8896 J . Org. Chem., Vol. 64, No. 24, 1999
Barr et al.
anism and are considerably weaker.43-46 In this context
the design of new materials with magnetic ordering at
higher temperatures should greatly benefit from ligands
which (a) have large spin densities on the coordination
sites and (b) have the ability to simultaneously bridge
more than one metal center. Compound 4 fulfills both
criteria nicely. We are currently actively pursuing dis-
crete complexes of 3 and 4 as well as 1-dimensional chain
complexes of 4 and will report on these in due course.
(330 mg, 1.59 mmol) in 5 mL of water was added a solution of
NaIO4 (260 mg, 1.22 mmol) in 7 mL of water. The solution
immediately turned bright yellow/orange, and within 5 min
of stirring a fine yellow solid precipitated. The reaction mixture
was then diluted into 100 mL of water and extracted with CH2-
Cl2. The organic layers were combined, dried over MgSO4, and
evaporated under reduced pressure. The residue was subjected
to flash chromatography on silica gel using ethyl acetate as
eluent to give 8 as yellow needles from chloroform/petroleum
ether, yield 130 mg (40%). The starting tetrazane 6 was also
1
recovered from the column in 40% yield. H NMR (CDCl3): δ
8.5 (d, 1H, J ) 5.1 Hz), 8.0 (d, 1H, J ) 8.1 Hz), 7.8 (td, 1H, J
) 7.7, 1.5 Hz), 7.3 (dd, 1H, J ) 7.4, 5.9 Hz), 3.3 (s, 3H), 3.1
ppm (s, 3H). 13C (CDCl3): 155.6, 147.8, 146.6, 145.2, 136.3,
124.4, 120.0, 36.6, 35.7 ppm. Mp: 90-92 °C. Anal. Calcd for
C9H11N5O: C, 52.67; H, 5.40; N, 34.13. Found: C, 52.88; H,
Exp er im en ta l Section
Gen er a l Meth od s. Unless stated otherwise, all reactions
and manipulations were carried out under an argon atmo-
sphere using standard Schlenk line or glovebox techniques.
Solvents were dried and distilled under argon prior to use
(CH2Cl2, from CaH2; benzene, toluene, and THF, from sodium/
benzophenone). All reagents were purchased from Aldrich and
used as received except as stated otherwise. NMR spectra were
recorded on 360 or 250 MHz instruments. Infrared spectra
were recorded as Nujol mulls on KBr plates or as KBr pressed
pellets. EPR spectra were recorded on a Varian E6S instru-
ment, and the spectra so obtained were simulated using the
WinEPR SimFonia program. Elemental analyses were carried
out by Canadian Microanalytical Services Ltd., Vancouver, BC,
Canada. Semiempirical MO calculations were carried out with
HyperChem 5.0.1. Cyclic voltammetry experiments were
performed with a Bioanalytical Systems CV50 voltammetric
analyzer. Typical electrochemical cells were consisted of a
three electrode setup containing acetonitrile solutions of
analyte (∼1 mM), electrolyte (0.1 M Bu4N+BF4-), and ferrocene
(0.5-1 mM), the last of which was added as an internal
reference.
Syn t h esis of Ca r b on ic Acid Bis(1-m et h ylh yd r a zid e)
(5). A solution of triphosgene (5.00 g, 17.2 mmol) in 60 mL of
benzene was added dropwise to a solution of methylhydrazine
(9.507 g, 0.206 mol) in 120 mL of CH2Cl2 at -42 °C (dry ice/
acetonitrile bath) under argon. The reaction mixture was
stirred for 15 h, and then the white precipitate of methylhy-
drazine hydrochloride was filtered out in vacuo and washed
with 2 × 10 mL of hexanes. The filtrate was evaporated in
vacuo to give 5 as a very hygroscopic white solid, yield 5.776
5.43; N, 34.33. IR (KBr): ν(NH) 3215 (s), ν(CdO) 1675 (s) cm-1
.
λ
max (CH2Cl2): 357 nm. MS (EI LR): m/z 205 (M+, 100%), 190
((M - CH3)+, 10), 78 (C5H4N+, 35).
Syn th esis of 3-(2-P yr id yl)-1,5-d im eth yl-6-oxover d a zyl
(3) (a s 1:1 Com p lex w ith Hyd r oqu in on e). To a stirred
solution of 6 (806 mg, 3.89 mmol) in 20 mL of hot benzene
was added 1,4-benzoquinone (630 mg, 5.82 mmol). The solution
immediately turned yellow and then became increasingly
darker in color. After being stirred for 1 h, the resulting
maroon microcrystalline solid was isolated by vacuum filtra-
tion and recrystallized from ethyl acetate/benzene to give
3-C6H6O2 as maroon needles, yield 1.16 g (95%). Mp: 90-92
°C. Anal. Calcd for C15H16N5O3: C, 57.32; H, 5.13; N, 22.28.
Found: C, 57.33; H, 5.17; N, 22.23. IR (KBr): ν(OH) 3294 (br,
w), ν(CdO) 1683 (s) cm-1. λmax (CH2Cl2): 238, 269, 409 nm.
MS (CI methane): m/z 205 (M + 1, 28%), 111 ( (hq + 1)+, 100).
Syn th esis of 4,6-Dim eth yl-2-p yr im id in eca r boxa ld e-
h yd e. tert-Butyllithium (10.7 mL of a 1.7 M pentane solution,
18.2 mmol) was added very slowly to a stirred solution of
2-bromo-4,6-dimethylpyrimidine47-49 (1.705 g, 9.11 mmol) in
75 mL of anhydrous diethyl ether at -110 °C. The clear light
yellow solution turned deep orange and slightly turbid. During
the addition the temperature was maintained below -90 °C.
The solution was stirred at low temperature for 1 h, and then
a solution of anhydrous dimethylformamide (DMF) (1.42 mL,
18.4 mmol) in 20 mL anhydrous diethyl ether was added
dropwise over 0.5 h. The solution was warmed to room
temperature for 1.5 h, poured into ice, and diluted with water.
The layers were separated, and the aqueous layer was
extracted with CH2Cl2. The combined organics were dried over
MgSO4 and filtered, and the solvent was evaporated under
reduced pressure. The resulting dark red oil was subjected to
chromatography (silica gel, 3:1 CH2Cl2/acetonitrile) to afford
4,6-dimethyl-2-pyrimidinecarboxaldehyde as an off-white solid
which was further purified by vacuum sublimation, yield 600
mg (48%). 1H NMR (CDCl3): δ 10.04 (s, 1H), 7.19 (s, 1H), 2.59
ppm (s, 6H). 13C NMR (CDCl3): δ 192.0, 168.1, 139.8, 122.5,
23.9 ppm. Anal. Calcd for C7H8N2O: C, 61.75; H, 5.92; N,
20.57. Found: C, 61.53; H, 5.88; N, 20.49. MS (CI methane):
m/z 137 (M + 1, 100%).
1
g (95%). The solid was stored at -35 °C in a drybox. H NMR
(CDCl3): δ 4.13 (br s, 4H), 2.92 ppm (s, 6H). 13C NMR
(CDCl3): δ 165.6, 41.65 ppm. IR (Nujol): ν(NH) 3310, 3198,
ν(CdO) 1633 cm-1
.
Syn th esis of 3-(2-P yr id yl)-1,5-d im eth yl-1,2,4,5-tetr a -
za n e 6-Oxid e (6). A solution of freshly vacuum-distilled
2-pyridinecarboxaldehyde (1.81 g, 16.9 mmol) in 55 mL of
methanol was added dropwise to a solution of 5 (1.993 g, 16.9
mmol) in 110 mL of hot methanol. After the addition was
complete, the solution was heated to reflux for 24 h. The
solvent was then removed under reduced pressure, and the
solid residue was recrystallized from methanol/ethyl acetate
to give 6 as large transparent blocks, yield 2.75 g (79%). 1H
NMR (CDCl3): δ 8.5 (d, 1H, J ) 2.9 Hz), 7.7 (td, 1H, J ) 5.9,
1.7 Hz), 7.4 (d, 1H, J ) 8.1 Hz), 7.3 (dd, 1H, J ) 7.0, 5.5 Hz),
4.85 (br s, 3H), 3.14 ppm (s, 6H). 13C NMR (CDCl3): δ 154.6,
153.7, 149.7, 137.4, 124.4, 123.7, 69.6, 38.2 ppm. IR (KBr): ν-
(NH) 3240 (m), 3183 (s), ν(CdO) 1630 (s) cm-1. Mp: 148-149
°C. Anal. Calcd for C9H13N5O: C, 52.16; H, 6.32; N, 33.79.
Found: C, 52.33; H, 6.36; N, 33.68. MS (CI methane): m/z
208 (M + 1, 100%).
Syn th esis of 3-(4,6-Dim eth yl-2-pyr im idyl)-1,5-dim eth yl-
1,2,4,5-tetr a za n e 6-Oxid e (7). A solution of 4,6-dimethyl-2-
pyrimidinecarboxaldehyde (0.173 g, 1.46 mmol) in 40 mL of
methanol was added dropwise to a solution of 5 (0.198 g, 1.47
mmol) in 30 mL of hot methanol. After the addition was
complete, the solution was heated to reflux for 15 h. The
solvent was then removed under reduced pressure, and the
solid residue was recrystallized from ethyl acetate to give 7
as large pale yellow crystals, yield 0.176 g (51%). Mp: 158-
Syn th esis of 3-(2-P yr id yl)-1,5-d im eth yl-1,2,5,6-tetr a h y-
d r o-1,2,4,5-tetr a zin e 6-Oxid e (8). To a stirred solution of 6
1
160 °C. H NMR (CDCl3): δ 7.01 (s, 1H), 4.90 (br s, 3H), 3.16
(s, 6H), 2.46 ppm (s, 6H). 13C NMR (CDCl3): δ 167.7, 162.3,
154.7, 120.2, 70.9, 38.1, 23.8 ppm. IR (KBr): ν(NH) 3249 (br,
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