An unprecedented strategy to access highly enantioenriched dihydropyrazoles is described. It involves formal [4+1] cycloadditions of in situ-derived azoalkenes and sulfur ylides catalyzed by a chiral copper/Tol-BINAP complex. A variety of synthetically and biologically important dihydropyrazoles have been obtained with high enantioselectivities (up to 97:3 er) in good yields (83-97%).
Revitalization by oxygen: A rhodium(III)-catalyzed oxidative CH/NH activation/annulation sequence provided access to a variety of substituted 1,2-benzothiazine derivatives from readily available NH-sulfoximines and alkynes (see scheme; Cp*=C5 Me5 ). The oxidation system consisted of molecular oxygen in combination with a catalytic amount of Fe(OAc)2 .
Rhodium-catalyzed directed CH-functionalizations have been used in hydroarylations of heterobicyclic alkenes with NH-sulfoximines. Unexpectedly, the bicyclic framework is retained, resulting in the formation of addition products being attractive intermediates for functionalized molecules that are difficult to prepare by other means.
A ruthenium-catalyzed arylation reaction of oxa-and azabicyclic alkenes with (hetero)arenes by C−H bond activation has been discovered. The reaction does not require additives and utilizes dioxygen in realizing the catalytic cycle leading to monosubstituted 7-oxa and 7-azabenzonorbornane derivatives.
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