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L. K. Sydnes et al.
enriched in the major product. Both these fractions were
subjected separately to a second flash chromatography elu-
tion and similar enrichments took place. This process was
repeated until pure samples of the two compounds had been
obtained and enabled us to perform structure elucidation by
spectroscopy and spectrometry. The minor compound
seemed to be 3-chloro-4-methyl-8-phenyl-1,6,8-triazabicy-
clo-[4.3.0]non-3-ene-7,9-dione (5a) whereas the major
compound was 3-bromo-4-methyl-8-phenyl-1,6,8-triazabi-
cyclo[4.3.0]non-3-ene-7,9-dione (5b).
subsequent workup gave mixtures of 3-chloro-8-phenyl-
1,6,8-triazabicyclo[4.3.0]non-3-ene-7,9-dione (5c [37–45])
and 3-bromo-8-phenyl-1,6,8-triazabicyclo[4.3.0]non-3-ene-
7,9-dione (5d). Based on the spectroscopic and spectro-
metric properties of these mixtures and those of an
authentic sample of 5c [35], the spectral data of 5d were
obtained.
3-Bromo-8-phenyl-1,6,8-triazabicyclo[4.3.0]non-3-ene-
7,9-dione (5d, C12H10N3O2Br)
1
IR (CHCl3): m ¼ 1; 755w; 1,723s, 1,603m, 630s cm-1; H
ꢀ
3-Chloro-4-methyl-8-phenyl-1,6,8-triazabicyclo-
[4.3.0]non-3-ene-7,9-dione (5a, C13H12N3O2Cl)
NMR (250 MHz, CDCl3, Me4Si): d = 4.20–4.27 (3H, m),
4.31–4.34 (1H, m), 6.25–6.29 (1H, m, =CH), 7.35–7.54
(5H, m) ppm; 13C NMR (62.5 MHz, CDCl3, Me4Si):
d = 45.1 (CH2), 49.6 (CH2), 113.6 (C), 122.3 (CH), 125.2
(2CH), 128.2 (CH), 129.1 (2CH), 130.8 (C), 151.9 (CO),
152.3 (CO) ppm; MS (EI): m/z (%) = 310 (M?, 9), 309
(M?, 76), 308 (M?, 10), 307 (M?, 80), 228 (9), 134 (9),
132 (93), 119 (93), 109 (100), 91 (34); HRMS (EI): m/z
calcd. for M?, C12H10N3O2Br, 308.99359; found
308.99623.
ꢀ
M.p. 201–202 °C (decomposition). IR (KBr): m ¼ 3; 061w;
2,965w, 2,914w, 2,852w, 1,771m, 1,717s, 1,598w, 1,503m,
1,427br, 1,345w, 1,306w, 1,261m, 1,135m, 1,082w, 940w,
913w, 798w, 750w, 690w, 642w cm-1
;
1H NMR
(200 MHz, CDCl3, Me4Si): d = 1.92-1.94 (3H, m, CH3),
4.11–4.13 (2H, m, CH2), 4.21–4.26 (2H, m, CH2), 7.33–
7.55 (5H, m) ppm; 13C NMR (50 MHz, CDCl3, Me4Si):
d = 16.6 (CH3), 47.5 (CH2), 47.8 (CH2), 119.3 (C), 124.6
(C), 125.2 (2CH), 128.1 (CH), 129.0 (2CH) 130.8 (C),
151.8 (CO), 152.0 (CO) ppm; MS (70 eV): m/z (%) = 277
(M?, 61), 242 (11), 123 (100), 119 (66), 182 (21), 91 (26)
and 67 (36); HRMS (EI): m/z calcd. for M?,
C13H12N3O2Cl, 277.0618; found 277.0617.
Thermolysis of 1-dibromo-2-chloromethyl-2-
methylcyclopropane (3c)
Monobromocyclopropane 3c (217 mg) was thermolyzed in
the gas phase at 417 °C/2.6 mmHg. The cold pyrolysate was
treated with PTAD, and the products were isolated by flash
chromatography (SiO2, n-hexane–ethyl acetate 7:3). Several
mixtures of unidentified products were obtained, but in
addition 46 mg of contaminated 3-methyl-8-phenyl-1,6,8-
triazabicyclo[4.3.0]non-3-ene-7,9-dione (5e) was isolated.
The IR, 1H NMR, and 13C NMR spectra of 5e showed all the
peaks exhibited by an authentic sample of the compound,
synthesized from isoprene as described by Gillis and Hagarty
[36]. Furthermore, the authentic sample co-eluted with 5e
when GC analyses were performed under various conditions,
and finally, their mass spectra were identical.
3-Bromo-4-methyl-8-phenyl-1,6,8-triazabicyclo[4.3.0]non-
3-ene-7,9-dione (5b, C13H12N3O2Br)
ꢀ
M.p. 197–198 °C (decomposition). IR (KBr): m ¼ 2; 955w;
2,921m, 2,851w, 1,775m, 1,710s, 1,600w, 1,503m,
1,430br, 1,338w, 1,306w, 1,261m, 1,134m, 1,089w,
1,076w, 1,024w, 907w, 792w, 745m, 715w, 687w cm-1
;
1H NMR (400 MHz, CDCl3, Me4Si): d = 1.96–1.97 (3H,
m, CH3), 4.13–4.14 (2H, m, CH2), 4.33–4.36 (2H, m, CH2),
7.46–7.53 (5H, m) ppm; 13C NMR (100 MHz, CDCl3,
Me4Si): d = 19.6 (CH3), 48.1 (CH2), 49.8 (CH2), 109.8 (C),
125.3 (2CH), 127.4 (C), 128.2 (CH), 129.1 (2CH), 130.8
(C), 151.7 (CO), 152.1 (CO) ppm; MS (70 eV): m/z
(%) = 321 (M?, 30), 242 (3), 207 (11), 123 (100), 119
(51), 91 (24), 67 (53); HRMS (EI): m/z calcd. for M?,
C13H12N3O2Br, 321.0113; found 321.0117.
Thermolysis of 1-dibromo-2-chloromethylcyclopropane
(3d)
Monobromocyclopropane 3d (0.18 g) was thermolyzed in
the gas phase at 470 °C/20 mmHg. When all the substrate
had passed through the tube a dichloromethane solution of
PTAD was added to the pyrolysate until the red colour
persisted. Column chromatography (SiO2, CHCl3) gave
68 mg (30%) 8-phenyl-1,6,8-triazabicyclo[4.3.0]non-3-
ene-7,9-dione (5f) whose spectroscopic properties were
identical with those of an authentic sample of the com-
pound prepared by independent synthesis [33, 34]. M.p.
155–157 °C (Ref. [33] 158–159 °C); MS (70 eV): m/z
(%) = 229 (M?, 100), 119 (83), 110 (19), 91 (27), 82 (36),
Thermolysis of 1,1-dibromo-2-
chloromethylcyclopropane (3b)
Dibromide 3b (201 mg) was thermolyzed in quinoline at
260 °C and a complex product mixture (75.2 mg) was
collected. The mixture contained two main components
which were formed in essentially equal amounts; these
were obtained in 13% total yield according to GC analysis,
and seemed to be 2-chlorobuta-1,3-diene (4c) [9, 21] and 2-
bromobuta-1,3-diene (4d) [21, 33, 34] according to 1H
NMR and MS spectra. Treatment with PTAD and
123