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p. 349-358
Received: 1 January 2003 / Published: 30 April 2003
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p. 359-362
Received: 29 November 2002; in revised form: 25 March 2003 / Accepted: 1 April 2003 / Published: 30 April 2003
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| Download PDF Full-text (174 KB) Abstract: A rapid and simple method for the preparation of 1-ethoxycarbonyl-4-substituted-semicarbazides has been developed. As examples the reaction of six different isocyanates with ethyl carbazate under solvent-free conditions are reported.
p. 363-373
Received: 22 September 2002; in revised form: 7 December 2002 / Accepted: 8 April 2003 / Published: 30 April 2003
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| Download PDF Full-text (290 KB) Abstract: The diazonium salt of 3-(4-aminophenyl)-2-methyl-3H-quinazolin-4-one (2a) and its 6-bromo derivative 2b reacted with some active methylene compounds, namely ethyl acetoacetate (3), ethyl cyanoacetate (4) and acetylacetone (5), to afford the corresponding hydrazono quinazolinone derivatives 6-8. Treatment of 6a,b with hydrazine hydrate or phenyl hydrazine in refluxing ethanol afforded the corresponding pyrazolin-5-one derivatives of 3H-quinazolin-4-one 9a-d. Cyclization of 7a,b with hydrazine hydrate yielded the corresponding products 10a,b. Reaction of 8a,b with phenyl hydrazine or with urea afforded the corresponding derivatives 11a,b and 12a,b, respectively. Compounds 6-12 were identified by C,H,N analysis, IR, 1 H-NMR, 13 C-NMR and mass spectroscopy.
p. 374-380
Received: 9 December 2002; in revised form: 13 January 2003 / Accepted: 31 March 2003 / Published: 30 April 2003
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| Download PDF Full-text (349 KB) Abstract: A solvent-free procedure using PhCOCl-Py/basic alumina under microwave irradiation has been developed for N-, O- and S-benzoylation.
p. 381-391
Received: 6 March 2003; in revised form: 2 April 2003 / Accepted: 3 April 2003 / Published: 30 April 2003
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| Download PDF Full-text (235 KB) Abstract: Domestic microwave ovens as well as laboratory reactors have been successfully employed to prepare dialkyl 1,4-dihydropyridine-3,5-dicarboxylates and to induce the synthesis of the corresponding aromatic derivatives. In that latter particular case, unexpected results have been reported.
p. 392-400
Received: 23 January 2003; in revised form: 25 March 2003 / Accepted: 27 March 2003 / Published: 30 April 2003
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| Download PDF Full-text (323 KB) Abstract: In the reaction of N-methylbenzenesulfenamide (1) with thioanisole (4) in the presence of trifluoroacetic acid (TFA), the initial rate υ0 of total appearance of 2- and 4-(methylthio)phenyl phenyl sulfides (5) is first and zero order with respect to the initial concentrations of 1 and 4, respectively: υ0 =kobs [1]0 . The pseudo-first order rate constant kobs is evaluated as 5.2×10-4 sec-1 with varying concentrations of 4 (0.72 to 5.0 M) in a mixture of 4 and CH2 Cl2 in the presence of TFA at 10 °C. This data supports the notion that a phenylsulfenium ion intermediate 3 interacting with both the counter ion and the unshared electron-pair of amine is generated by heterolytic N-S scission of the protonated sulfenamide 2, leading to the observed formation of 5.
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