We report the synthesis of cobalt complexes of novel iminopyridine–oxazoline (IPO) ligands and their application to the asymmetric hydroboration of 1,1-disubstituted aryl alkenes. The new catalysts ...afforded α-alkyl-β-pinacolatoboranes with exclusive regioselectivity in high yields with up to 99.5% ee. Furthermore, we have applied this method to an efficient synthesis of naproxen.
A novel enantioselective copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes has been developed, in which a variety of CF
-containing alkylnitriles are furnished with excellent ...enantiomeric excess. Preliminary mechanistic studies revealed (1) the reaction was initiated by a SET process between activated Togni's CF
reagent and a Cu(I) catalyst; (2) the released CF
radical readily added to styrene to provide a benzylic radical, which was then trapped by a chiral Cu(II) cyanide species to deliver the desired alkylnitriles; (3) a low concentration of the CN anion was crucial to obtain high enantioselectivity.
A novel asymmetric radical trifluoromethyl-arylation of alkenes has been developed, which provides an efficient approach to access chiral CF3-containing 1,1-diarylmethane derivatives with good to ...excellent enantioselectivity. Various vinyl arenes and aryl boronic acids are compatible with these conditions. The utility of the method is demonstrated by accessing modified bioactive molecules.
We have developed a copper-catalyzed enantioselective intermolecular aminoarylation of alkenes using a novel N-fluoro-N-alkylsulfonamide as the amine reagent, which could react with the Cu(I) ...catalyst to release a related amino radical. After addition to styrene, the generated benzylic radical could couple with a chiral L*CuIIAr complex to achieve enantioselective arylation. Various optical 2,2-diarylethylamines were efficiently synthesized from simple styrenes with high enantioselectivity, and these products can serve as valuable synthons toward bioactive molecules’ synthesis.
Trifluoromethoxy‐substituted stereogenic centers can be constructed with high enantioselectivity by a nickel‐catalyzed Suzuki–Miyaura coupling of readily available α‐bromobenzyl trifluoromethyl ...ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups, such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino, and vinyl moieties, were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without a decrease in enantioselectivity.
Trifluoromethoxy‐substituted stereogenic centers were constructed with high enantioselectivity in a nickel‐catalyzed Suzuki–Miyaura coupling of readily available α‐bromobenzyl trifluoromethyl ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups are well tolerated.
Nickel-catalyzed asymmetric cross-coupling of secondary alkyl electrophiles with different nucleophiles represents a powerful strategy for the construction of chiral tertiary carbon centers. Yet, the ...use of aryl Grignard reagents or aryl zinc halides in many reactions typically resulted in low enantioselectivity, mainly due to their slow transmetalation step in the catalytical cycle and consequently the requirement of relatively high temperature. Here we report that the use of lithium aryl zincate Ph
ZnBrLi facilitates the transmetalation step of the nickel-catalyzed cross-coupling reaction. Based on this discovery, a highly enantioselective construction of fluoroalkyl-substituted stereogenic center by a nickel-catalyzed asymmetric Suzuki-Miyaura coupling of α-bromobenzyl trifluoro-/difluoro-/mono- fluoromethanes with a variety of lithium aryl zincates Ph
ZnBrLi that were in situ generated from the reaction of lithium organoboronate with 1.0 equivalent of ZnBr
was described.
Abstract
Direct deoxyazidation of alcohols with NaN
3
is a straightforward method for the synthesis of widely used alkyl azides in organic chemistry. However, known methods have some limitations such ...as high reaction temperatures and narrow substrate scope. Herein, a general and practical method for the preparation of alkyl azides from alcohols using NaN
3
has been developed.
N
-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor) plays an important role in this deoxyazidation process, which converts a broad range of alcohols into alkyl azides at room temperature. The power of this deoxyazidation protocol has been demonstrated by successful late-stage deoxyazidation of natural products and pharmaceutically relevant molecules.
A shorter path: A highly enantioselective bromocyclization of tryptamine has been developed using an anionic chiral phase‐transfer catalyst. This method provides a direct approach for preparing ...chiral 3‐bromopyrroloindoline from tryptamine, which enables a four‐step enantioselective synthesis of (−)‐chimonanthine. PG=protecting group.
It is challenging to stereoselectively introduce a trifluoromethyl group (CF3) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been ...reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper‐catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.
Just the beginning: The title reaction enables propargylic trifluoromethylation and difluoroalkylation with high regioselectivity and stereoselectivity (see scheme) to provide versatile building blocks that undergo a wide variety of transformations. Inversion of configuration was observed for the copper‐catalyzed process, thus demonstrating that SN2‐type oxidative addition of copper to the secondary propargyl sulfonate may be involved in the reaction.
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