Stickstoff-Heterocyclen aus Carben-Komplexen und Alkenylisocyaniden

Abstract

Azafulven‐ und Azetidinyliden‐Komplexe wie 1 bzw. 2 entstehen aus Carben‐Komplexen und zwei Äquivalenten Alkenylisocyanid. Aus 1 ist der Pyrrolopyridin‐Komplex 3 zugänglich. 2 läßt sich oxidativ zum β‐Lactam 4 spalten.

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

“…The reaction product of nickelocene (di-π-cyclopentadienylnickel) with dimethylketene 145 has been reinvestigated. 146 It is identified as 62 (eq 19), i.e., the reaction consists of Metal vinylidene complexes, often generated in situ from carbene precursors or through prototropic rearrangement of η 2 -coordinated terminal alkynes, [152][153][154] are promising reactants for β-lactam syntheses [155][156][157][158][159] via [2+2] cycloaddition reactions of imines. Following a report of Fischer 160 (eq 20), Barrett et al 155 (eq 21) could isolate complexes 65, however in low yields.…”

“…The position of these equilibria may be responsible that in the iron system exclusively the azetidinylidene complexes 475 are formed with alkyl and aryl isocyanides, while the analogous tungsten Fischer carbene complexes give this reaction only with alkenyl isocyanides and only as a side reaction. 159 Tetrakis(aryl isocyanide)nickel complexes 477 react with diphenylacetylene in refluxing toluene (eq 124) to give diiminocyclobutenes 478 in 22-90% yields. 752 With R being 2,6-Me 2 -4-BrC 6 H 2 , the independently prepared mixed-ligand complex 479, as a suggested intermediate, gives an identical yield of 478 as in the one-pot reaction.…”