Mechanism and Regioselectivity of the Cycloaddition of Thiones Derived from Meldrum’s Acid, Malonates, or Other Dicarbonyls
摘要:
[GRAPHICS]Several alpha,alpha-dioxothiones were generated in situ and reacted with 1,3-dienes of varying electronic and steric properties. It was found that thiones 10a and 11a reacted well with electron-rich or electron-poor dienes and are complementary in their regioselectivities when steric effects are at play. The calculated preferred mechanistic pathway implies a thiiranium zwitterion intermediate.
Mechanism and Regioselectivity of the Cycloaddition of Thiones Derived from Meldrum’s Acid, Malonates, or Other Dicarbonyls
摘要:
[GRAPHICS]Several alpha,alpha-dioxothiones were generated in situ and reacted with 1,3-dienes of varying electronic and steric properties. It was found that thiones 10a and 11a reacted well with electron-rich or electron-poor dienes and are complementary in their regioselectivities when steric effects are at play. The calculated preferred mechanistic pathway implies a thiiranium zwitterion intermediate.
The reaction of 4-substituted 2-(t-butyldimethylsiloxy)-1,3-butadiene with acetoxy chromium Fischer carbene complexes afforded bicyclo[4.1.0]heptene derivative 3, 18, an intramolecular C-H insertion product of the initially formed Diels-Alder adduct 6. The role of the metal and the heteroatom ligand in the carbene complex, and of the substituent at 3-position in 6 on the C-H insertion has been examined.
[GRAPHICS]Several alpha,alpha-dioxothiones were generated in situ and reacted with 1,3-dienes of varying electronic and steric properties. It was found that thiones 10a and 11a reacted well with electron-rich or electron-poor dienes and are complementary in their regioselectivities when steric effects are at play. The calculated preferred mechanistic pathway implies a thiiranium zwitterion intermediate.