214958-04-0Relevant academic research and scientific papers
Reaction of 1-aryl-2-methylenecyclopropanes with rhodium(I) complexes leading to ring opening isomerization and π co-ordination of the C=C double bond
Osakada, Kohtaro,Takimoto, Hisami,Yamamoto, Takakazu
, p. 853 - 859 (2007/10/03)
1-Aryl-2-methylenecyclopropanes reacted with [RhCl(PPh3)3] at 50°C to give [RhCl(η4-CH2=CArCH=CH2)(PPh 3)2] (Ar = C6H5 1a, C6H4F-p 1b, C6H4Me-p 1c or C6H4OMe-p? 1d) via ring opening isomerization of the substrate and its subsequent co-ordination to Rh. The diene-co-ordinated rhodium complexes have been characterized by X-ray crystallography and NMR spectroscopy. Similar reaction at 0°C afforded the rhodium(I) complexes with πco-ordinated 1-aryl-2-methylenecyclopropane, [RhCl(η2-CH2=CCH2CHAr)(PPh 3)2] (Ar = C6H5 2a, C6H4F-p 2b, C6H4Me-p 2c or C6H4OMe-p 2d). Exchange of the ligand of 2a with added 1-aryl-2-methylenecyclopropanes occurs reversibly at 30-45°C with the thermodynamic parameters of the reactions 2a + CH2=CCH2CHC6H4X-p ? 2b (or 2c) + CH2=CCH2CHC6H5 being ΔH° = -10.3 kJ mol-1 and ΔS° = -32 J K-1 mol-1 for X = F and ΔH° = 2.2 kJ mol-1 and ΔS° = -2.6 J K-1 mol-1 for X = Me, respectively, at 298 K. The structure of a PEt3 co-ordinated analog, [RhCl(η2-CH2=CCH2CHC6H 4Me-p)(PEt3)2] 3c, has been determined by X-ray crystallography. The reaction of 1-methylene-2-phenylcyclopropane with [RhCl(PPh3)3] at 25°C gave a mixture of 1a and 2a. Heating of a benzene solution of 2a at 50°C turned it into 1a in low yield (3)3] at 50°C.
