Fluoromethylenation sulfoximines

Finch has demonstrated that the sulfoximine approach is a viable alternative for fluoromethylenation (Scheme 12). The fluorosulfoximine (54) is deprotonated with LDA in THF and the aldehyde or ketone added to the anion. Conversion to the alkene is carried out with the standard aluminum amalgam procedure to yield a 1 1 mixture of ( )- and (Z)-alkenes (56). The reaction is very effective for aromatic and aliphatic aldehydes and aliphatic and alicyclic ketones, but, while aromatic and a,p-unsaturated ketones give good yiel of the addition adduct, the reductive elimination results in a variable amount of product formation. This method was tilled to the synthesis of prostaglandin 9-fluoromethylene (58 equation IS).- ... [Pg.741]

Treatment of methyl phenyl sulfoxide with diethylaminosulfur trifluoride (DAST), in the presence of antimony trichloride provides 159 in quantitative yield (66). The reaction proceeds in good yield with dialkyl sulfoxides and alkyl aryl sulfoxides (163). Reoxidation of the a-fluorosulfide (165) to the corresponding sulfoxide (161), followed by pyrolysis, provides a direct synthesis of fluoroolefins (65). The reaction is believed to proceed by a Pummerer-type mechanism (l.e., a fluoro-Pummerer reaction, Scheme 48). Similarly, Umemoto (67) reported that N-fluorocollidine (167) converted sulfides to ot-fluorosulfides (170) presumably via an S-fluorosulfonium cation species 168 (Scheme 49). The synthetically challenging fluorovinyl ether nucleosides (175) and (176) were prepared using the fluoro-Pummerer reaction (Scheme 50) (60) the (E)-isomer (175) could be isomerized to 176 under photolytic conditions. Finch and co-workers (69) converted 160 to the sulfoximine 178 and demonstrated the utility of this compound as a mild fluoromethylene synthon (Scheme 51). Base-catalyzed condensation 178 with a carbonyl compound gave 179 which afforded... [Pg.126]

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