Flash vacuum pyrolysis of 1-benzyl-2,1-benzoxazolone
135.4 (d), 145.5 (s), 147.1 (s), 160.5 (s). The minor cis isomer
could not be isolated in a pure state.
Flash vacuum pyrolysis of 1-benzyl-2,1-benzoxazolone30 (80
mg) at 700 ЊC in the usual way gave four fractions after chrom-
atography. The first was 1,2-diphenylethane, mp 50–52 ЊC (30
mg, 91%). The three minor fractions could not be identified.
Dehydrochlorination of 28
(i) A mixture of trans-28 (160 mg), sodium hydroxide (400 mg),
ethanol (8 mL) and water (7 mL) was refluxed for 1 h. After
removal of solvent, the residue was boiled for 3 min with a
mixture of ethanol and 15% HCl (1:1, 30 mL). The solvent was
evaporated, the residue dissolved in dichloromethane, and the
solution was washed with NaHCO3. The organic product
(100 mg, 74%) was identical in all respects with the sample of 25
obtained above. (ii) When the 5:1 mixture of trans- and cis-28
was reacted with triethylamine in 1,2-dimethoxyethane for 1 h
at 80 ЊC, the product contained a 5:1 mixture of 27 and 25 (1H
NMR analysis).
Flash vacuum pyrolysis of 1-benzyl-2,1-benzothiazol-3(1H)-one
A solution of 9 (151 mg, 1 mmol), benzyl chloride (1.3 eq.) and
sodium methoxide (1.3 eq.) in methanol was refluxed for 14 h
under nitrogen. The solvent was removed and the ether soluble
fraction purified by chromatography (silica/CH2Cl2) to give the
title product (105 mg, 44%), mp 52 ЊC (lit.28 54–55 ЊC). δC(10 s
delay) 52.4 (t), 112.4 (d), 119.7 (d), 122.1 (s), 124.0 (d), 127.4
(d), 128.3 (d), 128.8 (d), 133.9 (d), 135.4 (s), 153.6 (s), 189.3 (s).
Flash vacuum pyrolysis of the compound at 700 ЊC (150 ЊC,
0.01 mm, 20 min) gave 1,2-diphenylethane (95%), mp 50–52 ЊC
(lit.31 52 ЊC) as the sole identifiable product. The structure
was confirmed by GC-MS comparison with an authentic
sample.
6-Phenyl-8H-quinazolino[4,3-b]quinazolin-8-one, 31
Reaction of 9 with 4-chloro-2-phenylquinazoline as described
above produced the title compound (80%), mp 292 ЊC (lit.33
292 ЊC). δH(CDCl3–CF3CO2H) 7.5–8.3 (m, 12H), 8.9 (d, J 4,
1H); δC(CDCl3–CF3CO2H) 113.2 (s), 118.0 (s), 120.5 (d), 125.6
(d), 127.7 (d), 128.5 (d), 128.9 (d), 129.0 (d), 129.7 (d), 131.5 (d),
132.0 (d), 138.4 (s), 137.0 (s), 138.6 (d), 139.4 (d), 143.3 (s),
150.6 (s), 156.9 (s), 176.8 (s).
Flash vacuum pyrolysis of 19
Triazole 1919 (300 mg) was pyrolysed at 700 ЊC (120 ЊC, 0.01
mm, 30 min) to give pyrido[1,2-a]benzimidazole 20 (165 mg,
64%), mp 179 ЊC (lit.17 179 ЊC), characterised by its spectral
properties. δC 110.0 (d), 110.2 (d), 117.6 (d), 120.8 (d), 125.0 (d),
125.4 (d), 129.1 (d), 144.1 (s), 148.1 (s).
Acknowledgements
Flash vacuum pyrolysis of 23
The authors are grateful to the Australian Research Council
for financial support. J. A. S. acknowledges an Australian
Postgraduate Award. We thank Dr M. R. Taylor for the single
crystal X-ray analysis of compound 14.
Triazole 2332 (120 mg), prepared by the method of Hubert and
Reimlinger,19 was pyrolysed at 600 ЊC (120 ЊC, 0.01 mm, 30 min)
to give benzimidazo[2,1-a]isoquinoline 24 (97 mg, 91%), mp
131 ЊC (lit.17 130 ЊC), characterised by its spectral properties.
δC 109.6 (d), 110.9 (d), 119.5 (d), 120.9 (d), 121.5 (d), 123.1 (s),
124.4 (d), 124.6 (d), 126.7 (d), 127.8 (d), 129.6 (d), 129.7 (s),
131.2 (s), 143.4 (s), 146.8 (s).
References
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Reaction of 9 with 1-chloroisoquinoline
A solution of 9 (230 mg) and 1-chloroisoquinoline (280 mg,
1 eq.) in 1,2-dimethoxyethane (20 mL) was refluxed under
nitrogen for 20 h. The mixture of products was washed with
NaHCO3 and chromatographed on silica (CH2Cl2). The first
product was 5-chloro-8H-isoquino[1,2-b]quinazolin-8-one, 25
(40 mg, 10%), mp 221 ЊC (CH2Cl2) (Found: C, 68.3; H, 3.1; N,
10.1%. C16H9ClN2O requires C, 68.45; H, 3.2; N, 10.0%); νmax
/
cmϪ1 1695, 1640, 1605; δH 7.5–8.05 (6H, m), 8.3–8.5 (1H, m),
8.7 (1H, s), 8.9–9.1 (1H, m); δC 117.4 (s), 120.1 (d), 120.8 (s),
123.9 (d), 126.4 (d), 127.3 (d), 127.4 (d), 127.7 (d), 129.6 (d),
131.4 (s), 132.5 (d), 135.3 (d), 145.1 (s), 146.7 (s), 158.3 (s).
The second product was 8H-isoquino[1,2-b]quinazolin-8-
one, 27 (80 mg, 22%), mp 197 ЊC (lit.32 197 ЊC); δC(10 s delay)
113.0 (d), 117.6 (s), 121.7 (d), 125.6 (d), 126.3 (d), 127.1 (d),
127.2 (s), 127.3 (d), 128.3 (d), 132.0 (d), 132.7 (s), 134.7 (d),
145.9 (s), 147.3 (s), 159.2 (s). Compound 27 was the major
product (75%) when 9 was reacted with isoquinoline as above.
5,6-Dichloro-5,6-dihydro-8H-isoquino[1,2-b]quinazolin-8-one,
28
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Gaseous chlorine was bubbled through a solution of 27 (50 mg)
in CH2Cl2 for 15 min and the solvent was then evaporated.
NMR analysis indicated the presence of two diastereomers in
the ratio of 5:1. Chromatography on silica (CH2Cl2) gave the
trans isomer of the title compound (30 mg, 47%) as colourless
crystals, mp 76 ЊC (pentane) (Found: Mϩ, 316.0166. C16H10-
35Cl2N2O requires M 316.0170). νmax/cmϪ1 1695, 1640, 1600;
δH 5.47 (1H, d, J 2.5), 7.37 (1H, d, J 2.5), 7.6–7.9 (6H, m), 8.3–
8.6 (2H, m); δC 55.3 (d), 64.3 (d), 120.3 (s), 127.5 (d), 127.8 (d),
128.2 (d), 128.6 (d), 128.8 (d), 130.6 (d), 132.7 (s), 132.8 (d),
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J. Chem. Soc., Perkin Trans. 1, 2000, 3212–3216
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