| Popis: |
The synthesis of sulfines 4 from a series of active methylene compounds is described. Deprotonation, followed by silylation, gives the trimethylsilyl compounds 2. Subsequent deprotonation to α-silyl carbanions and treatment with an excess of sulfur dioxide leads to the formation of sulfines 4, usually in good yields. The experimental conditions of this alkylidenation of sulfur dioxide, using the modified Peterson olefination, are discussed in detail. Hydrolytically sensitive sulfines can be prepared by using a dry work-up procedure. These sulfines can also be trapped with 2,3-dimethyl-1,3-butadiene to give dihydropyran S-oxides 5. Reaction of the α-silyl carbanions with some sulfines leads to alkenes 9, probably through the intermediacy of thiocarbonyl S-ylides. |
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