanorcaradiene (3h): This com-
pound was prepared according to General Procedure (1). Com-
pounds 1h (3.00 g, 10.2 mmol) and 2a, after stirring in CH2Cl2
(80 mL) at 0 °C for 2 h and purification by FC (CH2Cl2/Et2O/PE ϭ
1:1:1), yielded 3h (2.60 g, 8.50 mmol, 83%) as yellow crystals, m.p.
General Procedure (4) for the High-Pressure Synthesis of Tetracyclic
Azo Compounds 6e, 6o, 6q and 6r: The diazanorcaradiene 4 was
dissolved in CH2Cl2 or CH3CN (4Ϫ6 mL) in a high-pressure vessel.
After addition of 3,3-dimethylcyclopropene (2b), the reaction vessel
was pressurized to max. 8.0 kbar at a temperature of 56Ϫ100 °C
until completion of the reaction (reaction times: see below). After
evaporation of the solvent, the crude material was purified as de-
scribed below.
˜
117 °C. Ϫ IR (KBr): ν ϭ 3040, 2990, 2940, 2830, 1590, 1500, 1280,
1
1215, 1040, 850, 790, 700 cmϪ1. Ϫ H NMR (250 MHz, CDCl3):
δ ϭ 0.33 (dt, 2J ϭ 3.8, J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.15 (dt, 2J ϭ
3
3
3
3
3.8, J ϭ 9.1 Hz, 1 H, 7-Hanti), 2.70 (dd, J ϭ 4.9, J ϭ 9.1 Hz, 2
H, 1-H, 6-H), 3.89 (s, 6 H, OCH3), 7.05Ϫ7.81 (m, 8 H, Ar-H). Ϫ
UV/Vis (CH3CN): λmax (ε) ϭ 320 (19500) nm. Ϫ C19H18N2O2
(306.4): calcd. C 74.49, H 5.92, N 9.14; found C 74.18, H 6.00,
N 9.05.
Synthesis of the 3,4-Diazanorcaradienes 3d؊3l, 3n, 3o, 3q؊3u and
7v؊7z
2,5-Bis(trifluoromethyl)-3,4-diazanorcaradiene (3d): This compound
was prepared according to General Procedure (1). Compounds 1d
(530 mg, 2.43 mmol) and 2a, after stirring in CCl4 (10 mL) at room
temp. overnight, yielded 3d, which was purified by bulb-tube distil-
lation (50 °C/0.01 Torr) to give extremely moisture-sensitive yellow
crystals. No yield, melting point or elemental analysis could be
2,5-Bis(p-methoxyphenyl)-3,4-diazanorcaradiene (3i): This com-
pound was prepared according to General Procedure (1). Com-
pounds 1i (3.00 g, 10.2 mmol) and 2a, after stirring in CH2Cl2
(80 mL) at 0 °C for 1 h, purification by FC (CH2Cl2/EtOAc ϭ 1:1)
and recrystallization (CH2Cl2/EtOAc), yielded 3i (3.02 g,
˜
9.90 mmol, 97%) as yellow crystals, m.p. 224 °C. Ϫ IR (KBr): ν ϭ
˜
determined. Ϫ IR (CCl4): ν ϭ 1400, 1305, 1290, 1205, 1135, 1090,
3040, 3000, 2940, 2840, 1600, 1535, 1510, 1415, 1395, 1300, 1250,
1170, 1030, 840, 640 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ
0.30 (dt, 2J ϭ 3.8, 3J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.08 (dt, 2J ϭ 3.8,
1070, 1050, 900 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3, θ ϭ
233.1 K): δ ϭ 0.32Ϫ0.41 (m, 1 H, 7-Hsyn), 2.41Ϫ2.51 (m, 1 H, 7-
Hanti), 2.71 (m, 2 H, 1-H, 6-H). Ϫ MS (EI, 70 eV): m/z (%) ϭ 230
(36) [Mϩ].
3
3J ϭ 9.0 Hz, 1 H, 7-Hanti), 2.48 (dd, 3J ϭ 4.9, J ϭ 9.0 Hz, 2 H, 1-
H, 6-H), 3.87 (s, 6 H, OCH3), 6.96Ϫ8.12 (m, 8 H, Ar-H). Ϫ UV/
Vis (CH3CN): λmax (ε) ϭ 335 (27500) nm. Ϫ C19H18N2O2 (306.4):
calcd. C 74.49, H 5.92, N 9.14; found C 74.42, H 5.84, N 9.21.
2,5-Diphenyl-3,4-diazanorcaradiene (3e): This compound was pre-
pared according to General Procedure (1). Compounds 1e (3.00 g,
12.8 mmol) and 2a, after stirring in CH2Cl2 (50 mL) at 0 °C for 2,5-Bis(m-chlorophenyl)-3,4-diazanorcaradiene (3j): This compound
6 h, purification by FC (CH2Cl2 Ǟ CH2Cl2/EtOAc ϭ 1:1) and was prepared according to General Procedure (1). Compounds 1j
recrystallization (CH2Cl2/EtOAc), yielded 3e (2.65 g, 10.8 mmol,
(3.00 g, 9.90 mmol) and 2a, after stirring in CH2Cl2 (80 mL) at 0
°C for 1.5 h, purification by FC (CH2Cl2/EtOAc ϭ 1:1) and recrys-
84%) as yellow crystals, m.p. 198 °C (ref.[15] m.p. 196 °C). Ϫ IR
2632
Eur. J. Org. Chem. 2001, 2629Ϫ2638

[4ϩ2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes
tallization (CH2Cl2/EtOAc), yielded 3j (1.53 g, 4.90 mmol, 49%) as 0.43 (dt, 2J ϭ 4.0, 3J ϭ 4.8 Hz, 1 H, 7-Hsyn), 2.27 (dt, 2J ϭ 4.0,
FULL PAPER
3
3
yellow crystals, m.p. 191 °C. Ϫ IR (KBr): ν ϭ 3060, 1580, 1510, 3J ϭ 9.1 Hz, 1 H, 7-Hanti), 3.39 (dd, J ϭ 4.8, J ϭ 9.1 Hz, 2 H, 1-
˜
1435, 1400, 1260, 1030, 810, 790, 720, 700, 670 cmϪ1. Ϫ H NMR H, 6-H), 7.56 (d, J ϭ 3.2 Hz, 2 H, Ar-H), 8.03 (d, J ϭ 3.2 Hz, 2
1
3
3
2
3
(250 MHz, CDCl3): δ ϭ 0.35 (dt, J ϭ 3.9, J ϭ 4.9 Hz, 1 H, 7-
H, Ar-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 8.3 (ϪCH2Ϫ, 1 C),
Hsyn), 2.22 (dt, J ϭ 3.9, J ϭ 9.1 Hz, 1 H, 7-Hanti), 2.69 (dd, 3J ϭ 19.6 (ϭCH, 2 C), 123.4 (ϭCH, 2 C), 144.6 (ϭCH, 2 C), 158.1
2
3
4.9, 3J ϭ 9.1 Hz, 2 H, 1-H, 6-H), 7.40Ϫ8.14 (m, 8 H, Ar-H). Ϫ
(quat. C, 2 C), 166.3 (quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ
UV/Vis (1,4-dioxane): λmax (ε) ϭ 317 (18200) nm. Ϫ C17H12Cl2N2 260 (91) [Mϩ]. Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 252 (4790), 294
(315.2): calcd. C 64.78, H 3.84, N 8.89; found C 64.87, H 4.09, (4970), 377 (17000) nm. Ϫ C11H8N4S2 (260.4): calcd. C 50.74, H
N 8.81.
3.10, N 21.52; found C 50.99, H 3.60, N 21.33.
2,5-Bis(p-chlorophenyl)-3,4-diazanorcaradiene (3k): This compound
was prepared according to General Procedure (1). Compounds 1k
2,5-Bis(2-methyl-1,3,4-oxadiazol-5-yl)-3,4-diazanorcaradiene (3q):
This compound was prepared according to General Procedure (1).
(3.00 g, 9.90 mmol) and 2a, after stirring in CH2Cl2 (80 mL) at 0 Compounds 1q[16] (198 mg, 0.804 mmol) and 2a, after stirring in n-
°C for 1.5 h, purification by FC (CH2Cl2/EtOAc ϭ 1:1) and recrys- hexane (15 mL) at room temp. for 12 h, purification by FC
tallization (CH2Cl2/n-hexane), yielded 3k (2.97 g, 9.42 mmol, 95%)
as yellow crystals, m.p. 256 °C. Ϫ IR (KBr): ν˜ ϭ 3060, 1590, 1535,
(CH2Cl2/EtOAc/ethanol ϭ 15:1:1) and recrystallization (CH2Cl2/n-
hexane), yielded 3q (156 mg, 0.603 mmol, 75%) as yellow crystals,
1490, 1425, 1400, 1090, 1080, 1045, 1010, 985, 830, 720, 655 cmϪ1
.
m.p. 219Ϫ221 °C. Ϫ IR (KBr): ν ϭ 3095, 3040, 2995, 1555, 1410,
˜
Ϫ
1H NMR (250 MHz, CDCl3,): δ ϭ 0.36 (dt, 2J ϭ 3.9, 3J ϭ 1340, 1245, 1105, 1055, 1040, 990, 755 cmϪ1. Ϫ 1H NMR
2
3
2
4.9 Hz, 1 H, 7-Hsyn), 2.19 (dt, J ϭ 3.9, J ϭ 9.0 Hz, 1 H, 7-Hanti),
(250 MHz, CDCl3): δ ϭ 0.40 (dt, J ϭ 4.7, 3J ϭ 4.8 Hz, 1 H, 7-
3
3
2
3
2.71 (dd, J ϭ 4.9, J ϭ 9.0 Hz, 2 H, 1-H, 6-H), 7.45Ϫ8.12 (m, 8 Hsyn), 2.40 (dt, J ϭ 4.7, J ϭ 9.1 Hz, 1 H, 7-Hanti), 2.70 (s, 6 H,
H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 320 (22900) nm. Ϫ Ar-CH3), 3.35 (dd, J ϭ 4.8, J ϭ 9.1 Hz, 2 H, 1-H, 6-H). Ϫ 13C
3
3
C17H12Cl2N2 (315.2): calcd. C 64.78, H 3.84, N 8.89; found C
64.67, H 3.63, N 8.89.
NMR (63 MHz, CDCl3): δ ϭ 8.2 (ϪCH2Ϫ, 1 C), 11.2 (ϪCH3, 2
C), 20.0 (ϭCH, 2 C), 151.4 (quat. C, 2 C), 162.6 (quat. C, 2 C),
166.2 (quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 258 (74) [Mϩ].
Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 263 (10400), 324 (19600) nm.
Ϫ C11H10N6O2 (258.4): calcd. N 32.54; found N 32.28.
2,5-Bis(p-trifluoromethylphenyl)-3,4-diazanorcaradiene (3l): This
compound was prepared according to General Procedure (1). Com-
pounds 1l (3.00 g, 8.10 mmol) and 2a, after stirring in CH2Cl2
(80 mL) at 0 °C for 1 h, purification by FC (CH2Cl2/n-hexane ϭ 2,5-Bis(2-pyridyl)-3,4-diazanorcaradiene (3r): This compound was
1:1) and recrystallization (CH2Cl2/EtOAc), yielded 3l (2.02 g, prepared according to General Procedure (1). Compounds 1r
5.03 mmol, 65%) as yellow crystals, m.p. 244 °C. Ϫ IR (KBr): ν ϭ (2.36 g, 10.0 mmol) and 2a, after stirring in CH2Cl2 (60 mL) at 0
3070, 2940, 1615, 1420, 1330, 1170, 1130, 1070, 1030, 860, 850, °C for 5 h, purification by FC (CH2Cl2/ethanol ϭ 15:1) and recrys-
710, 690 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.41 (dt, 2J ϭ tallization (CH2Cl2/n-hexane), yielded 3r (1.93 g, 7.77 mmol, 78%)
˜
3
2
3
˜
3.9, J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.28 (dt, J ϭ 3.9, J ϭ 9.0 Hz, 1 as yellow crystals, m.p. 165Ϫ168 °C. Ϫ IR (KBr): ν ϭ 3050, 3000,
H, 7-Hanti), 2.77 (dd, 3J ϭ 4.9, 3J ϭ 9.0 Hz, 2 H, 1-H, 6-H),
2920, 1580, 1560, 1535, 1500, 1455, 1425, 1380, 1100, 1035, 940,
7.76Ϫ8.29 (m, 8 H, Ar-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 890, 730, 670 cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.29 (dt,
7.5 (ϪCH2Ϫ, 1 C), 18.4 (ϭCH, 2 C), 123.9 (quat. C, 2 C), 125.4 2J ϭ 3.6, 3J ϭ 4.8 Hz, 1 H, 7-Hsyn), 2.32 (dt, 2J ϭ 3.6, 3J ϭ 9.2 Hz,
1
(ϭCH, 4 C), 128.0 (ϭCH, 4 C), 132.8 (quat. C, 2 C), 139.5 (quat.
1 H, 7-Hanti), 3.48 (dd, 3J ϭ 4.8, 3J ϭ 9.2 Hz, 2 H, 1-H, 6-H),
C, 2 C), 158.7 (quat. C, 2 C). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 315 7.38Ϫ7.43 (m, 2 H, Ar-H), 7.78Ϫ7.85 (m, 2 H, Ar-H), 8.50Ϫ8.54
(11500) nm. Ϫ C19H12F6N2 (382.3): calcd. C 59.69, H 3.16, N 7.33; (m, 2 H, Ar-H), 8.73Ϫ8.76 (m, 2 H, Ar-H). Ϫ UV/Vis (CH3CN):
found C 59.92, H 3.23, N 7.38.
λmax (ε) ϭ 240 (11600), 323 (24400) nm. Ϫ C15H12N4 (248.3): calcd.
C 72.56, H 4.87, N 22.56; found C 72.48, H 4.88, N 22.45.
2,5-Bis(2-thienyl)-3,4-diazanorcaradiene (3n): This compound was
prepared according to General Procedure (1). Compounds 1n 2,5-Bis(3-pyridyl)-3,4-diazanorcaradiene (3s): This compound was
(2.46 g, 10.0 mmol) and 2a, after stirring in CH2Cl2 (70 mL) at prepared according to General Procedure (1). Compounds 1s
room temp. for 24 h, purification by FC (CH2Cl2/EtOAc ϭ 1:1)
and recrystallization (CH2Cl2/n-hexane), yielded 3n (1.90 g,
7.36 mmol, 74%) as yellow crystals, m.p. 169Ϫ170 °C. Ϫ IR (KBr):
(2.36 g, 10.0 mmol) and 2a, after stirring in CH2Cl2 (70 mL) at
room temp. for 24 h, purification by FC (CH2Cl2/ethanol ϭ 7:1)
and recrystallization (CH2Cl2/n-hexane), yielded 3s (1.47 g,
5.92 mmol, 59%) as yellow crystals, m.p. 191Ϫ192 °C. Ϫ IR (KBr):
˜
ν ϭ 3090, 3060, 2850, 1530, 1485, 1430, 1380, 1250, 1225, 1060,
1045, 1020, 840, 815, 790, 690 cmϪ1. Ϫ 1H NMR (250 MHz, ν˜ ϭ 3060, 1595, 1580, 1510, 1480, 1440, 1410, 1205, 1075, 1050,
CDCl3): δ ϭ 0.41 (dt, 2J ϭ 4.1, 3J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.04 (dt, 820, 720 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.43 (dt, 2J ϭ
2J ϭ 4.1, 3J ϭ 9.0 Hz, 1 H, 7-Hanti), 2.74 (dd, 3J ϭ 4.9, 3J ϭ 9.0 Hz, 3.9, J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.31 (dt, J ϭ 3.9, J ϭ 9.0 Hz, 1
3
2
3
3
3
2 H, 1-H, 6-H), 7.13 (dd, J ϭ 3.7, J ϭ 5.1 Hz, 2 H, Ar-H), 7.48 H, 7-Hanti), 2.80 (dd, 3J ϭ 4.9, 3J ϭ 9.0 Hz, 2 H, 1-H, 6-H),
4
(dd, 3J ϭ 5.1, 4J ϭ 1.1 Hz, 2 H, Ar-H) 7.64 (dd, 3J ϭ 3.7, J ϭ
7.42Ϫ7.48 (m, 2 H, Ar-H), 8.46Ϫ8.51 (m, 2 H, Ar-H), 8.75Ϫ8.77
1.1 Hz, 2 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 273 (13800), (m, 2 H, Ar-H), 9.30Ϫ9.32 (m, 2 H, Ar-H). Ϫ UV/Vis (CH3CN):
365 (32700) nm. Ϫ C13H10N2S2 (258.3): calcd. C 60.44, H 3.90, N λmax (ε) ϭ240 (11600), 323 (24400) nm. Ϫ C15H12N4 (248.3): calcd.
10.84; found C 60.33, H 3.88, N 10.78.
C 72.56, H 4.87, N 22.56; found C 72.46, H 4.74, N 22.31.
2,5-Bis(2-thiazolyl)-3,4-diazanorcaradiene (3o): This compound was
prepared according to General Procedure (1). Compounds 1o
2,5-Bis(4-pyridyl)-3,4-diazanorcaradiene (3t): This compound was
prepared according to General Procedure (1). Compounds 1t
(154 mg, 10.0 mmol) and 2a, after stirring in n-hexane (25 mL) at (2.36 g, 10.0 mmol) and 2a, after stirring in CH2Cl2 (60 mL) at 0
room temp. for 12 h, purification by FC (CH2Cl2/ethanol ϭ 15:1) °C for 5 h, purification by FC (CH2Cl2/ethanol ϭ 10:1) and recrys-
and recrystallization (CH2Cl2/n-hexane), yielded 3o (133 mg, tallization (CH2Cl2/n-hexane), yielded 3t (1.54 g, 5.87 mmol, 71%)
˜
0.511 mmol, 81%) as yellow crystals, m.p. 171Ϫ173 °C. Ϫ IR
(KBr): ν˜ ϭ 3100, 3070, 3050, 2995, 1530, 1475, 1420, 1260, 1050,
as yellow crystals, m.p. 204Ϫ207 °C. Ϫ IR (KBr): ν ϭ 3110, 3080,
3030, 2980, 1585, 1550, 1525, 1490, 1410, 1390, 1050, 990, 825,
1115, 865, 760, 730 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 700, 675 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.38 (dt, 2J ϭ
Eur. J. Org. Chem. 2001, 2629Ϫ2638
2633

J. Sauer et al.
FULL PAPER
3
2
3
4.0, J ϭ 4.9 Hz, 1 H, 7-Hsyn), 2.30 (dt, J ϭ 4.0, J ϭ 9.0 Hz, 1 2.60 (s, 3 H, SCH3), 7.41Ϫ7.48 (m, 3 H, Ar-H), 8.03Ϫ8.07 (m, 2
H, 7-Hanti), 2.78 (dd, 3J ϭ 4.9, 3J ϭ 9.0 Hz, 2 H, 1-H, 6-H), H, Ar-H). Ϫ MS (HR): calcd: 216.0721, found 216.0726.
7.97Ϫ8.00 (m, 4 H, Ar-H), 8.79Ϫ8.81 (m, 4 H, Ar-H). Ϫ UV/Vis
2-Methoxy-5-phenyl-3,4-diazanorcaradiene (7z): This compound
was prepared according to General Procedure (1). Compounds 1z
(417 mg, 2.17 mmol) and 2a, after stirring in Et2O (15 mL) at room
temp. for 5 h, yielded 7z (233 mg, 1.16 mmol, 54%) as a colourless
(CH3CN): λmax (ε) ϭ 225 (12200), 305 (14400) nm. Ϫ C15H12N4
(248.3): calcd. C 72.56, H 4.87, N 22.56; found C 72.54, H 4.97,
N 22.39.
2,5-Bis(2-pyrazyl)-3,4-diazanorcaradiene (3u): This compound was
prepared according to General Procedure (1). Compounds 1u
(414 mg, 1.74 mmol) and 2a, after stirring in CH2Cl2 (25 mL) at
room temp. for 12 h and purification by FC (CH2Cl2/EtOAc ϭ
2:1), yielded 3u (342 mg, 1.37 mmol, 79%) as yellow crystals, m.p.
precipitate, m.p. 106Ϫ107 °C. Ϫ IR (KBr): ν˜ ϭ 3050, 3030, 3000,
2955, 1575, 1450, 1390, 1240, 1000, 770, 690 cmϪ1. Ϫ 1H NMR
(250 MHz, CDCl3): δ ϭ 0.41 (ddd, 3J ϭ 9.0, 3J ϭ 9.2, 2J ϭ 4.4 Hz,
3
3
2
1 H, 7-Hsyn), 1.79 (ddd, J ϭ 4.6, J ϭ 4.7, J ϭ 4.4 Hz, 1 H, 7-
3
3
3
Hanti), 2.20 (ddd, J ϭ 7.8, J ϭ 9.2, J ϭ 4.7 Hz, 1 H, 1-H), 2.63
(ddd, 3J ϭ 7.8, 3J ϭ 9.0, 3J ϭ 4.7 Hz, 1 H, 6-H), 3.98 (s, 3 H,
OCH3), 7.43Ϫ7.46 (m, 3 H, Ar-H), 7.99Ϫ8.03 (m, 2 H, Ar-H). Ϫ
MS (HR): calcd: 200.0950, found 200.0945.
˜
204Ϫ205 °C. Ϫ IR (KBr): ν ϭ 3070, 2990, 1460, 1410, 1370, 1165,
1105, 1055, 1030, 1005, 845, 780, 750 cmϪ1. Ϫ 1H NMR (250 MHz,
CDCl3): δ ϭ 0.27 (dt, 2J ϭ 3.6, 3J ϭ 4.7 Hz, 1 H, 7-Hsyn), 2.29 (dt,
2J ϭ 3.6, 3J ϭ 9.1 Hz, 1 H, 7-Hanti), 3.42 (dd, 3J ϭ 4.7, 3J ϭ 9.1 Hz,
2 H, 1-H, 6-H), 8.67Ϫ8.69 (m, 4 H, Ar-H), 9.62Ϫ9.64 (m, 2 H, Ar-
H). Ϫ MS (EI, 70 eV): m/z (%) ϭ 250 (100) [Mϩ]. Ϫ UV/Vis (1,4-
dioxane): λmax (ε) ϭ 261 (5440), 337 (19500) nm. Ϫ C13H10N6
(250.3): calcd. N 33.58; found N 33.31.
Synthesis of 7,7-Dimethyl-3,4-diazanorcaradienes 4d, 4e, 4g, 4i,
4k؊4u, 8v and 8w
7,7-Dimethyl-2,5-bis(trifluoromethyl)-3,4-diazanorcaradiene
(4d):
This compound was prepared according to General Procedure (2).
Compounds 1d (890 mg, 4.08 mmol) and 2b (830 mg, 12.2 mmol),
after stirring in CCl4 (2 mL) at room temp. until the red colour of
the tetrazine had disappeared and purification by bulb-tube distil-
lation (70 °C/0.01 Torr), yielded 4d (845 mg, 3.87 mmol, 95%) as
2,5-Bis(methylthio)-3,4-diazanorcaradiene (7v): This compound was
prepared according to General Procedure (1). Compounds 1v
(510 mg, 2.93 mmol) and 2a, after stirring in Et2O (15 mL) at room
temp. for 6 h, yielded 7v (321 mg, 1.70 mmol, 58%) as a colourless
precipitate, m.p. 125Ϫ127 °C. Ϫ IR (KBr): ν˜ ϭ 3100, 3015, 2960,
˜
yellow crystals. Ϫ IR (film): ν ϭ 3060, 2980, 2940, 2880, 1570,
1
1540, 1370, 1320, 1120, 1090, 1070 cmϪ1. Ϫ H NMR (250 MHz,
1425, 1400, 1380, 1325, 1285, 1200, 1140, 1080, 1060, 1040, 960,
750 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.69 (s, 3 H, 7-
CH3-syn), 1.53 (s, 3 H, 7-CH3-anti), 2.49 (s, 2 H, 1-H, 6-H). Ϫ
Because of the high moisture sensitivity, no correct elemental ana-
lysis for compound 4d could be obtained.
CDCl3): δ ϭ 0.42 (dt, 2J ϭ 4.5, 3J ϭ 8.9 Hz, 7-Hsyn), 1.73 (dt, 2J ϭ
3
3
3
4.5, J ϭ 4.7 Hz, 1 H, 7-Hanti), 2.21 (dd, J ϭ 8.9, J ϭ 4.7 Hz, 2
H, 1-H, 6-H), 2.53 (s, 6 H, SCH3). Ϫ MS (HR): calcd: 186.0285,
found 186.0281.
7,7-Dimethyl-2,5-diphenyl-3,4-diazanorcaradiene (4e): This com-
pound was prepared according to General Procedure (2). Com-
pounds 1e (1.98 g, 8.46 mmol) and 2b (3.50 g, 51.4 mmol), after
stirring in Et2O (20 mL) at room temp. for 4 weeks and purification
by recrystallization (Et2O/n-hexane), yielded 4e (2.21 g, 7.32 mmol,
86%) as yellow crystals, m.p. 153Ϫ154 °C, ref. m.p. 156Ϫ157 °C.[17]
2-Methoxy-5-methylthio-3,4-diazanorcaradiene (7w): This com-
pound was prepared according to General Procedure (1). Com-
pounds 1w (364 mg, 2.30 mmol) and 2a, after stirring in Et2O
(15 mL) at room temp. for 5 h, yielded 7w (317 mg, 1.86 mmol,
81%) as a colourless precipitate, m.p. 78Ϫ80 °C. Ϫ IR (KBr): ν˜ ϭ
3100, 3020, 3000, 2950, 2940, 1590, 1455, 1390, 1370, 1260, 1060,
995 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.44 (ddd, 1 H,
˜
Ϫ IR (KBr): ν ϭ 3060, 3020, 2930, 1535, 1500, 1440, 1390, 770,
1
720, 690 cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.63 (s, 3 H,
3
2
3
3
3J ϭ 9.0, J ϭ 9.1, J ϭ 4.5 Hz, 7-Hsyn), 1.60 (ddd, J ϭ 4.7, J ϭ
2
3
3
3
7-CH3-syn), 1.61 (s, 3 H, 7-CH3-anti), 2.45 (s, 2 H, 1-H, 6-H),
7.0Ϫ8.0 (m, 10 H, Ar-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 14.5
(quat. C, 1 C), 15.0 (ϪCH3, 1 C), 25.9 (ϪCH3, 1 C), 31.9 (ϭCH,
2 C), 127.7 (ϭCH, 4 C), 128.5 (ϭCH, 4 C), 130.8 (ϭCH, 2 C),
137.3 (quat. C, 2 C), 157.6 (ϭCH, 2 C). Ϫ UV/Vis (CH3CN): λmax
(ε) ϭ 269 (22000), 326 (14900) nm.
4.7, J ϭ 4.5 Hz, 1 H, 7-Hanti), 2.08 (ddd, J ϭ 7.7, J ϭ 9.1, J ϭ
4.7 Hz, 1 H, 1-H), 2.26 (ddd, 3J ϭ 7.7, J ϭ 9.0, J ϭ 4.7 Hz, 1 H,
6-H), 2.50 (s, 3 H, SCH3), 3.89 (s, 3 H, OCH3). Ϫ MS (HR): calcd:
170.0514, found 170.0511.
3
3
2,5-Dimethoxy-3,4-diazanorcaradiene (7x): This compound was
prepared according to General Procedure (1). Compounds 1x
(283 mg, 1.99 mmol) and 2a, after stirring in Et2O (15 mL) at room
temp. for 4.5 h, yielded 7x (270 mg, 1.75 mmol, 88%) as a colour-
7,7-Dimethyl-2,5-bis(p-tolyl)-3,4-diazanorcaradiene (4g): This com-
pound was prepared according to General Procedure (2). Com-
pounds 1g (2.00 g, 5.15 mmol) and 2b (2.00 g, 29.4 mmol), after
stirring in CH2Cl2 (20 mL) under reflux for 40 h and purification
by FC (CH2Cl2/EtOAc ϭ 1:1), yielded 4g (1.90 g, 6.20 mmol, 83%)
˜
less precipitate, m.p. 67Ϫ69 °C. Ϫ IR (KBr): ν ϭ 3120, 3083, 2995,
2555, 1620, 1590, 1460, 1390, 1250, 1050, 1015, 1000, 775 cmϪ1. Ϫ
2
3
1H NMR (250 MHz, CDCl3): δ ϭ 0.51 (dt, J ϭ 4.6, J ϭ 9.1 Hz,
1 H, 7-Hsyn), 1.49 (dt, 2J ϭ 4.6, 3J ϭ 4.6 Hz, 1 H, 7-Hanti), 2.14
(dd, J ϭ 9.1, J ϭ 4.6 Hz, 2 H, 1-H, 6-H), 3.86 (s, 6 H, OCH3).
Ϫ MS (HR): calcd: 154.0742, found 154.0745.
˜
as yellow crystals, m.p. 204Ϫ205 °C. Ϫ IR (KBr): ν ϭ 3050, 2950,
2890, 1625, 1545, 1400, 1190, 1125, 840, 780, 730 cmϪ1. Ϫ 1H
NMR (250 MHz, CDCl3): δ ϭ 0.68 (s, 3 H, 7-CH3-syn), 1.66 (s, 3
H, 7-CH3-anti), 2.42 (s, 6 H, Ar-CH3), 2.46 (s, 2 H, 1-H, 6-H),
7.26Ϫ7.96 (m, 8 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 260
(9100), 325 (14100) nm. Ϫ C21H22N2 (302.4): calcd. C 83.40, H
7.33, N 9.26; found C 83.15, H 7.13, N 9.27.
3
3
2-Methylthio-5-phenyl-3,4-diazanorcaradiene (7y): This compound
was prepared according to General Procedure (1). Compounds 1y
(320 mg, 1.57 mmol) and 2a, after stirring in Et2O (10 mL) at room
temp. for 4 h, yielded 7y (161 mg, 0.744 mmol, 47%) as a colourless
˜
precipitate, m.p. 138Ϫ141 °C. Ϫ IR (KBr): ν ϭ 3055, 3000, 2925,
2,5-Bis(p-methoxyphenyl)-7,7-dimethyl-3,4-diazanorcaradiene (4i):
1540, 1505, 1450, 1395, 1380, 1130, 1090, 1060, 780, 700 cmϪ1. Ϫ This compound was prepared according to General Procedure (2).
1H NMR (250 MHz, CDCl3): δ ϭ 0.39 (ddd, J ϭ 9.0, J ϭ 9.2,
Compounds 1i (3.00 g, 10.2 mmol) and 2b (2.00 g, 29.4 mmol),
3
3
2J ϭ 4.0 Hz, 1 H, 7-Hsyn), 1.95 (ddd, 3J ϭ 4.9, 3J ϭ 4.9, 2J ϭ after stirring in CH2Cl2 (80 mL) under reflux for 7 d, purification
3
3
3
4.0 Hz, 1 H, 7-Hanti), 2.35 (ddd, J ϭ 7.7, J ϭ 9.2, J ϭ 4.9 Hz, 1 by FC (CH2Cl2/EtOAc ϭ 1:1) and recrystallization (CH2Cl2/
H, 1-H), 2.56 (ddd, 3J ϭ 7.7, 3J ϭ 9.0, 3J ϭ 4.9 Hz, 1 H, 6-H), EtOAc), yielded 4i (630 mg, 1.90 mmol, 53%) as yellow crystals,
2634
Eur. J. Org. Chem. 2001, 2629Ϫ2638

[4ϩ2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes
FULL PAPER
m.p. 196 °C. Ϫ IR (KBr): ν˜ ϭ 3010, 2940, 2850, 1600, 1510, 1410, syn), 1.80 (s, 3 H, 7-CH3-anti), 2.55 (s, 2 H, 1-H, 6-H), 6.98Ϫ7.25
1390, 1300, 1250, 1170, 840, 800 cmϪ1. Ϫ 1H NMR (250 MHz,
(m, 2 H, Ar-H), 7.35Ϫ7.66 (m, 4 H, Ar-H). Ϫ UV/Vis (CH3CN):
CDCl3): δ ϭ 0.67 (s, 3 H, 7-CH3-syn), 1.67 (s, 3 H, 7-CH3-anti), λmax (ε) ϭ 277 (16000), 365 (30200) nm. Ϫ C15H14N2S2 (286.4):
2.45 (s, 2 H, 1-H, 6-H), 3.87 (s, 6 H, OCH3), 7.00Ϫ8.00 (m, 8 H, calcd. C 62.90, H 4.92, N 9.78; found C 62.95, H 4.85, N 9.80.
Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 268 (8320), 336 (23400)
7,7-Dimethyl-2,5-bis(2-thiazolyl)-3,4-diazanorcaradiene (4o): This
nm. Ϫ C21H22N2O2 (334.4): calcd. C 75.42, H 6.63, N 8.38; found
compound was prepared according to General Procedure (2). Com-
C 75.36, H 6.60, N 8.33.
pounds 1o (900 mg, 3.62 mmol) and 2b (820 mg, 12.0 mmol), after
2,5-Bis(p-chlorophenyl)-7,7-dimethyl-3,4-diazanorcaradiene
(4k): stirring in CH2Cl2 (70 mL) at room temp. for 1 h and purification
This compound was prepared according to General Procedure (2).
Compounds 1k (2.00 g, 4.76 mmol) and 2b (2.00 g, 29.4 mmol),
after stirring in CH2Cl2 (20 mL) under reflux for 7 d, purification
by FC (CH2Cl2/EtOAc ϭ 1:1) and recrystallization (CH2Cl2/
by recrystallization (CH2Cl2/n-hexane), yielded 4o (620 mg,
2.15 mmol, 59%) as yellow crystals, m.p. 136Ϫ137 °C. Ϫ IR (KBr):
˜
ν ϭ 3130, 3100, 2970, 2940, 2870, 1540, 1480, 1425, 1285, 1195,
1105, 1065, 1030, 970, 880, 790, 760, 745 cmϪ1. Ϫ 1H NMR
EtOAc), yielded 4k (1.35 g, 5.10 mmol, 75%) as yellow crystals, (250 MHz, CDCl3): δ ϭ 0.80 (s, 3 H, 7-CH3-syn), 1.76 (s, 3 H, 7-
3
˜
m.p. 238 °C. Ϫ IR (KBr): ν ϭ 3080, 2960, 2930, 1590, 1570, 1390,
CH3-anti), 3.28 (s, 2 H, 1-H, 6-H), 7.60 (d, J ϭ 3.2 Hz, 2 H, Ar-
1090, 1010, 860, 840, 740, 610 cmϪ1. Ϫ 1H NMR (250 MHz, H), 8.08 (d, 3J ϭ 3.2 Hz, 2 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax
CDCl3): δ ϭ 0.70 (s, 3 H, 7-CH3-syn), 1.68 (s, 3 H, 7-CH3-anti), (ε) ϭ 240 (5930), 289 (6910), 376 (16900) nm. Ϫ C13H12N4S2
2.43 (s, 2 H, 1-H, 6-H), 7.10Ϫ8.00 (m, 8 H, Ar-H). Ϫ UV/Vis (288.4): calcd. C 54.14, H 4.19, N 19.43; found C 53.75, H 4.18,
(CH3CN): λmax (ε) ϭ 260 (7760), 325 (20900) nm. Ϫ C19H16Cl2N2 N 19.19.
(343.3): calcd. C 66.48, H 4.70, N 8.16; found C 66.70, H 4.74,
N 8.16.
2,5-Bis(2-furanyl)-7,7-dimethyl-3,4-diazanorcaradiene (4p): This
compound was prepared according to General Procedure (2). Com-
7,7-Dimethyl-2,5-bis(p-trifluoromethylphenyl)-3,4-diazanorcaradiene pounds 1p (436 mg, 2.04 mmol) and 2b (580 mg, 8.52 mmol), after
(4l): This compound was prepared according to General Procedure
(2). Compounds 1l (2.00 g, 5.40 mmol) and 2b (760 mg, room temp. and purification by FC (EtOAc), yielded 4p (416 mg,
11.2 mmol), after stirring in CH2Cl2 (20 mL) under reflux for 20 h 1.64 mmol, 80%) as yellow crystals, m.p. 159Ϫ160 °C. Ϫ IR (KBr):
and purification by recrystallization (CH2Cl2/PE), yielded 4l ν ϭ 3135, 3035, 2960, 2940, 2880, 1580, 1525, 1480, 1470, 1410,
stirring in CH2Cl2 (8 mL) under reflux for 11 h followed by 51 h at
˜
1
(1.98 g, 4.80 mmol, 89%) as yellow crystals, m.p. 234Ϫ235 °C. Ϫ
1230, 1160, 1060, 1020, 965, 910, 890, 770, 750 cmϪ1. Ϫ H NMR
˜
IR (KBr): ν ϭ 3050, 2950, 1625, 1550, 1420, 1330, 1185, 1130, (250 MHz, CDCl3): δ ϭ 0.70 (s, 3 H, 7-CH3-syn), 1.56 (s, 3 H, 7-
1
1075, 860, 710 cmϪ1. Ϫ H NMR (60 MHz, CDCl3): δ ϭ 0.79 (s, CH3-anti), 2.58 (s, 2 H, 1-H, 6-H), 6.56 (dd, 3J ϭ 3.5, 3J ϭ 1.8 Hz,
3 H, 7-CH3-syn), 1.80 (s, 3 H, 7-CH3-anti), 2.61 (s, 2 H, 1-H, 6-H), 2 H, Ar-H), 7.14 (dd, 3J ϭ 3.5, J ϭ 0.8 Hz, 2 H, Ar-H), 7.61 (dd,
4
7.76Ϫ8.31 (m, 8 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 254 2 H, 3J ϭ 1.8, 4J ϭ 0.8 Hz, Ar-H). Ϫ 13C NMR (63 MHz, CDCl3):
(18100), 322 (15200) nm. Ϫ C21H16F6N2 (410.4): calcd. C 61.47, H δ ϭ 14.9 (ϪCH3, 1 C), 15.3 (quat. C, 1 C), 26.0 (ϪCH3, 1C), 31.0
3.93, N 6.83; found C 61.52, H 3.98, N 6.82.
(ϭCH, 2 C), 112.3 (ϭCH, 2 C), 112.4 (ϭCH, 2 C), 145.2 (quat. C,
2 C), 149.4 (quat. C, 2 C), 152.6 (quat. C, 2 C). Ϫ MS (EI, 70 eV):
m/z (%) ϭ 254 (100) [Mϩ]. Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 291
(4300), 360 (22400) nm. Ϫ C15H14N2O2 (254.3): calcd. C 70.87, H
5.55, N 11.02; found C 70.87, H 5.63, N 11.06.
7,7-Dimethyl-2,5-bis(1-methyl-1H-pyrrol-2-yl)-3,4-diaza-
norcaradiene (4m): This compound was prepared according to Gen-
eral Procedure (2). Compounds 1m (500 mg, 2.08 mmol) and 2b
(845 mg, 12.4 mmol), after stirring in CHCl3 (10 mL) under reflux
for 20 h and another 114 h at room temp., purification by FC 7,7-Dimethyl-2,5-bis(2-methyl-1,3,4-oxadiazol-5-yl)-3,4-diaza-
(CH2Cl2/EtOAc ϭ 1:2) and recrystallization (EtOAc/PE ), yielded norcaradiene (4q): This compound was prepared according to Gen-
4m (430 mg, 1.53 mmol, 74%) as yellow crystals, m.p. 133Ϫ134 °C. eral Procedure (2). Compounds 1q (126 mg, 0.512 mmol) and 2b
Ϫ IR (KBr): ν˜ ϭ 3120, 3020, 2970, 1550, 1450, 1430, 1315, 1245, (109 mg, 1.60 mmol), after stirring in CH2Cl2 (10 mL) at room
1
1090, 1065, 1030, 1010, 990, 960, 735, 725, 720 cmϪ1. Ϫ H NMR temp. for 1 h, purification by FC (CH2Cl2/ethanol ϭ 20:1) and
(250 MHz, CDCl3): δ ϭ 0.65 (s, 3 H, 7-CH3-syn), 1.51 (s, 3 H, 7-
recrystallization (CH2Cl2/n-hexane), yielded 4q (142 mg,
CH3-anti), 2.35 (s, 2 H, 1-H, 6-H), 4.09 (s, 6 H, NCH3), 6.21 (dd, 0.496 mmol, 97%) as yellow crystals, m.p. 195Ϫ197 °C. Ϫ IR
3J ϭ 3.9, 3J ϭ 2.6 Hz, 2 H, Ar-H), 6.67 (dd, 3J ϭ 3.9, 4J ϭ 1.8 Hz,
(KBr): ν ϭ 3015, 2940, 2920, 1550, 1345, 1240, 1185, 1025, 975
˜
4
3
1
2 H, Ar-H), 6.78 (dd, J ϭ 1.8, J ϭ 2.6 Hz, 2 H, Ar-H). Ϫ 13C
cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.72 (s, 3 H, 7-CH3-
NMR (63 MHz, CDCl3): δ ϭ 14.7 (ϪCH3, 1 C), 15.2 (quat. C, 1 syn), 1.65 (s, 3 H, 7-CH3-anti), 2.70 (s, 6 H, Ar-CH3), 3.17 (s, 2 H,
C), 25.9 (ϪCH3, 1 C), 30.2 (ϭCH, 2 C), 38.2 (ϪCH3, 2 C), 108.1 1-H, 6-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 11.3 (ϪCH3, 2 C),
(ϭCH, 2 C), 115.9 (ϭCH, 2 C), 128.7 (ϭCH, 2 C), 130.7 (quat. C, 14.9 (ϪCH3, 1 C), 16.1 (quat. C, 1 C), 25.4 (ϪCH3, 1 C), 33.5 (ϭ
2 C), 149.4 (quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 280 (100) CH, 2 C), 149.5 (quat. C, 2 C), 163.0 (quat. C, 2 C), 166.1 (quat.
[Mϩ]. Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 298 (3270), 366 (30300) C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 286 (3) [Mϩ]. Ϫ UV/Vis
nm. Ϫ C17H20N4 (280.4): calcd. C 72.82, H 7.19, N 19.98; found
C 72.81, H 7.25, N 19.73.
(1,4-dioxane): λmax (ε) ϭ 275 (13100), 329 (11600) nm. Ϫ
C13H14N6O2 (286.3): calcd. C 54.54, H 4.93, N 29.35; found C
54.32, H 5.20, N 29.21.
7,7-Dimethyl-2,5-bis(2-thienyl)-3,4-diazanorcaradiene (4n): This
compound was prepared according to General Procedure (2). Com-
7,7-Dimethyl-2,5-bis(2-pyridyl)-3,4-diazanorcaradiene (4r): This
pounds 1n (1.89 g, 7.67 mmol) and 2b (1.07 g, 15.7 mmol), after compound was prepared according to General Procedure (2). Com-
stirring in CH2Cl2 (50 mL) at room temp. for 24 h, purification by pounds 1r (1.89 g, 8.00 mmol) and 2b (1.64 g, 24.1 mmol), after
FC (CH2Cl2/ethanol ϭ 7:1) and recrystallization (CH2Cl2/n-hex-
stirring in CH2Cl2 (70 mL) at 0 °C for 3 h and purification by
ane), yielded 4n (1.47 g, 5.13 mmol, 67%) as yellow crystals, m.p.
recrystallization (CH2Cl2/n-hexane), yielded 4r (1.97 g, 7.13 mmol,
˜
˜
170Ϫ172 °C. Ϫ IR (KBr): ν ϭ 3100, 3080, 3030, 2980, 2950, 2870, 89%) as yellow crystals, m.p. 162Ϫ164 °C. Ϫ IR (KBr): ν ϭ 3050,
1530, 1510, 1430, 1380, 1250, 1235, 1075, 1050, 845, 830, 765, 700 3000, 2960, 2930, 2870, 1580, 1560, 1540, 1495, 1455, 1425, 1375,
1
1
cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.72 (s, 3 H, 7-CH3-
1140, 1090, 990, 775, 740 cmϪ1. Ϫ H NMR (250 MHz, CDCl3):
Eur. J. Org. Chem. 2001, 2629Ϫ2638
2635

J. Sauer et al.
FULL PAPER
δ ϭ 0.67 (s, 3 H, 7-CH3-syn), 1.68 (s, 3 H, 7-CH3-anti), 3.33 (s, 2 pounds 1w (309 mg, 2.17 mmol) and 2b (500 mg, 7.34 mmol), after
H, 1-H, 6-H), 7.34Ϫ7.40 (m, 2 H, Ar-H), 7.75Ϫ7.82 (m, 2 H, Ar- stirring in Et2O (20 mL) at room temperature for 6 weeks, yielded
H), 8.49Ϫ8.54 (m, 2 H, Ar-H), 8.70Ϫ8.73 (m, 2 H, Ar-H). Ϫ UV/ 8w (260 mg, 1.42 mmol, 66%) as a colourless precipitate, m.p.
Vis (CH3CN): λmax (ε) ϭ 269 (22200), 326 (14900) nm. Ϫ 55.5Ϫ56.5 °C. Ϫ IR (KBr): ν˜ ϭ 2960, 1600, 1575, 1450, 1370, 1230,
C17H17N4 (276.3): calcd. C 73.89, H 5.84, N 20.27; found C 74.03, 1010, 965, 770 cmϪ1. Ϫ 1H NMR (250 MHz, nitrobenzene-d5): δ ϭ
H 5.67, N 20.12.
0.67 (s, 3 H, 7-CH3-syn), 1.20 (s, 3 H, 7-CH3-anti) 1.90 (s, 2 H, 1-H,
6-H), 3.78 (s, 6 H, OCH3). Ϫ C9H14N2O2 (182.2): calcd. C 59.33, H
7.74, N 15.46; found C 59.02, H 7.79, N 15.49.
7,7-Dimethyl-2,5-bis(3-pyridyl)-3,4-diazanorcaradiene (4s): This
compound was prepared according to General Procedure (2). Com-
pounds 1s (1.86 g, 7.87 mmol) and 2b (1.32 g, 19.4 mmol), after
stirring in CH2Cl2 (50 mL) at room temp. for 24 h, purification by
FC (CH2Cl2/ethanol ϭ 5:1) and recrystallization (CH2Cl2/n-hex-
ane), yielded 4s (1.43 g, 5.18 mmol, 66%) as yellow crystals, m.p.
159Ϫ160 °C. Ϫ IR (KBr): ν˜ ϭ 3060, 3020, 2970, 2950, 2920, 2870,
1590, 1565, 1530, 1495, 1400, 1385, 1180, 1000, 955, 815, 720, 690
Synthesis of the Tetracyclic Azo Compounds 5b؊5d, 5o, 5q and
5r؊5t
exo,exo-9,10-Diazatetracyclo[3.3.2.02·4.06·8]dec-9-ene-1,5-di-
carboxylic Acid (5b): Hydrolysis of the ester 5a (5.00 g, 20.0 mmol)
with KOH (3.90 g, 70.0 mmol) in aqueous methanol (60 mL, H2O/
methanol ϭ 1:2) and subsequent acidification with conc. HCl
yielded, after recrystallization (EtOAc), 5b (3.42 g, 15.4 mmol,
1
cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.74 (s, 3 H, 7-CH3-
syn), 1.72 (s, 3 H, 7-CH3-anti), 2.58 (s, 2 H, 1-H, 6-H), 7.42Ϫ7.47
(m, 2 H, Ar-H), 8.41Ϫ8.46 (m, 2 H, Ar-H), 8.74Ϫ8.77 (m, 2 H,
Ar-H), 9.17Ϫ9.18 (m, 2 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ
247 (12800), 320 (13500) nm. Ϫ C17H16N4 (276.3): calcd. C 73.89,
H 5.84, N 20.27 found C 74.09, H 5.64, N 20.20.
˜
78%) as colourless crystals, m.p. 218Ϫ219 °C. Ϫ IR (KBr): ν ϭ
1
3600Ϫ2500, 1735 cmϪ1. Ϫ H NMR (80 MHz, CD3OD): δ ϭ 0.00
2
3
2
3
(dt, J ϭ 7.2, J ϭ 3.6 Hz, 2 H, 3,7-Hsyn), 0.55 (dt, J ϭ 7.2, J ϭ
3
3
7.6 Hz, 2 H, 3,7-Hanti), 2.00 (dd, J ϭ 3.6, J ϭ 7.6 Hz, 4 H, 2-H,
4-H, 6-H, 8-H), 5.05 (s, 2 H, COOH). Ϫ MS (EI, 70 eV): m/z (%) ϭ
193 (35) [Mϩ Ϫ N2H]. Ϫ UV/Vis (methanol): λmax (ε) ϭ 370 (62)
nm. Ϫ C10H10N2S4 (222.2): calcd. C 54.05, H 4.54, N 12.60; found
C 53.99, H 4.48, N 12.57.
7,7-Dimethyl-2,5-bis(4-pyridyl)-3,4-diazanorcaradiene (4t): This
compound was prepared according to General Procedure (2). Com-
pounds 1t (1.89 g, 8.00 mmol) and 2b (1.54 g, 22.6 mmol), after
stirring in CH2Cl2 (70 mL) at 0 °C for 24 h, purification by FC
(CH2Cl2/ethanol ϭ 7:1) and recrystallization (CH2Cl2/n-hexane),
yielded 4t (1.60 g, 5.79 mmol, 72%) as yellow crystals, m.p.
exo,exo-9,10-Diazatetracyclo[3.3.2.02·4.06·8]dec-9-ene-1,5-di-
carbonitrile (5c): Acid 5b (0.46 g, 2.10 mmol) and SOCl2 (4.95 g,
41.2 mmol) were stirred at room temp. for 3 h. After removal of
excess SOCl2, addition of conc. ammonia (20 mL) in acetone
(6 mL) then gave the amide (0.20 g, 0.91 mmol, 41%) as colourless
crystals. A suspension of the latter and freshly distilled POCl3
(8.60 g, 5.00 mL, 5.50 mmol) in 1,2-dichloroethylene (50 mL) was
heated under reflux for 22 h. After concentration to dryness, the
crude material was purified by recrystallization (methanol), af-
fording 5c (1.37 g, 7.43 mmol, 55%) as colourless crystals, m.p.168
°C. Ϫ IR (KBr): ν˜ ϭ 3100Ϫ3000, 2240 cmϪ1. Ϫ 1H NMR
(80 MHz, CDCl3): δ ϭ 0.37 (m, 2 H, 3,7-Hsyn), 0.85 (m, 2 H, 3,7-
Hanti), 2.07 (m, 4 H, 2-H, 4-H, 6-H, 8-H). Ϫ MS (EI, 70 eV): m/z
(%) ϭ 155 (69) [Mϩ Ϫ N2H]. Ϫ UV/Vis (methanol): λmax (ε) ϭ
368 (83) nm. Ϫ C10H8N4 (184.2): calcd. C 65.20, H 4.38, N 30.42;
found C 64.98, H 4.04, N 30.28.
˜
202Ϫ205 °C. Ϫ IR (KBr): ν ϭ 3010, 2930, 2900, 2850, 1580, 1520,
1480, 1400, 1380, 1110, 1050, 980, 820, 780, 690 cmϪ1. Ϫ 1H NMR
(250 MHz, CDCl3): δ ϭ 0.71 (s, 3 H, 7-CH3-syn), 1.71 (s, 3 H, 7-
CH3-anti), 2.57 (s, 2 H, 1-H, 6-H), 7.72Ϫ8.03 (m, 4 H, Ar-H),
8.66Ϫ8.92 (m, 4 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 241
(22200), 320 (14900) nm. Ϫ C17H14N4 (276.3): calcd. C 73.89, H
5.84, N 20.27; found C 73.78, H 5.85, N 20.25.
7,7-Dimethyl-2,5-bis(2-pyrazinyl)-3,4-diazanorcaradiene (4u): This
compound was prepared according to General Procedure (2). Com-
pounds 1u (477 mg, 2.00 mmol) and 2b (544 mg, 8.00 mmol), after
stirring in CH2Cl2 (15 mL) at room temp. for 12 min and purifica-
tion by recrystallization (CH2Cl2/n-hexane), yielded 4u (537 mg,
1.93 mmol, 97%) as yellow crystals, m.p. 173Ϫ175 °C. Ϫ IR (KBr):
ν˜ ϭ 3035, 2975, 2955, 2850, 1540, 1505, 1450, 1415, 1360, 1160,
1145, 1070, 1045, 1005, 840, 790, 750 cmϪ1. Ϫ 1H NMR (250 MHz,
CDCl3): δ ϭ 0.68 (s, 3 H, 7-CH3-syn), 1.68 (s, 3 H, 7-CH3-anti),
3.26 (s, 2 H, 1-H, 6-H), 8.67 (m, 4 H, Ar-H), 9.72 (m, 2 H, Ar-H).
exo,exo-1,5-Bis(trifluoromethyl)-9,10-diazatetracyclo-
[3.3.2.02·4.06·8]dec-9-ene (5d): This compound was prepared accord-
ing to General Procedure (1). Compounds 1d (1.35 g, 6.19 mmol)
and 2a, after stirring in CCl4 (5 mL) at room temp. for 3 h, purifica-
tion by recrystallization (cyclohexane) and bulb-tube distillation
(75 °C/0.01 Torr), yielded 5d (780 mg, 2.89 mmol, 47%) as colour-
Ϫ
13C NMR: (63 MHz, CDCl3): δ ϭ 15.0 (ϪCH3, 1 C), 15.5 (quat.
C, 1 C), 25.9 (ϪCH3, 1 C), 33.5 (ϭCH, 2 C), 143.5 (ϭCH, 2 C),
144.1 (ϭCH, 2 C), 145.4 (ϭCH, 2 C), 149.9 (quat. C, 2 C), 159.4
(quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 278 (4) [Mϩ]. Ϫ
UV/Vis (1,4-dioxane): λmax (ε) ϭ 290 (11300), 345 (15000) nm. Ϫ
C15H14N6 (278.3): calcd. N 30.20; found N 29.90.
˜
less crystals, m.p. 120Ϫ122 °C. Ϫ IR (KBr): ν ϭ 3040, 1450, 1360,
1305, 1200, 1160, 1140, 1090, 1070, 1040, 1010, 980, 930, 920, 780
1
2
3
cmϪ1. Ϫ H NMR (80 MHz, CDCl3): δ ϭ 0.10 (dt, J ϭ 7.2, J ϭ
3.6 Hz, 2 H, 3,7-Hsyn), 0.60 (dt, 2J ϭ 7.2, 3J ϭ 7.7 Hz, 2 H, 3,7-
Hanti), 1.80 (dd, J ϭ 3.6, J ϭ 7.7 Hz, 4 H, 2-H, 4-H, 6-H, 8-H).
Ϫ UV/Vis (CCl4): λmax (ε) ϭ 366 (89) nm. Ϫ C10H8F6N2 (270.2):
calcd. C 44.46, H 2.96, N 10.37; found C 44.40, H 3.09, N 10.32.
7,7-Dimethyl-2,5-bis(methylthio)-3,4-diazanorcaradiene (8v): This
compound was prepared according to General Procedure (2). Com-
pounds 1v (830 mg, 4.76 mmol) and 2b (1.00 g, 14.7 mmol), after
stirring in Et2O (20 mL) at room temperature for 6 weeks and
washing with n-pentane, yielded 8v (570 mg, 2.65 mmol, 56%) as
colourless crystals, m.p. 86.5Ϫ87.5 °C. Ϫ IR (KBr): ν˜ ϭ 3100,
3
3
ex o, ex o - 1 , 5 - B i s ( 2 - t h i a z o l y l ) - 9 , 1 0 - d i a z a t e t ra c yc l o -
[3.3.2.02·4.06·8]dec-9-ene (5o): This compound was prepared accord-
ing to General Procedure (1). Compounds 1o (221 mg, 0.890 mmol)
and 2a, after stirring in CH2Cl2 (20 mL) at room temp. for 12 h,
purification by FC (CH2Cl2/ethanol ϭ 15:1) and washing with dry
Et2O, yielded 5o (92 mg, 0.308 mmol, 35%) as yellow crystals, m.p.
3015, 2960, 1540, 1370, 1320, 1120, 1090, 1070 cmϪ1. Ϫ H NMR
1
(250 MHz, CDCl3): δ ϭ 0.67 (s, 3 H, 7-CH3-syn), 1.27 (s, 3 H, 7-
CH3-anti), 1.94 (s, 2 H, 1-H, 6-H), 2.44 (s, 6 H, SCH3). Ϫ
C9H14N2S2 (214.3): calcd. C 50.44, H 6.58, N 13.14; found C 50.20,
H 6.66, N 13.07.
˜
163Ϫ164 °C. Ϫ IR (KBr): ν ϭ 3110, 3070, 3040, 3020, 2995, 1490,
1
2,5-Dimethoxy-7,7-dimethyl-3,4-diazanorcaradiene (8w): This com-
pound was prepared according to General Procedure (2). Com-
1435, 1285, 1220, 1160, 1150, 990, 915, 855, 730, 710 cmϪ1. Ϫ H
2
3
NMR (250 MHz, CDCl3): δ ϭ 0.27 (dt, J ϭ 7.0, J ϭ 3.6 Hz, 2
2636
Eur. J. Org. Chem. 2001, 2629Ϫ2638

[4ϩ2] Cycloadditions of 1,2,4,5-Tetrazines and Cyclopropenes
FULL PAPER
2
3
H, 3,7-Hsyn), 0.55 (dt, J ϭ 7.0, J ϭ 7.7 Hz, 2 H, 3,7-Hanti), 2.29 cedure (3). Compounds 3t (1.00 g, 4.03 mmol) and 2a, after stirring
(dd, 3J ϭ 3.6, 3J ϭ 7.7 Hz, 4 H, 2-H, 4-H, 6-H, 8-H), 7.48 (d, 3J ϭ
in CH2Cl2 (25 mL) at room temp. for 24 h, purification by FC
3.3 Hz, 2 H, Ar-H), 7.95 (d, 3J ϭ 3.3 Hz, 2 H, Ar-H). Ϫ 13C NMR (CH2Cl2/ethanol ϭ 10:1) and recrystallization (CH2Cl2/n-hexane),
(63 MHz, CDCl3): δ ϭ 6.0 (ϪCH2Ϫ, 2 C), 19.2 (ϭCH, 4 C), 74.2 yielded 5t (1.90 g, 7.36 mmol, 74%) as a colourless solid, m.p.
˜
(quat. C, 2 C), 120.1 (ϭCH, 2 C), 143.2 (ϭCH, 2 C), 171.6 (quat. 160Ϫ162 °C. Ϫ IR (KBr): ν ϭ 3080, 3040, 2920, 1585, 1550, 1520,
C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 271 (97) [Mϩ Ϫ N2H].
Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 252 (11400), 387 (43) nm. Ϫ
1485, 1410, 1400, 1380, 1310, 1265, 1055, 1035, 990, 805, 770, 670,
620 cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.43 (dt, J ϭ 6.6,
1
2
C14H12N4S2 (300.4): calcd. C 55.98, H 4.03, N 18.65; found C 3J ϭ 3.7 Hz, 2 H, 3,7-Hsyn), 0.83 (dt, J ϭ 6.6, J ϭ 7.7 Hz, 2 H,
2
3
3
3
55.68, H 4.23, N 18.39.
3,7-Hanti), 1.93 (dd, J ϭ 3.6, J ϭ 7.7 Hz, 4 H, 2-H, 4-H, 6-H, 8-
H), 7.79Ϫ7.82 (m, 4 H, Ar-H), 8.80Ϫ8.83 (m, 4 H, Ar-H). Ϫ UV/
Vis (CH3CN): λmax (ε) ϭ 250 (6890), 405 (73) nm. Ϫ C18H16N4
(288.4): calcd. C 74.98, H 5.59, N 19.42; found C 74.24, H 5.54,
N 18.90.
exo,exo-1,5-Bis(2-methyl-1,3,4-oxadiazol-5-yl)-9,10-diaza-
tetracyclo[3.3.2.02·4.06·8]dec-9-ene (5q): This compound was pre-
pared according to General Procedure (1). Compounds 1q (165 mg,
0.670 mmol) and 2a, after stirring in CH2Cl2 (20 mL) at room
temp. for 1 h, purification by FC (CH2Cl2/EtOAc ϭ 1:1) and
recrystallization (CH2Cl2/n-hexane), yielded 5q (180 mg,
0.603 mmol, 90%) as a colourless solid, m.p. 183 °C. Ϫ IR (KBr):
Synthesis of Tetramethyl-Substituted Tetracyclic Azo Compounds
6a؊6e, 6o, 6q and 6r
Dimethyl
exo,exo-3,3,7,7-Tetramethyl-9,10-diazatetracyclo-
˜
ν ϭ 2995, 1580, 1560, 1380, 1235, 1090, 1070, 1020, 935, 790, 675
[3.3.2.02·4.06·8]dec-9-ene-1,5-dicarboxylate (6a): This compound
was prepared according to General Procedure (2). Compounds 1a
(2.80 g, 14.1 mmol) and 2b (3.81 g, 55.9 mmol), after stirring in
CH3CN (30 mL) at room temp. for 96 h, purification by FC
(CH2Cl2) and recrystallization (methanol), yielded 6a (2.73 g,
cmϪ1. Ϫ 1H NMR (250 MHz, CD2Cl2): δ ϭ 0.33 (dt, 2J ϭ 7.0,
2
3
3J ϭ 3.6 Hz, 2 H, 3,7-Hsyn), 0.79 (dt, J ϭ 7.0, J ϭ 7.7 Hz, 2 H,
3
3
3,7-Hanti), 2.12 (dd, J ϭ 3.6, J ϭ 7.7 Hz, 4 H, 2-H, 4-H, 6-H, 8-
H), 2.63 (s, 6 H, Ar-CH3). Ϫ 13C NMR (63 MHz, CD2Cl2): δ ϭ
6.8 (ϪCH2Ϫ, 2 C), 11.3 (ϪCH3, 2 C), 15.9 (ϭCH, 4 C), 69.1 (quat.
C, 2 C), 165.7 (quat. C, 2 C), 166.7 (quat. C, 2 C). Ϫ MS (EI,
70 eV): m/z (%) ϭ 269 (100) [Mϩ Ϫ N2H]. Ϫ UV/Vis (1,4-dioxane):
λmax (ε) ϭ 383 (30) nm. Ϫ C14H14N6O2 (298.4): calcd. C 56.35, H
4.73, N 28.16; found C 56.15, H 5.10, N 27.71.
8.91 mmol, 63%) as colourless crystals, m.p. 149Ϫ150 °C. Ϫ IR
(KBr): ν ϭ 3020, 2840, 1740, 1720 cmϪ1. Ϫ H NMR (250 MHz,
1
˜
CD2Cl2): δ ϭ 0.92 (s, 6 H, 3,7-CH3-syn), 1.01 (s, 6 H, 3,7-CH3-
anti), 1.78 (s, 4 H, 2-H, 4-H, 6-H, 8-H), 4.01 (s, 6 H, OCH3). Ϫ
MS (EI, 70 eV): m/z (%) ϭ 263 (42) [Mϩ Ϫ N2 Ϫ CH3]. Ϫ UV/Vis
(methanol): λmax (ε) ϭ 372 (134) nm. Ϫ C16H22N2O4 (306.2): calcd.
C 62.72, H 7.24, N 9.14; found C 62.94, H 7.19, N 9.30.
exo,exo-1,5-Bis(2-pyridyl)-9,10-diazatetracyclo[3.3.2.02·4.06·8]dec-
9-ene (5r): This compound was prepared according to General Pro-
cedure (3). Compounds 3r (838 mg, 3.37 mmol) and 2a, after stir-
ring in CH2Cl2 (25 mL) at room temp. for 24 h, purification by FC
(CH2Cl2/EtOAc/n-hexane ϭ 1:5:1) and recrystallization (CH2Cl2/
n-hexane), yielded 5r (576 mg, 2.00 mmol, 59%) as a colourless
exo,exo-3,3,7,7-Tetramethyl-9,10-diazatetracyclo[3.3.2.02·4.06·8]-
dec-9-ene-1,5-dicarboxylic Acid (6b): Hydrolysis of ester 6a (5.10 g,
16.7 mmol) with KOH (3.90 g, 70.0 mmol) in aqueous methanol
(90 mL, H2O/methanol ϭ 1: 2) and subsequent acidification with
conc. HCl (water/ice bath) gave 6b (4.50 g, 16.2 mmol, 97%) as col-
ourless crystals, m.p. 273Ϫ275 °C. Ϫ IR (KBr): ν˜ ϭ 1715 cmϪ1. Ϫ
1H NMR (80 MHz, CD3OD): δ ϭ 0.93 (s, 6 H, 3,7-CH3-syn), 0.97
(s, 6 H, 3,7-CH3-anti), 1.88 (s, 4 H, 2-H, 4-H, 6-H, 8-H), 5.02 (s,
broad, 2 H, COOH). Ϫ MS (EI, 70 eV): m/z ϭ 278 [Mϩ]. Ϫ UV/
Vis (methanol): λmax (ε) ϭ 373 (130) nm. Ϫ C14H18N2O4 (278.3):
calcd. C 60.41, H 6.53, N 10.07; found C 60.38, H 6.52, N 10.10.
˜
solid, m.p. 168Ϫ170 °C. Ϫ IR (KBr): ν ϭ 3070, 3020, 2940, 1595,
1575, 1475, 1440, 1325, 1155, 1100, 1075, 1050, 1040, 825, 795,
780, 760, 705, 625 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 0.21
2
3
2
3
(dt, J ϭ 6.4, J ϭ 3.6 Hz, 2 H, 3,7-Hsyn), 0.54 (dt, J ϭ 6.4, J ϭ
3
3
7.7 Hz, 2 H, 3,7-Hanti), 2.22 (dd, J ϭ 3.6, J ϭ 7.7 Hz, 4 H, 2-H,
4-H, 6-H, 8-H), 7.29Ϫ7.35 (m, 2 H, Ar-H), 7.80Ϫ7.87 (m, 2 H, Ar-
H), 8.12Ϫ8.16 (m, 2 H, Ar-H), 8.73Ϫ8.76 (m, 2 H, Ar-H). Ϫ 13C
NMR (63 MHz, CDCl3): δ ϭ 6.1 (ϪCH3, 2 C), 17.9 (ϭCH, 4 C),
75.0 (quat. C, 2 C), 122.3 (ϭCH, 2 C), 122.6 (ϭCH, 2 C), 136.6
(ϭCH, 2 C), 149.3 (ϭCH, 2 C), 161.6 (quat. C, 2 C). Ϫ UV/Vis
(CH3CN): λmax (ε) ϭ 259 (7430), 379 (58) nm. Ϫ C18H16N4 (288.4):
calcd. C 74.98, H 5.59, N 19.43; found C 75.17, H 5.52, N 19.38.
exo,exo-3,3,7,7-Tetramethyl-9,10-diazatetracyclo[3.3.2.02·4.06·8]-
dec-9-ene-1,5-dicarbonitrile (6c): Dicarboxylic acid 6b (4.00 g,
14.4 mmol) and SOCl2 (24.8 g, 206 mmol) were stirred at room
temp. for 3 h. After removal of excess SOCl2, addition of 33% aque-
ous ammonia (75 mL) then gave the amide (3.70 g, 13.4 mmol,
93%) as colourless crystals. Trifluoroacetic anhydride (3.28 mL,
23.6 mmol) in 1,4-dioxane (8 mL) was added dropwise to a solution
of the amide (2.00 g, 7.20 mmol) in 1,4-dioxane (20 mL) and dry
pyridine (3.48 mL, 43.0 mmol). After 19 h of stirring at room
temp., the crude material was isolated. Recrystallisation (methanol)
yielded 6c (1.50 g, 62.5 mmol, 86%) as colourless crystals, m.p.
exo,exo-1,5-Bis(3-pyridyl)-9,10-diazatetracyclo[3.3.2.02·4.06·8]dec-
9-ene (5s): This compound was prepared according to General Pro-
cedure (3). Compounds 3s (750 mg, 3.02 mmol) and 2a, after stir-
ring in CH2Cl2 (25 mL) at room temp. for 24 h, purification by FC
(CH2Cl2/ethanol ϭ 10:1) and recrystallization (CH2Cl2/n-hexane),
yielded 5s (200 mg, 0.693 mmol, 23%) as a colourless solid, m.p.
229Ϫ231 °C. Ϫ IR (KBr): ν ϭ 2235, 2250 cmϪ1. Ϫ 1H NMR
˜
134Ϫ137 °C. Ϫ IR (KBr): ν ϭ 3080, 3030, 2970, 1570, 1515, 1475,
˜
1410, 1315, 1065, 1015, 810, 800, 710 cmϪ1. Ϫ 1H NMR (250 MHz,
(250 MHz, CDCl3): δ ϭ 1.02 (s, 6 H, 3,7-CH3-syn), 1.10 (s, 6 H,
3,7-CH3-anti), 1.86 (s, 4 H, 2-H, 4-H, 6-H, 8-H). Ϫ 13C NMR
(63 MHz, CDCl3): δ ϭ 18.6 (ϪCH3, 2 C), 24.7 (quat. C, 2 C), 30.1
(ϪCH3, 2 C), 35.8 (ϭCH, 4 C), 66.2 (quat. C, 2 C), 118.9 (quat.
C, 2 C). Ϫ MS (EI, 70 eV): m/z ϭ 240 [Mϩ]. Ϫ UV/Vis (methanol):
λmax (ε) ϭ 371 (226) nm. Ϫ C14H16N4 (240.3): calcd. C 69.96, H
6.72, N 23.52; found C 69.90, H 6.78, N 23.06.
2
3
CDCl3): δ ϭ 0.49 (dt, J ϭ 6.5, J ϭ 3.7 Hz, 2 H, 3,7-Hsyn), 0.90
(dt, 2J ϭ 6.5, 3J ϭ 7.7 Hz, 2 H, 3,7-Hanti), 1.95 (dd, 3J ϭ 3.7,
3J ϭ 7.7 Hz, 4 H, 2-H, 4-H, 6-H, 8-H), 7.47Ϫ7.52 (m, 2 H, Ar-H),
8.17Ϫ8.22 (m, 2 H, Ar-H), 8.73Ϫ8.77 (m, 2 H, Ar-H), 9.12Ϫ9.13
(m, 2 H, Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 266 (7100), 383
(90) nm. Ϫ C18H16N4 (288.4): calcd. C 74.96, H 5.59, N 19.42;
found C 74.75, H 5.66, N 18.97.
exo,exo-3,3,7,7-Tetramethyl-1,5-bis(trifluoromethyl)-9,10-diaza-
tetracyclo[3.3.2.02·4.06·8]dec-9-ene (6d): This compound was pre-
pared according to General Procedure (2). Compounds 1d (1.03 g,
exo,exo-1,5-Bis(4-pyridyl)-9,10-diazatetracyclo[3.3.2.02·4.06·8]dec-
9-ene (5t): This compound was prepared according to General Pro-
Eur. J. Org. Chem. 2001, 2629Ϫ2638
2637

J. Sauer et al.
4.72 mmol) and 2b (650 mg, 9.56 mmol), after stirring in CCl4 CD2Cl2): δ ϭ 11.4 (ϪCH3, 2 C), 19.1 (ϪCH3, 2 C), 24.8 (quat. C,
FULL PAPER
(7 mL) under reflux for 8 h and recrystallization (methanol),
yielded 6d (835 mg, 2.56 mmol, 54%) as colourless crystals, m.p.
2 C), 30.5 (ϪCH3, 2 C), 36.3 (ϭCH, 4 C), 72.2 (quat. C, 2 C),
165.8 (quat. C, 2 C), 167.6 (quat. C, 2 C). Ϫ MS (EI, 70 eV), m/z
163Ϫ164 °C. Ϫ IR (KBr): ν˜ ϭ 3040, 2980, 2940, 2880, 1455, 1360, (%) ϭ 311 (100) [Mϩ Ϫ N2 Ϫ CH3]. Ϫ UV/Vis (1,4-dioxane): λmax
1300, 1190, 1170, 1155, 1080, 1050, 1020, 910, 730 cmϪ1. Ϫ 1H (ε) ϭ 386 (203) nm. Ϫ C18H22N6O2 (354.4): calcd. C 61.00, H 6.26,
NMR (250 MHz, CDCl3): δ ϭ 0.96 (s, 6 H, 3,7-CH3-syn), 1.02 (s, N 23.71; found C 60.88, H 6.22, N 23.42.
6 H, 3,7-CH3-anti), 1.72 (s, 4 H, 2-H, 4-H, 6-H, 8-H). Ϫ UV/Vis
exo,exo-3,3,7,7-Tetramethyl-1,5-bis(2-pyridyl)-9,10-diaza-
(CCl4): λmax (ε) ϭ 369 (187) nm. Ϫ C14H16F6N2 (326.3): calcd. C
tetracyclo[3.3.2.02·4.06·8]dec-9-ene (6r): This compound was pre-
51.50, H 4.97, N 8.58; found C 51.24, H 5.17, N 8.40.
pared according to General Procedure (4). A solution of 4r
(587 mg, 2.12 mmol) and 2b (1.29 g, 18.9 mmol) in CH2Cl2 (3 mL)
was pressurized to 7.6 kbar in a suitable reaction vessel at 60 °C
for 5 d. Purification by FC (CH2Cl2/ethanol ϭ 15:1) and recrystal-
lization (CH2Cl2/n-hexane) yielded 6r (540 mg, 1.57 mmol, 74%) as
exo,exo-3,3,7,7-Tetramethyl-1,5-diphenyl-9,10-diazatetracyclo-
[3.3.2.02·4.06·8]dec-9-ene (6e): This compound was prepared accord-
ing to General Procedure (4). A solution of 4e (500 mg, 1.82 mmol)
and 2b (1.20 g, 17.6 mmol) in CH3CN (4 mL) was pressurized in a
suitable reaction vessel to 8.0 kbar at 100 °C for 65 h. Purification
by FC (Et2O/PE ϭ 1:1) and recrystallization (methanol) yielded 6e
(155 mg, 0.453 mmol, 25%) as colourless crystals, m.p. 180Ϫ182
˜
colourless crystals, m.p. 226Ϫ227 °C. Ϫ IR (KBr): ν ϭ 3050, 3000,
2950, 2930, 2870, 1580, 1570, 1465, 1430, 1315, 1120, 1095, 1035,
1000, 775, 750, 700, 615 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3):
δ ϭ 0.92 (s, 6 H, 3,7-CH3-syn), 1.08 (s, 6 H, 3,7-CH3-anti), 2.18 (s,
4 H, 2-H, 4-H, 6-H, 8-H), 7.25Ϫ7.45 (m, 2 H, Ar-H), 7.74Ϫ8.00
(m, 2 H, Ar-H), 8.16Ϫ8.35 (m, 2 H, Ar-H), 8.68Ϫ8.79 (m, 2 H,
Ar-H). Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 260 (7960), 392 (132) nm.
Ϫ C22H24N4 (344.5): calcd. C 76.71, H 7.02, N 16.26; found C
76.67, H 7.01, N 16.14.
˜
°C. Ϫ IR (KBr): ν ϭ 3060, 3040, 3000, 2960, 2930, 2880, 1600,
1580, 1515, 1490, 1445, 1375, 1315, 1255, 1175, 1130, 1020, 945,
820, 750, 695, 670 cmϪ1. Ϫ 1H NMR (250 MHz, CDCl3): δ ϭ 1.11
(s, 6 H, 3,7-CH3-syn), 1.23 (s, 6 H, 3,7-CH3-anti), 1.75 (s, 4 H, 2-
H, 4-H, 6-H, 8-H), 7.50Ϫ7.57 (m, 6 H, Ar-H), 7.72Ϫ7.75 (m, 4 H,
Ar-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 19.3 (ϪCH3, 2 C),
24.4 (quat. C, 2 C), 30.9 (ϪCH3, 2 C), 38.1 (ϭCH, 4 C), 78.2 (quat.
C, 2 C), 127.8 (ϭCH, 2 C), 128.1 (ϭCH, 4 C), 128.7 (ϭCH, 4 C),
143.5 (quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 314 (14) [Mϩ
Ϫ N2H]. Ϫ UV/Vis (CH3CN): λmax (ε) ϭ 339 (138), 387 (172) nm.
Ϫ C24H26N2 (342.5): calcd. C 84.17, H 7.65, N 8.18; found C 84.05,
H 7.68, N 8.19.
Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie and BASF AG for financial sup-
port of the research.
[1]
exo,exo-3,3,7,7-Tetramethyl-1,5-bis(2-thiazolyl)-9,10-diaza-
tetracyclo[3.3.2.02·4.06·8]dec-9-ene (6o): This compound was pre-
pared according to General Procedure (4). A solution of 4o
(574 mg, 1.99 mmol) and 2b (272 mg, 4.00 mmol) in CH2Cl2 (4 mL)
was pressurized in a suitable reaction vessel to 7.6 kbar at 56 °C
for 5 days. Purification by FC (CHCl3/ethanol ϭ 1:1) and recrystal-
lization (CH2Cl2/n-hexane) yielded 6o (518 mg, 1.47 mmol, 74%) as
R. A. Carboni, R. V. Lindsey, J. Am. Chem. Soc. 1959, 81,
4342Ϫ4346.
[2]
J. Sauer, 1,2,4,5-Tetrazines, Comprehensive Heterocyclic Chem-
istry II (Eds.: A. R. Katritzky, C. W. Rees, E. F. V. Scriven),
Pergamon Press, Oxford, 1996, vol. 6, p. 901Ϫ957.
A. Steigel, J. Sauer, D. A. Kleier, G. Binsch, J. Am. Chem. Soc.
1972, 94, 2770Ϫ2779.
H. D. Fühlhuber, C. Gousetis, T. Troll, J. Sauer, Tetrahedron
Lett. 1978, 41, 3903Ϫ3906.
R. Dyllick-Brenzinger, J. F. M. Oth, H. D. Fühlhuber, C. Gou-
[3]
[4]
˜
colourless crystals, m.p. 220 °C. Ϫ IR (KBr): ν ϭ 3100, 3075, 2995,
[5]
2975, 2870, 1490, 1290, 1220, 1340, 1150, 1135, 1110, 1050, 960,
1
890, 850, 725 cmϪ1. Ϫ H NMR (250 MHz, CDCl3): δ ϭ 0.91 (s,
setis, T. Troll, J. Sauer, Tetrahedron Lett. 1978, 41, 3970Ϫ3910.
[6]
6 H, 3,7-CH3-syn), 1.08 (s, 6 H, 3,7-CH3-anti), 2.20 (s, 4 H, 2-H,
4-H, 6-H, 8-H), 7.49 (d, 3J ϭ 3.2 Hz, 2 H, Ar-H), 7.49 (d, 3J ϭ
3.2 Hz, 2 H, Ar-H). Ϫ 13C NMR (63 MHz, CDCl3): δ ϭ 18.6
(ϪCH3, 2 C), 24.2 (quat. C, 2 C), 30.5 (ϪCH3, 2 C), 39.3 (ϭCH,
4 C), 77.5 (quat. C, 2 C), 120.0 (ϭCH, 2 C), 143.3 (ϭCH, 2 C),
173.0 (quat. C, 2 C). Ϫ MS (EI, 70 eV): m/z (%) ϭ 315 (11) [Mϩ
Ϫ N2 Ϫ CH3]. Ϫ UV/Vis (1,4-dioxane): λmax (ε) ϭ 242 (12200),
378 (132) nm. Ϫ C18H20N4S2 (356.5): calcd. C 60.73, H 5.66, N
15.72; found C 60.76, H 5.59, N 15.75.
C. Gousetis, J. Sauer, Tetrahedron Lett. 1978, 42, 1295Ϫ1298.
[7]
H. D. Fühlhuber, C. Goustis, J. Sauer, Tetrahedron Lett. 1979,
42, 1299Ϫ1302.
[8]
D. Paske, R. Ringshandl, J. Sellner, H. Sichert, J. Sauer, Angew.
Chem. 1980, 92, 464Ϫ465. Angew. Chem. Int. Ed. Engl. 1980,
19, 463Ϫ464.
H. Schuster, H. Sichert, J. Sauer, Tetrahedron Lett. 1983, 24,
1485Ϫ1488.
[9]
[10]
H. Stimmelmayr, Dissertation, Universität Regensburg, 1992.
[11]
F. Thalhammer, U. Wallfahrer, J. Sauer, Tetrahedron Lett. 1990,
31, 6851Ϫ6854.
[12]
exo,exo-3,3,7,7-Tetramethyl-1,5-bis(2-methyl-1,3,4-oxadiazol-5-yl)-
9,10-diazatetracyclo[3.3.2.02·4.06·8]dec-9-ene (6q): This compound
was prepared according to General Procedure (4). A solution of 4q
(80.9 mg, 0.283 mmol) and 2b (272 mg, 4.00 mmol) in CH2Cl2
(4 mL) was pressurized to 7.3 kbar in a suitable reaction vessel
at 55 °C for 5 d. Purification by FC (CH2Cl2/EtOAc ϭ 1:1) and
recrystallization (CH2Cl2/n-hexane) yielded 6q (88.0 mg,
0.248 mmol, 88%) as colourless crystals, m.p. 201Ϫ202 °C. Ϫ IR
J. Sauer, R. Sustmann, Angew. Chem. 1980, 92, 773Ϫ801. An-
gew. Chem. Int. Ed. Engl. 1980, 19, 779Ϫ807.
[13]
G. L. Closs, K. D. Krantz, J. Org. Chem. 1966, 31, 638.
[14]
F. X. Huber, J. Sauer, W. S. McDonald, H. Nöth, Chem. Ber.
1982, 115, 444Ϫ451.
[15]
G. Maier, Angew. Chem. 1963, 75, 920Ϫ921. Angew. Chem. Int.
Ed. Engl. 1963, 2, 621Ϫ622.
[16]
J. Sauer, G. R. Pabst, U. Holland, H.-S. Kim, S. Loebbecke,
Eur. J. Org. Chem. 2001, 697Ϫ706.
H. E. Zimmermann, W. Eberbach, J. Am. Chem. Soc. 1973,
˜
(KBr): ν ϭ 2950, 2920, 2870, 1585, 1520, 1380, 1340, 1235, 1110,
[17]
1080, 1050, 1020, 965 cmϪ1. Ϫ 1H NMR (250 MHz, CD2Cl2): δ ϭ
1.02 (s, 6 H, 3,7-CH3-syn), 1.09 (s, 6 H, 3,7-CH3-anti), 1.99 (s, 4 H,
2-H, 4-H, 6-H, 8-H), 2.65 (s, 6 H, Ar-CH3). Ϫ 13C NMR (63 MHz,
95, 3970Ϫ3979.
Received December 18, 2000
[O00642]
2638
Eur. J. Org. Chem. 2001, 2629Ϫ2638