TY - JOUR
T1 - Fused-Ring Thiadiazines
T2 - Preparation and Crystallographic Characterization of 3-Phenyl Derivative of Benzo-, Pyridio[2,3-e]-, Pyrazino[2,3-e]-, and Tetrafluorobenzo-[1,2,4]thiadiazines
AU - Zienkiewicz, Józef
AU - Kaszynski, Piotr
AU - Young, Victor G.
PY - 2004/4/2
Y1 - 2004/4/2
N2 - Four bicyclic 4H-[1,2,4]thiadiazines 1a-d were prepared in 74-88% yields in two steps from the corresponding amidines 2. Three of them, 1a, 1b, and 1d, were obtained by thermal elimination of propene from the intermediate S-propylsulfilimines 12. The pyrazino derivative 1c was formed upon thermolysis of sulfoxide 14c obtained from 2c. The Ei mechanism was investigated using DFT methods. The elimination in the sulfilimine appears to be more favorable by about 2 kcal/mol than in the analogous sulfoxide. Crystal and molecular structures of three out of the four thiadiazines were established by single-crystal X-ray analysis. All thiadiazines were found as the 4H tautomers with the heterocyclic ring puckered along the S(1)⋯N(4) line. The benzo derivative 1a forms a unidimensional N(4)-H⋯N(2) chain, the pyrazino derivative 1c forms dimeric pairs with two synergistic hydrogen bonds, and the crystal structure of 1d is characterized by strong C6F 4⋯C6H5 quadrupolar interactions.
AB - Four bicyclic 4H-[1,2,4]thiadiazines 1a-d were prepared in 74-88% yields in two steps from the corresponding amidines 2. Three of them, 1a, 1b, and 1d, were obtained by thermal elimination of propene from the intermediate S-propylsulfilimines 12. The pyrazino derivative 1c was formed upon thermolysis of sulfoxide 14c obtained from 2c. The Ei mechanism was investigated using DFT methods. The elimination in the sulfilimine appears to be more favorable by about 2 kcal/mol than in the analogous sulfoxide. Crystal and molecular structures of three out of the four thiadiazines were established by single-crystal X-ray analysis. All thiadiazines were found as the 4H tautomers with the heterocyclic ring puckered along the S(1)⋯N(4) line. The benzo derivative 1a forms a unidimensional N(4)-H⋯N(2) chain, the pyrazino derivative 1c forms dimeric pairs with two synergistic hydrogen bonds, and the crystal structure of 1d is characterized by strong C6F 4⋯C6H5 quadrupolar interactions.
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U2 - 10.1021/jo035835h
DO - 10.1021/jo035835h
M3 - Article
C2 - 15049657
AN - SCOPUS:1842451495
SN - 0022-3263
VL - 69
SP - 2551
EP - 2561
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 7
ER -