The enantioselective construction of axially chiral compounds by electrophilic carbothiolation of alkynes is disclosed for the first time. This enantioselective transformation is enabled by the use of a Ts‐protected bifunctional sulfide catalyst and Ms‐protected ortho‐alkynylaryl amines (Ts=tosyl; Ms=mesyl). Both electrophilic arylthiolating and electrophilic trifluoromethylthiolating reagents are suitable for this reaction. The obtained products of axially chiral vinyl–aryl amino sulfides can be easily converted into biaryl amino sulfides, biaryl amino sulfoxides, biaryl amines, vinyl–aryl amines, and other valuable difunctionalized compounds.
New approaches for the synthesis of enantiopure trifluoromethylthiolated molecules by chiral selenide-catalyzed allylic trifluoromethylthiolation and intermolecular difunctionalization of unactivated alkenes are disclosed. In these transformations, functional groups were well tolerated, and the desired products were obtained in good yields with excellent chemo-, enantio-, and diastereoselectivities. This reaction is nicely complementary to enantioselective trifluoromethylthiolation, allylic functionalization, and intermolecular alkene difunctionalization.
The development of catalysts for environmentally benign
organic
transformations is a very active area of research. Most of the catalysts
reported so far are based on transition-metal complexes. In recent
years, examples of catalysis by main-group metal compounds have been
reported. Herein, we report a series of magnesium pincer complexes,
which were characterized by NMR and X-ray single-crystal diffraction.
Reversible activation of H2 via aromatization/dearomatization
metal–ligand cooperation was studied. Utilizing the obtained complexes, the unprecedented homogeneous main-group
metal catalyzed semihydrogenation of alkynes and hydrogenation of
alkenes were demonstrated under base-free conditions, affording Z-alkenes and alkanes as products, respectively, with excellent
yields and selectivities. Control experiments and DFT studies reveal
the involvement of metal–ligand cooperation in the hydrogenation
reactions. This study not only provides a new approach for the semihydrogenation
of alkynes and hydrogenation of alkenes catalyzed by magnesium but
also offers opportunities for the hydrogenation of other compounds
catalyzed by main-group metal complexes.
An efficient and
convenient pathway was developed
for enantioselective synthesis of chiral
sulfides by chiral bifunctional selenide-catalyzed electrophilic azidothiolation
and oxythiolation of N-allyl sulfonamides. By this
protocol, a variety of chiral vicinal azidosulfides and oxysulfides
were obtained in good yields with high enantioselectivities and diastereoselectivities.
In this transformation, not only electrophilic arylthiolating reagents
but also a wide range of electrophilic alkylthiolating reagents worked
very well. The practical application of this method was elucidated
by further transformations of the products into the diversified compounds.
Enantioselective electrophilic three-component thioarylation of alkenes by chiral selenide catalysis with free phenols as arylating sources is disclosed. A variety of chiral phenols were achieved in high regio-, enantio-, and diastereoselectivities. Mechanistic studies revealed that this transformation went through carbon nucleophilic attack to give the products rather than the process of intramolecular rearrangement of phenolic ether intermediates. The application of this organocatalytic method in the alkylation of methoxy-substituted benzenes elucidated its generality.
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