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(2 mmol) was added to phosphotungstic acid (2 mmol)
dissolved in 8 mL of water. To this was added crotonal-
dehyde (3 mmol) in 15 mL of toluene and the mixture
stirred vigorously at a temperature of 100 °C for 2 h. The
lower aqueous layer was separated and basified using
sodium hydroxide solution and the liberated quinaldine
extracted with ethyl acetate, the extract dried over
anhydrous sodium sulfate, concentrated and then purified
by column chromatography over silica gel eluting with a
mixture of ethyl acetate/pet ether (15:85).
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(b) Microwave irradiation conditions: aniline (2 mmol)
was adsorbed on silica gel (0.4 g) and mixed well with
phosphotungstic acid (0.2 g). To this was added croton-
aldehyde (3 mmol) separately adsorbed on silica gel (0.4 g)
and mixed well. The mixture was then irradiated with
microwaves at a power of 80% at a pulse rate of 45 s for
10 min. After completion of the reaction, the mixture was
eluted with ethyl acetate, the extract dried over anhydrous
sodium sulfate, concentrated and then purified by column
chromatography over silica gel eluting with a mixture of
ethyl acetate/pet ether (15:85). Spectral data: quinaldine,
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Tokyo, 1992; p 99.
1
2a: IR (KBr): cmÀ1. 1601, 1504, 1424, 819, 746. H NMR
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(500 MHz, CDCl3): d = 2.70 (s, 3H), 7.20 (d, 1H,
J = 8.6 Hz), 7.42 (m, 1H), 7.63 (m, 1H), 7.70 (d, 1H,
J = 8.6 Hz), 7.96 (d, 1H, J = 8.6 Hz), 7.99 (d, 1H,
J = 8.6 Hz). 13C NMR (125 MHz, CDCl3): d = 25.46,
121.99, 126.55, 127.55, 127.59, 129.51, 136.26, 136.31,
147.85, 159.03. MS: m/z 143 (M+).
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