A general method has been developed for in situ trapping of arylmetal intermediates by halogen, sulfur, ketone, and aldehyde electrophiles affording the functionalization of the most acidic position ...in arene. Pentafluorobenzene, benzothiazole, and benzoxazole can be functionalized by using K3PO4 base. For less acidic arenes, tBuOLi base is required. Arenes with DMSO pK a values of 35 or less are reactive.
A highly regioselective, one-pot sequential iodination-copper-catalyzed cross-coupling of arene C-H bonds has been developed affording an efficient method for biaryl synthesis.
A method for copper-catalyzed oxidative dimerization of nitronates and enolates using oxygen as the terminal oxidant has been developed. Cyclization through oxidative intramolecular coupling is also ...feasible for both nitronates and enolates. The mild reaction conditions lead to good functional group tolerance.
A new class of chiral phosphines belonging to the P-aryl-2-phosphabicyclo3.3.0octane family (PBO) has been prepared by enantioselective synthesis starting from lactate esters and ...2,2-dimethylcyclopentanone enolate 5. A selective enolate alkylation method has been developed for preparation of 9 and 10 using a chelating ester substituent in the triflate alkylating agent 11. Subsequent conversion to the PBO catalysts 2 and 39 relies on a diastereoselective cyclization from the cyclic sulfate 17 and LiPHAr to afford the more hindered endo-aryl phosphines. These phosphines function as efficient catalysts for the kinetic resolutions of aryl alkyl carbinols by benzoylation (16, 21, 22) or iso-butyroylation in the case of the less hindered aryl alkyl carbinol substrates. With o-substituted aryl alkyl carbinols, the enantioselectivities exceed 100, and s = 380 ± 10 has been demonstrated in the case of methyl mesityl carbinol. The PBO-catalyzed acylations probably involve a P-acylphosphonium carboxylate intermediate and a tightly ion paired transition state.
Aryl-substitued α-diimines were prepared by means of an operationally simple copper iodide-mediated Stille-type coupling between polyfluoro(chloro)aryl tributylstannanes and bis(imidoyl ...chlorides). Reactions proceed in commercial grade N, N-dimethylformamide (DMF) solvent at 70 °C and require no additives or bases. Couplings are successful for aryl stannanes possessing two or more fluoro or chloro substituents on the aromatic ring. Products are obtained in moderate to good yields. This methodology allows for a simple synthesis of α-diimine ligands potentially useful in olefin polymerization as well as other catalytic transformations.
Silylaryl bromides and iodides can be prepared in one step from commercially available starting materials. Arynes can be generated from these compounds under conditions nearly identical to those ...employed for silylaryl triflates. Three distinct transformations, ortho-arylation of N-tritylanilines, intermolecular addition of arynes to amides, and reaction of ureas with arynes, were shown to be successful for the new aryne precursors. The main advantage of silylaryl halides relative to silyl aryl triflates is their one-step preparation from commercially available starting materials.
N
-Aminopyridinium ylide-directing group is employed for copper-promoted chalcogenation of sp
2
C─H bonds with aryl and alkyl disulfides as well as diphenyl diselenide. Reactions proceed in ...hexafluoroisopropanol (HFIP) solvent at elevated temperatures and are promoted by copper(II) acetate.
In this paper, we introduce arylphosphinic acid aminoquinoline amides as competent substrates for cobalt-catalyzed sp2 C–H bond functionalization. Specifically, the feasibility of their coupling with ...alkynes, alkenes, and allyl pivalate has been demonstrated. Reactions are catalyzed by simple Co(NO3)2 hydrate in ethanol or mixed dioxane/tBuOH solvent in the presence of Mn(OAc)3·2H2O additive, sodium pivalate, or acetate base and use oxygen from the air as an oxidant. Directing group removal affords ortho-functionalized P,P-diarylphosphinic acids.
We report structural characterization of a new member of m‐phenylene ethynylene ring family. This shape‐persistent macrocycle also co‐crystallizes with hexafluoro‐, 1,2,4,5‐tetrafluoro‐, ...1,3,5‐trifluoro, and 1,4‐difluorobenzene. The four complexes are almost isostructural, and all show the fluoroarene included into the central cavity of the macrocycle. Characterized by multiple short CH⋅⋅⋅FC contacts, these inclusion complexes further dimerize in the solid state into a 2+2 assembly, in which the two macrocycles embrace each other by their large hydrophobic groups that are rotated by 60° relative to one another.
Planar and shape‐persistent m‐phenylene ethynylene macrocyclic host crystallizes in 1:1 complexes with a series of fluoroarene guests, including 1,3,5‐trifluorobenzene. The combination of (pseudo)sixfold symmetry of the host and threefold symmetry of the guest is reminiscent of the combination of symmetries observed in the arabesques of Alhmabra (see figure).
N-Iminopyridinium ylides are competent monodentate directing groups for cobalt-catalysed annulation of sp
2
C-H bonds with internal alkynes. The pyridine moiety in the ylide serves as an internal ...oxidant and is cleaved during the reaction. The annulation reactions possess excellent compatibility with heterocyclic substrates, tolerating furan, thiophene, pyridine, pyrrole, pyrazole, and indole functionalities.
N-Iminopyridinium ylides are used as directing groups and internal oxidants for cobalt-catalysed annulation of sp
2
C-H bonds with internal alkynes. The reactions possess excellent compatibility with heterocyclic substrates.
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