Vielstufige zirconiumkatalysierte Reaktionssequenzen von Hydrazinen mit Alkinen: ein Weg zu Indolen, der nicht dem Fischer-Typ entspricht

Redox Non-Innocent Behavior of a Terminal Iridium Hydrazido(2-) Triple Bond

The synthesis of the first terminal Group 9 hydrazido(2-) complex, Cp*IrN(TMP) (6) (TMP=2,2,6,6-tetramethylpiperidine) is reported. Electronic structure and X-ray diffraction analysis indicate that this complex contains an Ir-N triple bond, similar to Bergman's seminal Cp*Ir(Nt Bu) imido complex. However, in sharp contrast to Bergman's imido, 6 displays remarkable redox non-innocent reactivity owing to the presence of the Nβ lone pair. Treatment of 6 with MeI results in electron transfer from Nβ to Ir prior to oxidative addition of MeI to the iridium center. This behavior opens the possibility of carrying out facile oxidative reactions at a formally IrIII metal center through a hydrazido(2-)/isodiazene valence tautomerization.

Divergent reactivity in palladium-catalyzed annulation with diarylamines and α,β-unsaturated acids: direct access to substituted 2-quinolinones and indoles

A palladium-catalyzed CH activation strategy has been successfully employed for exclusive synthesis of a variety of 3-substituted indoles. A [3+3] annulation for synthesizing substituted 2-quinolinones was recently developed by reaction of α,β-unsaturated carboxylic acids with diarylamines under acidic conditions. In the present work, an analogous [3+2] annulation is achieved from the same set of starting materials under basic conditions to generate 1,3-disubstituted indoles exclusively. Mechanistic studies revealed an ortho-palladation-π-coordination-β-migratory insertion-β-hydride elimination reaction sequence to be operative under the reaction conditions.

Facile preparation of indoles and 1,2-benzothiazine 1,1-dioxides: nucleophilic addition of sulfonamides to bromoacetylenes and subsequent palladium-catalyzed cyclization

Bromine as a double agent: The bromine atom in 1-bromo-1-alkynes works as an electron-withdrawing group to effect the nucleophilic addition of sulfonamides. It again plays a pivotal role in the palladium-catalyzed cyclization of the resultant (Z)-2-(sulfonylamino)-1-bromoalkenes into nitrogen heterocycles (see scheme).