Synthesis and reactions of 1,2,3-triazinium salts

Article abstract of DOI:10.1055/s-2003-37344

The synthesis of monosubstituted 1,2,3-triazinium salts 7-9 and their reactivity towards C-nucleophiles is described. The nucleophilic attack at 7-9 is regioselective at position 5, isolation of dihydroproducts was possible and an unusual ring contraction was observed.

Full text of DOI:10.1055/s-2003-37344

PAPER
413
Synthesis and Reactions of 1,2,3-Triazinium Salts
S
ynthesis and Reaction
i
s
of 1,
c
h
um
S
alts ael Mättner, Hans Neunhoeffer*
Darmstadt University of Technology, Clemens Schöpf Institute of Organic Chemistry and Biochemistry, Petersenstr. 22,
64289 Darmstadt, Germany
Fax +49(6151)166016; E-mail: di88@hrzpub.tu-darmstadt.de
Received 22 August 2002; revised 28 November 2002
our knowledge, this is the first time that the activation of
monosubstituted 1,2,3-triazines via substitution on N-2
and the reactivity of the resulting cations is studied.
Abstract: The synthesis of monosubstituted 1,2,3-triazinium salts
7–9 and their reactivity towards C-nucleophiles is described. The
nucleophilic attack at 7–9 is regioselective at position 5, isolation of
dihydroproducts was possible and an unusual ring contraction was
observed.
1,2,3-Triazines 6 are synthesized from their correspond-
ing pyrazoles 4 (Scheme 2).7,8 The first step is an electro-
philic amination with hydroxylamin-O-sulfonic acid
followed by a two-phase oxidation using sodium meta pe-
riodate in the aqueous phase (Table 1).
Key words: 1,2,3-triazines, cations, nucleophilic additions, π-defi-
cient heterocycles, regioselectivity
The concept of nucleophilic aromatic substitution of hy-
drogen (SNH) in azines was introduced by Chupakhin,
Charushin and van der Plas et al. and has been successful-
ly used for the introduction of a number of nucleophiles
into electrophilic arenes, non-benzoid aromatic systems
and hetarenes.1
It was shown that the SNH-reaction proceeds in a stepwise
fashion2. The initial attack of a nucleophile at 1 forms a σ-
adduct 2 (Scheme 1), which rearomatizes to 3 either by
oxidation or by hydride transfer1. However, if heterocy-
clic cations or electron deficient heterocycles are used in
SNH synthesis, the isolation of the formed dihydro adducts
2 is often possible.1,3–5
Scheme 2
Table 1 Reaction Parameters and Overall Yields for the Synthesis
of 1,2,3-Triazines 6
R1
R2
Temp.
Time
Overall
Yield (%)
4a
4b
4c
4d
Ph
H
H
20 °C
20 °C
5 °C
5 d
5 d
478
49
Ph
H
Me
H
72 h
72 h
228
308
Me
5 °C
Scheme 1
All known procedures for the activation of 4,6-disubstitut-
ed 1,2,3-triazines like methyliodide9 or 1-chloroethyl
chloroformate10 failed with compounds 6, because of the
high reactivity of the formed salts towards nucleophiles.
We had to search for an activating reagent, which forms
an unreactive anion and succeeded finally by using the
Meerwein salt.11
It was predicted,1 that electron poor heterocyclic systems
should show a high reactivity towards even weak nucleo-
philes, increasing with the number of aza groups in the ar-
omatic ring. The stability of the primarily formed σ-
adduct 2 should increase while lowering the π-electron
density in the heterocyclic ring system.
Ethylation of the phenyl substituted 1,2,3-triazines 6a,b
with triethyloxonium tetrafluoroborate and the methyl
substituted 1,2,3-triazines 6c,d with triethyloxonium
hexafluorophosphate under argon led to the correspond-
ing 1,2,3-triazinium salts 7 (Scheme 3).
In this connection 1,2,3-triazinium salts6 are interesting
heterocyclic systems which to our knowledge have not yet
been studied in SN reactions. In this paper we describe
the synthesis of monosubstituted 1,2,3-triazinium salts
and their reactivity towards C-nucleophiles.
H
The 2-ethyl-1,2,3-triazinium salts 7 are stable under Ar at
0 °C for only a few days and have to be prepared freshly
for further reactions. (15N,1H)-HMBC-NMR studies indi-
cated, that the ethylation took place only at N-2 and the
EIMS (70eV) spectra show no elimination of nitrogen
([M+] – 28 peak is missing).
We concentrated in our work on monosubstituted 1,2,3-
triazines with two possible reaction sites. To the best of
Synthesis 2003, No. 3, Print: 28 02 03.
Art Id.1437-210X,E;2003,0,03,0413,0425,ftx,en;T09402SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

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M. Mättner, H. Neunhoeffer
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Scheme 4
The position of the protonation could not be clarified by
1H NMR studies. We observed a small NOE-effect be-
tween N–H and the phenyl ring for the 4-phenylated
1,2,3-triazinium-tetrafluoroborate 8a, but this result was
not satisfying. Due to the poor solubility of 8a,b no 15N-
NMR spectra were recorded. By analogy with the ethylat-
ed 1,2,3-triazinium salts 7 we assume that the solid 1,2,3-
triazinium salt 8 is protonated at N-2 due to thermody-
namic effects. Ab initio calculations on B3Lyp/6-311G*//
HF/6-31G*+0.89ZPE (HF/6-31G*)12–14 level (Table 3)
showed again a thermodynamic energy difference be-
tween the three possible isomers.
Scheme 3
Figure 1
Figure 1 shows the 15N-signals (internal standard ni-
tromethane) of the 1,2,3-triazines 6 and the corresponding
1,2,3-triaziniumsalts 7. All nitrogen signals shift to a
higher field compared to the corresponding 1,2,3-triazines
6 (see experimental for details). For δ = –69.93 (7a) and
Table 3 Calculated Relative Energies for the Three Possible Iso-
mers of 1,2,3-Triazinium Salts 8
8a
8b
N-1 protonated
N-2 protonated15
N-3 protonated
3.4 kJmol–1
0 kJmol–1
14.7 kJmol–1
36.5 kJmol–1
0 kJmol–1
–
3
δ = –81.46 (7b) one observes J-coupling between N-2
and –CH3 as well as 3J-coupling N-2/H-6 but no coupling
to H-5. For δ = –21.46 (7a) and δ = –17.49 (7b) N-1/N-3
coupling to H-5, H-6 and the –CH2– group is observed,
making the two nitrogen signals significantly different
and clearing the position for the ethyl group.
Once more the N-2 substituted isomer is the most stable
one, but in the case of 1,2,3-triazinium salt 8a the energy
difference between N-1 and N-2 is so small, that one can
assume that a shift of the proton in solution takes place
very easily.
This evidence is supported by ab initio calculations on
B3Lyp/6-311G*//HF/6-31G*+0.89ZPE (HF/6-31G*)12–14
level (Table 2).
The calculation shows, that the N-2 substituted 1,2,3-tri-
azine 7 is around 30 kJmol–1 more stable than the other
isomers. Although the calculated structures refer to the
gas phase at 0 K there is at least a significant energy dif-
ference between the three possible isomers.
Recently, the synthetic utility of hypervalent iodine has
been extensively exploited,16 and diaryliodinium salts
have been used to arylate a wide variety of substrates17.
We report the first arylation of heteroarenes with hyperva-
lent iodonium salts leading to a cationic product.
When 1,2,3-triazines 6 were treated with tetrafluoroboric
acid, the isolation of protonated 1,2,3-triazinium salts 8
was possible in the case of phenylated 1,2,3-triazines 6a,b
(Scheme 4). The methylated 1,2,3-triazines 6c,d decom-
posed under similar conditions.
Kang et al. reported the copper-catalyzed arylation of
several amines with hypervalent iodonium salts.18 We
used this method to arylate 1,2,3-triazines 6 leading to
N-phenylated 1,2,3-triazinium hexafluorophosphates 9
(Scheme 5).
Table 2 Calculated Relative Energies for the Three Possible Isomers of 1,2,3-Triazinium Salts 7
7a
7b
7c
7d
N-1 ethylated
N-2 ethylated15
N-3 ethylated
12.7 kJmol–1
0 kJmol–1
42.2 kJmol–1
38.2 kJmol–1
0 kJmol–1
–
24.4 kJmol–1
0 kJmol–1
31.5 kJmol–1
33.0 kjmol–1
0 kJmol–1
–
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

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Synthesis and Reactions of 1,2,3-Triazinium Salts
415
In a typical procedure the 1,2,3-triazinium salt 7a was dis-
solved under argon in absolute dichloromethane (or abso-
lute acetonitrile for 7c) and the C-nucleophile was added
at room temperature. The reaction was observed by TLC
and stopped when no further changes were detectable. We
never observed a complete conversion of the starting ma-
terial 7, but failed to recovering the salts 7. The primarily
formed adduct 10 (A = C, Q = N) rearomatizes immedi-
ately without any deprotonating agent1 and the dihydroad-
ducts 11 were isolated by column chromatography and
completely characterized. See Table 4 for experimental
details, nucleophiles and yields of isolated dihydroad-
ducts 11.
Scheme 5
The resulting 1,2,3-triazinium salts 9 are stable under inert
gas for several months. 1H NMR and EIMS (70 eV) stud-
ies indicated again that the phenylated 1,2,3-triazines 9
are substituted on N-2 only. Due to their poor solubility no
(H,N)-HMBC-NMR studies were possible.
When 4-phenyl- and 4-methyl-1,2,3-triazinium salts 7a,c
were treated with indole (14) and pyrole (15) an unusual
byproduct was observed (Scheme 7).
When the prepared 2-ethyl-1,2,3-triazinium salts 7a–d
were allowed to react with electron rich heterocyclic sys-
tems as weak C-nucleophiles, the expected nucleophilic
attack occurred in case of 1,2,3-triazinium salts 7a and 7c.
Both 5-substituted 2-ethyl-1,2,3-triazinium salts 7b,d did
not react. This indicates again, that the 1,2,3-triazinium
salts 7 are substituted only at N-2 and because of that, no
reaction takes place at the blocked C-5 position. In case of
the 4-substituted 2-ethyl-1,2,3-triazinium salts 7a,c only
the 4,5-disubstituted products 11 were isolated (Table 4).
No reaction occurred at the free C-6 position and no re-
aromatization took place leading to the SNH-product 13
(Scheme 6). This is in good agreement with the predicted
reactivity of π-deficient heterocyclic systems.1 Oxidation
of 11 by air or DDQ in dioxane failed and led only to de-
composition products.
Scheme 7
A ring contraction took place, leading to these unexpected
tetrasubstituted pyrazoles 12. The position of the ethyl
group in pyrazoles 12 was clarified by 1H NMR-NOESY
experiments. We were able to prove the existence of am-
Scheme 6
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M. Mättner, H. Neunhoeffer
PAPER
monium tetrafluoroborate in the residue with Nesslers ondary reaction of the nucleophilic attack and ammonia is
reagent19 and succeeded in preparing the pyrazole 12a di- eliminated. We suggest the following mechanism for this
rectly from the corresponding dihydro adduct 11a by reaction (Scheme 8).
treatment with tetrafluoroboric acid in dichloromethane at
room temperature. The ring contraction has to be a sec-
Table 4 Parameters and Products of the Reaction of 1,2,3-Triazinium Salts 7 with C-Nucleophiles
Entry Solventa
Reaction X–
Time
Nucleophile
Product 11, Yield
R1
Ph
R2
R3
R4
R5
H
A
C
Q
N
%
–
7a
7c
CH2Cl2
CH3CN
3 d
BF4
11a
11b
H
Ar
Ar
15%
14
–
3 d
PF6
BF4
Me
H
H
C
N
14%
14
15
15
–
7a
7c
7a
CH2Cl2
CH3CN
CH2Cl2
2 d
1 h
1 d
11c
11d
Ph
Ph
H
H
H
H
H
H
H
H
N
C
C
N
23%
8%
–
PF6
BF4
11e
11f
Me
Ph
H
H
H
H
H
N
C
C
N
5%
–
Ar
Ar
Me
21%
15
–
7c
CH3CN
1 d
PF6
11g
Me
H
Me
C
N
27%
16
17
17
18
18
–
7a
7c
7a
7c
CH2Cl2
CH3CN
CH2Cl2
CH3CN
1 d
1 d
1 d
16 h
BF4
11h
11i
Ph
Me
H
H
H
H
H
H
H
H
C
N
C
C
N
C
N
N
23%
5%
–
PF6
Me
Ph
Me
Me
Me
–
BF4
11j
11k
H
Me
Me
46%
33%
–
PF6
Me
H
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Synthesis and Reactions of 1,2,3-Triazinium Salts
417
Table 4 Parameters and Products of the Reaction of 1,2,3-Triazinium Salts 7 with C-Nucleophiles (continued)
Entry Solventa
Reaction X–
Time
Nucleophile
Product 11, Yield
R1
Ph
R2
R3
H
R4
R5
A
C
Q
N
%
–
7a
7c
CH2Cl2
CH3CN
1 d
BF4
11l
H
Me Me
11%
19
19
–
16 h
PF6
11m
11n
Me
Me
H
H
H
Me Me
Me
C
N
N
C
9%
Me
H
11%
a Absolute CH2Cl2 and CH3CN were used.
ucts and both decomposed immediately after addition of
the nucleophile. This supports our theory, that the position
of the proton in solution is not fixed on N-2. If the proton
shifts to N-1/N-3 an attack at C-6 is possible leading to the
observed products. This is a known reaction for 1,2,3-tri-
azines with nucleophiles like sodium methanolate or sodi-
um hydroxide.20
The N-phenylated 1,2,3-triazinium salts 9a,c react with
indole (14), 2-methylindole (16) and N-methylpyrrole
(17) in the expected way and form the dihydro adducts 22
(Scheme 10).
Scheme 8 Proposed reaction mechanism for the formation of 12.
The initial protonation of 11 at N-3 is the key step of this
reaction. During the formation of the dihydroadduct 11
(see Scheme 6), tetrafluoroboric acid (or hexafluorophos-
phoric acid) is formed and this initiates the secondary re-
action leading to the pyrazole 12.
When the protonated 1,2,3-triazinium salts 8 were treated
with the nucleophiles 14–17, we could not isolate the ex-
pected dihydro adducts. A gas forming reaction took place
instantly after the nucleophile was added and only decom-
position products 20 and 21 were isolated (Scheme 9).
Scheme 10
The reaction was followed by TLC and stopped when no
further changes were detectable. Again the transformation
of the 1,2,3-triazinium salts 9 was not complete, but this
time we could recover the salts 9 in yields up to 30–40%.
Similarly to 7, the nucleophilic attack took place only on
C-5. Therefore it can be concluded that the position of the
phenyl group is just like the ethyl group in 7 fixed on N-2.
All reactions with these C-nucleophiles suffer from poor
yields. This is due to the weak nucleophilicity and the in
situ formation of protons, which initiates decomposition
or secondary reactions. Therefore we used substances
with acidic protons 23, deprotonated them with sodium
hydride and added the 1,2,3-triazinium salts 7a,c
(Scheme 11), which is known to work for 4,6-disubstitut-
Scheme 9
Noteworthy is the fact, that there is no obvious difference
between the 4-phenyl- and 5-phenyl substituted 1,2,3-tri-
azinium salt 8a,b. Both salts led to the same type of prod-
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M. Mättner, H. Neunhoeffer
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N-Aminopyrazoles (5)7 and 1,2,3-Triazines (6a,c,d)6,7 were synthe-
sized by known methods.
ed 1,2,3-triazinium salts.21 A fast reaction was observed
by TLC and the expected dihydroadducts 24 were isolated
in all cases in moderate to good yields. Oxidation by air or
DDQ in dioxane led to the 1,2,3-triazinylidenes 25. Sub-
sequent protonation with tetrafluoroboric acid did not lead
to the completion of the SNH-reaction. We only observed
slow decomposition even under very mild conditions.
4-Phenyl-1,2,3-triazine (6a)
15N-NMR (50.7 MHz, acetone-d6): δ = 83.14 (N-1, N-3), 8.32 (N-
2).
5-Phenyl-1,2,3-triazine (6b)
To a solution of N-aminopyrazole 5b (8.00 g, 51.3 mmol) in CHCl3
(300 mL) was carefully added an aq soln (500 mL) of sodium meta
periodate (21.5 g, 0.10 mol). The two phase reaction mixture was
stirred at r.t. for 5 d. The two phases were seperated and the aqueous
layer was extracted with CHCl3 (3 × 200 mL). The combined or-
ganic layers were dried over MgSO4 and the solvent removed under
reduced pressure. The crude product was purified by column chro-
matography (cyclohexane–EtOAc, 1:1); yield: 4.20 g (54%); yel-
low needles; mp 145 °C (EtOAc).
1H NMR (300 MHz, CDCl3): δ = 9.25 (s, 2 H, 4-H, 6-H), 7.69–7.63
(m, 2 H, Ph), 7.57–7.51 (m, 3 H, Ph).
13C NMR (75.7 MHz, CDCl3): δ = 147.39, 130.98, 131.42, 130.11,
127.26.
15N-NMR (50.7 MHz, DMSO-d6): δ = 71.48 (N-1, N-3), 10.62 (N-
2).
MS (EI, 70 eV): m/z (%) = 158 (2) [M+ + 1], 157 (12) [M+], 129
(72), 102 (100), 87 (14), 76 (72), 63 (49), 50 (64), 39 (35).
Anal. Calcd for C9H7N3: C, 68.78; H, 4.49; N, 26.73. Found: C,
68.81; H, 4.52; N, 26.67.
N-Ethylated 1,2,3-Triazinium Salts 7; General Procedure
Triethyloxonium tetrafluoroborate (650 mg, 3.42 mmol) in CHCl3
(5 mL) or triethyloxonium hexafluorophosphate (840 mg, 3.38
mmol) in CH2Cl2 (5 mL) was added to a cooled (0 °C) solution of
1,2,3-triazine 6a–d (2.20 mmol) in CHCl3 (6a,b) or CH2Cl2 (6c,d)
(5 mL) and the mixture kept for 3 d at –20 °C. The crystals that
formed were isolated and dried under vacuum.
Scheme 11
Ethylation, protonation and phenylation of 1,2,3-triazines
6 occurred only at N-2 of the 1,2,3-triazine ring systems.
This was proved for the N-ethylated salts 7 by (N,H)-
HMBC-NMR studies. Ab initio calculations support our
experimental results and indicate, that thermodynamic ef-
fects are the reason for this regioselectivity.
2-Ethyl-4-phenyl-1,2,3-triazinium Tetrafluoroborate (7a)
Yield: 881 mg (95%); light yellow crystals; mp 130–132 °C
(CHCl3).
IR (KBr): 3063, 2925, 1561, 1392, 1067, 787, 685 cm–1.
1H NMR (300 MHz, acetone-d6): δ = 9.94 (d, 1 H, 3J5,6 = 6.2 Hz,
Monosubstituted 1,2,3-triazinium salts 7, 9 showed high
reactivity towards weak C-nucleophiles leading to dihy-
dro 1,2,3-triazines 11 and 22 in rather poor yields. No
rearomatization took place and also oxidation with DDQ
or oxygen failed. If the in situ formation of protons is
avoided and stronger nucleophiles are used, one can iso-
late the expected dihydroadducts 24 in moderate to good
yields and functionalize the 1,2,3-triazine system by that
method. Oxidation of 24 led to 1,2,3-triazinylidens 25 and
not to the completion of the SNH-reaction.
3
6-H), 9.15 (d, 1 H, J5,6 = 6.2 Hz, 5-H), 8.45–8.42 (m, 2 H, Ph),
7.84–7.72 (m, 3 H, Ph), 5.46 (q, 2 H, 3J = 7.2 Hz, –CH2–), 1.94 (t,
3 H, 3J = 7.2 Hz, –CH3).
13C NMR (75.7 MHz, acetone-d6): δ = 166.80, 159.11, 135.81,
130.93, 129.74, 129.32, 67.96, 14.34.
15N-NMR (50.7 MHz, acetone-d6): δ = –21.46 (N-1, N-3), –69.93
(N-2).
MS (FD, 15 mA): m/z (%) = 459 (19) [M + K+], 186 (100) [K+], 78
(16).
–
Anal. Calcd for C11H12N3+ BF4 : C, 48.40; H, 4.06; N, 15.39. Found:
C, 48.29; H, 4.16; N, 15.39.
All reactions were carried out under Ar atmosphere with purified
solvents (p.a. from Merck, VWR International Inc., Darmstadt;
dried over molecular sieve). IR spectra were obtained on a Nicolet
2-Ethyl-5-phenyl-1,2,3-triazinium Tetrafluoroborate (7b)
Yield: 910 mg (98%); colorless crystals; mp 123 °C (CHCl3).
IR (KBr): 3073, 2986, 1591, 1566, 1321, 1056, 766, 695 cm–1.
1H NMR (300 MHz, acetone-d6): δ = 10.41 (s, 2 H, 4-H, 6-H), 8.28–
8.25 (m, 2 H, Ph), 7.84–7.74 (m, 3 H, Ph), 5.32 (q, 2 H, 3J = 7.3 Hz,
–CH2–), 1.90 (t, 3 H, 3J = 7.3 Hz, –CH3).
13C NMR (75.7 MHz, acetone-d6): δ = 155.17, 138.74, 131.21,
139.70, 128.72, 129.84, 60.78, 15.13.
1
impact 400 spectrometer. H and 13C NMR spectra were recorded
on a Bruker AC-300, ARX-300 and DRX-500 spectrometer with
tetramethylsilane as internal standard. 15N NMR spectra were re-
corded on a Bruker DRX-500 spectrometer with nitromethane as in-
ternal standard. MS were determined on a Varian 212 instrument at
70 eV. Elemental analysis were obtained on a Perkin-Elmer CHN
240 A or 240 B. Silicagel 60 from FLUKA was used for column
chromatography.
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Synthesis and Reactions of 1,2,3-Triazinium Salts
419
15N-NMR (50.7 MHz, acetone-d6): δ = –17.49 (N-1, N-3), –81.46
13C NMR (75.7 MHz, CD3CN): δ = 153.24, 139.93, 132.06, 131.59,
(N-2).
130.56, 131.92.
MS (FD, 20 mA): m/z (%) = 460 (31) [M + K+], 186 (100) [K+], 78
MS (FD, 15 mA): m/z (%) = 158 (19) [K+], 157 (100) [K+ – 1], 68
(22).
(36).
–
Anal. Calcd for C11H12N3+ BF4 : C, 48.40; H, 4.06; N, 15.39. Found:
C, 48.25; H, 4.24; N, 15.52.
Due to the hygroscopic nature of the product, no elemental analysis
was possible.
2-Ethyl-4-methyl-1,2,3-triazinium Hexafluorophosphate (7c)
Yield: 510 mg (56%); colorless crystals; mp 78 °C (CH2Cl2).
IR (KBr): 3078, 2961, 1591, 1454, 837, 573 cm–1.
N-Phenylated 1,2,3-Triazinium Salts 9; General Procedure
To a soln of the 1,2,3-triazines 6a–d (1.50 mmol) and diphenyliodo-
nium hexafluorophosphate (640 mg, 1.50 mmol) in CH2Cl2 (8 mL)
was added CuI (30.0 mg, 0.15 mmol) and the soln was stirred for 3
d. The formed product is filtrated, washed with CH2Cl2 (2 × 5 mL)
and dried under reduced pressure.
1H NMR (300 MHz, CD3CN): δ = 9.55 (d, 1 H, 3J5,6 = 5.8 Hz, 6-H),
3
3
8.30 (d, 1 H, J5,6 = 5.8 Hz, 5-H), 5.15 (q, 2 H, J = 7.3 Hz,
–CH2–), 2.90 (s, 3 H, 4-CH3), 1.72 (t, 3 H, 3J = 7.3 Hz, –CH3).
13C NMR (75.7 MHz, CD3CN): δ = 172.66, 157.92, 129.01, 67.96,
22.35,14.69.
MS (FD, 15 mA): m/z (%) = 393 (45) [M + K+], 124 [K+] (100).
2,4-Diphenyl-1,2,3-triazinium Hexafluorophosphate (9a)
Yield: 386 mg (68%); light green crystals; mp 206–207 °C
(CH2Cl2).
IR (KBr): 3134, 3098, 1561, 1403, 1342, 843, 751, 557 cm–1.
1H NMR (300 MHz, CD3CN): δ = 9.79 (d, 1 H, 3J5,6 = 6.1 Hz, 6-H),
8.80 (d, 1 H, 3J5,6 = 6.1 Hz, 5-H), 8.57–8.55 (m, 2 H, Ph), 8.43–8.40
(m, 2 H, Ph), 7.93–7.63 (m, 6 H, Ph).
–
Anal. Calcd for C6H10N3+ PF6 : C, 26.78; H, 3.75; N, 15.61. Found:
C, 26.93; H, 3.72; N, 15.69.
2-Ethyl-5-methyl-1,2,3-triazinium Hexafluorophosphate (7d)
13C NMR (75.7 MHz, CD3CN): δ = 166.95, 158.96, 136.59, 131.84,
131.32, 130.03, 124.89, 123.90, 148.50, 130.62.
Yield: 521 mg (57%); violet crystals; mp 152 °C (CH2Cl2).
IR (KBr): 3093, 2996, 1586, 1408, 837, 557 cm–1.
MS (EI, 70 eV): m/z (%) = 234 (42) [K+], 107 (50), 77 (100), 51
(22).
1H NMR (300 MHz, CD3CN): δ = 9.60 (s, 2 H, 4-H, 6-H), 5.16 (q,
2 H, 3J = 7.3 Hz, –CH2–), 2.74 (s, 3 H, 5-CH3), 1.77 (t, 3 H, 3J = 7.3
Hz, –CH3).
13C NMR (75.7 MHz, CD3CN): δ = 159.41, 144.10, 66.70, 17.30,
14.33.
MS (FD, 15 mA): m/z (%) = 613 (4) [M + K+], 253 (4), 234 (100)
[K+], 78 (2).
–
Anal. Calcd for C15H12N3+ PF6 : C, 47.51; H, 3.19; N, 11.08. Found:
MS (FD, 15 mA): m/z (%) = 393 (15) [M + K+], 219 (43), 124 (100)
C, 47.62; H, 3.26; N, 11.14.
[K+].
2,5-Diphenyl-1,2,3-triazinium Hexafluorophosphate (9b)
Yield: 120 mg (29%); colorless crystals; mp >330 °C (CH2Cl2).
IR (KBr): 3068, 2930, 1576, 1382, 837, 766, 680, 562 cm–1.
–
Anal. Calcd for C6H10N3+ PF6 : C, 26.78; H, 3.75; N, 15.61. Found:
C, 26.88; H, 3.65; N, 15.52.
1H NMR (300 MHz, CD3CN): δ = 10.13 (s, 2 H, 4-H, 6-H), 8.43 (m,
2 H, Ph), 8.25 (m, 2 H, Ph), 8.08 (m, 4 H, Ph), 7.87 (m, 2 H, Ph).
N-Protonated 1,2,3-Triazinium Tetrafluoroborates 8a,b; Gen-
eral Procedure
To a cooled solution (0 °C) of 1,2,3-triazine 6a,b (315 mg, 2.00
mmol) in CHCl3 (5 mL) was slowly added tetrafluoroboric acid
(54% in Et2O, Merck) (0.2 mL) in CHCl3 (5 mL). Shortly after the
first addition a solid product is formed. Directly after the last addi-
tion the product is filtrated, washed with CHCl3 (2 × 5 mL) and
dried under reduced pressure.
13C NMR (75.7 MHz, CD3CN): δ = 155.06, 136.83, 135.88, 133.61,
132.20, 131.88, 130.44, 124.09, 134.20, 128.56.
MS (FD, 15 mA): m/z (%) = 613 (1) [M + K+], 457 (2), 375 (2), 234
(100) [K+], 78 (100).
–
Anal. Calcd for C15H12N3+ PF6 : C, 47.51; H, 3.19; N, 11.08. Found:
C, 47.65; H, 3.28; N, 11.10.
N-Hydro-4-phenyl-1,2,3-triazinium Tetrafluroborate (8a)
Yield: 290 mg (92%); colorless crystals; mp 94 °C, dec. (CHCl3).
IR (KBr): 3312, 3052, 2976, 1596, 1571, 1316, 1077, 751 cm–1.
4-Methyl-2-phenyl-1,2,3-triazinium Hexafluorophosphate (9c)
Yield: 205 mg (43%); light green crystals; mp 167 °C (CH2Cl2).
1H NMR (300 MHz, CD3CN): δ = 13.10 (br s, 1 H, N–H), 8.77 (d,
1 H, 3J5,6 = 6.7 Hz, 6-H), 8.33–8.27 (m, 2 H, Ph), 7.72–7.67 (m, 4
H, Ph, 5-H).
IR (KBr): 3108, 3073, 1576, 1342, 1311, 837, 751, 680, 557 cm–1.
1H NMR (300 MHz, CD3CN): δ = 9.67 (d, 1 H, 3J5,6 = 5.8 Hz, 6-H),
8.44–8.42 (m, 2 H, Ph), 8.34 (d, 1 H, 3J5,6 = 5.8 Hz, 5-H), 7.88–7.87
(m, 1 H, Ph), 7.80–7.76 (m, 2 H, Ph), 3.00 (s, 3 H, 4-CH3).
13C NMR (75.7 MHz, CD3CN): δ = 163.53, 149.48, 135.77, 131.05,
130.24, 134.44, 116.96.
13C NMR (75.7 MHz, CD3CN): δ = 172.59, 157.93, 143.40, 136.33,
131.80, 128.77, 124.72, 22.55.
MS (FD, 15 mA): m/z (%) = 159 (6) [K+ + 1], 158 (18) [K+], 157
(100) [K+ – 1], 102 (1), 78 (20).
MS (FD, 18 mA): m/z (%) = 489 (22) [M + K+], 341 (7), 172 (100)
Due to the hygroscopic nature of the product, no elemental analysis
was possible.
[K+], 78 (3).
–
Anal. Calcd for C10H10N3+ PF6 : C, 37.87; H, 3.18; N, 13.25. Found:
C, 37.98; H, 3.28; N, 13.26.
N-Hydro-5-phenyl-1,2,3-triazinium Tetrafluroborate (8b)
Yield: 278 mg (88%); light yellow crystals; mp 126 °C (CHCl3).
IR (KBr): 3287, 3037, 1561, 1306, 1067, 781 cm–1.
5-Methyl-2-phenyl-1,2,3-triazinium Hexafluorophosphate (9d)
Yield: 124 mg (26%); violet crystals; mp 159 °C (CH2Cl2).
1H NMR (300 MHz, CD3CN): δ = 12.60 (br s, 1 H, N–H), 8.15–8.12
IR (KBr): 3078, 1545, 1245, 837, 756, 685, 562 cm–1.
(m, 2 H, 4-H, 6-H), 7.86–7.63 (m, 5 H, Ph).
1H NMR (300 MHz, CD3CN): δ = 9.72 (s, 2 H, 4-H, 6-H), 8.41–
8.38 (m, 2 H, Ph), 7.90–7.80 (m, 3 H, Ph), 2.80 (s, 3 H, 5-CH3).
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

420
M. Mättner, H. Neunhoeffer
PAPER
HRMS: m/z calcd for C14H16N4, 240.1375; found, 240.1385.
13C NMR (75.7 MHz, CD3CN): δ = 171.30, 159.58, 151.25, 135.86,
131.78, 124.19, 17.97.
Fraction 2: 12b; yield: 27 mg (8%); red oil.
IR (KBr): 3409, 2966, 1464, 1265, 802, 741 cm–1.
FDMS (18 mA): m/z (%) = 489 (3) [M + K+], 354 (11), 239 (100),
172 (65) [K+], 95 (14).
1H NMR (300 MHz, CDCl3): δ = 8.18 (br s, 1 H, N–H), 8.14 (m, 1
H, Ph), 7.74 (br s, 1 H, N–H), 7.33–7.25 (m, 2 H, Ph), 7.15–7.01 (m,
6 H, Ph), 6.70 (m, 1 H, Ph), 4.17 (q, 2 H, 3J = 7.2 Hz, –CH2–), 2.13
(s, 3 H, 5-CH3), 1.49 (t, 3 H, 3J = 7.2 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 145.23, 137.21, 136.21, 135.87,
127.85, 126.30, 123.83, 123.29, 122.19, 122.03, 120.80, 120.61,
120.06, 119.67, 109.94, 109.76, 102.66, 44.34, 15.62, 10.13.
Anal. Calcd for C10H10N3+ PF6 : C, 37.87; H, 3.18; N, 13.25. Found:
C, 38.02; H, 3.29; N, 13.32.
–
Reactions of 1,2,3-Triazinium Salts with Electron Rich Hetero-
cycles; General Procedure
To a soln of the N-ethyl-1,2,3-triazinium salt 7 (1.00 mmol) in a
chlorinated solvent (5 mL) (see Table 4) was added a solution (3 mL
of the same solvent) of the heterocycle (1.00 mmol) at r.t. The reac-
tion was followed by TLC and stopped when no further changes
were observable. The solvent was removed under reduced pressure
and the crude residue purified by column chromatography (for exact
experimental details see Table 4).
MS (EI, 70 eV): m/z (%) = 340 (1) [M+], 279 (26), 167 (44), 149
(100), 117 (16), 113 (15), 70 (24), 57 (44), 43 (42).
HRMS: m/z calcd for C22H20N4, 340.1663; found, 340.1688.
2-Ethyl-4-phenyl-5-(pyrrol-2′-yl)-2,5-dihydro-1,2,3-triazine
(11c), 2-Ethyl-4-phenyl-5-pyrrol-3′-yl-2,5-dihydro-1,2,3-triaz-
ine (11d) and 1-Ethyl-3,4-bis(pyrrol-2′-yl)-5-phenyl-pyrazole
(12c)
2-Ethyl-5-(indol-3′-yl)-4-phenyl-2,5-dihydro-1,2,3-triazine
(11a) and 1-Ethyl-3,4-bis(indol-3′-yl)-5-phenyl-pyrazole (12a)
Column chromatography with cyclohexane–EtOAc, 1:1.
Column chromatography with cyclohexane–EtOAc, 1:1.
Fraction 1: 11a ; yield: 45 mg (15%); red oil.
IR (KBr): 3420, 2966, 1622, 1566, 1454, 748, 702 cm–1.
Fraction 1: 11c; yield: 57 mg (23%); red oil.
IR (KBr): 3394, 2971, 1632, 1561, 1438, 756, 700 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.92 (m, 1 H, N–H), 7.70–7.66 (m,
2 H, Ph), 7.33–7.12 (m, 7 H, Ph), 7.06 (d, 1 H, 3J5,6 = 4.4 Hz, 6-H),
6.81–6.79 (m, 1 H, Ph), 4.87 (d, 1 H, 3J5,6 = 4.4 Hz, 5-H), 4.02 (q, 2
H, 3J = 7.1 Hz, –CH2–), 1.17 (t, 3 H, 3J = 7.1 Hz, –CH3).
MS (EI, 70 eV): m/z (%) = 302 (11) [M+], 287 (11), 260 (43), 245
(100), 217 (10), 187 (25), 172 (10), 144 (19), 130 (17), 117 (33),
102 (88), 89 (11), 77 (34), 51 (19).
1H NMR (300 MHz, CDCl3): δ = 8.13 (br s, 1 H, N–H), 7.75–7.64
(m, 2 H, Ph), 7.29–7.24 (m, 3 H, Ph), 7.03 (d, 1 H, 3J5,6 = 4.45 Hz,
6-H), 6.50–6.49 (m, 1 H, 5′-H), 6.00–5.99 (m, 1 H, 3′-H or 4′-H),
5.85–5.84 (m, 1 H, 3′-H or 4′-H), 4.67 (d, 1 H, 3J5,6 = 4.45 Hz,
5-H), 3.73 (q, 2 H, 3J = 7.1 Hz, –CH2–), 1.30 (t, 3 H, 3J = 7.1 Hz,
–CH3).
13C NMR (75.7 MHz, CDCl3): δ = 139.05, 138.21, 134.30, 133.42,
129.47, 128.64, 126.41, 118.31, 108.22, 106.68, 54.57, 31.02,
13.02.
HRMS: m/z calcd for C19H18N4, 302.1531; found, 302.1563.
Fraction 2: 12a; yield: 60 mg (15%); red oil.
MS (EI, 70 eV, 80 °C): m/z (%) = 253 (9) [M+ + 1], 252 (100) [M+],
223 (10), 195 (30), 175 (19), 168 (31), 92 (29), 79 (12), 65 (20), 39
(11).
IR (KBr): 3429, 3151, 3029, 2976, 1566, 1459, 1102, 731, 700
cm–1.
1H NMR (300 MHz, CDCl3): δ = 10.25 (s, 1 H, N–H), 9.95 (s, 1 H,
N–H), 8.55 (m, 1 H, 2′-H Ind.), 7.42–7.31 (m, 7 H, Ph), 7.24–7.21
(m, 1 H, Ph), 7.14–7.10 (m, 4 H, Ph), 7.09 (m, 1 H, Ph), 6.80 (m, 1
HRMS: m/z calcd for C15H16N4, 252.1375; found, 252.1416.
Fraction 2: 11d; yield: 20 mg (8%); red oil.
IR (KBr): 3414, 2971, 1566, 1448, 1367, 802, 756, 690 cm–1.
3
H, 2′-H Ind.), 4.19 (q, 2 H, J = 7.1 Hz, –CH2–), 1.50 (t, 3 H,
3J = 7.1 Hz, -CH3).
1H NMR (300 MHz, CDCl3): δ = 8.02 (br s, 1 H, N–H), 7.75–7.64
(m, 2 H, Ph), 7.30–7.24 (m, 3 H, Ph), 6.98 (d, 1 H, 3J5,6 = 4.43 Hz,
6-H), 6.60–6.59 (m, 1 H, 2′-H or 5′-H), 6.50–6.49 (m, 1 H, 2′-H or
5′-H), 6.04–6.03 (m, 1 H, 4′-H), 4.52 (d, 1 H, 3J5,6 = 4.43 Hz,
5-H), 3.77 (q, 2 H, 3J = 7.1 Hz, –CH2–), 1.30 (t, 3 H, 3J = 7.1 Hz,
–CH3).
13C NMR (75.7 MHz, CDCl3): δ = 147.11, 142.98, 137.36, 137.06,
132.02, 130.76, 129.02, 128.84, 127.30, 125.61, 125.44, 124.17,
124.01, 123.38, 122.29, 122.08, 120.53, 120.02, 119.73, 112.20,
112.15, 111.73, 111.08, 111.06, 110.67, 109.31, 45.12, 16.03.
MS (FD, 15 mA): m/z (%) = 402 (100) [M+], 202 (3), 78 (62).
13C NMR (75.7 MHz, CDCl3): δ = 138.61, 132.38, 129.48, 128.64,
HRMS: m/z calcd for C27H22N4, 402.1844; found, 402.1861.
126.41, 119.88, 118.40, 115.97, 107.83, 54.53, 29.73, 13.21.
2-Ethyl-5-(indol-3′-yl)-4-methyl-2,5-dihydro-1,2,3-triazine
(11b) and 1-Ethyl-3,4-bis(indol-3′-yl)-5-methyl-pyrazole (12b)
Column chromatography with cyclohexane–EtOAc, 1:1.
MS (EI, 70 eV, 80 °C): m/z (%) = 253 (12) [M+ + 1], 252 (100)
[M+], 195 (34), 175 (14), 168 (37), 102 (43), 92 (33), 77 (12), 65
(15), 51 (14), 39 (14).
Fraction 1: 11b; yield: 33 mg (14%); red oil.
IR (KBr): 3404, 2971, 1459, 1260, 802, 746 cm–1.
HRMS: m/z calcd for C15H16N4, 252.1375; found, 252.1399.
Fraction 3: 12c; yield: 30 mg (10%); brown oil.
IR (KBr): 3399, 2966, 1566, 1443, 736, 700 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.23 (br s, 1 H, N–H), 7.47 (m, 1
H, 4′-H or 7′-H), 7.34 (m, 1 H, 4′-H or 7′-H), 7.13 (m, 1 H, 5′-H
or 6′-H), 7.05 (m, 1 H, 5′-H or 6′-H), 6.98 (m, 1 H, 2′-H), 6.80 (d, 1
H, 3J5,6 = 2.2 Hz, 6-H), 3.10 (q, 2 H, 3J = 7.1 Hz, –CH2–), 3.51 (d, 1
1H NMR (300 MHz, CDCl3): δ = 9.09 (br s, 1 H, N–H), 8.86 (br s,
1 H, N–H), 7.35–7.30 (m, 2 H, Ph), 7.25–7.21 (m, 3 H, Ph), 6.70–
6.65 (m, 2 H, 5′-H), 6.20 (m, 1 H, 3′-H or 4′-H), 6.13–6.05 (m, 2
H, 3′-H or 4′-H), 5.94 (m, 1 H, 3′-H or 4′-H), 4.00 (q, 2 H,
3J = 7.2 Hz, –CH2–), 1.31 (t, 3 H, 3J = 7.2 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 150.15, 142.18, 132.36, 130.19,
129.57, 128.50, 118.12, 117.88, 116.98, 116.58, 113.68, 110.60,
109.30, 108.95, 107.09, 44.72, 16.05.
3
H, 3J5,6 = 2.2 Hz, 5-H), 1.83 (s, 3 H, 4-CH3), 1.28 (t, 3 H, J = 7.1
Hz, -CH3).
13C NMR (75.7 MHz, CDCl3): δ = 142.13, 136.51, 134.51, 126.70,
123.06, 122.61, 120.20, 118.82, 111.59, 54.09, 34.09, 19.99, 12.99.
MS (EI, 70 eV): m/z (%) = 241 (11) [M+ + 1], 240 (100) [M+], 225
(40), 183 (29), 156 (20), 143 (24), 129 (27), 115 (39), 32 (17).
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis and Reactions of 1,2,3-Triazinium Salts
421
MS (EI, 70 eV): m/z (%) = 303 (14) [M+ + 1], 302 (67) [M+], 237
(15), 197 (9), 168 (12), 102 (100).
MS (EI, 70 eV): m/z (%) = 255 (4) [M+ + 1], 254 (54) [M+], 239
(28), 197 (22), 156 (11), 130 (26), 121 (11), 88 (30), 86 (93), 84
(100), 47 (47).
HRMS: m/z calcd for C19H18N4, 302.1531; found, 302.1557.
HRMS: m/z calcd for C15H18N4, 254.1532; found, 254.1552.
2-Ethyl-4-methyl-5-(pyrrol-2′-yl)-2,5-dihydro-1,2,3-triazine
(11e) and 1-Ethyl-5-methyl-3,4-bis(pyrrol-2′-yl)-pyrazole (12d)
Column chromatography with cyclohexane–EtOAc, 1:1.
2-Ethyl-5-(1′-methylpyrrol-3′-yl)-4-phenyl-2,5-dihydro-1,2,3-
triazine (11h)
Column chromatography with CH2Cl2–EtOAc, 5:1; yield: 61 mg
(23%); red oil.
IR (KBr): 2966, 1520, 1443, 1357, 1158, 776, 756, 695 cm–1.
Fraction 1: 11e; yield: 10 mg (5%); red oil.
IR (KBr): 3236, 2961, 1586, 1459, 797, 705 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.08 (br s, 1 H, N–H), 6.85 (d, 1
H, 3J5,6 = 3.4 Hz, 6-H), 6.59 (mc, 1 H, 5′-H), 6.03 (mc, 1 H, 3′-H or
4′-H), 5.99 (mc, 1 H, 3′- H, 4′-H), 3.67–3.53 (m, 3 H, –CH2– and
5-H), 1.93 (s, 3 H, 4-CH3), 1.21 (t, 3 H, –CH3).
MS (EI, 70 eV): m/z (%) = 191 (7) [M+ + 1], 190 (69) [M+], 175
(40), 161 (16), 106 (46), 92 (100), 79 (67), 65 (56), 52 (24), 41 (30),
39 (36).
1H NMR (300 MHz, CDCl3): δ = 7.76–7.27 (m, 2 H, Ph), 7.30–7.23
(m, 3 H, Ph), 6.96 (d, 1 H, 3J5,6 = 4.46 Hz, 6-H), 6.39–6.37 (m, 1 H,
2′-H or 5′-H), 6.30–6.28 (m, 1 H, 2′-H or 5′-H), 5.93–5.91 (m, 1
3
3
H, 4-H), 4.46 (d, 1 H, J5,6 = 4.46 Hz, 5-H), 3.77 (q, 2 H, J = 7.0
Hz, –CH2–), 3.45 (s, 3 H, N–CH3), 1.32 (t, 3 H, 3J = 7.0 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 138.78, 134.47, 128.86, 128.47,
126.31, 130.4, 122.13, 119.90, 107.57, 54.35, 36.32, 29.70, 13.19.
MS (EI, 70 eV): m/z (%) = 266 (29) [M+], 209 (26), 182 (59), 167
(31), 152 (10), 139 (25), 115 (27), 106 (100), 94 (22), 83 (78), 77
(78), 63 (27), 51 (56), 42 (75), 39 (52), 35 (64).
HRMS: m/z calcd for C10H14N4, 190.1219; found, 190.1235.
Fraction 2: 12d; yield: 10 mg (4%); red oil.
IR (KBr): 3399, 3251, 1622, 1489, 802, 731 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.05 (br s, 1 H, N–H), 8.24 (br s,
1 H, N–H), 6.80–6.78 (m, 1 H, 5′-H), 6.69–6.68 (m, 1 H, 5′-H),
6.24–6.21 (m, 1 H, 3′-H or 4′-H), 6.13–6.12, 6.11, 6.07–6.02 (3m,
3 H, 3′-H or 4′-H), 4.07 (q, 2 H, 3J = 7.2 Hz, –CH2–), 2.18 (s, 3 H,
4-CH3), 1.39 (t, 3 H, 3J = 7.2 Hz, –CH3).
MS (EI, 70 eV): m/z (%) = 241 (11) [M+ + 1], 240 (100) [M+], 212
(11), 169 (13), 105 (9), 32 (75).
HRMS: m/z calcd for C16H18N4, 266.1531; found, 266.1533.
2-Ethyl-4-methyl-5-(1′-methylpyrrol-2′yl)-2,5-dihydro-1,2,3-
triazine (11i)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 10
mg (5%); red oil.
IR (KBr): 2966, 1703, 1566, 1408, 807, 715 cm–1.
1H NMR (300 MHz, CDCl3): δ = 6.71 (d, 1 H, 3J5,6 = 2.1 Hz, 6-H),
6.57 (m, 1 H, 5′-H), 6.07 (m, 1 H, 3′-H or 4′-H), 5.91 (m, 1 H,
3′-H or 4′-H), 3.59 (q, 2 H, 3J = 7.2 Hz, –CH2–), 3.50 (s, 3 H, N–
CH3), 3.16 (d, 1 H, 3J5,6 = 2.1 Hz, 5-H), 1.87 (s, 3 H, 4-CH3), 1.25
(t, 3 H, 3J = 7.2 Hz, –CH3).
MS (EI, 70 eV): m/z (%) = 205 (11) [M+ + 1], 204 (100) [M+], 189
(46), 175 (10), 147 (16), 120 (31), 106 (38), 94 (23), 77 (35), 42
(68).
HRMS: m/z calcd for C14H16N4, 240.1375; found, 240.1398.
2-Ethyl-5-(2′-methylindol-3′-yl)-4-phenyl-2,5-dihydro-1,2,3-
triazine (11f)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 67
mg (21%); violet oil.
IR (KBr): 3409, 2956, 1555, 1459, 751, 695 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.76 (br s, 1 H, N–H), 7.56–7.53
(m, 2 H, Ph), 7.49–7.48 (m, 1 H, 4′-H), 7.17–7.11 (m, 4 H, Ph, 7′-
H), 7.06–7.00 (m, 2 H, 5′-H, 6′-H), 6.78 (d, 1 H, 3J5,6 = 3.5 Hz, 6-
H), 4.56 (d, 1 H, 3J5,6 = 3.5 Hz, 5-H), 3.81 (q, 2 H, 3J = 7.12 Hz,
–CH2–), 2.33 (s, 3 H, 2′-CH3), 1.35 (t, 3 H, 3J = 7.12 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 137.91, 136.10, 135.08, 134.87,
132.79, 128.74, 128.23, 127.73, 126.31, 121.56, 119.98, 118.18,
110.43, 110.29, 54.31, 28.18, 13.27, 12.14.
HRMS: m/z calcd for C11H16N4, 204.1375; found, 204.1390.
(2′,5′-Dimethylpyrrol-3′-yl)-2-ethyl-4-phenyl-2,5-dihydro-
1,2,3-triazine (11j)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 129
mg (46%); red crystals; mp 116 °C (CH2Cl2).
IR (KBr): 3424, 3373, 3063, 2981, 2930, 1611, 1448, 1357, 797,
761, 695 cm–1.
MS (EI, 70 eV): m/z (%) = 317 (23) [M+ + 1], 316 (100) [M+], 301
(30), 259 (57), 239 (16), 156 (20), 143 (49), 130 (71), 115 (9), 84
(35), 77 (9), 69 (15), 56 (77), 41 (39), 32 (37).
1H NMR (300 MHz, CDCl3): δ = 7.66–7.62 (m, 2 H, Ph), 7.27 (br
s, 1 H, N–H), 7.27–7.20 (m, 3 H, Ph), 6.86 (d, 1 H, 3J5,6 = 4.18 Hz,
6-H), 5.47 (m, 1 H, 4′-H), 4.27 (d, 1 H, 3J5,6 = 4.18 Hz, 5-H), 3.73
HRMS: m/z calcd for C20H20N4, 316.1688; found, 316.1710.
3
(q, 2 H, J = 7.17 Hz, –CH2–), 2.15 (s, 3 H, 2′-CH3 or 5′-CH3),
2.05 (s, 3 H, 2′-CH3 or 5′-CH3), 1.30 (t, 3 H, 3J = 7.17 Hz, –CH3).
2–Ethyl-4-methyl-5-(2′-methylindol-3′-yl)-2,5-dihydro-1,2,3-
triazine (11g)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 69
mg (27%); violet oil.
13C NMR (75.7 MHz, CDCl3): δ = 138.82, 136.09, 136.53, 134.71,
128.74, 128.39, 126.29, 125.81, 116.63, 106.62, 54.27, 29.36,
13.17, 13.05, 11.47.
MS (EI, 70 eV): m/z (%) = 281 (9) [M+ + 1], 280 (84) [M+], 265
(17), 223 (20), 203 (17), 120 (19), 107 (24), 94 (83), 85 (100), 83
(100), 77 (26), 47 (45).
IR (KBr): 3261, 2966, 1622, 1510, 1464, 802, 751 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.03 (br s, 1 H, N–H), 7.35–7.24
(m, 2 H, 4′-H, 7′-H), 7.11–6.97 (m, 2 H, 5′-H, 6′-H), 6.71 (d, 1
H, 3J5,6 = 1.7 Hz, 6-H), 3.73 (q, 2 H, 3J = 7.05 Hz, –CH2–), 3.22 (d,
1 H, 3J5,6 = 1.7 Hz, 5-H), 2.27 (s, 3 H, 2′-CH3), 1.71 (s, 3 H, 4-CH3),
1.35 (t, 3 H, 3J = 7.05 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 150,67, 142.64, 135.44, 127.90,
135.72, 121.70, 120.06, 118.18, 110.67, 107.47, 54.11, 34.20,
19.53, 13.05, 11.87.
HRMS: m/z calcd for C17H20N4, 280.1688; found, 280.1670.
5-(2′,5′-Dimethylpyrrol-3′-yl)-2-ethyl-4-methyl-2,5-dihydro-
1,2,3-triazine (11k)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 72
mg (33%); red oil.
IR (KBr): 3261, 2966, 2915, 1540, 1438, 1377, 812, 741, 680 cm–1.
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

422
M. Mättner, H. Neunhoeffer
PAPER
1H NMR (300 MHz, CDCl3): δ = 7.53 (br s, 1 H, N–H), 6.63 (d, 1
H, 3J5,6 = 1.9 Hz, 6-H), 5.56 (s, 1 H, 4′-H), 3.63 (q, 2 H, 3J = 7.1 Hz,
–CH2–), 2.96 (d, 1, 3J5,6 = 1.9 Hz, 5-H), 2.14, 2.07 (2s, 6 H, 2′-CH3,
5′-CH3), 1.78 (s, 3 H, 4-CH3), 1.22 (t, 3 H, 3J = 7.1 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 141.85, 134.66, 124.97, 122.17,
114.11, 105.44, 52.90, 33.78, 18.63, 11.91, 11.80, 9.98.
Reactions of N-Phenylated 1,2,3-Triazinium Salts 9 with Elec-
tron Rich Heterocycles; General Procedure
To a soln of N-phenyl-1,2,3-triazinium salt 9 (0.40 mmol) in
CH3CN (5 mL) was added the heterocycle (0.40 mmol) in CH3CN
(5 mL) at r.t. The reaction was observed by TLC and stopped when
no further changes were observable. The solvent was removed un-
der reduced pressure and the crude material purified by column
chromatography. The insoluble residue (prior to chromatography)
is mainly 1,2,3-triazinium salt 9 and can be used for further reac-
tions.
MS (EI, 70 eV): m/z (%) = 218 (67) [M+], 203 (62), 134 (28), 120
(29), 107 (26), 94 (100), 77 (15), 42 (29).
HRMS: m/z calcd for C12H18N4, 218.1532; found, 218.1540.
2,4-Diphenyl-5-(2′-methylindol-3′-yl)-2,5-dihydro-1,2,3-triaz-
ine (22a)
Reaction time 3 d; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 22 mg (15%); violet oil.
5-(2′,4′-Dimethylpyrrol-3′-yl)-2-ethyl-4-phenyl-2,5-dihydro-
1,2,3-triazine (11l)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 30
mg (11%); brown oil.
IR (KBr): 3404, 3058, 2966, 1606, 1489, 756, 700 cm–1.
IR (KBr): 3409, 3063, 2971, 2940, 1561, 1443, 1362, 1265, 802,
766, 695 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.81 (br s, 1 H, N–H), 7.75–7.71
(m, 4 H, Ph), 7.51–7.48 (m, 1 H, Ind), 7.35–7.30 (m, 3 H, Ind),
7.19–7.15 (m, 3 H, Ph), 7.05–7.01 (m, 3 H, Ph), 6.89 (d, 1 H,
3J5,6 = 3.6 Hz, 6-H), 4.82 (d, 1 H, 3J5,6 = 3.6 Hz, 5-H), 2.21 (s, 3 H,
2′-CH3).
13C NMR (75.7 MHz, CDCl3): δ = 146.09, 137.60, 136.07, 133.43,
127.54, 125.22, 115.40, 134.91, 129.02, 128.38, 126.13, 122.63,
121.72, 120.28, 117.66, 110.61, 27.19, 12.19.
MS (EI, 70 eV): m/z (%) = 365 (32) [M+ + 1], 364 [M+] (100), 349
(35), 336 (18), 287 (15), 272 (33), 260 (34), 246 (14), 234 (24), 217
(13), 182 (10), 169 (17), 143 (79), 130 (77), 115 (12), 91 (12), 77
(50).
1H NMR (300 MHz, CDCl3): δ = 7.88 (br s, 1 H, N–H), 7.65–7.61
(m, 2 H, Ph), 7.45–7.18 (m, 3 H, Ph), 7.21–7.18 (superimposed d, 1
H, 6-H), 6.63 (m, 1 H, 5′-H), 4.38 (d, 1 H, 3J5,6 = 4.38 Hz, 5-H), 3.74
(q, 2 H, 3J = 7.2 Hz, –CH2–), 1.90, 1.89 (2s, 6 H, 2′-CH3, 4′-CH3),
1.34 (t, 3 H, 3J = 7.2 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 138.92, 136.17, 135.28, 129.45,
128.62, 127.04, 129.53, 126.29, 127.42, 107.73, 54.58, 30.96,
29.11, 12.96.
MS (EI, 70 eV): m/z (%) = 280 [M+] (16), 265 (12), 186 (11), 107
(16), 98 (11), 84 (100), 77 (10).
HRMS: m/z calcd for C17H20N4, 280.1688; found, 280.1686.
HRMS: m/z calcd for C24H20N4, 364.1688; found, 364.1672.
5-(2′,4′-Dimethylpyrrol-3′-yl)-2-ethyl-4-methyl-2,5-dihydro-
1,2,3-triazine (11m)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 20
mg (9%); red oil.
5-(Indol-3′-yl)-4-methyl-2-phenyl-2,5-dihydro-1,2,3-triazine
(22b)
Reaction time 5 d; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 18 mg (16%); red oil.
IR (KBr): 3399, 2966, 2930, 1688, 1545, 1428, 1382, 802, 705
cm–1.
IR (KBr): 3434, 3068, 2971, 2915, 1601, 1510, 1469, 766, 741, 700
cm–1.
1H NMR (300 MHz, DMSO-d6): δ = 11.23 (br s, 1 H), 7.75–7.72
(m, 2 H, Ph), 7.56–7.50 (m, 4 H, Ph), 7.37–7.32 (m, 3 H, Ph), 7.20–
7.04 (m, 2 H, 6-H, Ph), 4.79 (m, 1 H, 5-H), 2.14 (s, 3 H, 4-CH3).
1H NMR (300 MHz, CDCl3): δ = 7.57 (br s, 1 H, N–H), 6.87–6.83
3
(m, 1 H, 5′-H), 6.57 (d, 1 H, J5,6 = 1.7 Hz, 6-H), 3.64 (q, 2 H,
3J = 7.12 Hz, –CH2–), 2.92 (d, 1 H, 3J5,6 = 1.7 Hz, 5-H), 1.97, 1.87,
3
1.68 (3s, 9 H, 2′-CH3, 4′-CH3, 4-CH3), 1.25 (t, 3 H, J = 7.12 Hz,
13C NMR (75.7 MHz, DMSO-d6): δ = 147.10, 143.69, 139.52,
136.19, 127.20, 128.98, 125.62, 123.98, 122.34, 120.97, 119.23,
118.61, 111.58, 38.59, 12.99.
–CH3).
MS (EI, 70 eV): m/z (%) = 218 [M+] (3), 217 [M+–1] (7), 167 (14),
149 (38), 139 (17), 124 (35), 113 (13), 96 (29), 84 (76), 67 (58), 57
(47), 38 (100), 28 (100).
MS (EI, 70 eV): m/z (%) = 289 [M+ + 1] (28), 288 [M+] (100), 246
(18), 219 (12), 144 (11), 77 (23).
HRMS: m/z calcd for C12H18N4, 218.1688; found, 218.1691.
HRMS: m/z calcd for C18H16N4, 288.1375; found, 288.1363.
5-(3′,5′-Dimethylpyrrol-2′-yl)-2-ethyl-4-methyl-2,5-dihydro-
1,2,3-triazine (11n)
Column chromatography with cyclohexane–EtOAc, 1:1; yield: 24
mg (11%); red oil.
2,4-Diphenyl-5-(N-methylpyrrol-3′-yl)-2,5-dihydro-1,2,3-tri-
azine (22c)
Reaction time 16 h; column chromatography with cyclohexane–
EtOAc (1:1); yield: 28 mg (23%); red oil.
IR (KBr): 3434, 2976, 1448, 802, 700 cm–1.
IR (KBr): 3052, 2971, 1591, 1494, 751, 695, 608 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.64 (br s, 1 H, N–H), 6.63 (d, 1
3
1H NMR (300 MHz, CDCl3): δ = 7.87–7.84 (m, 2 H, Ph), 7.74–7.71
(m, 2 H, Ph), 7.33–7.28 (m, 5 H, Ph), 7.10 (d, 1 H, 3J5,6 = 4.4 Hz,
6-H), 6.40–6.38 (m, 1 H, 2′-H or 5′-H), 6.32–6.31 (m, 1 H, 2′-H or
5′-H), 5.96–5.94 (m, 1 H, 4′-H), 4.55 (d, 1 H, 3J5,6 = 4.4 Hz, 5-H),
3.43 (s, 3 H, N–CH3).
H, J5,6 = 1.5 Hz, 6-H), 5.60–5.59 (m, 1 H, 4′-H), 3.67 (q, 2 H,
3
3J = 7.1 Hz, –CH2–), 2.99 (d, 1 H, J5,6 = 1.5 Hz, 5-H), 2.14, 2.07,
1.76 (3s, 9 H, 3′-CH3, 5′-CH3, 4-CH3), 1.45 (t, 3 H, 3J = 7.1 Hz,
–CH3).
MS (EI, 70 eV): m/z (%) = 218 [M+] (4), 169 (100), 147 (30), 119
13C NMR (75.7 MHz, CDCl3): δ = 146.51, 139.01, 135.48, 135.19,
129.31, 128.89, 128.54, 126.58, 122.73, 122.41, 119.93, 115.74,
120.62, 107.44, 36.32, 29.81.
(46), 97 (10), 69 (70), 32 (100).
HRMS: m/z calcd for C12H18N4, 218.1688; found, 218.1665.
MS (EI, 70 eV): m/z (%) = 315 (29) [M+ + 1], 314 (100) [M+], 313
(43) [M+–1], 237 (12), 210 (14), 184 (29), 167 (13), 106 (20), 94
(32), 77 (61).
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis and Reactions of 1,2,3-Triazinium Salts
423
HRMS: m/z calcd for C20H18N4, 314.1531, found, 314.1517.
1H NMR (300 MHz, CDCl3): δ = 7.68–7.63 (m, 2 H, Ph), 7.33–7.26
3
(m, 3 H, Ph), 6.78 (d, 1 H, J6′,5′ = 4.5 Hz, 6′-H), 4.56 (dd, 1 H,
3
4-Methyl-5-(N-methylpyrrol-3′-yl)-2-phenyl-2,5-dihydro-
1,2,3-triazine (22d)
3J5′,6′ = 4.5 Hz, J5′,2 = 9.5 Hz, 5′-H), 3.86–3.79 (m, 3 H, –CH2–,
2-H), 2.03 (s, 3 H, –CH3), 1.88 (s, 3 H, –CH3), 1.33 (t, 3 H, 3J = 7.1
Reaction time 2 h; column chromatography with CHCl3; yield: 21
mg (21%); red oil.
IR (KBr): 2966, 1545, 1418, 797, 705 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.60–7.57 (m, 2 H, Ph), 7.28–7.24
(m, 2 H, Ph), 6.98–6.93 (m, 1 H, Ph), 6.81 (d, 1 H, 3J5,6 = 2.9 Hz, 6-
H), 6.49–6.47 (m, 1 H, 2′-H or 5′-H), 6.38–6.37 (m, 1 H, 2′-H or
5′-H), 5.93–5.92 (m, 1 H, 4′-H), 3.58 (d, 1 H, 3J5,6 = 2.9 Hz, 5-H),
3.54 (s, 3 H, N–CH3), 1.51 (s, 3 H, 4-CH3).
Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 202.81, 201.65, 135.31, 134.18,
128.80, 129.69, 126.39, 131.95, 58.28, 53.36, 31.90, 29.78, 30.41,
13.15.
MS (EI, 70 eV): m/z (%) = 286 (1) [M+ + 1], 285 (6) [M+], 242 (25),
186 (100), 103 (28), 77 (10), 43 (18).
HRMS: m/z calcd for C16H19N3O2, 285.1477; found, 285.1477.
MS (EI, 70 eV): m/z (%) = 253 (1) [M+ + 1], 252 (10) [M+], 221
(10), 167 (24), 149 (42), 125 (15), 111 (43), 97 (60), 83 (72), 57
(100), 43 (87).
3-(2′-Ethyl-4′-methyl-2′,5′-dihydro-1,2,3-triazin-5′-yl)-pentan-
2,4-dione (24d)
Reaction time 1 h; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 74 mg (33%); yellow oil.
HRMS: m/z calcd for C15H16N4, 252.1375; found, 252.1402.
IR (film): 2966, 2930, 1738, 1714, 1565 cm–1.
Reactions with C,H-Acidic Compounds; General Procedure
To a cooled (0 °C) soln of compound 22 (1.20 mmol) in THF (5
mL) was added NaH (29 mg, 1.20 mmol), suspended in THF (2
mL). After 30 min, when no further gas formation was observed, the
1,2,3-triazinium salt 7 (1.00 mmol) in CH3CN (5 mL) was added.
The reaction mixture was warmed to r.t. and stirred for several
hours (TLC control). The solvent was removed under reduced pres-
sure and the crude material purified by column chromatography.
1H NMR (500 MHz, CDCl3): δ = 6.55–6.52 (m, 1 H, 6′-H), 3.75–
3.72 (superimposed q, 2 H, –CH2–), 3.63 (d, 1 H, 3J2,5′ = 9.6 Hz,
2-H), 3.46 (dd, 1 H, 3J5′,6′ = 4.1 Hz, 3J5′,2 = 9.6 Hz, 5′-H), 2.13, 2.07,
1.93 (3s, 9 H, 1-CH3, 5-CH3, 4′-CH3), 1.16 (superimposed t, 3 H,
–CH3).
13C NMR (125 MHz, CDCl3): δ = 200.79, 199.58, 148.08, 130.17,
61.26, 58.52, 57.52, 40.02, 34.87, 29.43, 15.77. Superimposition
due to a small amount of the enol form.
MS (EI, 70 eV): m/z (%) = 224 (2) [M+ + 1], 223 (12) [M+], 222
Dimethyl 2-(2′-ethyl-4′-phenyl-2′,5′-dihydro-1,2,3-triazin-
5′-yl) Malonate (24a)
Reaction time 16 h; column chromatography with CH2Cl2–EtOAc,
5:1; yield: 123 mg (39%); yellow oil.
(100) [M+–1], 179 (24), 124 (38), 43 (18).
HRMS: m/z calcd for C11H17N3O2, 223.1321, found, 223.1267.
IR (KBr): 3063, 2951, 1739, 1443, 1260, 766, 700 cm–1.
Ethyl 2-(2′-ethyl-4′-phenyl-2′,5′-dihydro-1,2,3-triazin-5′-yl)-3-
oxobutyrate (24e)
Reaction time 16 h; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 212 mg (67%); orange oil.
1H NMR (300 MHz, CDCl3): δ = 7.71–7.68 (m, 2 H, Ph), 7.37–7.24
3
(m, 3 H, Ph), 6.87 (d, 1 H, J6′,5′ = 4.5 Hz, 6′-H), 4.53 (dd, 1 H,
3
3
3J5′,6′ = 4.5 Hz, J5′,2 = 10.3 Hz, 5′-H), 3.83 (q, 2 H, J = 7.2 Hz,
–CH2–), 3.67 (s, 3 H, –OCH3), 3.35 (d, 1 H, 3J2,5′ = 10.3 Hz, 2-H),
3.20 (s, 3 H, –OCH3), 1.35 (t, 3 H, 3J = 7.2 Hz, –CH3).
IR (film): 3068, 2991, 2930, 1729, 1591, 1367, 766, 690 cm–1.
1H NMR (300 MHz, CDCl3): δ = 13.21 (br s, 0.25 H, -OH of the
enol form), 7.72–7.68 (m, 2 H, Ph), 7.30–7.24 (m, 3 H, Ph), 6.85–
6.83 (superimposed d, 1 H, 6′-H), 4.59–4.53 (superimposed dd, 1 H,
5′-H), 4.11–4.08 (superimposed d, 1 H, 5′-H, enol), 3.86–3.81 (su-
perimposed q, 2 H, –CH2–), 3.68–3.61 (superimposed q, 2 H,
13C NMR (75.7 MHz, CDCl3): δ = 167.65, 149.45, 134.51, 130.36,
129.31, 128.60, 125.93, 54.50, 53.16, 52.67, 46.09, 31.23, 13.40.
MS (EI, 70 eV): m/z (%) = 317 [M+] (11), 186 (100), 158 (20), 115
(20), 104 (28), 77 (14).
3
–CH2–), 3.54 (d, 1 H, J2,5′ = 10.2 Hz, 2-H), 2.06 (s, 3 H, 4-CH3),
HRMS: m/z calcd for C16H19N3O4, 317.1376; found, 317.1359.
1.96 (s, 3 H, 4-CH3), 1.36 (t, 3 H, –CH3), 0.75 (t, 3 H, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 202.08, 167.47, 135.03, 134.73,
131.62, 130.88, 129.75, 129.35, 129.09, 128.90, 126.09, 62.00,
61.23, 54.47, 53.99, 52.95, 31.42, 31.27, 30.87, 29,62, 14.08, 13.57,
13.41. The keto/enol forms exist in soln in a 3:1 ratio.
MS (EI, 70 eV): m/z (%) = 316 (1) [M+ + 1], 315 (10) [M+], 224
(10), 186 (100), 158 (14), 115 (10), 103 (38), 77 (14).
Dimethyl 2-(2′-ethyl-4′-methyl-2′,5′-dihydro-1,2,3-triazin-
5′-yl) Malonate (24b)
Reaction time 1 h; column chromatography with CH2Cl2–EtOAc,
5:1; yield: 240 mg (94%); yellow oil.
IR (film): 2961, 2869, 1739, 1443, 1245, 1026, 975, 843 cm–1.
3
1H NMR (300 MHz, CDCl3): δ = 6.62 (d, 1 H, J6′,5′ = 4.0 Hz,
HRMS: m/z calcd for C17H21N3O3, 315.1556; found, 315.1597.
6′-H), 3.69–3.61 (m, 9 H, 2 × OCH3, –CH2–, 5′-H), 3.40–3.32 (d, 1
H, 3J2,5′ = 9.9 Hz, 2-H), 1.97 (s, 3 H, 4′-CH3), 1.23 (t, 3 H, 3J = 7.1
Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 166.95, 166.47, 136.14, 127.95,
52.97, 51.89, 51.81, 45.10, 34.60, 19.98, 11.90.
MS (EI, 70 eV): m/z (%) = 255 [M+] (4), 181 (9), 164 (10), 124
Ethyl 2-(2′-Ethyl-4′-methyl-2′,5′-dihydro-1,2,3-triazin-5′-yl)-3-
oxobutyrate (24f)
Reaction time 1 h; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 192 mg (76%); red oil.
IR (film): 2986, 2940, 1744, 1713, 1581, 1240, 1016 cm–1.
(100), 96 (11), 85 (19), 83 (21), 42 (18).
3
1H NMR (500 MHz, CDCl3): δ = 6.68 (d, 1 H, J6′,5′ = 4.0 Hz,
HRMS: m/z calcd for C11H17N3O4, 255.1219; found, 255.1233.
6′-H), 6.66 (d, 1 H, 3J6′,5′ = 4.0 Hz, 6′-H), 4.22–4.18 (superimposed
q, 4 H, OCH2–), 3.77–3.61 (m, 8 H, N–CH2–, 5′-H, 2-H), 2.26 (s,
3 H, 4-CH3), 2.16 (s, 3 H, 4-CH3), 2.04, 2.02 (2s, 6 H, 4′-CH3),
1.32–1.25 (superimposed t, 12 H, –CH3).
3-(2′-Ethyl-4′-phenyl-2′,5′-dihydro-1,2,3-triazin-5′-yl)-pen-
tan-2,4-dione (24c)
Reaction time 3 h; column chromatography with cyclohexane–
EtOAc, 1:1; yield: 205 mg (72%); yellow oil.
13C NMR (125 MHz, CDCl3): δ = 201.61, 200.58, 167.60, 167.08,
138.35, 138.18, 130.06, 129.88, 61.08, 54.00, 53.74, 53.44, 35.43,
IR (KBr): 3068, 2981, 2925, 1734, 1708, 1581, 776, 690 cm–1.
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

424
M. Mättner, H. Neunhoeffer
PAPER
35.25, 30.69, 29.88, 21.42, 21.21, 14.01, 12.89, 12.87. The keto/
enol forms exist in soln in a 1:1 ratio.
MS (EI, 70 eV): m/z (%) = 254 (1) [M+ + 1], 253 (7) [M+], 180 (10),
1H NMR (300 MHz, CDCl3): δ = 9.29 (s, 1 H, 6-H), 3.92 (q, 2 H,
3J = 7.3 Hz, –CH2–), 2.27, 2.23, 1.85 (3 s, 9 H, 1-CH3, 5-CH3,
4′-CH3), 1.24 (t, 3 H, 3J = 7.3 Hz, –CH3).
124 (100), 96 (9).
MS (EI, 70 eV): m/z (%) = 222 (1) [M+ + 1], 221 (27) [M+], 220
(100) [M+–1], 178 (27), 122 (17), 43 (37).
HRMS: m/z calcd for C12H19N3O3, 253.1427; found, 253.1400.
HRMS: m/z calcd for C11H15N3O2, 221.1164; found, 221.1201.
Oxidation of the Dihydroadducts 24; General Procedure
To a soln of the dihydroadduct 24 (0.50 mmol) in dioxane (6 mL)
was added DDQ (227 mg, 1.00 mmol) in dioxane (8 mL) at r.t. The
reaction mixture was stirred for 2 h (TLC-control). The soln was
then concentrated under vacuum and the hydrochinone removed by
filtration. The remaining solvent was removed under reduced pres-
sure and the crude product purified by column chromatography (cy-
clohexane–EtOAc, 1:1).
Ethyl 2-(2′-Ethyl-4′-phenyl-2′H-1,2,3-triazin-5′-yliden)-3-
oxobutyrate (25e)
Yield: 75 mg (48%); red oil.
IR (film): 3012, 2984, 2941, 1738, 1560, 1348, 775, 701 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.33 (s, 1 H, 6′-H), 7.43–7.35 (m,
3
2 H, Ph), 7.32–7.24 (m, 3 H, Ph), 4.26 (q, 2 H, J = 7.2 Hz,
3
–OCH2–) 3.95 (q, 2 H, J = 7.2 Hz, –CH2–), 2.10 (s, 3 H, 4-CH3),
1.86 (t, 3 H, 3J = 7.2 Hz, –CH3), 1.24 (t, 3 H, 3J = 7.2 Hz, –CH3).
Dimethyl (2′-Ethyl-4′-phenyl-2′H-1,2,3-triazin-5′-yliden)
Malonate (25a)
Yield: 155 mg (98%); yellow oil.
MS (EI, 70 eV): m/z (%) = 314 (2) [M+ + 1], 313 (27) [M+], 222
(14), 184 (100), 156 (20), 101 (45), 77 (37).
IR (KBr): 3007, 2966, 1723, 1683, 1545, 1268, 802, 705 cm–1.
HRMS: m/z calcd for C17H19N3O3, 313.1426; found, 314.1432.
1H NMR (300 MHz, CDCl3): δ = 9.14 (s, 1 H, H-6), 7.44–7.39 (m,
2 H, Ph), 7.34–7.28 (m, 3 H, Ph), 4.14 (q, 2 H, J = 7.3 Hz,
3
Ethyl 2-(2′-Ethyl-4′-methyl-2′H-1,2,3-triazin-5′-yliden)-3-
oxobutyrate (24f)
Yield: 37 mg (48%); red oil.
IR (film): 2993, 2931, 1735, 1567, 1298, 1030 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.02 (s, 1 H, 6′-H), 4.34 (q, 2 H,
–OCH2–), 3.58 (q, 2 H, –CH2–), 2.15 (s, 3 H, 4-CH3), 2.02, (s, 3 H,
4′-CH3), 1.43–1.36 (superimposed t, 6 H, –CH3).
MS (EI, 70 eV): m/z (%) = 252 (1) [M+ + 1], 251 (18) [M+], 178
(10), 122 (100), 94 (11).
–CH2–), 3.63 (s, 3 H, OCH3), 2.90 (s, 3 H, OCH3), 1.42 (t, 3 H,
3J = 7.3 Hz, –CH3).
13C NMR (75.7 MHz, CDCl3): δ = 167.43, 166.28, 146.61, 138.29,
136.22, 129.29, 128.56, 126.98, 128.32, 101.49, 56.57, 51.87,
51.28, 14.46.
MS (EI, 70 eV): m/z (%) = 316 (1) [M+ + 1], 315 (35) [M+], 284
(10), 255 (100), 241 (10), 224 (32), 197 (12), 182 (26), 173 (15),
140 (17), 115 (21), 105 (89), 77 (57), 69 (26), 55 (46), 43 (51).
HRMS: m/z calcd for C16H17N3O4, 315.1219; found, 315.1231.
HRMS: m/z calcd for C12H17N3O3, 251.1270; found, 251.1258.
Dimethyl (2′-Ethyl-4-methyl-2′H-1,2,3-triazin-5′-yliden)
Malonate (25b)
Yield: 38 mg (30%); yellow oil.
References
(1) (a) Chupakhin, O. N.; Charushin, V. N.; van der Plas, H. C.
In Nucleophilic Aromatic Substitution of Hydrogen;
Academic Press: San Diego, 1994, ; and references cited
therein. (b) Chupakhin, O. N.; Charushin, V. N.; van der
Plas, H. C. Tetrahedron 1988, 44, 1.
IR (KBr): 2966, 1729, 1688, 1566, 1438, 1031, 807 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.43 (s, 1 H, 6-H), 4.06 (q, 2 H,
3J = 7.2 Hz, –CH2–), 3.70, 3.69 (2 s, 6 H, OCH3), 2.09 (s, 3 H, 4-
CH3), 1.34 (t, 3 H, 3J = 7.2 Hz, –CH3).
MS (EI, 70 eV): m/z (%) = 254 (6) [M+ + 1], 253 (79) [M+], 222
(77), 208 (10), 190 (100), 163 (48), 153 (17), 137 (27), 123 (14),
105 (26), 77 (22), 67 (26), 51 (46).
(2) Charushin, V. N.; Chupakhin, O. N.; Sidorov, E. O.; Beiles,
Y. I. Zh. Org. Khim. 1978, 14, 140.
(3) (a) Rusinov, V. L.; Zyryanov, G. V.; Pilicheva, T. L.;
Chupakhin, O. N.; Neunhoeffer, H. J. Heterocycl. Chem.
1997, 34, 1013. (b) Kojevnikov, D. N.; Ulomsky, E. N.;
Rusinov, V. L.; Chupakhin, O. N.; Neunhoeffer, H.
Mendeleev Commun. 1997, 116. (c) Chupakhin, O. N.;
Rusinov, V. L.; Ulomsky, E. N.; Kojevnikov, D. N.;
Neunhoeffer, H. Mendeleev Commun. 1997, 66.
(4) Stupnikova, T. V.; Petrenko, V. V. Khim. Geterotskil.
Soedin. 1984, 1383.
(5) Pozharskii, A. F.; Gulevskaya, A. V. Chem. Heterocycl.
Cmpds. 2001, 37, 1480; and references cited therein.
(6) For a review on 1,2,3-triazines see: (a) Ohsawa, A.; Itoh, T.
In Comprehensive Heterocyclic Chemistry II; Boulton, A. J.,
Ed.; Elsevier: Oxford, 1996, 483–505. (b) Ohsawa, A.; Itoh,
T. In Comprehensive Heterocyclic Chemistry II; Boulton, A.
J., Ed.; Elsevier: Oxford, 1996, 1177–1307.
HRMS: m/z calcd for C11H15N3O4, 253.1063; found, 253.1101.
3-(2′-Ethyl-4′-phenyl-2′H-1,2,3-triazin-5′-yliden)-pentan-
2,4-dione (25c)
Yield: 35 mg (24%); as yellow oil.
IR (KBr): 3013, 2976, 1745, 1716, 1565, 782, 701 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.27 (s, 1 H, 6′-H), 7.46–7.38 (m,
3
2 H, Ph), 7.31–7.24 (m, 3 H, Ph), 4.04 (q, 2 H, J = 7.1 Hz,
–CH2–), 2.10 (s, 3 H, –CH3), 1.96 (s, 3 H, –CH3), 1.27 (t, 3 H,
3J = 7.1 Hz, –CH3).
MS (EI, 70 eV): m/z (%) = 284 (4) [M+ + 1], 283 (48) [M+], 240
(28), 184 (100), 101 (31), 77 (18).
HRMS: m/z calcd for C16H17N3O2, 285.1321; found, 285.1344.
(7) (a) Okatani, T.; Koyama, J.; Tagahara, K. Heterocycles
1989, 29(9), 1809. (b) Neunhoeffer, H.; Bopp, R.; Diehl, W.
Liebigs Ann. Chem. 1993, 367.
(8) Neunhoeffer, H.; Clausen, M.; Vötter, H.-D.; Ohl, H.;
Krüger, C.; Angermund, K. Liebigs Ann. Chem. 1985, 9,
1732.
3-(2′-Ethyl-4′-methyl-2′H-1,2,3-triazin-5′-yliden)-pentan-
2,4-dione (25d)
Yield: 34 mg (31%); yellow oil.
IR (film): 2978, 1745, 1721, 1578 cm–1.
Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
(9) Ohsawa, A.; Arai, H.; Ohnishi, H.; Kaihoh, T.; Itoh, T.;
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(15) Energies for N-2 ethylated and N-2 protonated 1,2,3-
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(19) Neßlers reagent for ammonium salts from Merck VWR
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(12) Ab initio calculations done with Gaussian 9412 with standard
basic set 6–311G*, geometries were optimized on HF/6–
31G* level and characterized as minima by vibrational
frequency analysis (number of imaginary frequencies = zero
for minima). These provided the zero-point vibrational
energies (ZPEs) which were scaled for the calculation of
relative energies by an empirical factor of 0.89.13
(13) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
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Synthesis 2003, No. 3, 413–425 ISSN 0039-7881 © Thieme Stuttgart · New York