The first catalytic asymmetric α-arylation of pyrazol-5-ones has been established by using 2-indolylmethanols as direct electrophilic arylation reagents under the cooperative catalysis of Pd(0) and a chiral phosphoric acid, which afforded the α-arylation products of pyrazol-5-ones in generally high yields and good enantioselectivities (up to 99% yield, >99% ee).
The first application of 3-methyl-2-vinylindoles in catalytic asymmetric Povarov reactions has been established via the three-component reactions of 3-methyl-2-vinylindoles, aldehydes, and anilines in the presence of chiral phosphoric acid, providing easy access to chiral indole-derived tetrahydroquinolines with three contiguous stereogenic centers at high yields (up to 99%) and with excellent diastereo- and enantioselectivities (all >95:5 dr, up to 96% ee). This mode of catalytic asymmetric three-component reaction offers a step-economic and atom-economic strategy for accessing enantioenriched indole-derived tetrahydroquinolines with structural diversity and complexity.
Abstract:The first catalytic asymmetric [3+2] cycloaddition of 2-indolylmethanols with 3-vinylindoles has been established, which makes use of C-3 unsubstituted 2-indolylmethanol as a C 3 building block in the presence of a chiral phosphoric acid. By using this strategy, biologically important cyclopenta [b]indole frameworks were efficiently constructed with regiospecificity in high yields (up to 99%), excellent diastereo-and enantioselectivities (up to > 95:5 dr, 96:4 er). This reaction not only represents the first catalytic asymmetric [3+2] cycloaddition of C-3 unsubstituted 2-indolylmethanols, but also has confronted the great challenges in 2-indolylmethanol-involved enantioselective transformations.
A regioselective and stereoselective difluoromethylation of enamides with bench-stable and easily accessible difluoromethyltriphenylphosphonium bromide is described. A broad array of synthetically important and geometrically defined β-difluoromethylated enamides bearing various functional groups are obtained with up to 91% yield.
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