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Regioselektive 1,3‐dipolare Cycloadditionen von Thiocarbonyl‐yliden mit 1,3‐Thiazol‐5(4 H )‐thionen
Author(s) -
Mlostoń Grzegorz,
Linden Anthony,
Heimgartner Heinz
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740703
Subject(s) - chemistry , regioselectivity , steric effects , thiazole , stereochemistry , yield (engineering) , medicinal chemistry , organic chemistry , catalysis , materials science , metallurgy
Regioselective 1,3‐Dipolar Cycloadditions of Thiocarbonyl Ylides with 1,3‐Thiazole‐5(4 H )‐thiones The thiocarbonyl ylides 13 and 1,3‐thiazol‐5(4 H )‐thiones 1 undergo a smooth reaction to yield spirocyclic 1,3‐dithiolanes 14 – 16 ( Schemes 4–6 ). The 1,3‐dipolar cycloadditions occur in a regioselective manner, but the orientation of the thiobcnzophenone‐ S ‐methylide ( 13b ) differs from that of the cycloalkane thione‐ S ‐methylides 13a and 13c . Whereas the 1,3‐cycloadduct with 13b is formed in accordance with frontier‐orbital considerations, the inverse orientation in the reactions with 13a and 13c most likely is the result of steric hindrance in the transition state. The thiocarbonyl ylides have been prepared in situ from the corresponding 2,5‐dihydro‐1,3,4‐thiadiazoles 12 . The more stable aliphatic precursors 12a and 12c undergo decomposition at 50°, the unstable 12b at −30°.