Florian Jaroschik

Tracking gold acetylides in gold(I)-catalyzed cycloisomerization reactions of enynes

The intermediacy of gold acetylides in the gold(I)-catalyzed cycloisomerization of enynes was questioned. While dinuclear gold complexes are observed under electrospray ionization conditions, the solution reactivity of gold acetylides also leads to the conclusion of their high affinity for the second coordination of a gold moiety, leading to dinuclear gold complexes. However, the involvement of gold acetylides and the corresponding diaurated species in the elementary steps of cycloisomerization mechanisms of enynes appears unlikely.

Synthesis of a new stable, neutral organothulium(II) complex by reduction of a thulium(III) precursor

The new stable, neutral Tm(II) complex (Cp(ttt))2Tm [Cp(ttt) = 1,2,4-tris(tert-butyl)cyclopentadienyl] can be obtained either by direct reaction of NaCp(ttt) with TmI2 or by reduction of (Cp(ttt))2TmI in non-polar solvents; this latter route may prove itself useful for the isolation of other neutral non-classical low-valent organolanthanide species.

New mono- and bis-carbene samarium complexes: synthesis, X-ray crystal structures and reactivity

New samarium carbene complexes have been synthesized and characterized by X-ray diffraction analysis; the carbenic nature was assessed by reactivity studies.

Titanium‐Catalyzed Hydroalumination of Conjugated Dienes: Access to Fulvene‐Derived Allylaluminium Reagents and Their Diastereoselective Reactions with Carbonyl Compounds

The described titanium-catalyzed hydroalumination of conjugated dienes opens up a new way to allylaluminium reagents. The reaction is carried out by using diisobutylaluminium hydride (DIBAL-H) and a catalytic amount of [Cp2TiCl2] (Cp = cyclopentadienyl). When applied to mono- and disubstitued pentafulvenes, this reaction proceeds in a highly endocyclic manner. The formed allylaluminium compounds react regio- and stereoselectively with both aldehydes and ketones to afford homoallylic alcohols that are suitable synthons for functionalized cyclopentanones. An extension of this methodology to simple dienes was also investigated. In the proposed mechanism, the initially formed bimetallic species (Ti/Al) are involved in the two possible catalytic cycles with a direct hydroalumination or/and a hydrotitanation followed by a titanium to aluminium transmetallation.

Generation of ε,ε-difluorinated metal-pentadienyl species through lanthanide-mediated C-F activation

Heavy metal on Lewis acid: The combination of lanthanide metals and AlCl3 has been employed for selective single C-F activation in benzofulvenes comprising an exocyclic CF3 substituent. Intermediate ϵ,ϵ-difluorinated metal-dienyl species react with a large variety of aldehydes in a highly regio- and diastereoselective fashion to afford 1,1-disubstituted indenes bearing a difluorovinyl group. These new building blocks have been further transformed through a hydrogenation-cyclization process into fluorinated heterocyclic spiro compounds.

A divalent heteroleptic lanthanoid fluoride complex stabilised by the tetraphenylcyclopentadienyl ligand, arising from C–F activation of pentafluorobenzene

The divalent heteroleptic lanthanoid fluoride complex, [Yb(C5Ph4H)(μ-F)(thf)2]2, as well as [Yb(C5Ph4H)2(thf)] and [Yb(C5Ph4H)(C6F5)(thf)2] were obtained from reactions of ytterbium metal with Hg(C6F5)2 and tetraphenylcyclopentadiene under different conditions, and C-F activation of C6F5H by Yb metal was observed.

Lewis Acid Catalyzed Regioselective Hydroheteroarylation of Pentafulvenes

A diverse approach toward the catalytic regioselective nucleophilic addition of nitrogen heterocycles to Lewis acid activated pentafulvenes has been established. The developed protocol introduces pentafulvenes as nonsymmetrical alkenes for the hydroheteroarylation reaction, providing alkylidenecyclopentenylation at the C-3 position of indoles and the C-2 position of pyrrole.

Titanium and Zirconium Hydride-Catalyzed Regioselective Isomerization of 1,4-Dihydrofulvenes: Access to 1-Substituted 1,2-Dihydrofulvenes

Zirconium hydride-catalyzed C═C double bond migration from nonconjugated to conjugated dienes is described. Applied to 1-substituted 1,4-dihydrofulvenes, the migration leads selectively to 1-substituted 1,2-dihydrofulvenes. The C═C double bond migration can also be catalyzed by titanium hydride, allowing a one-pot procedure to provide 1-substituted 1,2-dihydrofulvenes from pentafulvenes via two titanium-catalyzed steps. This sequence was proven to be temperature-dependent, allowing the selective access to a conjugated or nonconjugated adduct by a simple temperature tuning. The synthetic potential of the methodology was illustrated by the diastereoselective synthesis of a polyhydroxycyclopentane.

Lewis acid catalyzed C-3 alkylidenecyclopentenylation of indoles: an easy access to functionalized indoles and bisindoles

A Lewis acid catalyzed C-3 alkylidenecylopentenylation of indoles through the ring opening of pentafulvene derived diazabicyclic olefins has been developed. The present protocol offers an efficient route toward the synthesis of indole and bisindole derivatives. The role of the hydrazine group, as a reaction carrier in the strategy has also been demonstrated by the stepwise synthesis of functionalized bisindole.

Single or Synergistic Kinetic Resolutions of Chiral Allylalanes: Two Complementary Routes for the Asymmetric Synthesis of Syn Homoallylamines

Two strategies based on kinetic resolution(s) of chiral alanes and providing enantioenriched syn homoallylamines are reported. The first implies a single kinetic resolution of the alane using camphor; the second requires two sequential kinetic resolutions using the synergistic combination of (-)-camphor/(R)-tert-butylsulfinamide-derived imines. This syn selectivity, specific to the use of allyaluminum, opens the way to the preparation of valuable building blocks as illustrated by the synthesis of (+)-epilupinamine.