TY  - JOUR
A1  - Rasovic, Aleksandar
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Markovic, Rade
T1  - Studies of the regioselective ring-opening closing mode of functionally different thiazolidine type enaminones - en route to the synthesis of trithiaazapentalene derivatives
JF  - Tetrahedron
N2  - Trithiaazapentalene derivatives were prepared by the reaction of 2-alkylidene-4-oxothiazolidines with Lawesson's reagent. They are classified as two structurally different trithiaazapentalene compounds that have different contributions of monocyclic 1,2-dithiole and 1,2,4-dithiazole structures and degrees of aromaticity of the bicyclic trithiaazapentalene system. The electron-donating ability of substituents at the C(5) position of the trithiaazapentalene system is recognized as the main cause for changes in pi-Celectron distribution. This is the first complete study of substituent effects on the structure of trithiapentalenes. (C) 2013 Elsevier Ltd. All rights reserved.
KW  - Trithiapentalene
KW  - 1,2-Dithiole
KW  - 1,2,4-Dithiazole
KW  - 4-Oxothiazolidine
KW  - Rearrangement to trithiaazapentalene
KW  - Push-pull character
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.10.088
SN  - 0040-4020
VL  - 69
IS  - 51
SP  - 10849
EP  - 10857
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Dzambaski, Zdravko
A1  - Markovic, Rade
A1  - Kleinpeter, Erich
A1  - Baranac-Stojanovic, Marija
T1  - 2-Alkylidene-4-oxothiazolidine S-oxides - synthesis and stereochemistry
JF  - Tetrahedron
N2  - A series of 5-unsubstituted and 5-substituted 2-alkylidene-4-oxothiazolidine-S-oxides were synthesized by the sulfur-oxidation with m-CPBA. The stereochemistry of 5-substituted sulfoxides was determined by means of NMR spectroscopy and DFT theoretical calculations. It was found that the thermodynamically less stable anti-isomer was initially formed in the course of the oxidation, but it underwent epimerization to the mixture enriched in the more stable syn-isomer, during the work-up process. The higher stability of syn-isomers is ascribed to the stronger hyperconjugative sigma(C-H)->sigma*(S-O) interaction versus the weaker sigma(C-C)->sigma*(S-O) delocalization in their anti-counterparts and to the existence of intramolecular 1,5-CH center dot center dot center dot C hydrogen bonds.
KW  - 2-Alkylidene-4-oxothiazolidine
KW  - Sulfoxide
KW  - Diastereoselectivity
KW  - Density functional calculations
KW  - CH center dot center dot center dot O hydrogen bonds
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.05.087
SN  - 0040-4020
VL  - 69
IS  - 31
SP  - 6436
EP  - 6447
PB  - Elsevier
CY  - Oxford
ER  -