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Molecules 2001, 6(6), 557-573; doi:10.3390/60600557
Article

Regioselectivity of Electrophilic Attack on 4-Methyl-1-thioxo-1,2,4,5-tetrahydro[1,2,4]triazolo[4,3-a]quinazolin-5-one. Part 1: Reactions at the Sulfur Atom

1, 1,2 and 1,*
Received: 16 July 2000 / Revised: 21 May 2001 / Accepted: 23 May 2001 / Published: 31 May 2001
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Abstract

The regioselectivity of the model compound 4-methyl-1-thioxo-1,2,4,5-tetrahydro[1,2,4]triazolo[4,3-a]quinazolin-5-one (3) towards different electrophiles was studied. Compound 3 reacts with alkyl and aryl halides to give the corresponding S-substituted derivatives. The reaction of the model thioamide with acyl halides proceeds by the formation of kinetically controlled S-acyl derivatives followed by a transacylation reaction to give the N2-acyl derivatives as thermodynamically controlled products. Theoretical DFT computational studies supported the explanation of these results. The synthesized compounds were characterized by FTIR, 1H-NMR, 13C-NMR, and mass spectroscopy.
Keywords: Cyclic thioamides; regioselective reactions; 4-methyl-1-thioxo- 1; 2; 4; 5-tetrahydro[1; 2; 4]triazolo[4; 3-a]quinazolin-5-one; DFT computational studies Cyclic thioamides; regioselective reactions; 4-methyl-1-thioxo- 1; 2; 4; 5-tetrahydro[1; 2; 4]triazolo[4; 3-a]quinazolin-5-one; DFT computational studies
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Fathalla, W.; Čajan, M.; Pazdera, P. Regioselectivity of Electrophilic Attack on 4-Methyl-1-thioxo-1,2,4,5-tetrahydro[1,2,4]triazolo[4,3-a]quinazolin-5-one. Part 1: Reactions at the Sulfur Atom. Molecules 2001, 6, 557-573.

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