Limits...
Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S -methanides

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Ferrocenyl hetaryl thioketones react smoothly with in situ generated thiocarbonyl S-methanides to give 1,3-dithiolanes. In the case of aromatic S-methanides, the sterically more crowded 4,4,5,5-tetrasubstituted 1,3-dithiolanes (2-CH2 isomers) were formed as sole products. The reactions with cycloaliphatic S-methanides led to mixtures of 2-CH2 and 5-CH2 isomers with the major component being the sterically more crowded 2-CH2 isomers. The preferred formation of the latter products is explained by the assumption that the formal [3 + 2]-cycloadducts were formed via a stepwise reaction mechanism with a stabilized 1,5-diradical as a key intermediate. The complete change of the reaction mechanism toward the concerted [3 + 2]-cycloaddition was observed in the reaction of a sterically crowded cycloaliphatic thiocarbonyl ylide with ferrocenyl methyl thioketone.

No MeSH data available.


Reactions of aromatic thiocarbonyl S-methanides 2a,b with ferrocenyl thioketones 1 (Table 1).
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4979640&req=5

C1: Reactions of aromatic thiocarbonyl S-methanides 2a,b with ferrocenyl thioketones 1 (Table 1).

Mentions: The precursors of aromatic S-methanides 2a,b, i.e., 1,3,4-thiadiazolines 3a,b, were prepared from thiobenzophenone (4a) and thiofluorenone (4b), respectively, and diazomethane at –60 °C in THF solution [6] (Scheme 1). After addition of an equimolar amount of a ferrocenyl hetaryl thioketone 1, the reaction mixture was slowly warmed to room temperature. The crude mixture was examined by 1H NMR spectroscopy, and in all cases only one single product 5 was detected (Table 1).


Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S -methanides
Reactions of aromatic thiocarbonyl S-methanides 2a,b with ferrocenyl thioketones 1 (Table 1).
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979640&req=5

C1: Reactions of aromatic thiocarbonyl S-methanides 2a,b with ferrocenyl thioketones 1 (Table 1).
Mentions: The precursors of aromatic S-methanides 2a,b, i.e., 1,3,4-thiadiazolines 3a,b, were prepared from thiobenzophenone (4a) and thiofluorenone (4b), respectively, and diazomethane at –60 °C in THF solution [6] (Scheme 1). After addition of an equimolar amount of a ferrocenyl hetaryl thioketone 1, the reaction mixture was slowly warmed to room temperature. The crude mixture was examined by 1H NMR spectroscopy, and in all cases only one single product 5 was detected (Table 1).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Ferrocenyl hetaryl thioketones react smoothly with in situ generated thiocarbonyl S-methanides to give 1,3-dithiolanes. In the case of aromatic S-methanides, the sterically more crowded 4,4,5,5-tetrasubstituted 1,3-dithiolanes (2-CH2 isomers) were formed as sole products. The reactions with cycloaliphatic S-methanides led to mixtures of 2-CH2 and 5-CH2 isomers with the major component being the sterically more crowded 2-CH2 isomers. The preferred formation of the latter products is explained by the assumption that the formal [3 + 2]-cycloadducts were formed via a stepwise reaction mechanism with a stabilized 1,5-diradical as a key intermediate. The complete change of the reaction mechanism toward the concerted [3 + 2]-cycloaddition was observed in the reaction of a sterically crowded cycloaliphatic thiocarbonyl ylide with ferrocenyl methyl thioketone.

No MeSH data available.