A visible-light-mediated hydrotrifluoromethylation of unactivated alkenes that uses the Umemoto reagent as the CF(3) source and MeOH as the reductant is disclosed. This effective transformation operates at room temperature in the presence of 5 mol % Ru(bpy)(3)Cl(2); the process is characterized by its operational simplicity and functional group tolerance.
This paper describes a new catalytic method for the regio-and stereocontrolled fluorination of allylic carbonates. This transformation uses TBAF$4tBuOH as the fluoride source and [Ir(COD)Cl] 2 as the catalyst; the most commonly used [Ir(COD)Cl] 2 /phosphoramidite system is ineffective. Synthetically, this reaction is characterized by a high degree of structural conservation in going from substrates to the products. The fluorination of (E)-allylic carbonates leading to linear (E)-allylic fluorides (l : b > 20 : 1, E : Z > 20 : 1) is unprecedented and a unique feature of fluoride as the nucleophile. The first examples of transition metal catalyzed fluorination affording (Z)-allyl fluorides (Z : E ratio >20 : 1) are disclosed along with the successful fluorination of branched, linear (E)-and (Z)-allyl carbonates with [ 18 F] fluoride in the presence of [Ir(COD)Cl] 2 . 18 O-Labeling of the reactant reveals internal return during the allylic ionization step, and pathways for effective intra-and intermolecular isotope exchange.
The F-labeling of 5-(trifluoromethyl)-dibenzothiophenium trifluoromethanesulfonate, commonly referred to as the Umemoto reagent, has been accomplished applying a halogen exchangeF-fluorination with F-fluoride, followed by oxidative cyclization with Oxone and trifluoromethanesulfonic anhydride. This newF-reagent allows for the direct chemoselective F-labeling of unmodified peptides at the thiol cysteine residue.
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