A method for cobalt‐catalyzed, aminoquinoline‐ and picolinamide‐directed C(sp2)H bond alkenylation by alkynes was developed. The method shows excellent functional‐group tolerance and both internal ...and terminal alkynes are competent substrates for the coupling. The reaction employs a Co(OAc)2⋅4 H2O catalyst, Mn(OAc)2 co‐catalyst, and oxygen (from air) as a terminal oxidant.
In the air: Excellent functional‐group tolerance is observed in the title reaction, and both internal and terminal alkynes are competent substrates for the coupling. The reaction employs Co(OAc)2⋅4 H2O as the catalyst, Mn(OAc)2 as the co‐catalyst, and oxygen (from air) as the terminal oxidant. Piv=pivalate.
In recent years, carbon–hydrogen bond functionalization has evolved from an organometallic curiosity to a tool used in mainstream applications in the synthesis of complex natural products and drugs. ...The use of C–H bonds as a transformable functional group is advantageous because these bonds are the most abundant functionality in organic molecules. One-step conversion of these bonds to the desired functionality shortens synthetic pathways, saving reagents, solvents, and labor. Less chemical waste is generated as well, showing that this chemistry is environmentally beneficial. This Account describes the development and use of bidentate, monoanionic auxiliaries for transition-metal-catalyzed C–H bond functionalization reactions. The chemistry was initially developed to overcome the limitations with palladium-catalyzed C–H bond functionalization assisted by monodentate directing groups. By the use of electron-rich bidentate directing groups, functionalization of unactivated sp3 C–H bonds under palladium catalysis has been developed. Furthermore, a number of abundant base-metal complexes catalyze functionalization of sp2 C–H bonds. At this point, aminoquinoline, picolinic acid, and related compounds are among the most used and versatile directing moieties in C–H bond functionalization chemistry. These groups facilitate catalytic functionalization of sp2 and sp3 C–H bonds by iron, cobalt, nickel, copper, ruthenium, rhodium, and palladium complexes. Exceptionally general reactivity is observed, enabling, among other transformations, direct arylation, alkylation, fluorination, sulfenylation, amination, etherification, carbonylation, and alkenylation of carbon–hydrogen bonds. The versatility of these auxilaries can be attributed to the following factors. First, they are capable of stabilizing high oxidation states of transition metals, thereby facilitating the C–H bond functionalization step. Second, the directing groups can be removed, enabling their use in synthesis and functionalization of natural products and medicinally relevant substances. While the development of these directing groups presents a significant advance, several limitations of this methodology are apparent. The use of expensive second-row transition metal catalysts is still required for efficient sp3 C–H bond functionalization. Furthermore, the need to install and subsequently remove the relatively expensive directing group is a disadvantage.
Taking direction well: Substituted phenylalanine derivatives were prepared by CH bond functionalization (see scheme). The syntheses are highly convergent and employ an N‐phthaloylalanine with a ...2‐thiomethylaniline directing group. The use of an 8‐aminoquinoline directing group allows for the diarylation of methyl and the diastereoselective arylation of methylene groups.
A method for direct carbonylation of aminoquinoline benzamides has been developed. Reactions proceed at room temperature in trifluoroethanol solvent, use oxygen from air as an oxidant, and require ...Mn(OAc)3 as a cocatalyst. Benzoic and acrylic acid derivatives can be carbonylated by carbon monoxide affording imides in good yields. Halogen, nitro, ether, cyano, and ester functional groups are tolerated. The directing group can be removed under mild conditions affording phthalimides.
A method for aminoquinoline-directed, cobalt-promoted dimerization of benzamides has been developed. Reactions proceed in ethanol solvent in the presence of Mn(OAc)2 cocatalyst and Na2CO3 base and ...use oxygen as a terminal oxidant. Bromo, iodo, nitro, ether, and ester moieties are compatible with the reaction conditions. Cross-coupling of electronically dissimilar aminoquinoline benzamides proceeds with modest yields and selectivities.
We have developed a method for direct, copper-catalyzed, auxiliary-assisted fluorination of β-sp2 C–H bonds of benzoic acid derivatives and γ-sp2 C–H bonds of α,α-disubstituted benzylamine ...derivatives. The reaction employs a CuI catalyst, a AgF fluoride source, and DMF, pyridine, or DMPU solvent at moderately elevated temperatures. Selective mono- or difluorination can be achieved by simply changing reaction conditions. The method shows excellent functional group tolerance and provides a straightforward way for the preparation of ortho-fluorinated benzoic acids.
A method for five- and six-membered heterocycle formation by palladium-catalyzed C–H/N–H coupling is presented. The method employs a picolinamide directing group, PhI(OAc)2 oxidant, and toluene ...solvent at 80–120 °C. Cyclization is effective for sp2 as well as aliphatic and benzylic sp3 C–H bonds.
Here we report that the tri-1-adamantylphosphine-nickel complex Ad
PNiBr
Ad
PH
upon activation with an alkylaluminoxane catalyzes the polymerization of ethylene to ultrahigh-molecular-weight, nearly ...linear polyethylene (M
up to 1.68 × 10
g mol
) with initial activities reaching 3.7 million turnovers per h
at 10 °C. Copolymerizations of ethylene with α-olefins such as 1-hexene and 1-octadecene, as well as tert-butyldimethyl(dec-9-en-1-yloxy)silane give the corresponding copolymers with no decrease in activity.
Amine meets arene: A method for direct amination of β‐C(sp2)H bonds of benzoic acid derivatives and γ‐C(sp2)H bonds of benzylamine derivatives has been developed. The reaction is catalyzed by ...Cu(OAc)2 and a Ag2CO3 cocatalyst, and shows high generality and functional‐group tolerance, as well as providing a straightforward means for the preparation of ortho‐aminobenzoic acid derivatives.
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