STUDIES ON VINYL ISOCYANIDES

Article abstract of DOI:10.1016/S0040-4020(01)96674-8

The vinyl isocyanides 2,4,6-(CH3)3C6H2CH=CHNC and (CH3)3CCH=CHNC and the new 1,3-dienyl isocyanide CH3CH=CH(CH3)-CH=CHNC have been prepared from the corresponding aldehydes and methyl isocyanide using a method first developed by Schoellkopf, Stafforst, and Jentsch.⁵ The new vinyl isocyanides (CH2)2C=CHNC and CH3CH=C(CH3)NC have been prepared by the Cu2O-catalyzed isomerization of the corresponding allyl isocyanides.The liquid vinyl isocyanides may be characterized by the formation of solid cis-(RNC)2Mo(CO)4 derivatives through reaction with norbornadienetetracarbonylmolibdenum in hexane solution at ambient temperature.Examination of these molybdenum carbonyl complexes by proton and carbon-13 NMR spectroscopy indicates that the isocyanide carbon atom but not the carbon-carbon double bond of the vinyl isocyanide ligands is bonded to the molybdenum atom.The proton-decoupled carbon-13 NMR spectra of the vinyl isocyanides, but not their molybdenum carbonyl complexes, indicate coupling of the isocyanide nitrogen to both the isocyanide carbon (¹J(C-N)=6 Hz.) and the vinyl carbon bearing the isocyanide group (¹J(C-N)=11-13 Hz.) leading to 1:1:1 triplets for these resonances.The vinyl carbonyl resonances are used to estimate the cis-trans isomer ratios in vinyl isocyanides of the type RCH=CHNC.Such studies suggest that the formation of vinyl isocyanides by the copper(I) catalyzed isomerization of the corresponding allylic isocyanides is more nearly stereospecific than the formation of vinyl isocyanides by the elimination reaction of the Schollkopf/Stafforst/Jentsch synthetic method.