Metallacycloalkane, V. Darstellung eines Rhodacycloheptans durch oxidative Kopplung von 3,3‐Dimethylcyclopropen an Rhodium(I)‐Komplexe

Abstract

Aus Tris(tripheny1phosphan)rhodium-chlorid oder Carbonylbis(tripheny1phosphan)rhodiumchlorid und 3,3-Dimethylcyclopropen (1) ist das Rhodacycloheptan-Derivat 2 leicht und in guten Ausbeuten zuganglich. Spektroskopische Daten wie auch eine Rontgenstrukturanalyse zeigen, dal3 2 monomer ist und einesyn,anti,syn-Struktur besitzt. Mit CO wird der Kohlenwasserstoffrest von 2 unter Bildung des Hexamethyl-tris-o-homobenzols (5) und des Hexamethyl-tris-o-homotropons (4) im Verhaltnis 1 : 4 abgespalten. Von 4 wird die Rontgenstrukturanalyse angegeben. Metallacycloalkanes, V l) Preparation of a Rhodacycloheptane by Oxidative Coupling of 3,3-Dimethylcyclopropene to Rhodiurn(1) ComplexesThe rhodacycloheptane derivative 2 is easily prepared in good yields from tris(tripheny1phospha-ne)rhodium chloride or carbonylbis(tripheny1phosphane)rhodium chloride and 3,3-dimethylcyclopropene. Spectroscopic data and an X-ray analysis show that 2 is monomeric and has a syn,anti,syn structure. The hydrocarbon group of 2 is eliminated by reaction of 2 with CO to give hexamethyl-tris-o-homobenzene (5) and hexamethyl-tris-o-homotropone (4) in a ratio of 1 : 4. The X-ray structure of 4 is also given.Vor einiger Zeit ist es uns gelungen, 3,3-Dimethylcyclopropen (1) wie auch andere, in 3-Stellung dialkylierte Cyclopropene metallkatalysiert zu cyclooligomerisieren 2,3). In Anwesenheit von Kohlenmonoxid konnten dabei cyclische Ketone gewonnen werden4, 5). Als Katalysatoren eignen sich vor allem Nickel (0)

gem-Dimethylcyclopropanation of dibenzylideneacetone using triisopropyl sulfoxonium tetrafluoroborate

“…All but three of these have the (CyP-CO-CyP) moiety as part of a cyclic structure, with the majority being derived from 1,4-benzoquinone. Only two structures are reported which have two dimethylcyclopropyl groups, one being derived from benzoquinone (Edwards et al, 2008) and the other based on tropone (Cetinkaya et al, 1982). Thus, the crystal structure of (IV), with the dimethylcyclopropyl groups and carbonyl group in an acyclic arrangement, appears to be the first of its type to be reported.…”

Rhodium-Catalyzed Hydroformylation of Cyclopropenes

“…The long-standing challenge associated with the use of coordinatively unsaturated electron-deficient transition metal catalysts derived from metal carbonyl complexes in cyclopropene chemistry lies in the significantly more facile migratory insertion of cyclopropene into a metal−carbon bond (Scheme , Path II) as compared to the CO insertion step (Path I). Another commonly encountered problem is a very fast formal [2 + 2] dimerization of cyclopropenes occurring in the presence of electron-poor transition metal reagents (Scheme , Path III). , These two dominating side processes do not allow efficient incorporation of the carbonyl function into the final product, leading instead to the formation of polymers and mixtures of oligocarbocyclic hydrocarbons and ketones . To date, only one highly selective carbonylative transformation involving cyclopropenes, the Pauson-Khand reaction, has been reported; however, this process requires use of at least stoichiometric amounts of metal carbonyl complexes …”