The first alpha-fluoroallenylphosphonate, the synthesis of conjugated fluoroenynes, and the stereoselective synthesis of vinylfluorophosphonates using a new multifunctional fluorine-containing building block
Limitations on current methodologies for the introduction of CF(2) and CFH in complex alpha-fluorophosphonates led to the synthesis of a fluorine-containing building block TIPS-C&tbd1;CCFXP(O)(OEt)(2), where X = H or F. This multifunctional fluorine synthon reacts with carbonyl compounds under WHE conditions to give high yields of fluorinated conjugated enynes and enediyne. When X = F, trapping of the desilylated anion with an electrophile after TIPS removal provided exclusive access to gamma-substituted derivatives of alpha-fluorophosphonates. When X = H, TBAF deprotection of the silyl group yields H(2)C=C=CFP(O)(OEt)(2) through an allenyl-propargyl resonance stabilized anion. The allene moiety has been used as template in the stereoselective synthesis of alpha-fluoro-beta, gamma-diiodopropenyl phosphonate, via electrophilic iodination, and alpha-fluoro-gamma-amino-alpha,beta-unsaturated phosphonates, including unsaturated phosphononucleosides, by nucleophilic displacement of an allylic iodide. Hydroamination of H(2)C=C=CFP(O)(OEt)(2) using secondary amines produced (Z)-alpha-fluoroenaminophosphonates, whereas Diels-Alder cycloaddition with cyclopentadiene provides the corresponding exocyclic vinylfluorophosphonate.
Zapata
AJ
Department of Chemistry and Biochemistry, University of Massachusetts-Dartmouth, North Dartmouth, Massachusetts 02747-2300, USA.
Gu
Y
Hammond
GB