Heinz Hoberg

Nickel(0)-induzierte CC-verknüpfung zwischen kohlendioxid und alkinen sowie alkenen

Abstract CO 2 and alkynes or alkenes undergo a 1/1 coupling in the presence of (Lig)Ni 0 complexes to give five-membered cyclic nickela complexes of types V and XVII. The influence of temperature and of the ligands upon the regioselectivity of the CC coupling in the case of monosubstituted olefins is reported, and the significance of these ring systems in preparative chemistry is emphasized. Oxanickelacyclopentenones (V) react with alkynes to form oxanickelacycloheptadienones (XIII). The structure of one of the compounds of this class has been determined by X-ray crystallography. Special features of these novel compounds, which can be readily prepared from CO 2 , are discussed together with the probable reaction mechanisms.

Nickel(0)-induzierte CC-verknüpfung zwischen kohlendioxid und ethylen sowie mono- oder di-substituierten alkenen

Abstract The nickel(0)-induced coupling of CO 2 with ethylene or with mono- or di-substituted alkenes is described. The regioselectivity of this reaction has been determined.

Nickelaverbindungen als zwischenkomplexe der [2+2+2′]-cycloaddition von alkinen mit isocyanaten zu 2-pyridonen

Abstract Diphenylacetylene and phenylisocyanate react with TMEDA/Ni 0 to give an azanickela-5-ring (IVa) which yields the azanickela-7-ring (IIb) with an activated alkyne. It is shown that both IVa and IIb are intermediates in the nickel-catalysed 2-pyridone synthesis. Pyrimidinediones are formed from diphenylacetylene and alkylisocyanates with TMEDA/Ni 0 .

Diencarbonsäuren aus 1,3-dienen und CO2 durch C-C-verknüpfung an nickel(0)

Abstract (Lig)Ni 0 systems react with 1,3-dienes in the presence of CO 2 to give nickela carboxylates. The influence of ligands and temperature on the regioselectivity of the CC bond formation is elucidated. In some cases the nickela carboxylates undergo reductive elimination under the influence of maleic anhydride, and the coupled diene/CO 2 moiety rearranges to give the diene carboxylic acid. A possible reaction sequence is discussed.

Nickel(0)-induzierte CC-verknüpfung zwischen 1,2-dienen und kohlendioxid

Abstract 1,2-Dienes react with CO 2 at nickel(O) under the influence of basic chelate ligands to form nickela carboxylates. The structures of these five-membered complexes have been determined by spectroscopic and chemical methods. The regioselectivity of the CC bond formation is discussed.

Modellkomplex des nickels für die cc verknüpfung von alkinen mit isocyanaten

Abstract Azanickelacyclopenten derivatives, which can easily be prepared from alkynes, isocyanates and nickel(0) compounds, are shown to be intermediates in the nickel-catalysed synthesis of 2-pyridones.

Modellkomplexe des nickels für die [2+2+2′]-cycloaddition von alkinen mit kohlendioxid

Abstract The oxanickelacyclopentenone (I), formed from 2-butyne, CO 2 and nickel(0), reacts with activated alkynes by insertion to give oxanickelacycloheptadienones (II). It is suggested that these novel nickela complexes are intermediates in the nickel-catalysed synthesis of 2-pyrones from alkynes and CO 2 .

(Pentaphenyl)aluminacyclopentadiene as a complexing ligand. The molecular structure of (pentaphenyl)aluminacyclopentadiene and its complex with 1,5-cyclooctadienenickel

The molecular conformations of a (pentaphenyl)aluminacyclopentadiene ligand (I) and its complex with 1,5-cycloactadienenickel (II) have been determined from single crystal X-ray data collected at room temperature with counter methods. The free ligand crystallizes in the monoclinic space group Cc with 4 molecules in a unit cell of dimensions a 10.5598(5), b 22.7089(12), c 13.3417(4) A, β 98.064(3)°; its (COD)Ni complex Crystallizes in the monoclinic space group P 2 1 / n with 4 molecules in a unit cell of the dimensions a 11.9948(8), b 16.9758 (13), c 18.7721(14) A. β 97.958(3)°. Both structures have been refined anisotropically to R values of 0.0577 and 0.0493, respectively. Upon complexation of I to the nickel atom the planarity of the ring system is distorted, with the aluminum being bent away from the nickel. A direct metal—metal interaction in II (NiAl: 2.748(1) A) cannot be ruled out.

Oxanickelacyclopenten-derivate, ein neuer typ vielseitig verwendbarer synthone

Abstract Oxanickelacyclopentene derivatives (I), which can easily be prepared from carbon dioxide, alkynes and nickel(0) compounds, are shovel to be versatile synthones. Some representative examples are given.

LIGANDGESTEUERTE RINGKONTRAKTION VON NICKELA-FUNF-IN VIERRINGKOMPLEXE : NEUARTIGE STARTSYSTEME FUR DIE PRAPARATIVE CHEMIE

Abstract Nickela-compounds with a five-membered ring, 4 , are formed on Ni 0 from CO 2 and alkenes in the presence of the heterodifunctional ligand (cyclo-C 6 H 11 ) 2 PCH 2 CH 2 -2-pyridyl ( 2 ). A ring contraction occurs on addition of a promoteor, such as BeCl 2 , or on heating. The greater reactivity of the nickela-complex with a four-membered ring, 6 , can be used in the former reactions with CO 2 , CO or CH 2 CH 2 . Such a sequence of reactions can be employed for the catalytic reaction of ethene with acrylic anilide on a (C 6 H 11 ) 3 P/Ni 0 system.