[2 + 1] Cycloaddition Reactions of a 1-Seleno-2-silylethene to 2-Sulfonylacrylates: Stereoselective Synthesis of Sulfone-Substituted Cyclopropanes
摘要:
Reaction of 1-(phenylseleno)-2-(trimethylsilyl)ethene 1 and methyl or ethyl 2-p-toluene- or benzene-sulfonylacrylates 3 in the presence of SnCl4 at -78 degrees C gave sulfone-substituted cyclopropanes 4 as single stereoisomers. The structure of one of these crystalline cyclopropane products was elucidated by X-ray crystallographic analysis. The relative stereochemistry of the cyclopropane ring carbon (C-2) and selenosilylmethyl group was determined as R,R and S,S, which is consistent with previous mechanical considerations and the NOE determination. 2-Sulfinyl acrylate 2 did not undergo this cycloaddition. The difference in reactivity of the sulfoxide 2 and sulfones 3 toward 1 was explained by comparison of LUMO levels of 2-SnCl4 and 3-SnCl4 complexes and activation energies in the synclinal addition of 1 to the complexes.
[2 + 1] Cycloaddition Reactions of a 1-Seleno-2-silylethene to 2-Sulfonylacrylates: Stereoselective Synthesis of Sulfone-Substituted Cyclopropanes
摘要:
Reaction of 1-(phenylseleno)-2-(trimethylsilyl)ethene 1 and methyl or ethyl 2-p-toluene- or benzene-sulfonylacrylates 3 in the presence of SnCl4 at -78 degrees C gave sulfone-substituted cyclopropanes 4 as single stereoisomers. The structure of one of these crystalline cyclopropane products was elucidated by X-ray crystallographic analysis. The relative stereochemistry of the cyclopropane ring carbon (C-2) and selenosilylmethyl group was determined as R,R and S,S, which is consistent with previous mechanical considerations and the NOE determination. 2-Sulfinyl acrylate 2 did not undergo this cycloaddition. The difference in reactivity of the sulfoxide 2 and sulfones 3 toward 1 was explained by comparison of LUMO levels of 2-SnCl4 and 3-SnCl4 complexes and activation energies in the synclinal addition of 1 to the complexes.
Reaction of 1-(phenylseleno)-2-(trimethylsilyl)ethene 1 and methyl or ethyl 2-p-toluene- or benzene-sulfonylacrylates 3 in the presence of SnCl4 at -78 degrees C gave sulfone-substituted cyclopropanes 4 as single stereoisomers. The structure of one of these crystalline cyclopropane products was elucidated by X-ray crystallographic analysis. The relative stereochemistry of the cyclopropane ring carbon (C-2) and selenosilylmethyl group was determined as R,R and S,S, which is consistent with previous mechanical considerations and the NOE determination. 2-Sulfinyl acrylate 2 did not undergo this cycloaddition. The difference in reactivity of the sulfoxide 2 and sulfones 3 toward 1 was explained by comparison of LUMO levels of 2-SnCl4 and 3-SnCl4 complexes and activation energies in the synclinal addition of 1 to the complexes.