A (fluor)ry of activity: The transfer of an intact trifluoromethyl group from a hypervalent iodine reagent to an aliphatic alcohol occurs smoothly upon activation by zinc bis(triflimide). This constitutes a straightforward method for the preparation of trifluoromethoxy alkyl derivatives, compounds otherwise difficult to access.

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Effective CF(3) transfer: Various electron-rich nitrogen heterocycles (pyrazoles, triazoles, and tetrazoles) can be directly N-trifluoromethylated by a hypervalent iodine reagent in an efficient manner. The optimized procedure, which includes an in situ silylation of the substrate followed by an acid-catalyzed CF(3) transfer, provides ready access to a series of new and previously challenging or inaccessible NCF(3) compounds.

Schieb mal rüber: Der Transfer einer intakten Trifluormethylgruppe von einem hypervalenten Iodreagens zu einem aliphatischen Alkohol verläuft glatt bei einer Aktivierung durch Zinkbis(triflimid). Dies ist eine einfache Methode zur Synthese von Trifluormethoxyalkyl‐Derivaten, die sonst nur schwer zugänglich sind.

The unique features the trifluoromethyl group imparts to pharmaceuticals, crop-protection agents, and functional materials emphasize the necessity to design and develop new reagents and methods for the direct trifluoromethylation of a wide range of organic substrates. Electrophilic trifluoromethylation, that is, the reaction of a suitable reagent capable of formally transferring an intact CF 3 + unit, has been shown to be one of these methods.[1] However, despite the availability of several such effective reagents, the electrophilic trifluoromethylation of hard nucleophiles, for example, oxygen-or nitrogen-centered ones, remains challenging. In particular, the formation of a N À CF 3 bond by such a reaction is still extremely rare. In fact, the NCF 3 unit is usually constructed by the interconversion of suitable functional groups. Thus, fluorination of N-formylamines, [2] thiuram sulfides, [3] isocyanates, [4] and trichloromethylamines, [5] the reaction of secondary amines with CBr 2 F 2 and tetrakis(dimethylamino)ethylene, [6] and the electrochemical fluorination of alkylamines [7] constitute the still relatively modest set of methods. Of these, the most frequently used approach is the oxidative desulfurization-fluorination of dithiocarbamates first described for the generation of NCF 3 groups by Hiyama and Kuroboshi.[8]The single, still very recent report of a direct trifluoromethylation at nitrogen is due to Umemoto and co-workers.[9] They describe the direct N-trifluoromethylation of amines, anilines, and pyridines under very mild conditions achieved with in situ generated and thermally unstable O-(trifluoromethyl)dibenzofuranium salts (corresponding reactions of alcohols and phenols are also known). However, this type of reagent suffers from several shortcomings. The active CF 3 source is obtained by photochemical decomposition of diazonium salts at very low temperature, and the synthesis requires several steps including the construction of a CF 3 O-aryl moiety. It is therefore likely that this methodology will not replace the corresponding functional-group interconversions in the near future.We have shown that a new generation of readily accessible trifluoromethylation reagents based on hypervalent iodine, such as compounds 1 and 2 (Scheme 1), display the desired reactivity towards a number of C-, S-, P-, and O-centered nucleophiles. Despite their purported soft nature, reagents 1 and 2 do trifluoromethylate alcohols and sulfonic acids upon activation with Lewis [10] and Brønsted acids, [11] respectively, thus significantly expanding their application range.During a recent investigation of the direct electrophilic trifluoromethylation of heteroarenes [12] using reagent 1 and catalytic amounts of bis(trifluoromethanesulfonyl)imide (HNTf 2 ) in acetonitrile, we surprisingly found that benzotriazole (3) is converted to the corresponding N-substituted N-trifluoroimidoyl derivative 4, as shown in Scheme 2. The generation of compound 4 corresponds to a novel Rittertype [13] reaction during which a new NÀCF 3 bond...

The highly selective palladium-catalyzed Negishi coupling of secondary alkylzinc reagents with heteroaryl halides is described. The development of a series of biarylphosphine ligands has led to the identification of an improved catalyst for the coupling of electron-deficient heterocyclic substrates. Preparation and characterization of oxidative addition complex (L)(Ar)PdBr provided insight into the unique reactivity of catalysts based on CPhos-type ligands in facilitating challenging reductive elimination processes.

Intermolecular nucleophilic substitution of a CF(3) group of bis(trifluoromethyl)phosphanes by a lithiated Ugi's amine (4) affords both diastereoisomers of the corresponding P-stereogenic trifluoromethylphosphanes 6 and 7. Separation of the isomers by column chromatography on silica gel followed by substitution of the dimethylamino group with phosphanes or pyrazoles yields the bidentate P^P (9 and 10) or P^N ligands (12 and 13) without epimerization at the stereogenic phosphorus center. The coordination properties of these bidentate ligands were investigated on the basis of crystal structures of the corresponding palladium and rhodium complexes. IR spectroscopic measurements of rhodium-carbonyl complexes 16-23 indicated the strongly electronic-withdrawing character of these phosphanes. The catalytic potential of these ligands was demonstrated in the rhodium-catalyzed hydrogenation of olefins as well as in the palladium-catalyzed allylic alkylation reaction, where high activities and enantioselectivities were observed.

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