Atom Transfer Radical Coupling Enables Highly Enantioselective Carbo-Oxygenation of Alkenes with Hydrocarbons.

The selective functionalization of C(sp3)-H bonds has emerged as a transformative approach for streamlining synthetic routes, offering remarkable efficiency in the preparation and modification of complex organic molecules. However, the direct enantioselective transformation of hydrocarbons to medicinally valuable chiral molecules remains a significant challenge that has yet to be addressed. In this study, we adopt an atom transfer radical coupling (ATRC) strategy to achieve the asymmetric functionalization of C(sp3)-H bonds in hydrocarbons. This approach involves intermolecular H atom transfer (HAT) between a hydrocarbon and an alkoxy radical, leading to the formation of a carbon-centered radical. The resulting radical adds to alkenes, generating a new radical species that is intercepted by a chiral copper-mediated C-O bond coupling. By employing this method, we can directly access valuable chiral lactones bearing a quaternary stereocenter with high efficiency and excellent enantioselectivity. Importantly, ATRC exhibits great potential as a versatile platform for achieving stereoselective transformations of hydrocarbons.

Nickel/Photo-Cocatalyzed Regioselective Ring Opening of N-Tosyl Styrenyl Aziridines with Aldehydes.

Aldehydes and aziridines are both intrinsic electrophilic reagents, and thus the coupling reaction between these two compounds is highly challenging. In this protocol, the merger of nickel and hydrogen-atom-transfer photocatalysis successfully enables the ring opening of N-tosyl styrenyl aziridines with aldehydes, providing a novel and atom-economical access to a variety of ß-amino ketones with complete regiocontrol. The preliminary mechanistic studies reveal that the ring opening reaction proceeds with a cooperative catalytic mode: aldehydes are converted into acyl radicals by tetrabutylammonium decatungstate under irradiation, whereas the nickel catalyst is engaged in the ring opening of aziridines and the following carbon-carbon bond-forming step.

Nickel-catalyzed asymmetric reductive aryl-allylation of unactivated alkenes.

Herein we report a nickel-catalyzed asymmetric reductive aryl-allylation of aryl iodide-tethered unactivated alkenes, wherein both acyclic allyl carbonates and cyclic vinyl ethylene carbonates can serve as the coupling partners. Furthermore, the direct use of allylic alcohols as the electrophilic allyl source in this reaction is also viable in the presence of BOC anhydride. Remarkably, this reaction proceeds with high linear/branched-, E/Z- and enantio-selectivity, allowing the synthesis of various chiral indanes and dihydrobenzofurans (50 examples) containing a homoallyl-substituted quaternary stereocenter with high optical purity (90-98% ee). In this reductive reaction, the use of pregenerated organometallics can be circumvented, giving this process good functionality tolerance and high step-economy.

Merger of C-F and C-N Bond Cleavage in Cross-Electrophile Coupling for the Synthesis of gem-Difluoroalkenes.

Herein we successfully applied Katritzky salts as the alkyl electrophile in the reductive allylic defluorinative cross-coupling reaction with α-trifluoromethyl alkenes. The merger of C-F and C-N bond cleavage via the synergistic effect of nickel and zinc allows the efficient synthesis of diverse gem-difluoroalkenes with a good tolerance for various functional groups.

Nickel-Catalyzed Asymmetric Reductive Arylbenzylation of Unactivated Alkenes.

Herein, we report a nickel-catalyzed asymmetric two-component reductive dicarbofunctionalization of aryl iodide-tethered unactivated alkenes using benzyl chlorides as the challenging coupling partner. This arylbenzylation reaction enables the efficient synthesis of diverse benzene-fused cyclic compounds bearing a quaternary stereocenter with a high tolerance of sensitive functionalities in highly enantioselective manner. The preliminary mechanistic investigations suggest a radical chain reaction mechanism.

Nickel-Catalyzed Reductive Arylalkylation via a Migratory Insertion/Decarboxylative Cross-Coupling Cascade.

Reported is a nickel-catalyzed reductive arylalkylation of unactivated alkenes tethered to aryl iodides with redox active N-hydroxyphthalimide esters as the alkyl source through successful merging of migratory insertion and decarboxylative cross-coupling in a cascade. This new method avoids the use of pregenerated organometallic reagents and thus enables the synthesis of diverse benzene-fused carbo- and heterocyclic compounds with high tolerance of a wide range of functional groups.

Nickel-Catalyzed Asymmetric Intramolecular Reductive Heck Reaction of Unactivated Alkenes.

An asymmetric Ni-catalyzed intramolecular reductive Heck reaction of unactivated alkenes tethered to aryl bromides has been accomplished, providing a variety of benzene-fused cyclic compounds bearing a quaternary stereogenic center in good to excellent yields and high enantioselectivities. A mechanism has been proposed, which involves the enantiodetermining migratory insertion and the following protonation with water or alcoholic solvents as the proton source.

Nickel-Catalyzed Asymmetric Reductive Arylalkylation of Unactivated Alkenes.

Reported is an asymmetric reductive dicarbofunctionalization of unactivated alkenes. Under the catalysis of a Ni/BOX system, various aryl bromides, incorporating a pendant olefinic unit, were successfully reacted with an array of primary alkyl bromides in the presence of Zn as a reductant, furnishing a series of benzene-fused cyclic compounds bearing a quaternary stereocenter in high enantioselectivities. Notably, this reaction avoids the use of pregenerated organometallics and demonstrates high tolerance of sensitive functionalities. The preliminary mechanistic investigations reveal that this Ni-catalyzed reaction proceeds as a cascade consisting of migratory insertion and cross-coupling with a nickel(I)-mediated intramolecular 5-exo cyclization as the enantiodetermining step.

Epoxide-Mediated Stevens Rearrangements of α-Amino-Acid-Derived Tertiary Allylic, Propargylic, and Benzylic Amines: Convenient Access to Polysubstituted Morpholin-2-ones.

A new strategy has been established for the synthesis of polysubstituted morpholin-2-ones through Stevens rearrangements of tertiary amines via in situ activation with epoxides. A range of α-amino acid-derived tertiary allylic, propargylic, and benzylic amines reacted with epoxides in the presence of zinc halide catalysts to afford structurally diverse allyl-, allenyl-, and benzyl-substituted morpholin-2-ones, respectively, in moderate-to-good yields with high regioselectivity. The process involves [2,3]- and [1,2]-Stevens rearrangements of quaternary ammonium ylide intermediates and constitutes a very convenient method to prepare polysubstituted morpholin-2-ones through tandem formation of C-N, C-O, and C-C bonds. Moreover, replacing epoxides with aziridines permitted the synthesis of polysubstituted piperazin-2-ones.

Ni-catalysed reductive arylalkylation of unactivated alkenes.

In this protocol Ni-catalysed reductive arylalkylation of unactivated alkenes tethered to aryl bromides with primary alkyl bromides has been accomplished, providing a new path to construct diverse benzene-fused carbo- and heterocyclic cores including indanes, tetrahydroisoquinolines, indolines and isochromanes. Notably, this new method circumvents the pregeneration of organometallics and demonstrates high tolerance to a wide range of functional groups. The preliminary mechanistic investigations suggest a reaction pathway with an intermediate reduction.