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The heterobicyclic core retained hydroarylation of oxa/azabenzonorbornadienes with quinoline N-oxides has been achieved under rhodium catalysis, giving quinoline N-oxide substituted heterobicyclic structures with excellent regioselectivity and in good yields. As the first example of the direct introduction of quinoline N-oxides onto heterobicyclic structures, the strained heterobicyclic core was well retained in the reaction. The products could be successfully transformed into a series of useful compounds, including epibatidine analogues. [ABSTRACT FROM AUTHOR]

A cascade reaction of homopropargyl azides in the presence of a Cu catalyst was achieved, affording 3-(trifluoromethyl)but-3-enenitriles with good yields and excellent regioselectivity. This reaction appears to be the first direct conversion of homopropargyl azides into trifluoromethylated nitriles. Mechanistic studies indicate that the transformation proceeds by addition of a CF3 radical to the alkyne, C-C cleavage by 1,4-aryl radical migration, and nitrile formation. This protocol provides a novel strategy for transforming azides into nitriles via C-C cleavage derived from radical migration. [ABSTRACT FROM AUTHOR]

As the first cascade C-H activation directed by a transient group, reaction of alkynols and 7-oxabenzonorbornadienes has been achieved via synergistic rhodium and scandium catalysis to afford spirocyclic dihydrobenzo[a]fluorenefurans. This transformation proceeds by a transient hemiketal group directed C-H activation, dehydrative naphthylation, and intramolecular Prins-type cyclization. Mechanistic studies and density functional theory calculations indicate that the rate-determining step is C-H bond cleavage and both the transient hemiketal group and synergistic RhIII/ScIII catalysis play key roles. [ABSTRACT FROM AUTHOR]

Rhodium-catalyzedaddition–cyclization of hydrazines withalkynes has been achieved to afford highly substituted pyrazoles undermild conditions. The cascade reaction involves two transformations:addition of the C–N bond of hydrazines to alkynes via unexpectedC–N bond cleavage and intramolecular dehydration cyclization. [ABSTRACT FROM AUTHOR]

Intermolecular benzylic methylene functionalization of exo-cyclic enol ethers has been achieved using imines as reagents and potassium tert-butoxide as the catalyst. Depending on the solvent used, the reaction proceeds by two pathways. In THF, an addition/elimination reaction of exo-cyclic enol ethers with imines provides dihydroisobenzofuran derivatives in good yield. In DMSO, an addition/ring-opening/cyclization cascade reaction occurs with unexpected cleavage of C–O and C–C bonds, affording isoquinolin-1(2H)-one products in high yield under ambient reaction conditions. [ABSTRACT FROM AUTHOR]

We report a step-economic strategy for the direct synthesis of bridged polycyclic skeletons by merging oxidative C-H annulation and cascade cycloaddition. In the protocol, spiro[cyclopentane-1,3'-indoline]-2,4-dien-2'-ones were first synthesized by oxidative C-H annulation of ethylideneoxindoles with alkynes. Subsequent cascade [4 + 2] cycloaddition with dienophiles gave the bridged bicyclo[2.2.1]quinolin-2(1 H )-ones and enabled the one-pot construction of two quaternary carbon centers and three C-C bonds. Mechanistic investigations of the latter suggest a cascade ring-opening, 1,5-sigmatropic rearrangement, and [4 + 2] cycloaddition process.

A novel copper-catalyzed radical cyanotrifluoromethylation has been achieved through a multicomponent reaction of isocyanides, Togni's reagent, and trimethylsilyl cyanides, affording trifluoroacetimidoyl nitriles in good yields. This reaction demonstrates a unique feature of merging two valuable functional groups-trifluoromethyl (CF 3 ) and cyan (CN)-onto the same C atom. The transformation proceeds by the initial addition of the CF 3 radical to isocyanide and the subsequent intermolecular C-CN formation. The products can be successfully transformed to a series of CF 3 -containing amines and imines that may serve in the synthesis of valuable pharmaceuticals and agrochemicals.

As the first cascade C-H activation directed by a transient group, reaction of alkynols and 7-oxabenzonorbornadienes has been achieved via synergistic rhodium and scandium catalysis to afford spirocyclic dihydrobenzo[a]fluorenefurans. This transformation proceeds by a transient hemiketal group directed C-H activation, dehydrative naphthylation, and intramolecular Prins-type cyclization. Mechanistic studies and density functional theory calculations indicate that the rate-determining step is C-H bond cleavage and both the transient hemiketal group and synergistic Rh III /Sc III catalysis play key roles.

A facile Pd-catalyzed sequential reaction has been developed for the synthesis of δ-carbolines from 2-iodoanilines and N-tosyl-enynamines. This protocol involves Larock heteroannulation/elimination/electrocyclization/oxidative aromatization cascade sequences and allows access to multisubstituted δ-carbolines in moderate to good yields., (© 2011 American Chemical Society)

An interesting sequential Sonogashira coupling/alkynyl imine-allenyl imine isomerization/aza-Diels-Alder/elimination-aromatization reaction, providing a facile synthesis of substituted 2-azaanthracenes from 1,6-diynes and imidoyl chlorides, is reported. The easy procedure accessing the products efficiently from readily available starting materials may imply a potential synthetic application.