In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an ...uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo‐differentiation of remote motifs away from the radical reaction site. We herein describe a copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P‐ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3‐enynes as well as radical precursors with excellent functional group tolerance.
A copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes is realized, providing diverse tetrasubstituted chiral allenes. The utilization of the copper/chiral N,N,P‐ligand is crucial for the enantiocontrol over the allenyl radicals, which is difficult due to their elongated linear configuration that necessitates the stereo‐differentiation of remote motifs away from the reaction site.
A copper-catalyzed enantioconvergent Suzuki–Miyaura C(sp3)–C(sp2) cross-coupling of various racemic alkyl halides with organoboronate esters has been established in high enantioselectivity. ...Critical to the success is the use of a chiral cinchona alkaloid-derived N,N,P-ligand for not only enhancing the reducing capability of copper catalyst to favor a stereoablative radical pathway over a stereospecific SN2-type process but also providing an ideal chiral environment to achieve the challenging enantiocontrol over the highly reactive radical species. The reaction has a broad scope with respect to both coupling partners, covering aryl- and heteroarylboronate esters, as well as benzyl-, heterobenzyl-, and propargyl bromides and chlorides with good functional group compatibility. Thus, it provides expedient access toward a range of useful enantioenriched skeletons featuring chiral tertiary benzylic stereocenters.
The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)−H bonds has been impeded by the use of a base at elevated temperature that leads to ...racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)−H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzodoxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)−H bond and the involvement of alkyl radical species under the reaction conditions.
The use of a cinchona‐alkaloid‐derived N,N,P‐ligand leads to the direct enantioconvergent coupling of racemic alkyl bromides with azole C(sp2)−H bonds by copper catalysis. The key to success is the ligand‐enabled facile oxidative addition at approximately room temperature that suppresses product racemization at elevated temperature. This method provides a range of enantioenriched α‐chiral alkylated azoles.
We describe a copper‐catalyzed Sonogashira coupling reaction of alkyl halides with terminal alkynes under ambient conditions, efficiently providing a versatile tool for the construction of ...substituted alkynes. A new proline‐based N,N,P‐ligand is utilized to promote the transformation under a mild reaction condition. Diverse alkyl halides, such as primary and secondary (hetero)benzyl chlorides and bromides, secondary and tertiary α‐bromo amides and propargylic bromide, are applicable to provide a wide array of alkynes.
A first catalytic enantioselective intermolecular radical aminotrifluoromethylation of alkene with hydrazine and Togni's reagent by Cu(I)/CPA cooperative catalysis has been reported, accessing ...diversely substituted CF3‐containing enantioenriched diarylmethylamines bearing an α‐tertiary stereocenter with high enantioselectivity and excellent chemoselectivity. The highly asymmetric induction of C−N bond formation between hydrazine and the carbocation intermediate was achieved by using a CPA catalyst via hydrogen‐bonding and ion pair interaction.
Alkene difunctionalization: A chiral Cu(I)/CPA‐catalyzed asymmetric intermolecular radical aminotrifluoromethylation of alkene with hydrazine and Togni's reagent has been established, which offered enantioenriched diarylmethylamines bearing an α‐tertiary stereocenter in generally good yields and enantioselectivities. The obtained enantioenriched products represent key structural motifs of a large of biologically molecules in medicinal chemistry, which can also be easily transformed into other valuable chiral CF3‐containing hindered primary amines.
The copper-promoted cascade radical reaction of N-sulfonyl-2-allylanilines with 60fullerene has been developed to efficiently provide novel and scarce (2-indolinyl)methylated hydrofullerenes, ...featuring a broad substrate scope and excellent functional group tolerance. A plausible reaction mechanism for the formation of (2-indolinyl)methylated hydrofullerenes is proposed on the basis of the experimental results. In addition, further transformation into other carbocyclic derivatives of 60fullerene as well as their applications in organic photovoltaic devices of the obtained products has also been explored.
Atmospheric pressure nonequilibrium plasma jet has been applied to the synthesis of 60fullerene oxides (C60On) for the first time. C60O and C60O2 were produced and isolated in high yields up to 44% ...and 21%, respectively. The structural assignment of C60O was confirmed by comparison with the reported spectroscopic data. Theoretical calculations of 13C NMR chemical shifts for eight isomers of C60O2 were performed and compared with the experimental data to assign the most possible structure for the obtained C60O2 dominantly as an e isomer.
A general and facile annulation of various diol motifs to 60fullerene has been developed. This protocol can afford not only 6- to 10-membered-ring fullerenyl diethers in one step from simple acyclic ...diols but also directly couple 60fullerene with a variety of structurally diverse sugars. The 60fullerene-sugar conjugates formed do not require any linker moiety and maintain their inherent structural integrity. The electrochemistry of the fullerenyl diethers and 60fullerene-sugar conjugates has also been investigated.
The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)−H bonds has been impeded by the use of a base at elevated temperature that leads to ...racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)−H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzodoxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)−H bond and the involvement of alkyl radical species under the reaction conditions.
The use of a cinchona‐alkaloid‐derived N,N,P‐ligand leads to the direct enantioconvergent coupling of racemic alkyl bromides with azole C(sp2)−H bonds by copper catalysis. The key to success is the ligand‐enabled facile oxidative addition at approximately room temperature that suppresses product racemization at elevated temperature. This method provides a range of enantioenriched α‐chiral alkylated azoles.
In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an ...uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo‐differentiation of remote motifs away from the radical reaction site. We herein describe a copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P‐ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3‐enynes as well as radical precursors with excellent functional group tolerance.
A copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes is realized, providing diverse tetrasubstituted chiral allenes. The utilization of the copper/chiral N,N,P‐ligand is crucial for the enantiocontrol over the allenyl radicals, which is difficult due to their elongated linear configuration that necessitates the stereo‐differentiation of remote motifs away from the reaction site.
PDF
