No abstract

The development of new strategies for synthesis of trifluoromethylthiolate compounds is of considerable importance in pharmaceuticals, agrochemicals, and advanced materials. Accordingly, currently much attention is being devoted to the development of effective methods and reagents for their synthesis. In contrast, considerably less effort has been afforded to the development of preparing CSeCF3 bonds. Herein we report a concise route to synthesize a family of copper(I) trifluoromethylselenolate reagents by the reaction of CuI with the Ruppert's reagent (Me3 SiCF3 ), KF, and elemental selenium in the presence of dinitrogen ligands in CH3 CN at room temperature. The reagent [Cu(bpy)(SeCF3 )]2 was proven to be air-stable and highly efficient for nucleophilic trifluoromethylthselenolation of a broad range of (hetero)aryl halides and alkyl halides. This method represents a powerful protocol for the construction trifluoromethylselenolate compounds.

The copper(I) thiophenolato complexes 1–3 containing 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (Me2phen) were isolated in excellent yields from reactions of [CuOtBu]4 with the dative ligands and subsequent addition of 1 equiv of arylthiol and characterized spectroscopically. X-ray structural analysis of a single crystal of [(phen)Cu(µ-SC6H5)]2 (1) revealed that this complex adopts a neutral dimeric form with a weak Cu–Cu bonding interaction. These complexes were found to react with iodoarenes to form aryl sulfide products. The intermediacy of such complexes in copper-catalyzed thioetherification of aryl halides was demonstrated by the reactivity with p-tolyl iodide and o-tolyl iodide to form two aryl thioethers with selectivities similar to those of catalytic reactions conducted with the same two iodoarenes.

The first catalytic trifluoromethoxylation of unactivated alkenes has been developed, in which Pd(CH3CN)2Cl2 was used as catalyst, AgOCF3 as trifluoromethoxide source, and Selectfluor-BF4 as oxidant. A variety of 3-OCF3 substituted piperidines were selectively obtained in good yields. Direct evidence was provided to address the facile reductive elimination of Pd(IV)-OCF3 complex to form sp(3) C-OCF3 bond.

A selective palladium-catalyzed trifluoroethylation reaction of indoles has been developed. The C-H bond activation process, using CF 3 CH 2 I as the fluoroalkyl source, can be employed to prepare a variety of 2-CF 3 CH 2 substituted indoles. Moreover, because it displays a wide functional group tolerance, the process can be employed to synthesize CF 3 CH 2 -containing bioactive indoles through late-stage trifluoroethylation. The results of a preliminary mechanistic study and DFT calculations show that a β-diketone, acting as an ionic palladium ligand, plays an important role in governing the efficiency of the palladiumcatalyzed trifluoroethylation reaction by accelerating the oxidative addition step. In contrast, transfer of the indole N-H proton in the palladium center is involved in the rate-determining step.

A novel asymmetric 6-endo aminoacetoxylation of unactivated alkenes by palladium catalysis, which yields chiral β-acetoxylated piperidines with excellent chemo-, regio- and enantioselectivities under very mild reaction conditions, has been established herein by employing a new designed pyridine-oxazoline (Pyox) ligand. Importantly, introducing a sterically bulky group into the C-6 position of Pyox is crucial to enhance the reactivity of the aminoacetoxylation of alkenes.

A catalytic trifluoromethylselenolation of aryl and alkyl halides by a Cu(I) catalyst has been developed. A key intermediate, [(phen)Cu(SeCF3)]2 (5) was successfully isolated and characterized by X-ray diffraction. The important role of silver in the transmetalation process during the catalytic cycle was elucidated. A wide range of trifluoromethylselanes have been prepared from readily available starting materials from a method that tolerates various important functional groups.

Copper(I) fluoride complexes ligated by phenanthroline derivatives have been synthesized and structurally characterized by X-ray crystallography. These complexes adopt as either ionic or neutral forms in the solid state, depending on the steric bulkiness of the substituent groups on the phenanthroline ligands. These complexes react with primary and secondary alkyl bromides to produce the corresponding alkyl fluorides in modest to good yields. This new method is compatible with a variety of important functional groups such as ether, thioether, amide, nitrile, methoxyl, hydroxyl, ketone, ester, and heterocycle moieties.