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Study of ring closure reaction of substituted phenyl N ‐(2‐thiocarbamoylphenyl)carbamates catalysed by methoxide ion
Author(s) -
Hanusek Jiří,
Sedlák Miloš,
Jansa Petr,
Štěrba Vojeslav
Publication year - 2006
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.999
Subject(s) - chemistry , methoxide , reaction rate constant , ring (chemistry) , medicinal chemistry , reaction mechanism , carbamate , ion , kinetics , catalysis , stereochemistry , organic chemistry , physics , quantum mechanics
Studies were made of the kinetics of methoxide ion‐catalysed reactions of seven substituted phenyl N ‐(2‐thiocarbamoylphenyl)carbamates, 4‐methoxyphenyl N ‐(2‐thiocarbamoylphenyl)‐ N ‐(methyl)carbamate and five substituted phenyl N ‐(4‐thiocarbamoylphenyl)carbamates, leading to the respective cyclisation products (i.e. 4‐thioxo‐1 H ,3 H ‐quinazolin‐2‐one or 1‐methyl‐4‐thioxo‐1 H ,3 H ‐quinazolin‐2‐one) and/or methanolysis product, i.e. methyl N ‐(4‐thiocarbamoylphenyl)carbamate. The comparison of the rate constants, β lg , and ρ constants of the 2‐thiocarbamoyl derivatives (β lg = −1.15, ρ = 3.1 ± 0.1) and 4‐thiocarbamoyl derivatives (ρ = 4.6 ± 0.2, β lg = −1.55) shows that the ring closure reaction proceeds by the B Ac 2 mechanism with the splitting off of phenoxide anion being the rate‐limiting step, while the methanolysis follows the E 1 cB mechanism. The ring closure reaction of 4‐methoxyphenyl N ‐(2‐thiocarbamoyl)‐ N ‐(methyl)carbamate proceeds kinetically in two steps, the respective rate constants differing by one order of magnitude. The NMR spectrum, spectral record and computational calculations of the ring closure reaction indicate that the process involves parallel reactions of two rotamers formed due to hindered rotation. Copyright © 2005 John Wiley & Sons, Ltd.