Stereospecific synthesis of polysubstituted E-olefins by reaction of acyclic nitrones with free and platinum(II) coordinated organonitriles.
Free nitriles NCCH2R (1a R = CO2Me, 1b R = SO2Ph, and 1c R = COPh) with an acidic alpha-methylene react with acyclic nitrones -O+N(Me)=C(H)R' (2a R' = 4-MeC6H4 and 2b R' = 2,4,6-Me3C6H2), in refluxing CH2Cl2, to afford stereoselectively the E-olefins (NC)(R)C=C(H)R' (3a-3c and 3a'-3c'), whereas, when coordinated at the platinum(II) trans-[PtCl2(NCCH2R)2] complexes (4a R = CO2Me and 4b R = Cl), they undergo cycloaddition to give the (oxadiazoline)-PtII complexes trans-[PtCl2{N=C(CH2R)ON(Me)C(H)R'}2] (R = CO2Me, Cl and R' = 4-MeC6H4, 2,4,6-Me3C6H2) (5a-5d). Upon heating in CH2Cl2, 5a affords the corresponding alkene 3a. The reactions are greatly accelerated when carried out under focused microwave irradiation, particularly in the solid phase (SiO2), without solvent, a substantial increase of the yields being also observed. The compounds were characterized by IR and 1H, 13C, and 195Pt NMR spectroscopies, FAB+-MS, elemental analyses and, in the cases of the alkene (NC)(CO2Me)C=C(H)(4-MeC6H4) 3a and of the oxadiazoline complex trans-[PtCl2{N=C(CH2Cl)ON(Me)C(H)(4-C6H4Me)}2] 5c, also by X-ray diffraction analyses.
Lasri
Jamal
J
Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Avenida Rovisco Pais, 1049-001, Lisbon, Portugal.
Charmier
M Adília Januario
MA
Haukka
Matti
M
Pombeiro
Armando J L
AJ
D000475:Alkenes / Q000138:chemical synthesis*; D002413:Cations, Divalent; D006839:Hydrocarbons, Acyclic / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D008956:Models, Chemical; D009570:Nitriles / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010069:Oxadiazoles / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D000475:Alkenes; D002413:Cations, Divalent; D006839:Hydrocarbons, Acyclic; D009570:Nitriles; D009589:Nitrogen Oxides; D010069:Oxadiazoles; C015388:nitrones; D010984:Platinum; D012822:Silicon Dioxide